ecode: add customizable debugger panel layouts

- add a reusable right-side panel managed at the application level
  - migrate debugger tabs to UITabWidgetSplitter instances
  - support moving and splitting debugger tabs across bottom and right panels
  - restrict debugger tab drops to debugger-owned panel targets
  - serialize debugger tab layouts, panel state, and table column widths
  - add pixel and percentage column-width modes to UIAbstractTableView
  - support XML/CSS configuration and an optional width-mode context menu
  - preserve percentage totals across resizing, fit-to-content, minimum widths,
    scrollbar changes, and pixel-density rounding
  - add splitter edge hiding while preserving splitter-always-show precedence
  - use EventConnection ownership for safe widget and controller lifetimes
  - validate serialized splitter layouts with structural limits
  - display project-relative source paths in debugger stack frames
  - add ecode localization strings, CSS documentation, tests, and agent rules

.agent/SOUL.md

@@ -8,8 +8,19 @@ Your name is Negen (from negentropy: the process of creating order out of chaos)
 1. **Performance & Memory Management:**
    - Performance is the absolute key in `eepp`.
    - Favor stack-allocated memory over heap allocations whenever possible.
+   - Prefer eepp's internal container layer when it provides the required semantics. Check
+     `include/eepp/core/containers.hpp`, `small_vector.hpp`, `lrucache.hpp`, and related core
+     containers before introducing standard-library or third-party containers directly.
+   - Also consider `include/eepp/core/small_function.hpp` for frequently stored callbacks with
+     known, bounded capture sizes. It is not a general replacement for `std::function`: use it only
+     when its inline-capacity, callable semantics, and object-size tradeoff fit the concrete use.
    - Any heap allocation must be heavily justified.
    - Exercise reason: maximize stack use for speed, but actively calculate boundaries to prevent stack-overflows.
+   - Review the memory layout of every new or materially changed struct and class. Order members
+     and select appropriately sized enum/integer storage to minimize alignment padding, and verify
+     meaningful changes with compiler layout data or `sizeof` instead of guessing. Do not use packed
+     layouts or otherwise force misaligned access, and preserve public ABI unless the change is
+     explicitly authorized.
    - Before finalizing C++ changes, perform an explicit allocation audit:
      - Review every heap allocation, string copy, container insertion, `std::function`, lambda capture, and async handoff introduced or touched by the change.
      - Prefer move captures for owned temporary strings, buffers, vectors, and other heap-backed objects passed into lambdas.

.agent/rules/project-introduction.md

@@ -17,9 +17,24 @@ When working on this project, rely on the following resources to understand exis
 *   **Implementation Examples:** A wide variety of examples showing how to use the library are located in `src/examples/`.
 *   **General Context:** The `README.md` at the root directory contains deeper project details.
 
+## Localization
+
+The locale catalogs under `bin/assets/i18n/` belong to **ecode**; the other applications are not
+currently localized. Whenever an ecode feature introduces or changes a user-facing i18n key, add or
+update that key in every catalog in this directory. Do not rely only on the fallback string embedded
+in the source. Keep all locale files structurally valid and verify that every supported catalog
+contains the new or renamed key.
+
 ## C++ Virtual Method Style
 Follow the convention already used by the class being edited. In particular, when a class declares
 virtual methods without the `override` specifier, do not introduce `override` on new methods in that
 class. Mixing the styles can enable Clang's inconsistent-missing-override warnings for the existing
 declarations. A class-wide conversion is a separate change and must update all applicable methods
 together.
+
+## Namespace Style
+
+Follow eepp's established namespace style: prefer the appropriate `using namespace EE::...`
+declarations and unqualified eepp type names, such as `UISplitter`, over repeatedly spelling fully
+qualified names such as `EE::UI::UISplitter`. Keep explicit qualification only where it is required
+to resolve ambiguity or avoid importing an unusually broad namespace into an unsuitable scope.

.agent/rules/unit-tests.md

@@ -5,20 +5,22 @@ This project relies on a comprehensive suite of unit tests to prevent regression
 ## Running Tests
 The test binary manages its own current working directory, so you can execute it from anywhere.
 
+*   **Prefer the release test binary during normal development:**
+    When AddressSanitizer or other debug-only diagnostics are not required, build and run `bin/unit_tests/eepp-unit_tests`. The optimized release suite is substantially faster and should be the default for iterative testing. Use `bin/unit_tests/eepp-unit_tests-debug` when investigating memory safety, assertions, or other behavior that specifically requires the debug configuration.
 *   **Default Execution for Agents on Linux & FreeBSD:**
     Always run unit tests through the project wrapper unless the user explicitly asks for a different harness:
-    `projects/scripts/xvfb-run-eepp bin/unit_tests/eepp-unit_tests-debug`
+    `projects/scripts/xvfb-run-eepp bin/unit_tests/eepp-unit_tests`
 *   **Why the wrapper is required:**
     Tests open ~400 individual windows. The wrapper runs them in an isolated framebuffer, enables race-safe automatic display selection for concurrent agent test runs, sets the default screen to `1280x1024x24`, and injects `ASAN_OPTIONS=detect_leaks=0` automatically.
 *   **Do not skip the wrapper for filtered tests:**
     A focused test still needs the same wrapper:
-    `projects/scripts/xvfb-run-eepp bin/unit_tests/eepp-unit_tests-debug --filter="FontRendering.*Offset*"`
+    `projects/scripts/xvfb-run-eepp bin/unit_tests/eepp-unit_tests --filter="FontRendering.*Offset*"`
 *   **Fallback only when the wrapper itself fails:**
     If `projects/scripts/xvfb-run-eepp` fails before launching the test binary, report that wrapper failure and then use this fallback to keep verification moving:
-    `ASAN_OPTIONS=detect_leaks=0 xvfb-run -a -s "-screen 0 1280x1024x24" bin/unit_tests/eepp-unit_tests-debug`
+    `xvfb-run -a -s "-screen 0 1280x1024x24" bin/unit_tests/eepp-unit_tests`
     Do not use plain `xvfb-run` as the first attempt for GUI/unit tests.
 *   **Direct Execution (Only for non-window tests or explicit user requests):**
-    `bin/unit_tests/eepp-unit_tests-debug`
+    `bin/unit_tests/eepp-unit_tests`
 *   **Filtering Tests:**
     Use the `--filter` parameter to run specific tests (supports glob patterns).
     Keep the wrapper in front of the binary unless the test is known not to create windows.

bin/assets/i18n/de.xml

@@ -890,6 +890,8 @@ in der Baumansicht und in Öffen-/Schließdialogen aktivieren.</string>
 	<string name="uifiledialog_select_file">Eine Datei auswählen</string>
 	<string name="uifiledialog_select_folder">Einen Ordner auswählen</string>
 	<string name="uifiledialog_table">Tabelle</string>
+	<string name="uitable_fit_columns_to_view">Spalten an Ansicht anpassen</string>
+	<string name="uitable_free_column_widths">Freie Spaltenbreiten</string>
 	<string name="uiterminal_copy">Kopieren</string>
 	<string name="uiterminal_open_link">Link öffnen</string>
 	<string name="uiterminal_paste">Einfügen</string>

bin/assets/i18n/en.xml

@@ -874,6 +874,8 @@ the directory tree and in file dialogs to open a folder or file.</string>
 	<string name="uifiledialog_select_file">Select a file</string>
 	<string name="uifiledialog_select_folder">Select a folder</string>
 	<string name="uifiledialog_table">Table</string>
+	<string name="uitable_fit_columns_to_view">Fit Columns to View</string>
+	<string name="uitable_free_column_widths">Free Column Widths</string>
 	<string name="uiterminal_copy">Copy</string>
 	<string name="uiterminal_open_link">Open Link</string>
 	<string name="uiterminal_paste">Paste</string>

bin/assets/i18n/fr.xml

@@ -865,6 +865,8 @@ dans l'arborescence de répertoires ainsi que dans les boites de dialogues de s
 	<string name="uifiledialog_select_file">Sélectionner un fichier</string>
 	<string name="uifiledialog_select_folder">Sélectionner un dossier</string>
 	<string name="uifiledialog_table">Table</string>
+	<string name="uitable_fit_columns_to_view">Ajuster les colonnes à la vue</string>
+	<string name="uitable_free_column_widths">Largeurs de colonnes libres</string>
 	<string name="uiterminal_copy">Copier</string>
 	<string name="uiterminal_open_link">Ouvrir un lien</string>
 	<string name="uiterminal_paste">Coller</string>

bin/assets/i18n/zh.xml

@@ -663,6 +663,8 @@ file in the directory tree.</string>
 	<string name="uifiledialog_select_file">选择文件</string>
 	<string name="uifiledialog_select_folder">选择文件夹</string>
 	<string name="uifiledialog_table">Table</string>
+	<string name="uitable_fit_columns_to_view">列宽适应视图</string>
+	<string name="uitable_free_column_widths">自由调整列宽</string>
 	<string name="uiterminal_copy">复制</string>
 	<string name="uiterminal_open_link">打开链接</string>
 	<string name="uiterminal_paste">粘贴</string>

docs/articles/cssspecification.md

@@ -534,6 +534,30 @@ Sets the width of the child elements of a grid layout.
 
 ---
 
+### column-width-mode
+
+Selects how table and tree view column widths are represented and resized.
+
+* Applicable to: EE::UI::UIAbstractTableView (TableView, TreeView)
+* Data Type: [string-list](#string-list-data-type)
+* Value List:
+  * `pixels`: Column widths are stored as fixed pixel lengths and can extend beyond the available content width.
+  * `percentage`: Visible column widths are stored as normalized percentages of the available content width. Resizing a column adjusts an adjacent visible column to preserve the total.
+* Default value: `pixels`
+
+---
+
+### column-width-mode-menu
+
+Enables a context menu on table and tree view column headers for switching between pixel and
+percentage column width modes.
+
+* Applicable to: EE::UI::UIAbstractTableView (TableView, TreeView)
+* Data Type: [boolean](#boolean-data-type)
+* Default value: `false`
+
+---
+
 ### cursor
 
 Read [cursor](https://developer.mozilla.org/en-US/docs/Web/CSS/cursor) documentation.
@@ -1934,8 +1958,8 @@ Sets the [skin](#skin) tint color.
 
 ### splitter-always-show
 
-Sets if the splitter divisor is always visible. If false it will be shown only if two views are
+Sets whether the splitter divisor remains visible whenever two views are attached. This property
-attached to the splitter.
+overrides `splitter-hide-on-edge`.
 
 * Applicable to: EE::UI::UISplitter (Splitter)
 * Data Type: [boolean](#boolean-data-type)
@@ -1943,6 +1967,17 @@ attached to the splitter.
 
 ---
 
+### splitter-hide-on-edge
+
+Hides the splitter divisor when its percentage partition is exactly `0%` or `100%`, allowing one
+view to consume the complete splitter. This has no effect when `splitter-always-show` is `true`.
+
+* Applicable to: EE::UI::UISplitter (Splitter)
+* Data Type: [boolean](#boolean-data-type)
+* Default value: `false`
+
+---
+
 ### splitter-partition
 
 Sets the space occupied by the first view contained by the splitter.

include/eepp/ui/abstract/uiabstracttableview.hpp

@@ -6,6 +6,7 @@
 #include <eepp/ui/uitablecell.hpp>
 #include <eepp/ui/uitableheadercolumn.hpp>
 #include <eepp/ui/uitablerow.hpp>
+#include <nlohmann/json_fwd.hpp>
 #include <unordered_map>
 
 using namespace EE::Math;
@@ -20,6 +21,8 @@ namespace EE { namespace UI { namespace Abstract {
 
 class EE_API UIAbstractTableView : public UIAbstractView {
   public:
+	enum class ColumnWidthMode : Uint8 { Pixels, Percentage };
+
 	enum TableFlags : Uint32 {
 		TableFlagNone = 0,
 		TableFlagHeaders = ( 1 << 0 ),
@@ -85,6 +88,30 @@ class EE_API UIAbstractTableView : public UIAbstractView {
 
 	const Float& getColumnWidth( const size_t& colIndex ) const;
 
+	Float getColumnWidthPercentage( const size_t& colIndex ) const;
+
+	std::vector<Float> getColumnsWidthPercentage() const;
+
+	ColumnWidthMode getColumnWidthMode() const;
+
+	void setColumnWidthMode( ColumnWidthMode mode, bool convertCurrentWidths = true );
+
+	bool isColumnWidthModeMenuEnabled() const;
+
+	void setColumnWidthModeMenuEnabled( bool enabled );
+
+	void setColumnWidthPercentage( const size_t& colIndex, Float percentage );
+
+	void setColumnsWidthPercentage( const std::vector<Float>& percentages );
+
+	/** Serializes the column width mode and widths. Pixel widths are stored as dp. */
+	nlohmann::json serializeColumnWidths() const;
+
+	/** Restores column widths serialized by serializeColumnWidths(). Legacy percentage arrays are
+	 * also accepted. Percentage values may be partial or contain surplus entries; pixel widths must
+	 * match the model. Returns false if the data is invalid or incompatible with the model. */
+	bool unserializeColumnWidths( const nlohmann::json& widths );
+
 	virtual Float getMaxColumnContentWidth( const size_t& colIndex, bool bestGuess = false );
 
 	bool getAutoExpandOnSingleColumn() const;
@@ -180,6 +207,7 @@ class EE_API UIAbstractTableView : public UIAbstractView {
 		Float minHeight{ 0 };
 		Float maxWidth{ 0 };
 		Float width{ 0 };
+		Float percentage{ 0 };
 		bool visible{ true };
 		bool manuallySet{ false };
 		UIPushButton* widget{ nullptr };
@@ -210,6 +238,10 @@ class EE_API UIAbstractTableView : public UIAbstractView {
 	std::function<void( UITableCell* )> mSetupCellCb;
 	Float mRowHeaderWidth{ 0 };
 	Uint32 mTableFlags{ UITABLE_DEFAULT_FLAGS };
+	ColumnWidthMode mColumnWidthMode{ ColumnWidthMode::Pixels };
+	bool mColumnWidthModeMenuEnabled{ false };
+	bool mUpdatingColumnsForScrollbars{ false };
+	std::string mPendingSerializedColumnWidths;
 
 	virtual ~UIAbstractTableView();
 
@@ -231,6 +263,8 @@ class EE_API UIAbstractTableView : public UIAbstractView {
 
 	virtual void updateColumnsWidth();
 
+	void restorePendingColumnWidths();
+
 	virtual Uint32 onFocus( NodeFocusReason reason );
 
 	virtual Uint32 onFocusLoss();
@@ -252,6 +286,8 @@ class EE_API UIAbstractTableView : public UIAbstractView {
 
 	virtual void onScrollChange();
 
+	virtual void onContentSizeChange();
+
 	virtual void onRowCreated( UITableRow* row );
 
 	virtual void onSortColumn( const size_t& colIndex );
@@ -270,6 +306,10 @@ class EE_API UIAbstractTableView : public UIAbstractView {
 
 	void resetColumnData();
 
+	void updatePercentageColumnWidths();
+
+	int adjacentVisibleColumn( size_t column ) const;
+
 	void buildRowHeader();
 
 	void updateRowHeader( int realRowIndex, const ModelIndex& index, Float yOffset );

include/eepp/ui/css/propertyids.hpp

@@ -232,6 +232,7 @@ enum class PropertyId : Uint16 {
 	TabAllowSwitchTabsInEmptySpaces,
 	SplitterPartition,
 	SplitterAlwaysShow,
+	SplitterHideOnEdge,
 	DroppableHoveringColor,
 	TextAsFallback,
 	SelectOnClick,
@@ -304,6 +305,8 @@ enum class PropertyId : Uint16 {
 	IconSize,
 	SortIconSize,
 	MainColumn,
+	ColumnWidthMode,
+	ColumnWidthModeMenu,
 	RowHeaderWidth,
 	TableFlags,
 	IndentWidth,

include/eepp/ui/tools/uitabwidgetsplitter.hpp

@@ -1,6 +1,8 @@
 #ifndef EE_UI_TOOLS_UITABWIDGETSPLITTER_HPP
 #define EE_UI_TOOLS_UITABWIDGETSPLITTER_HPP
 
+#include <eepp/core/containers.hpp>
+#include <eepp/scene/eventconnection.hpp>
 #include <eepp/system/mutex.hpp>
 #include <eepp/ui/splitdirection.hpp>
 #include <eepp/ui/uiscenenode.hpp>
@@ -130,6 +132,8 @@ class EE_API UITabWidgetSplitter {
 
 	void setOnTabWidgetCreateCb( std::function<void( UITabWidget* )> cb );
 
+	void setOnTabWidgetCloseCb( std::function<void( UITabWidget* )> cb );
+
 	void closeSplitter( UISplitter* splitter );
 
 	void addRemainingTabWidgets( Node* widget );
@@ -254,10 +258,13 @@ class EE_API UITabWidgetSplitter {
 	Float mVisualSplitEdgePercent{ 0.1 };
 	Mutex mTabWidgetMutex;
 	std::function<void( UITabWidget* )> mOnTabWidgetCreateCb;
+	std::function<void( UITabWidget* )> mOnTabWidgetCloseCb;
 	std::function<bool( SplitDirection direction, UIWidget* widget )> mCanCreateSplitFn;
 	TabTryCloseCallback mTabTryCloseCb;
 	mutable Mutex mWidgetTypesMutex;
-	std::unordered_map<std::string, WidgetTypeCallback> mWidgetTypes;
+	UnorderedMap<std::string, WidgetTypeCallback> mWidgetTypes;
+	UnorderedMap<UITabWidget*, Scene::EventConnectionList> mTabWidgetEventConnections;
+	UnorderedMap<UIWidget*, Scene::EventConnectionList> mWidgetEventConnections;
 
 	UITabWidgetSplitter( Client* client, UISceneNode* sceneNode );
 

include/eepp/ui/uisplitter.hpp

@@ -1,6 +1,7 @@
 #ifndef EE_UI_UISPLITTER_HPP
 #define EE_UI_UISPLITTER_HPP
 
+#include <eepp/scene/eventconnection.hpp>
 #include <eepp/ui/uilayout.hpp>
 
 namespace EE { namespace UI {
@@ -23,6 +24,10 @@ class EE_API UISplitter : public UILayout {
 
 	void setAlwaysShowSplitter( bool alwaysShowSplitter );
 
+	const bool& hideSplitterOnEdge() const;
+
+	void setHideSplitterOnEdge( bool hideSplitterOnEdge );
+
 	const StyleSheetLength& getSplitPartition() const;
 
 	void setSplitPartition( const StyleSheetLength& divisionSplit );
@@ -49,10 +54,12 @@ class EE_API UISplitter : public UILayout {
   protected:
 	UIOrientation mOrientation;
 	bool mAlwaysShowSplitter;
+	bool mHideSplitterOnEdge;
 	StyleSheetLength mSplitPartition;
 	UIWidget* mSplitter;
 	UIWidget* mFirstWidget;
 	UIWidget* mLastWidget;
+	Scene::EventConnectionList mEventConnections;
 
 	UISplitter();
 
@@ -63,6 +70,8 @@ class EE_API UISplitter : public UILayout {
 	void updateFromDrag();
 
 	void updateSplitterDragFlags();
+
+	bool shouldShowSplitter() const;
 };
 
 }} // namespace EE::UI

include/eepp/ui/uitableheadercolumn.hpp

@@ -20,7 +20,7 @@ class EE_API UITableHeaderColumn : public UIPushButton {
   protected:
 	UIAbstractTableView* mView;
 	size_t mColIndex;
-	mutable UIImage* mImage{nullptr};
+	mutable UIImage* mImage{ nullptr };
 
 	Uint32 onCalculateDrag( const Vector2f& position, const Uint32& flags );
 
@@ -34,6 +34,8 @@ class EE_API UITableHeaderColumn : public UIPushButton {
 
 	Uint32 onMouseClick( const Vector2i& position, const Uint32& flags );
 
+	Uint32 onMouseUp( const Vector2i& position, const Uint32& flags );
+
 	Uint32 onMouseDoubleClick( const Vector2i& position, const Uint32& flags );
 
 	Uint32 onDragStop( const Vector2i& pos, const Uint32& flags );

include/eepp/ui/uitabwidget.hpp

@@ -2,6 +2,7 @@
 #define EE_UI_UITABWIDGET_HPP
 
 #include <deque>
+#include <eepp/scene/eventconnection.hpp>
 #include <eepp/ui/splitdirection.hpp>
 #include <eepp/ui/uitab.hpp>
 #include <eepp/ui/uiwidget.hpp>
@@ -260,6 +261,7 @@ class EE_API UITabWidget : public UIWidget {
 	UIListView* mTabSwitcher{ nullptr };
 	TabJumpMode mTabJumpMode{ TabJumpMode::Linear };
 	std::function<bool( const UIWidget* widget )> mAcceptsDropOfWidgetFn;
+	Scene::EventConnectionList mEventConnections;
 
 	UITabWidget();
 

src/eepp/ui/abstract/uiabstracttableview.cpp

@@ -9,6 +9,7 @@
 #include <eepp/ui/uiscrollbar.hpp>
 #include <eepp/window/engine.hpp>
 #include <eepp/window/input.hpp>
+#include <nlohmann/json.hpp>
 
 namespace EE { namespace UI { namespace Abstract {
 
@@ -104,6 +105,166 @@ const Float& UIAbstractTableView::getColumnWidth( const size_t& colIndex ) const
 	return columnData( colIndex ).width;
 }
 
+Float UIAbstractTableView::getColumnWidthPercentage( const size_t& colIndex ) const {
+	return columnData( colIndex ).percentage;
+}
+
+std::vector<Float> UIAbstractTableView::getColumnsWidthPercentage() const {
+	std::vector<Float> percentages;
+	size_t count = getModel() ? getModel()->columnCount() : mColumn.size();
+	percentages.reserve( count );
+	for ( size_t i = 0; i < count; ++i )
+		percentages.emplace_back( columnData( i ).percentage );
+	return percentages;
+}
+
+UIAbstractTableView::ColumnWidthMode UIAbstractTableView::getColumnWidthMode() const {
+	return mColumnWidthMode;
+}
+
+void UIAbstractTableView::setColumnWidthMode( ColumnWidthMode mode, bool convertCurrentWidths ) {
+	if ( mode == mColumnWidthMode )
+		return;
+	if ( mode == ColumnWidthMode::Percentage && getModel() ) {
+		setAutoColumnsWidth( false );
+		if ( convertCurrentWidths ) {
+			Float totalWidth = 0;
+			for ( size_t i = 0; i < getModel()->columnCount(); ++i )
+				if ( !isColumnHidden( i ) )
+					totalWidth += columnData( i ).width;
+			if ( totalWidth > 0 )
+				for ( size_t i = 0; i < getModel()->columnCount(); ++i )
+					if ( !isColumnHidden( i ) )
+						columnData( i ).percentage = columnData( i ).width / totalWidth * 100.f;
+		}
+	}
+	mColumnWidthMode = mode;
+	createOrUpdateColumns( false );
+}
+
+bool UIAbstractTableView::isColumnWidthModeMenuEnabled() const {
+	return mColumnWidthModeMenuEnabled;
+}
+
+void UIAbstractTableView::setColumnWidthModeMenuEnabled( bool enabled ) {
+	mColumnWidthModeMenuEnabled = enabled;
+}
+
+void UIAbstractTableView::setColumnWidthPercentage( const size_t& colIndex, Float percentage ) {
+	if ( mColumnWidthMode != ColumnWidthMode::Percentage )
+		setColumnWidthMode( ColumnWidthMode::Percentage );
+	if ( !getModel() || colIndex >= getModel()->columnCount() )
+		return;
+	auto& column = columnData( colIndex );
+	int adjacent = adjacentVisibleColumn( colIndex );
+	if ( adjacent >= 0 ) {
+		auto& sibling = columnData( adjacent );
+		Float combined = column.percentage + sibling.percentage;
+		column.percentage = eeclamp( percentage, 0.f, combined );
+		sibling.percentage = combined - column.percentage;
+	} else {
+		column.percentage = 100.f;
+	}
+	createOrUpdateColumns( false );
+}
+
+void UIAbstractTableView::setColumnsWidthPercentage( const std::vector<Float>& percentages ) {
+	const size_t columnCount = getModel() ? getModel()->columnCount() : percentages.size();
+	if ( mColumn.size() < columnCount )
+		mColumn.resize( columnCount );
+	const size_t suppliedColumnCount = eemin( percentages.size(), columnCount );
+	Float total = 0;
+	for ( size_t i = 0; i < suppliedColumnCount; ++i ) {
+		columnData( i ).percentage = eemax( 0.f, percentages[i] );
+		if ( !getModel() || !isColumnHidden( i ) )
+			total += columnData( i ).percentage;
+	}
+	size_t missingVisibleColumns = 0;
+	for ( size_t i = suppliedColumnCount; i < columnCount; ++i )
+		if ( !getModel() || !isColumnHidden( i ) )
+			++missingVisibleColumns;
+	const Float missingPercentage =
+		missingVisibleColumns > 0 ? eemax( 0.f, 100.f - total ) / missingVisibleColumns : 0.f;
+	for ( size_t i = suppliedColumnCount; i < columnCount; ++i ) {
+		columnData( i ).percentage = !getModel() || !isColumnHidden( i ) ? missingPercentage : 0.f;
+		total += columnData( i ).percentage;
+	}
+	if ( total > 0 )
+		for ( size_t i = 0; i < columnCount; ++i )
+			if ( !getModel() || !isColumnHidden( i ) )
+				columnData( i ).percentage = columnData( i ).percentage / total * 100.f;
+	setAutoColumnsWidth( false );
+	mColumnWidthMode = ColumnWidthMode::Percentage;
+	if ( getModel() )
+		createOrUpdateColumns( false );
+}
+
+nlohmann::json UIAbstractTableView::serializeColumnWidths() const {
+	if ( !getModel() && !mPendingSerializedColumnWidths.empty() )
+		return nlohmann::json::parse( mPendingSerializedColumnWidths, nullptr, false, true );
+	nlohmann::json saved;
+	const bool percentage = mColumnWidthMode == ColumnWidthMode::Percentage;
+	saved["mode"] = percentage ? "percentage" : "pixels";
+	if ( percentage ) {
+		saved["widths"] = getColumnsWidthPercentage();
+		return saved;
+	}
+	std::vector<Float> widths;
+	if ( !getModel() )
+		return saved;
+	widths.reserve( getModel()->columnCount() );
+	for ( size_t i = 0; i < getModel()->columnCount(); ++i )
+		widths.emplace_back( PixelDensity::pxToDp( getColumnWidth( i ) ) );
+	saved["widths"] = std::move( widths );
+	return saved;
+}
+
+bool UIAbstractTableView::unserializeColumnWidths( const nlohmann::json& saved ) {
+	const nlohmann::json* widths = &saved;
+	ColumnWidthMode mode = ColumnWidthMode::Percentage;
+	if ( saved.is_object() ) {
+		if ( !saved.contains( "widths" ) || !saved["widths"].is_array() )
+			return false;
+		widths = &saved["widths"];
+		if ( saved.value( "mode", "percentage" ) == "pixels" )
+			mode = ColumnWidthMode::Pixels;
+	} else if ( !saved.is_array() ) {
+		return false;
+	}
+	std::vector<Float> values;
+	values.reserve( widths->size() );
+	for ( const auto& value : *widths ) {
+		if ( !value.is_number() )
+			return false;
+		values.emplace_back( value.get<Float>() );
+	}
+	if ( !getModel() ) {
+		mPendingSerializedColumnWidths = saved.dump();
+		return true;
+	}
+	mPendingSerializedColumnWidths.clear();
+	if ( mode == ColumnWidthMode::Percentage ) {
+		setColumnsWidthPercentage( values );
+	} else {
+		if ( values.size() != getModel()->columnCount() )
+			return false;
+		setColumnWidthMode( mode, false );
+		for ( size_t i = 0; i < values.size(); ++i )
+			setColumnWidth( i, PixelDensity::dpToPx( values[i] ) );
+	}
+	return true;
+}
+
+void UIAbstractTableView::restorePendingColumnWidths() {
+	if ( !getModel() || mPendingSerializedColumnWidths.empty() )
+		return;
+	std::string serialized( std::move( mPendingSerializedColumnWidths ) );
+	mPendingSerializedColumnWidths.clear();
+	auto widths = nlohmann::json::parse( serialized, nullptr, false, true );
+	if ( !widths.is_discarded() )
+		unserializeColumnWidths( widths );
+}
+
 void UIAbstractTableView::selectAll() {
 	getSelection().clear();
 	for ( size_t itemIndex = 0; itemIndex < getItemCount(); ++itemIndex ) {
@@ -139,11 +300,13 @@ void UIAbstractTableView::onModelUpdate( unsigned flags ) {
 			[this] {
 				modelUpdate( mPendingUpdateFlags.exchange( 0 ) );
 				createOrUpdateColumns( true );
+				restorePendingColumnWidths();
 			},
 			Time::Zero, onModelUpdateTag );
 	} else {
 		UIAbstractView::onModelUpdate( flags );
 		createOrUpdateColumns( true );
+		restorePendingColumnWidths();
 	}
 }
 
@@ -196,6 +359,9 @@ void UIAbstractTableView::createOrUpdateColumns( bool resetColumnData ) {
 		col.widget->setPixelsSize( col.width, getHeaderHeight() );
 	}
 
+	if ( mColumnWidthMode == ColumnWidthMode::Percentage )
+		updatePercentageColumnWidths();
+
 	if ( mAutoColumnsWidth && visibleColCount > 1 ) {
 		Float contentWidth = getContentSpaceWidth();
 		bool shouldVScrollBeVisible = shouldVerticalScrollBeVisible();
@@ -311,9 +477,92 @@ void UIAbstractTableView::onSizeChange() {
 	createOrUpdateColumns( false );
 }
 
-void UIAbstractTableView::onColumnSizeChange( const size_t&, bool fromUserInteraction ) {
+void UIAbstractTableView::onColumnSizeChange( const size_t& colIndex, bool fromUserInteraction ) {
 	if ( fromUserInteraction && mAutoColumnsWidth )
 		mAutoColumnsWidth = false;
+	if ( fromUserInteraction && mColumnWidthMode == ColumnWidthMode::Percentage && getModel() ) {
+		int adjacent = adjacentVisibleColumn( colIndex );
+		Float contentWidth = getContentSpaceWidth();
+		if ( adjacent >= 0 && contentWidth > 0 ) {
+			auto& column = columnData( colIndex );
+			auto& sibling = columnData( adjacent );
+			Float combined = column.percentage + sibling.percentage;
+			Float minPercentage = column.minWidth / contentWidth * 100.f;
+			Float siblingMinPercentage = sibling.minWidth / contentWidth * 100.f;
+			column.percentage = eeclamp( column.width / contentWidth * 100.f, minPercentage,
+										 combined - siblingMinPercentage );
+			sibling.percentage = combined - column.percentage;
+			updatePercentageColumnWidths();
+			updateHeaderSize();
+		}
+	}
+}
+
+void UIAbstractTableView::updatePercentageColumnWidths() {
+	if ( !getModel() )
+		return;
+	Float contentWidth = getContentSpaceWidth();
+	Float totalPercentage = 0;
+	int visibleColumns = 0;
+	for ( size_t i = 0; i < getModel()->columnCount(); ++i ) {
+		if ( !isColumnHidden( i ) ) {
+			totalPercentage += columnData( i ).percentage;
+			visibleColumns++;
+		}
+	}
+	if ( totalPercentage <= 0 && visibleColumns > 0 ) {
+		for ( size_t i = 0; i < getModel()->columnCount(); ++i )
+			if ( !isColumnHidden( i ) )
+				columnData( i ).percentage = 100.f / visibleColumns;
+		totalPercentage = 100.f;
+	}
+	contentWidth = eefloor( contentWidth );
+	Float cumulativePercentage = 0;
+	Float previousBoundary = 0;
+	Float assignedWidth = 0;
+	for ( size_t i = 0; i < getModel()->columnCount(); ++i ) {
+		if ( isColumnHidden( i ) )
+			continue;
+		auto& column = columnData( i );
+		cumulativePercentage += column.percentage;
+		Float boundary = eefloor( contentWidth * cumulativePercentage / totalPercentage + 0.5f );
+		Float width = boundary - previousBoundary;
+		Float minWidth = eeceil( column.minWidth );
+		width = column.maxWidth != 0
+					? eeclamp( width, minWidth, eemax( minWidth, eefloor( column.maxWidth ) ) )
+					: eemax( width, minWidth );
+		column.setWidth( width, true );
+		assignedWidth += width;
+		previousBoundary = boundary;
+	}
+	Float overflow = assignedWidth - contentWidth;
+	for ( size_t i = getModel()->columnCount(); overflow > 0 && i > 0; --i ) {
+		if ( isColumnHidden( i - 1 ) )
+			continue;
+		auto& column = columnData( i - 1 );
+		Float shrink = eemin( overflow, column.width - eeceil( column.minWidth ) );
+		if ( shrink > 0 ) {
+			column.setWidth( column.width - shrink, true );
+			overflow -= shrink;
+		}
+	}
+	for ( size_t i = 0; i < getModel()->columnCount(); ++i ) {
+		auto& column = columnData( i );
+		if ( column.widget && !isColumnHidden( i ) )
+			column.widget->setPixelsSize( column.width, getHeaderHeight() );
+	}
+}
+
+int UIAbstractTableView::adjacentVisibleColumn( size_t column ) const {
+	if ( !getModel() )
+		return -1;
+	for ( size_t i = column + 1; i < getModel()->columnCount(); ++i )
+		if ( !isColumnHidden( i ) )
+			return i;
+	for ( size_t i = column; i > 0; --i )
+		if ( !isColumnHidden( i - 1 ) )
+			return i - 1;
+	return -1;
 }
 
 Float UIAbstractTableView::getMaxColumnContentWidth( const size_t&, bool ) {
@@ -322,6 +571,10 @@ Float UIAbstractTableView::getMaxColumnContentWidth( const size_t&, bool ) {
 
 void UIAbstractTableView::onColumnResizeToContent( const size_t& colIndex ) {
 	columnData( colIndex ).setWidth( getMaxColumnContentWidth( colIndex, true ) );
+	if ( mColumnWidthMode == ColumnWidthMode::Percentage ) {
+		onColumnSizeChange( colIndex, true );
+		return;
+	}
 	createOrUpdateColumns( false );
 }
 
@@ -582,6 +835,31 @@ void UIAbstractTableView::onScrollChange() {
 	mHeader->setPixelsPosition( mRowHeaderWidth + -mScrollOffset.x, 0 );
 }
 
+void UIAbstractTableView::onContentSizeChange() {
+	if ( mUpdatingColumnsForScrollbars ) {
+		UIScrollableWidget::onContentSizeChange();
+		return;
+	}
+
+	bool verticalScrollWasVisible = mVScroll->isVisible();
+	UIScrollableWidget::onContentSizeChange();
+	const bool columnsDependOnContentWidth =
+		mColumnWidthMode == ColumnWidthMode::Percentage || mAutoColumnsWidth ||
+		( mAutoExpandOnSingleColumn && visibleColumnCount() == 1 );
+	if ( !columnsDependOnContentWidth || verticalScrollWasVisible == mVScroll->isVisible() )
+		return;
+
+	mUpdatingColumnsForScrollbars = true;
+	for ( int iteration = 0; iteration < 2; ++iteration ) {
+		bool visibilityUsedForColumns = mVScroll->isVisible();
+		createOrUpdateColumns( false );
+		UIScrollableWidget::onContentSizeChange();
+		if ( visibilityUsedForColumns == mVScroll->isVisible() )
+			break;
+	}
+	mUpdatingColumnsForScrollbars = false;
+}
+
 void UIAbstractTableView::bindNavigationClick( UIWidget* widget ) {
 	mWidgetsClickCbId[widget].push_back(
 		widget->on( Event::MouseDoubleClick, [this]( const Event* event ) {
@@ -1012,6 +1290,14 @@ bool UIAbstractTableView::applyProperty( const StyleSheetProperty& attribute ) {
 		case PropertyId::MainColumn:
 			setMainColumn( attribute.asInt() );
 			break;
+		case PropertyId::ColumnWidthMode:
+			setColumnWidthMode( String::iequals( attribute.getValue(), "percentage" )
+									? ColumnWidthMode::Percentage
+									: ColumnWidthMode::Pixels );
+			break;
+		case PropertyId::ColumnWidthModeMenu:
+			setColumnWidthModeMenuEnabled( attribute.asBool() );
+			break;
 		case PropertyId::RowHeaderWidth:
 			setRowHeaderWidth(
 				lengthFromValue( attribute.getValue(), PropertyRelativeTarget::None ) );
@@ -1063,6 +1349,10 @@ std::string UIAbstractTableView::getPropertyString( const PropertyDefinition* pr
 			return String::fromFloat( (Float)getSortIconSize(), "px" );
 		case PropertyId::MainColumn:
 			return String::toString( (Int64)getMainColumn() );
+		case PropertyId::ColumnWidthMode:
+			return getColumnWidthMode() == ColumnWidthMode::Percentage ? "percentage" : "pixels";
+		case PropertyId::ColumnWidthModeMenu:
+			return isColumnWidthModeMenuEnabled() ? "true" : "false";
 		case PropertyId::RowHeaderWidth:
 			return String::fromFloat( getRowHeaderWidth(), "px" );
 		case PropertyId::TableFlags: {
@@ -1099,9 +1389,10 @@ std::string UIAbstractTableView::getPropertyString( const PropertyDefinition* pr
 
 std::vector<PropertyId> UIAbstractTableView::getPropertiesImplemented() const {
 	auto props = UIAbstractView::getPropertiesImplemented();
-	props.insert( props.end(),
+	props.insert( props.end(), { PropertyId::RowHeight, PropertyId::IconSize,
-				  { PropertyId::RowHeight, PropertyId::IconSize, PropertyId::SortIconSize,
+								 PropertyId::SortIconSize, PropertyId::MainColumn,
-					PropertyId::MainColumn, PropertyId::RowHeaderWidth, PropertyId::TableFlags } );
+								 PropertyId::ColumnWidthMode, PropertyId::ColumnWidthModeMenu,
+								 PropertyId::RowHeaderWidth, PropertyId::TableFlags } );
 	return props;
 }
 

src/eepp/ui/css/stylesheetspecification.cpp

@@ -336,6 +336,10 @@ void StyleSheetSpecification::registerDefaultProperties() {
 		.setType( PropertyType::NumberLength );
 	registerProperty( PropertyId::MainColumn, "main-column", "0" )
 		.setType( PropertyType::NumberInt );
+	registerProperty( PropertyId::ColumnWidthMode, "column-width-mode", "pixels" )
+		.setType( PropertyType::String );
+	registerProperty( PropertyId::ColumnWidthModeMenu, "column-width-mode-menu", "false" )
+		.setType( PropertyType::Bool );
 	registerProperty( PropertyId::RowHeaderWidth, "row-header-width", "" )
 		.setType( PropertyType::NumberLength );
 	registerProperty( PropertyId::TableFlags, "table-flags", "" )
@@ -590,6 +594,8 @@ void StyleSheetSpecification::registerDefaultProperties() {
 		.setRelativeTarget( PropertyRelativeTarget::LocalBlockWidth );
 	registerProperty( PropertyId::SplitterAlwaysShow, "splitter-always-show", "true" )
 		.setType( PropertyType::Bool );
+	registerProperty( PropertyId::SplitterHideOnEdge, "splitter-hide-on-edge", "false" )
+		.setType( PropertyType::Bool );
 
 	registerProperty( PropertyId::DroppableHoveringColor, "droppable-hovering-color", "#FFFFFF20" )
 		.setType( PropertyType::Color );

src/eepp/ui/tools/uicodeeditorsplitter.cpp

@@ -1926,6 +1926,8 @@ void UICodeEditorSplitter::onTabClosed( const TabEvent* tabEvent ) {
 					Node* remainingNode = tabWidget == splitter->getFirstWidget()
 											  ? splitter->getLastWidget()
 											  : splitter->getFirstWidget();
+					// Keep the surviving subtree out of closeSplitter()'s recursive bookkeeping.
+					remainingNode->detach();
 					closeSplitter( splitter );
 					eeASSERT( parent->getChildCount() == 0 );
 					remainingNode->setParent( parent );

src/eepp/ui/tools/uitabwidgetsplitter.cpp

@@ -17,7 +17,13 @@ UITabWidgetSplitter::UITabWidgetSplitter( UITabWidgetSplitter::Client* client,
 										  UISceneNode* sceneNode ) :
 	mUISceneNode( sceneNode ), mClient( client ) {}
 
-UITabWidgetSplitter::~UITabWidgetSplitter() {}
+UITabWidgetSplitter::~UITabWidgetSplitter() {
+	mTabWidgetEventConnections.clear();
+	mWidgetEventConnections.clear();
+	mTabWidgets.clear();
+	mCurWidget = nullptr;
+	mClient = nullptr;
+}
 
 UITabWidget* UITabWidgetSplitter::tabWidgetFromWidget( UIWidget* widget ) const {
 	if ( widget )
@@ -49,15 +55,15 @@ void UITabWidgetSplitter::setCurrentWidget( UIWidget* curWidget ) {
 std::pair<UITab*, UIWidget*>
 UITabWidgetSplitter::createWidgetInTabWidget( UITabWidget* tabWidget, UIWidget* widget,
 											  const std::string& tabName, bool focus ) {
-	eeASSERT( curWidgetExists() );
 	if ( nullptr == tabWidget )
 		return std::make_pair( (UITab*)nullptr, (UIWidget*)nullptr );
 	UITab* tab = tabWidget->add( tabName, widget );
 	widget->setData( (UintPtr)tab );
-	widget->on( Event::OnFocusWithin, [this]( const Event* event ) {
+	auto& connections = mWidgetEventConnections[widget];
+	connections += widget->connect( Event::OnFocusWithin, [this]( const Event* event ) {
 		setCurrentWidget( event->getNode()->asType<UIWidget>() );
 	} );
-	widget->on( Event::OnTitleChange, [this]( const Event* event ) {
+	connections += widget->connect( Event::OnTitleChange, [this]( const Event* event ) {
 		const TextEvent* tevent = static_cast<const TextEvent*>( event );
 		UIWidget* widget = event->getNode()->asType<UIWidget>();
 		UITabWidget* tabWidget = tabWidgetFromWidget( widget );
@@ -157,7 +163,8 @@ UITabWidget* UITabWidgetSplitter::createTabWidget( Node* parent ) {
 			},
 			mVisualSplitEdgePercent );
 	}
-	tabWidget->on( Event::OnTabSelected, [this]( const Event* event ) {
+	auto& connections = mTabWidgetEventConnections[tabWidget];
+	connections += tabWidget->connect( Event::OnTabSelected, [this]( const Event* event ) {
 		UITabWidget* tabWidget = event->getNode()->asType<UITabWidget>();
 		eeASSERT( nullptr != tabWidget && nullptr != tabWidget->getTabSelected() &&
 				  nullptr != tabWidget->getTabSelected()->getOwnedWidget() );
@@ -175,7 +182,7 @@ UITabWidget* UITabWidgetSplitter::createTabWidget( Node* parent ) {
 			}
 			return false;
 		} );
-	tabWidget->on( Event::OnTabClosed, [this]( const Event* event ) {
+	connections += tabWidget->connect( Event::OnTabClosed, [this]( const Event* event ) {
 		onTabClosed( static_cast<const TabEvent*>( event ) );
 	} );
 	if ( mOnTabWidgetCreateCb )
@@ -285,6 +292,7 @@ void UITabWidgetSplitter::closeTab( UIWidget* widget,
 									UITabWidget::FocusTabBehavior focusTabBehavior ) {
 	if ( widget ) {
 		UITabWidget* tabWidget = tabWidgetFromWidget( widget );
+		mWidgetEventConnections.erase( widget );
 		if ( tabWidget )
 			tabWidget->removeTab( (UITab*)widget->getData(), true, false, focusTabBehavior );
 		if ( mCurWidget == widget )
@@ -497,9 +505,12 @@ void UITabWidgetSplitter::closeTabWidgets( UISplitter* splitter ) {
 	Node* node = splitter->getFirstChild();
 	while ( node ) {
 		if ( node->isType( UI_TYPE_TABWIDGET ) ) {
-			auto it =
+			auto tabWidget = node->asType<UITabWidget>();
-				std::find( mTabWidgets.begin(), mTabWidgets.end(), node->asType<UITabWidget>() );
+			auto it = std::find( mTabWidgets.begin(), mTabWidgets.end(), tabWidget );
 			if ( it != mTabWidgets.end() ) {
+				if ( mOnTabWidgetCloseCb )
+					mOnTabWidgetCloseCb( tabWidget );
+				mTabWidgetEventConnections.erase( tabWidget );
 				Lock l( mTabWidgetMutex );
 				mTabWidgets.erase( it );
 			}
@@ -622,6 +633,9 @@ void UITabWidgetSplitter::onTabClosed( const TabEvent* tabEvent ) {
 	if ( tabWidget->getTabCount() == 0 ) {
 		UISplitter* splitter = splitterFromWidget( widget );
 		if ( splitter && splitter->isFull() ) {
+			if ( mOnTabWidgetCloseCb )
+				mOnTabWidgetCloseCb( tabWidget );
+			mTabWidgetEventConnections.erase( tabWidget );
 			tabWidget->close();
 			auto itWidget = std::find( mTabWidgets.begin(), mTabWidgets.end(), tabWidget );
 			if ( itWidget != mTabWidgets.end() ) {
@@ -647,6 +661,7 @@ void UITabWidgetSplitter::onTabClosed( const TabEvent* tabEvent ) {
 				Node* remainingNode = tabWidget == splitter->getFirstWidget()
 										  ? splitter->getLastWidget()
 										  : splitter->getFirstWidget();
+				remainingNode->detach();
 				closeSplitter( splitter );
 				eeASSERT( parent->getChildCount() == 0 );
 				remainingNode->setParent( parent );
@@ -676,6 +691,10 @@ void UITabWidgetSplitter::setOnTabWidgetCreateCb( std::function<void( UITabWidge
 	mOnTabWidgetCreateCb = std::move( cb );
 }
 
+void UITabWidgetSplitter::setOnTabWidgetCloseCb( std::function<void( UITabWidget* )> cb ) {
+	mOnTabWidgetCloseCb = std::move( cb );
+}
+
 bool UITabWidgetSplitter::getVisualSplitting() const {
 	return mVisualSplitting;
 }

src/eepp/ui/uisplitter.cpp

@@ -12,29 +12,33 @@ UISplitter::UISplitter() :
 	UILayout( "splitter" ),
 	mOrientation( UIOrientation::Horizontal ),
 	mAlwaysShowSplitter( true ),
+	mHideSplitterOnEdge( false ),
 	mSplitPartition( StyleSheetLength( "50%" ) ),
 	mFirstWidget( NULL ),
 	mLastWidget( NULL ) {
 	mFlags |= UI_OWNS_CHILDREN_POSITION;
 	mSplitter = UIWidget::NewWithTag( "splitter::separator" );
 	mSplitter->setDragEnabled( true );
-	mSplitter->on( Event::OnDragStart,
+	mEventConnections += mSplitter->connect( Event::OnDragStart, [this]( const Event* ) {
-				   [this]( const Event* ) { mSplitter->pushState( UIState::StateSelected ); } );
+		mSplitter->pushState( UIState::StateSelected );
-	mSplitter->on( Event::OnDragStop,
+	} );
-				   [this]( const Event* ) { mSplitter->popState( UIState::StateSelected ); } );
+	mEventConnections += mSplitter->connect( Event::OnDragStop, [this]( const Event* ) {
+		mSplitter->popState( UIState::StateSelected );
+	} );
 	mSplitter->setParent( this );
 	mSplitter->setMinWidth( 4 );
 	mSplitter->setMinHeight( 4 );
-	mSplitter->on( Event::OnSizeChange, [this]( const Event* ) {
+	mEventConnections += mSplitter->connect( Event::OnSizeChange, [this]( const Event* ) {
 		setLayoutDirty( LayoutInvalidation::ContainerLayout );
 	} );
-	mSplitter->on( Event::MouseEnter, [this]( const Event* ) {
+	mEventConnections += mSplitter->connect( Event::MouseEnter, [this]( const Event* ) {
 		getUISceneNode()->setCursor( mOrientation == UIOrientation::Horizontal ? Cursor::SizeWE
 																			   : Cursor::SizeNS );
 	} );
-	mSplitter->on( Event::MouseLeave,
+	mEventConnections += mSplitter->connect( Event::MouseLeave, [this]( const Event* ) {
-				   [this]( const Event* ) { getUISceneNode()->setCursor( Cursor::Arrow ); } );
+		getUISceneNode()->setCursor( Cursor::Arrow );
-	mSplitter->on( Event::OnPositionChange, [this]( const Event* ) {
+	} );
+	mEventConnections += mSplitter->connect( Event::OnPositionChange, [this]( const Event* ) {
 		if ( mSplitter->isDragging() && !mDirtyLayout )
 			updateFromDrag();
 	} );
@@ -77,6 +81,17 @@ void UISplitter::setAlwaysShowSplitter( bool alwaysShowSplitter ) {
 	}
 }
 
+const bool& UISplitter::hideSplitterOnEdge() const {
+	return mHideSplitterOnEdge;
+}
+
+void UISplitter::setHideSplitterOnEdge( bool hideSplitterOnEdge ) {
+	if ( hideSplitterOnEdge != mHideSplitterOnEdge ) {
+		mHideSplitterOnEdge = hideSplitterOnEdge;
+		setLayoutDirty( LayoutInvalidation::ContainerLayout );
+	}
+}
+
 const StyleSheetLength& UISplitter::getSplitPartition() const {
 	return mSplitPartition;
 }
@@ -127,6 +142,9 @@ bool UISplitter::applyProperty( const StyleSheetProperty& attribute ) {
 		case PropertyId::SplitterAlwaysShow:
 			setAlwaysShowSplitter( attribute.asBool() );
 			break;
+		case PropertyId::SplitterHideOnEdge:
+			setHideSplitterOnEdge( attribute.asBool() );
+			break;
 		case PropertyId::Orientation:
 			setOrientation( String::iequals( attribute.getValue(), "horizontal" )
 								? UIOrientation::Horizontal
@@ -149,6 +167,8 @@ std::string UISplitter::getPropertyString( const PropertyDefinition* propertyDef
 			return getSplitPartition().toString();
 		case PropertyId::SplitterAlwaysShow:
 			return alwaysShowSplitter() ? "true" : "false";
+		case PropertyId::SplitterHideOnEdge:
+			return hideSplitterOnEdge() ? "true" : "false";
 		case PropertyId::Orientation:
 			return getOrientation() == UIOrientation::Horizontal ? "horizontal" : "vertical";
 		default:
@@ -159,7 +179,7 @@ std::string UISplitter::getPropertyString( const PropertyDefinition* propertyDef
 std::vector<PropertyId> UISplitter::getPropertiesImplemented() const {
 	auto props = UIWidget::getPropertiesImplemented();
 	auto local = { PropertyId::SplitterPartition, PropertyId::SplitterAlwaysShow,
-				   PropertyId::Orientation };
+				   PropertyId::SplitterHideOnEdge, PropertyId::Orientation };
 	props.insert( props.end(), local.begin(), local.end() );
 	return props;
 }
@@ -204,7 +224,7 @@ void UISplitter::onChildCountChange( Node* child, const bool& removed ) {
 
 void UISplitter::updateFromDrag() {
 	mDirtyLayout = true;
-	mSplitter->setVisible( !mAlwaysShowSplitter && !mLastWidget ? false : true );
+	mSplitter->setVisible( shouldShowSplitter() );
 	mSplitter->setEnabled( mSplitter->isVisible() );
 
 	if ( UIOrientation::Horizontal == mOrientation ) {
@@ -351,7 +371,7 @@ void UISplitter::updateLayout() {
 		return;
 	}
 
-	mSplitter->setVisible( !mAlwaysShowSplitter && !mLastWidget ? false : true );
+	mSplitter->setVisible( shouldShowSplitter() );
 	mSplitter->setEnabled( mSplitter->isVisible() );
 	Float totalSpace = mOrientation == UIOrientation::Horizontal
 						   ? mSize.getWidth() - mPaddingPx.Left - mPaddingPx.Right
@@ -426,6 +446,14 @@ void UISplitter::updateSplitterDragFlags() {
 																		 : UI_DRAG_HORIZONTAL );
 }
 
+bool UISplitter::shouldShowSplitter() const {
+	if ( !mLastWidget )
+		return false;
+	return mAlwaysShowSplitter || !mHideSplitterOnEdge ||
+		   mSplitPartition.getUnit() != StyleSheetLength::Percentage ||
+		   ( mSplitPartition.getValue() > 0.f && mSplitPartition.getValue() < 100.f );
+}
+
 Uint32 UISplitter::onMessage( const NodeMessage* Msg ) {
 	switch ( Msg->getMsg() ) {
 		case NodeMessage::LayoutAttributeChange: {

src/eepp/ui/uitableheadercolumn.cpp

@@ -1,4 +1,6 @@
 #include <eepp/ui/abstract/uiabstracttableview.hpp>
+#include <eepp/ui/uimenuitem.hpp>
+#include <eepp/ui/uipopupmenu.hpp>
 #include <eepp/ui/uiscenenode.hpp>
 #include <eepp/ui/uitableheadercolumn.hpp>
 
@@ -31,7 +33,7 @@ Uint32 UITableHeaderColumn::onCalculateDrag( const Vector2f& position, const Uin
 		}
 		Vector2f pos( eefloor( position.x ), eefloor( position.y ) );
 		if ( mDragPoint != pos && std::abs( mDragPoint.x - pos.x ) > 1.f ) {
-			Sizef dragDiff( ( Float )( mDragPoint.x - pos.x ), 0 );
+			Sizef dragDiff( (Float)( mDragPoint.x - pos.x ), 0 );
 			if ( onDrag( pos, flags, dragDiff ) ) {
 				mDragPoint = pos;
 				eventDispatcher->setNodeDragging( this );
@@ -77,6 +79,30 @@ Uint32 UITableHeaderColumn::onMouseClick( const Vector2i& position, const Uint32
 	return UIPushButton::onMouseClick( position, flags );
 }
 
+Uint32 UITableHeaderColumn::onMouseUp( const Vector2i& position, const Uint32& flags ) {
+	if ( ( flags & EE_BUTTON_RMASK ) && mView->isColumnWidthModeMenuEnabled() ) {
+		auto* menu = UIPopUpMenu::New();
+		menu->addRadioButton( i18n( "uitable_fit_columns_to_view", "Fit Columns to View" ),
+							  mView->getColumnWidthMode() ==
+								  UIAbstractTableView::ColumnWidthMode::Percentage )
+			->setId( "percentage" );
+		menu->addRadioButton( i18n( "uitable_free_column_widths", "Free Column Widths" ),
+							  mView->getColumnWidthMode() ==
+								  UIAbstractTableView::ColumnWidthMode::Pixels )
+			->setId( "pixels" );
+		menu->on( Event::OnItemClicked, [view = mView]( const Event* event ) {
+			if ( !event->getNode()->isType( UI_TYPE_MENUITEM ) )
+				return;
+			view->setColumnWidthMode( event->getNode()->getId() == "percentage"
+										  ? UIAbstractTableView::ColumnWidthMode::Percentage
+										  : UIAbstractTableView::ColumnWidthMode::Pixels );
+		} );
+		menu->setCloseOnHide( true );
+		menu->showAtScreenPosition( position.asFloat() );
+	}
+	return UIPushButton::onMouseUp( position, flags );
+}
+
 Uint32 UITableHeaderColumn::onDrag( const Vector2f& position, const Uint32&,
 									const Sizef& dragDiff ) {
 	Vector2f localPos( convertToNodeSpace( position ) );

src/eepp/ui/uitabwidget.cpp

@@ -87,8 +87,10 @@ UITabWidget::UITabWidget() :
 	mTabScroll = UIScrollBar::NewHorizontalWithTag( "scrollbarmini" );
 	mTabScroll->setParent( mTabBar );
 	mTabScroll->setLayoutSizePolicy( SizePolicy::Fixed, SizePolicy::WrapContent );
-	mTabScroll->on( Event::OnSizeChange, [this]( const Event* ) { updateScrollBar(); } );
+	mEventConnections +=
-	mTabScroll->on( Event::OnValueChange, [this]( const Event* ) { updateScroll(); } );
+		mTabScroll->connect( Event::OnSizeChange, [this]( const Event* ) { updateScrollBar(); } );
+	mEventConnections +=
+		mTabScroll->connect( Event::OnValueChange, [this]( const Event* ) { updateScroll(); } );
 
 	onSizeChange();
 
@@ -560,6 +562,10 @@ UITab* UITabWidget::add( const String& text, UINode* nodeOwned, DrawablePtr icon
 
 UITabWidget* UITabWidget::add( UITab* tab ) {
 	tab->setParent( mTabBar );
+	if ( tab->getOwnedWidget() && tab->getOwnedWidget()->isWidget() )
+		tab->getOwnedWidget()->asType<UIWidget>()->setLayoutSizePolicy( SizePolicy::Fixed,
+																		SizePolicy::Fixed );
+	refreshOwnedWidget( tab );
 
 	mTabs.push_back( tab );
 

src/tests/unit_tests/uitabwidgetsplitter_tests.cpp

@@ -3,6 +3,8 @@
 #include <eepp/system/sys.hpp>
 #include <eepp/ui/tools/uitabwidgetsplitter.hpp>
 #include <eepp/ui/uiapplication.hpp>
+#include <eepp/ui/uiscrollbar.hpp>
+#include <eepp/ui/uitableview.hpp>
 #include <eepp/ui/uiwidget.hpp>
 #include <nlohmann/json.hpp>
 
@@ -21,6 +23,415 @@ class TestClient : public UITabWidgetSplitter::Client {
 	void onWidgetFocusChange( UIWidget* ) override { focusChangeCount++; }
 };
 
+class TransferTestTabWidget : public UITabWidget {
+  public:
+	static TransferTestTabWidget* New() { return eeNew( TransferTestTabWidget, () ); }
+
+	void detachTab( UITab* tab ) { removeTab( tab, false, false, false ); }
+
+	const Sizef& getContainerPixelsSize() const { return mNodeContainer->getPixelsSize(); }
+};
+
+class ThreeColumnModel : public Model {
+  public:
+	explicit ThreeColumnModel( size_t rows = 1 ) : mRows( rows ) {}
+
+	size_t rowCount( const ModelIndex& = ModelIndex() ) const override { return mRows; }
+	size_t columnCount( const ModelIndex& = ModelIndex() ) const override { return 3; }
+	std::string columnName( const size_t& column ) const override {
+		return String::format( "Column %zu", column );
+	}
+	ModelIndex index( int row, int column,
+					  const ModelIndex& parent = ModelIndex() ) const override {
+		return row == 0 && column >= 0 && column < 3 && !parent.isValid()
+				   ? createIndex( row, column )
+				   : ModelIndex{};
+	}
+	Variant data( const ModelIndex&, ModelRole = ModelRole::Display ) const override {
+		return "Value";
+	}
+
+  protected:
+	size_t mRows;
+};
+
+class PercentageTestTable : public UITableView {
+  public:
+	static PercentageTestTable* New() { return eeNew( PercentageTestTable, () ); }
+
+	void userResizeColumn( size_t column, Float width ) {
+		columnData( column ).setWidth( width, true );
+		onColumnSizeChange( column, true );
+	}
+
+	void setColumnMinimumWidth( size_t column, Float width ) {
+		columnData( column ).minWidth = width;
+		createOrUpdateColumns( false );
+	}
+
+	void resizeColumnToContent( size_t column, Float width ) {
+		mContentWidth = width;
+		onColumnResizeToContent( column );
+	}
+
+	Float getMaxColumnContentWidth( const size_t&, bool ) override { return mContentWidth; }
+
+  protected:
+	Float mContentWidth{ 0 };
+};
+
+UTEST( UISplitter, HideSplitterOnEdge ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+
+	auto* splitter = UISplitter::New();
+	splitter->setParent( app.getUI() );
+	splitter->setPixelsSize( 800, 600 );
+	UIWidget::New()->setParent( splitter );
+	UIWidget::New()->setParent( splitter );
+	auto* separator = splitter->findByTag( "splitter::separator" );
+	ASSERT_TRUE( separator != nullptr );
+
+	splitter->setHideSplitterOnEdge( true );
+	splitter->setAlwaysShowSplitter( false );
+	splitter->setSplitPartition( StyleSheetLength( "100%" ) );
+	splitter->updateLayout();
+	EXPECT_FALSE( separator->isVisible() );
+	EXPECT_EQ( splitter->getFirstWidget()->getPixelsSize().getWidth(), 800.f );
+	EXPECT_EQ( splitter->getLastWidget()->getPixelsSize().getWidth(), 0.f );
+
+	splitter->setSplitPartition( StyleSheetLength( "75%" ) );
+	splitter->updateLayout();
+	app.getUI()->update( Milliseconds( 16 ) );
+	EXPECT_TRUE( separator->isVisible() );
+
+	splitter->setSplitPartition( StyleSheetLength( "0%" ) );
+	splitter->updateLayout();
+	EXPECT_FALSE( separator->isVisible() );
+	EXPECT_EQ( splitter->getFirstWidget()->getPixelsSize().getWidth(), 0.f );
+	EXPECT_EQ( splitter->getLastWidget()->getPixelsSize().getWidth(), 800.f );
+
+	splitter->setAlwaysShowSplitter( true );
+	splitter->updateLayout();
+	EXPECT_TRUE( separator->isVisible() );
+}
+
+UTEST( UISplitter, ControlsMatchParentChildWidth ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+
+	auto* splitter = UISplitter::New();
+	splitter->setParent( app.getUI() );
+	splitter->setPixelsSize( 800, 600 );
+	auto* first = UIWidget::New();
+	first->setParent( splitter );
+	auto* last = UIWidget::New();
+	last->setLayoutSizePolicy( SizePolicy::MatchParent, SizePolicy::MatchParent );
+	last->setParent( splitter );
+	splitter->setSplitPartition( StyleSheetLength( "75%" ) );
+	splitter->updateLayout();
+
+	EXPECT_TRUE( first->getPixelsSize().getWidth() > 590.f &&
+				 first->getPixelsSize().getWidth() < 600.f );
+	EXPECT_TRUE( last->getPixelsSize().getWidth() > 190.f &&
+				 last->getPixelsSize().getWidth() < 200.f );
+}
+
+UTEST( UIAbstractTableView, PercentageColumnWidthsScaleAndPreserveAdjacentTotal ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 400, 200 );
+	table->setModel( std::make_shared<ThreeColumnModel>() );
+	table->setColumnWidth( 0, 100 );
+	table->setColumnWidth( 1, 200 );
+	table->setColumnWidth( 2, 100 );
+	table->setColumnWidthMode( UIAbstractTableView::ColumnWidthMode::Percentage );
+
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 25.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 50.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 25.f ) < 0.01f );
+
+	table->setPixelsSize( 800, 200 );
+	Float contentWidth = table->getContentSpaceWidth();
+	EXPECT_TRUE( std::abs( table->getColumnWidth( 0 ) - contentWidth * 0.25f ) < 1.f );
+	EXPECT_TRUE( std::abs( table->getColumnWidth( 1 ) - contentWidth * 0.5f ) < 1.f );
+	EXPECT_TRUE( std::abs( table->getColumnWidth( 2 ) - contentWidth * 0.25f ) < 1.f );
+
+	table->userResizeColumn( 0, contentWidth * 0.4f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 40.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 35.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 25.f ) < 0.01f );
+
+	table->setColumnWidthPercentage( 0, 70.f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 70.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 5.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 25.f ) < 0.01f );
+	EXPECT_TRUE( table->getColumnWidth( 0 ) >= 0 && table->getColumnWidth( 1 ) >= 0 &&
+				 table->getColumnWidth( 2 ) >= 0 );
+}
+
+UTEST( UIAbstractTableView, PercentageColumnWidthsPreserveMinimumWidths ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 150, 200 );
+	table->setModel( std::make_shared<ThreeColumnModel>() );
+	table->setColumnsWidthPercentage( { 25.f, 50.f, 25.f } );
+	table->setColumnMinimumWidth( 0, 80.f );
+	table->setColumnMinimumWidth( 1, 80.f );
+	table->setColumnMinimumWidth( 2, 80.f );
+	app.getUI()->update( Milliseconds( 16 ) );
+
+	EXPECT_TRUE( table->getColumnWidth( 0 ) >= 80.f );
+	EXPECT_TRUE( table->getColumnWidth( 1 ) >= 80.f );
+	EXPECT_TRUE( table->getColumnWidth( 2 ) >= 80.f );
+	EXPECT_TRUE( table->getColumnWidth( 0 ) + table->getColumnWidth( 1 ) +
+					 table->getColumnWidth( 2 ) >
+				 table->getContentSpaceWidth() );
+	EXPECT_TRUE( table->getHorizontalScrollBar()->isVisible() );
+}
+
+UTEST( UIAbstractTableView, PercentageColumnWidthsAcceptPartialAndSurplusValues ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 400, 200 );
+	table->setModel( std::make_shared<ThreeColumnModel>() );
+
+	table->setColumnsWidthPercentage( { 20.f, 30.f } );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 20.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 30.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 50.f ) < 0.01f );
+
+	table->setColumnsWidthPercentage( { 10.f, 20.f, 70.f, 500.f } );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 10.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 20.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 70.f ) < 0.01f );
+
+	EXPECT_TRUE( table->unserializeColumnWidths( nlohmann::json{ 25.f, 25.f } ) );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 25.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 25.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 50.f ) < 0.01f );
+}
+
+UTEST( UIAbstractTableView, PercentageColumnResizeToContentPreservesAdjacentTotal ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 400, 200 );
+	table->setModel( std::make_shared<ThreeColumnModel>() );
+	table->setColumnsWidthPercentage( { 25.f, 50.f, 25.f } );
+	const Float contentWidth = table->getContentSpaceWidth();
+
+	table->resizeColumnToContent( 0, contentWidth * 0.4f );
+
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 40.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 35.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 25.f ) < 0.01f );
+
+	table->setColumnsWidthPercentage( { 25.f, 50.f, 25.f } );
+	table->setColumnMinimumWidth( 1, contentWidth * 0.3f );
+	table->resizeColumnToContent( 0, contentWidth * 0.6f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 45.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 1 ) - 30.f ) < 0.01f );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 2 ) - 25.f ) < 0.01f );
+}
+
+UTEST( UIAbstractTableView, ColumnWidthModeAndMenuCanBeConfiguredFromXML ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* defaultTable =
+		app.getUI()->loadLayoutFromString( R"xml(<TableView />)xml" )->asType<UITableView>();
+	EXPECT_FALSE( defaultTable->isColumnWidthModeMenuEnabled() );
+	auto* table = app.getUI()
+					  ->loadLayoutFromString( R"xml(<TableView column-width-mode="percentage"
+				column-width-mode-menu="true" />)xml" )
+					  ->asType<UITableView>();
+	EXPECT_TRUE( table->getColumnWidthMode() == UIAbstractTableView::ColumnWidthMode::Percentage );
+	EXPECT_TRUE( table->isColumnWidthModeMenuEnabled() );
+	auto* cssRoot = app.getUI()->loadLayoutFromString( R"xml(
+		<vbox>
+			<style>#css_table { column-width-mode-menu: true; }</style>
+			<TableView id="css_table" />
+		</vbox>)xml" );
+	auto* cssTable = cssRoot->querySelector( "#css_table" )->asType<UITableView>();
+	EXPECT_TRUE( cssTable->isColumnWidthModeMenuEnabled() );
+}
+
+UTEST( UIAbstractTableView, PercentageRoundingDoesNotCreatePhantomHorizontalScroll ) {
+	Float previousDensity = PixelDensity::getPixelDensity();
+	PixelDensity::setPixelDensity( 1.5f );
+	UIApplication app(
+		WindowSettings( 828, 300, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 828, 300 );
+	table->setModel( std::make_shared<ThreeColumnModel>() );
+	table->setColumnsWidthPercentage( { 100.f / 3.f, 100.f / 3.f, 100.f / 3.f } );
+	app.getUI()->update( Milliseconds( 16 ) );
+
+	EXPECT_EQ( table->getColumnWidth( 0 ) + table->getColumnWidth( 1 ) + table->getColumnWidth( 2 ),
+			   table->getContentSpaceWidth() );
+	EXPECT_FALSE( table->getHorizontalScrollBar()->isVisible() );
+
+	table->setColumnsWidthPercentage( { 25.f, 50.f, 25.f } );
+	table->setColumnMinimumWidth( 2, 208.f );
+	app.getUI()->update( Milliseconds( 16 ) );
+	EXPECT_EQ( table->getColumnWidth( 0 ) + table->getColumnWidth( 1 ) + table->getColumnWidth( 2 ),
+			   table->getContentSpaceWidth() );
+	EXPECT_TRUE( table->getColumnWidth( 2 ) >= 208.f );
+	EXPECT_FALSE( table->getHorizontalScrollBar()->isVisible() );
+	PixelDensity::setPixelDensity( previousDensity );
+}
+
+UTEST( UIAbstractTableView, PercentageColumnsRecomputeWhenVerticalScrollbarAppears ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 400, 100 );
+	table->setModel( std::make_shared<ThreeColumnModel>( 100 ) );
+	table->setColumnsWidthPercentage( { 25.f, 50.f, 25.f } );
+	app.getUI()->update( Milliseconds( 16 ) );
+
+	EXPECT_TRUE( table->getVerticalScrollBar()->isVisible() );
+	EXPECT_EQ( table->getColumnWidth( 0 ) + table->getColumnWidth( 1 ) + table->getColumnWidth( 2 ),
+			   table->getContentSpaceWidth() );
+	EXPECT_FALSE( table->getHorizontalScrollBar()->isVisible() );
+}
+
+UTEST( UIAbstractTableView, AutoPixelColumnsRecomputeWhenVerticalScrollbarAppears ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 400, 100 );
+	table->setModel( std::make_shared<ThreeColumnModel>( 100 ) );
+	table->setAutoColumnsWidth( true );
+	app.getUI()->update( Milliseconds( 16 ) );
+
+	EXPECT_TRUE( table->getColumnWidthMode() == UIAbstractTableView::ColumnWidthMode::Pixels );
+	EXPECT_TRUE( table->getVerticalScrollBar()->isVisible() );
+	EXPECT_FALSE( table->getHorizontalScrollBar()->isVisible() );
+}
+
+UTEST( UIAbstractTableView, ColumnWidthsSerializationRoundTripsBothModes ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	auto* table = PercentageTestTable::New();
+	table->setParent( app.getUI() );
+	table->setPixelsSize( 400, 200 );
+	table->setModel( std::make_shared<ThreeColumnModel>() );
+	table->setColumnsWidthPercentage( { 20.f, 30.f, 50.f } );
+	auto percentageWidths = table->serializeColumnWidths();
+	table->setColumnWidthMode( UIAbstractTableView::ColumnWidthMode::Pixels );
+	EXPECT_TRUE( table->unserializeColumnWidths( percentageWidths ) );
+	EXPECT_TRUE( table->getColumnWidthMode() == UIAbstractTableView::ColumnWidthMode::Percentage );
+	EXPECT_TRUE( std::abs( table->getColumnWidthPercentage( 0 ) - 20.f ) < 0.01f );
+
+	table->setColumnWidthMode( UIAbstractTableView::ColumnWidthMode::Pixels );
+	table->setColumnWidth( 0, PixelDensity::dpToPx( 80.f ) );
+	table->setColumnWidth( 1, PixelDensity::dpToPx( 120.f ) );
+	table->setColumnWidth( 2, PixelDensity::dpToPx( 160.f ) );
+	auto pixelWidths = table->serializeColumnWidths();
+	table->setColumnsWidthPercentage( { 25.f, 50.f, 25.f } );
+	EXPECT_TRUE( table->unserializeColumnWidths( pixelWidths ) );
+	EXPECT_TRUE( table->getColumnWidthMode() == UIAbstractTableView::ColumnWidthMode::Pixels );
+	EXPECT_EQ( table->getColumnWidth( 0 ), PixelDensity::dpToPx( 80.f ) );
+	EXPECT_EQ( table->getColumnWidth( 1 ), PixelDensity::dpToPx( 120.f ) );
+	EXPECT_EQ( table->getColumnWidth( 2 ), PixelDensity::dpToPx( 160.f ) );
+
+	EXPECT_TRUE( table->unserializeColumnWidths( nlohmann::json{ 25.f, 50.f, 25.f } ) );
+	EXPECT_TRUE( table->getColumnWidthMode() == UIAbstractTableView::ColumnWidthMode::Percentage );
+
+	auto* deferredTable = PercentageTestTable::New();
+	deferredTable->setParent( app.getUI() );
+	deferredTable->setPixelsSize( 400, 200 );
+	EXPECT_TRUE( deferredTable->unserializeColumnWidths( percentageWidths ) );
+	EXPECT_TRUE( deferredTable->serializeColumnWidths() == percentageWidths );
+	deferredTable->setModel( std::make_shared<ThreeColumnModel>() );
+	EXPECT_TRUE( deferredTable->getColumnWidthMode() ==
+				 UIAbstractTableView::ColumnWidthMode::Percentage );
+	EXPECT_TRUE( std::abs( deferredTable->getColumnWidthPercentage( 0 ) - 20.f ) < 0.01f );
+}
+
+UTEST( UITabWidget, TransferTabPreservesDestinationTabsAndOwnedWidgets ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+
+	auto* source = TransferTestTabWidget::New();
+	source->setParent( app.getUI() );
+	auto* destination = TransferTestTabWidget::New();
+	destination->setParent( app.getUI() );
+	destination->setPixelsSize( 240, 180 );
+	auto* sourceWidget = UIWidget::New();
+	auto* destinationWidgetA = UIWidget::New();
+	auto* destinationWidgetB = UIWidget::New();
+	auto* movedTab = source->add( "Moved", sourceWidget );
+	destination->add( "Existing A", destinationWidgetA );
+	destination->add( "Existing B", destinationWidgetB );
+
+	source->detachTab( movedTab );
+	destination->add( movedTab );
+	destination->setTabSelected( movedTab );
+
+	EXPECT_EQ( source->getTabCount(), Uint32{ 0 } );
+	EXPECT_EQ( destination->getTabCount(), Uint32{ 3 } );
+	EXPECT_TRUE( destination->getTab( 0 )->getOwnedWidget() == destinationWidgetA );
+	EXPECT_TRUE( destination->getTab( 1 )->getOwnedWidget() == destinationWidgetB );
+	EXPECT_TRUE( destination->getTab( 2 )->getOwnedWidget() == sourceWidget );
+	EXPECT_TRUE( destination->isParentOf( sourceWidget ) );
+	EXPECT_TRUE( destination->isParentOf( destinationWidgetA ) );
+	EXPECT_TRUE( destination->isParentOf( destinationWidgetB ) );
+	EXPECT_TRUE( sourceWidget->getPixelsSize() == destination->getContainerPixelsSize() );
+	EXPECT_TRUE( sourceWidget->isVisible() );
+	EXPECT_FALSE( destinationWidgetA->isVisible() );
+	EXPECT_FALSE( destinationWidgetB->isVisible() );
+}
+
+UTEST( UITabWidgetSplitter, ClosingSplitNotifiesBeforeTabWidgetDestruction ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - unit tests" ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), 1 ) );
+	TestClient client;
+	auto* splitter = UITabWidgetSplitter::New( &client, app.getUI() );
+	auto* container = UILayout::New();
+	container->setParent( app.getUI() );
+	auto* firstTabWidget = splitter->createTabWidget( container );
+	auto* firstWidget = UIWidget::New();
+	splitter->createWidgetInTabWidget( firstTabWidget, firstWidget, "First" );
+	auto* secondTabWidget = splitter->splitTabWidget( SplitDirection::Right, firstTabWidget );
+	auto* secondWidget = UIWidget::New();
+	splitter->createWidgetInTabWidget( secondTabWidget, secondWidget, "Second" );
+	UITabWidget* closedTabWidget = nullptr;
+	splitter->setOnTabWidgetCloseCb(
+		[&closedTabWidget]( UITabWidget* tabWidget ) { closedTabWidget = tabWidget; } );
+
+	splitter->closeTab( secondWidget, UITabWidget::FocusTabBehavior::Default );
+	app.getUI()->update( Milliseconds( 16 ) );
+
+	EXPECT_EQ( closedTabWidget, secondTabWidget );
+	EXPECT_EQ( splitter->getTabWidgets().size(), 1UL );
+	eeDelete( splitter );
+}
+
 UTEST( UITabWidgetSplitter, Serialization ) {
 	UIApplication app(
 		WindowSettings( 800, 600, "eepp - unit tests" ),
@@ -34,15 +445,14 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		auto* tabWidget = splitter->createTabWidget( (Node*)app.getUI() );
 
 		bool saved = false;
-		splitter->registerWidgetType(
+		splitter->registerWidgetType( "testwidget",
-			"testwidget",
+									  { [&]( UIWidget* ) {
-			{ [&]( UIWidget* ) {
+										   saved = true;
-				 saved = true;
+										   return nlohmann::json{ { "custom_key", 42 } };
-				 return nlohmann::json{ { "custom_key", 42 } };
+									   },
-			 },
+										[]( const nlohmann::json& ) -> WidgetLoadResult {
-			  []( const nlohmann::json& ) -> WidgetLoadResult {
+											return { nullptr, nullptr, "" };
-				  return { nullptr, nullptr, "" };
+										} } );
-			  } } );
 
 		auto* w = UIWidget::New();
 		w->addClass( "testwidget" );
@@ -93,9 +503,8 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		splitter->createWidgetInTabWidget( tabWidget, ghost, "Ghost" );
 
 		splitter->registerWidgetType(
-			"known",
+			"known", { []( UIWidget* ) { return nlohmann::json{ { "val", 1 } }; },
-			{ []( UIWidget* ) { return nlohmann::json{ { "val", 1 } }; },
+					   []( const nlohmann::json& ) -> WidgetLoadResult { return {}; } } );
-			  []( const nlohmann::json& ) -> WidgetLoadResult { return {}; } } );
 
 		auto* reg = UIWidget::New();
 		reg->addClass( "known" );
@@ -117,13 +526,12 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		auto* tabWidget = splitter->createTabWidget( (Node*)app.getUI() );
 
 		splitter->registerWidgetType(
-			"panewidget",
+			"panewidget", { []( UIWidget* ) { return nlohmann::json{ { "pane", true } }; },
-			{ []( UIWidget* ) { return nlohmann::json{ { "pane", true } }; },
+							[]( const nlohmann::json& j ) -> WidgetLoadResult {
-			  []( const nlohmann::json& j ) -> WidgetLoadResult {
+								auto* w = UIWidget::New();
-				  auto* w = UIWidget::New();
+								w->addClass( "panewidget" );
-				  w->addClass( "panewidget" );
+								return { w, nullptr, j.value( "title", "" ) };
-				  return { w, nullptr, j.value( "title", "" ) };
+							} } );
-			  } } );
 
 		auto* w1 = UIWidget::New();
 		w1->addClass( "panewidget" );
@@ -163,13 +571,12 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		auto* tab1 = splitter1->createTabWidget( (Node*)app.getUI() );
 
 		splitter1->registerWidgetType(
-			"mywidget",
+			"mywidget", { []( UIWidget* ) { return nlohmann::json{ { "data", "hello" } }; },
-			{ []( UIWidget* ) { return nlohmann::json{ { "data", "hello" } }; },
+						  []( const nlohmann::json& j ) -> WidgetLoadResult {
-			  []( const nlohmann::json& j ) -> WidgetLoadResult {
+							  auto* w = UIWidget::New();
-				  auto* w = UIWidget::New();
+							  w->addClass( "mywidget" );
-				  w->addClass( "mywidget" );
+							  return { w, nullptr, j.value( "title", "" ) };
-				  return { w, nullptr, j.value( "title", "" ) };
+						  } } );
-			  } } );
 
 		auto* wa = UIWidget::New();
 		wa->addClass( "mywidget" );
@@ -186,14 +593,13 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		auto* splitter2 = UITabWidgetSplitter::New( &client2, app.getUI() );
 		auto* tab2 = splitter2->createTabWidget( (Node*)app.getUI() );
 
-		splitter2->registerWidgetType(
+		splitter2->registerWidgetType( "mywidget",
-			"mywidget",
+									   { []( UIWidget* ) { return nlohmann::json::object(); },
-			{ []( UIWidget* ) { return nlohmann::json::object(); },
+										 []( const nlohmann::json& j ) -> WidgetLoadResult {
-			  []( const nlohmann::json& j ) -> WidgetLoadResult {
+											 auto* w = UIWidget::New();
-				  auto* w = UIWidget::New();
+											 w->addClass( "mywidget" );
-				  w->addClass( "mywidget" );
+											 return { w, nullptr, j.value( "title", "" ) };
-				  return { w, nullptr, j.value( "title", "" ) };
+										 } } );
-			  } } );
 
 		splitter2->fromJSON( saved );
 
@@ -256,14 +662,13 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		auto* splitter1 = UITabWidgetSplitter::New( &client1, app.getUI() );
 		auto* tab1 = splitter1->createTabWidget( (Node*)app.getUI() );
 
-		splitter1->registerWidgetType(
+		splitter1->registerWidgetType( "partwidget",
-			"partwidget",
+									   { []( UIWidget* ) { return nlohmann::json::object(); },
-			{ []( UIWidget* ) { return nlohmann::json::object(); },
+										 []( const nlohmann::json& j ) -> WidgetLoadResult {
-			  []( const nlohmann::json& j ) -> WidgetLoadResult {
+											 auto* w = UIWidget::New();
-				  auto* w = UIWidget::New();
+											 w->addClass( "partwidget" );
-				  w->addClass( "partwidget" );
+											 return { w, nullptr, j.value( "title", "" ) };
-				  return { w, nullptr, j.value( "title", "" ) };
+										 } } );
-			  } } );
 
 		auto* w1 = UIWidget::New();
 		w1->addClass( "partwidget" );
@@ -287,14 +692,13 @@ UTEST( UITabWidgetSplitter, Serialization ) {
 		auto* splitter2 = UITabWidgetSplitter::New( &client2, app.getUI() );
 		splitter2->createTabWidget( (Node*)app.getUI() );
 
-		splitter2->registerWidgetType(
+		splitter2->registerWidgetType( "partwidget",
-			"partwidget",
+									   { []( UIWidget* ) { return nlohmann::json::object(); },
-			{ []( UIWidget* ) { return nlohmann::json::object(); },
+										 []( const nlohmann::json& j ) -> WidgetLoadResult {
-			  []( const nlohmann::json& j ) -> WidgetLoadResult {
+											 auto* w = UIWidget::New();
-				  auto* w = UIWidget::New();
+											 w->addClass( "partwidget" );
-				  w->addClass( "partwidget" );
+											 return { w, nullptr, j.value( "title", "" ) };
-				  return { w, nullptr, j.value( "title", "" ) };
+										 } } );
-			  } } );
 
 		splitter2->fromJSON( saved );
 

src/tools/ecode/appconfig.cpp

@@ -121,6 +121,7 @@ void AppConfig::load( const std::string& confPath, std::string& keybindingsPath,
 	windowState.winIcon = ini.getValue( "window", "winicon", resPath + "icon/ecode.png" );
 	windowState.panelPartition = iniState.getValue( "window", "panel_partition", "15%" );
 	windowState.statusBarPartition = iniState.getValue( "window", "status_bar_partition", "85%" );
+	windowState.rightPanelPartition = iniState.getValue( "window", "right_panel_partition", "75%" );
 	windowState.displayIndex = iniState.getValueI( "window", "display_index", 0 );
 	windowState.position.x = iniState.getValueI( "window", "x", -1 );
 	windowState.position.y = iniState.getValueI( "window", "y", -1 );
@@ -331,6 +332,7 @@ void AppConfig::save( const std::vector<std::string>& recentFiles,
 	iniState.setValueF( "window", "pixeldensity", windowState.pixelDensity );
 	iniState.setValue( "window", "panel_partition", panelPartition );
 	iniState.setValue( "window", "status_bar_partition", statusBarPartition );
+	iniState.setValue( "window", "right_panel_partition", windowState.rightPanelPartition );
 	iniState.setValueI( "window", "display_index", windowState.displayIndex );
 	iniState.setValueI( "window", "x", windowState.position.x );
 	iniState.setValueI( "window", "y", windowState.position.y );

src/tools/ecode/appconfig.hpp

@@ -90,6 +90,7 @@ struct WindowStateConfig {
 	bool maximized{ false };
 	std::string panelPartition;
 	std::string statusBarPartition;
+	std::string rightPanelPartition{ "75%" };
 	int displayIndex{ 0 };
 	Vector2i position{ -1, -1 };
 	Uint32 lastRunVersion{ 0 };

src/tools/ecode/applayout.xml.hpp

@@ -615,6 +615,7 @@ TabWidget::container > ImageViewer > TextView {
 		</RelativeLayout>
 		<Tab id="treeview_tab" text='@string("project", "Project")' owns="project_view_cont" text-as-fallback="true" icon="icon(folder-open, 12dp)" />
 	</TabWidget>
+	<Splitter id="right_panel_splitter" splitter-partition="100%" splitter-always-show="false" splitter-hide-on-edge="true">
 	<vbox>
 		<Splitter id="main_splitter" lw="mp" lh="0" lw8="1" orientation="vertical">
 			<RelativeLayout id="main_splitter_cont">
@@ -706,6 +707,8 @@ TabWidget::container > ImageViewer > TextView {
 			<Widget class="status_sep" lw="0" lw8="1" lh="1dp" />
 		</statusbar>
 	</vbox>
+	<RelativeLayout id="right_panel_container"></RelativeLayout>
+	</Splitter>
 </Splitter>
 <Image id="settings" lw="16dp" lh="16dp" lg="top|right" gravity="center" />
 <TextView id="menu_hint" class="app_hint" lw="wc" lh="wc" lg="bottom|right" visible="false"

src/tools/ecode/ecode.cpp

@@ -6,10 +6,12 @@
 #include "fontpickercontroller.hpp"
 #include "keybindingshelper.hpp"
 #include "pathhelper.hpp"
+#include "plugins/debugger/statusdebuggercontroller.hpp"
 #include "settingsactions.hpp"
 #include "settingsmenu.hpp"
 #include "uibuildsettings.hpp"
 #include "uidownloadwindow.hpp"
+#include "uirightpanel.hpp"
 #include "uitreeviewfs.hpp"
 #include "uiwelcomescreen.hpp"
 #include "version.hpp"
@@ -860,6 +862,8 @@ bool App::loadConfig( const LogLevel& logLevel, const Sizeu& displaySize, bool s
 void App::saveConfig() {
 	if ( !mCurrentProject.empty() )
 		saveSidePanelTabsOrder();
+	if ( mRightPanel )
+		mRightPanel->saveState();
 
 	mConfig.save(
 		mRecentFiles, mRecentFolders,
@@ -3810,6 +3814,17 @@ UISplitter* App::getMainSplitter() const {
 	return mMainSplitter;
 }
 
+UIRightPanel* App::getRightPanel() const {
+	return mRightPanel.get();
+}
+
+StatusDebuggerController* App::getStatusDebuggerController() const {
+	if ( !mStatusBar )
+		return nullptr;
+	auto element = mStatusBar->getStatusBarElement( "status_app_debugger" );
+	return static_cast<StatusDebuggerController*>( element.get() );
+}
+
 StatusTerminalController* App::getStatusTerminalController() const {
 	return mStatusTerminalController.get();
 }
@@ -4979,6 +4994,8 @@ void App::init( InitParameters& params ) {
 		mSplitter->setOpenDocumentsInMainSplit( mConfig.editor.openDocumentsInMainSplit );
 		mSplitter->setRestoreEditorSelectionOnFocus( mConfig.editor.restoreEditorSelectionOnFocus );
 		mSplitter->setOnTabWidgetCreateCb( [this]( UITabWidget* tabWidget ) {
+			tabWidget->setAcceptsDropOfWidgetFn(
+				[]( const UIWidget* widget ) { return !widget->hasClass( "debugger-tab" ); } );
 			tabWidget->getTabBar()->onDoubleClick(
 				[this]( const MouseEvent* ) { mSplitter->createEditorInNewTab(); } );
 		} );
@@ -5032,6 +5049,10 @@ void App::init( InitParameters& params ) {
 		mMainSplitter = mUISceneNode->find<UISplitter>( "main_splitter" );
 		mMainSplitter->setSplitPartition(
 			StyleSheetLength( mConfig.windowState.statusBarPartition ) );
+		auto rightPanelSplitter = mUISceneNode->find<UISplitter>( "right_panel_splitter" );
+		auto rightPanelContainer = mUISceneNode->find<UILayout>( "right_panel_container" );
+		mRightPanel =
+			std::make_unique<UIRightPanel>( rightPanelSplitter, rightPanelContainer, &mConfig );
 		mStatusBar = mUISceneNode->find<UIStatusBar>( "status_bar" );
 		mPluginManager->setMainSplitter( mMainSplitter );
 

src/tools/ecode/ecode.hpp

@@ -35,6 +35,8 @@ class DateTimeController;
 class FontPickerController;
 class SettingsMenu;
 class UITreeViewFS;
+class StatusDebuggerController;
+class UIRightPanel;
 
 class App : public UICodeEditorSplitter::Client, public PluginContextProvider {
   public:
@@ -599,6 +601,10 @@ class App : public UICodeEditorSplitter::Client, public PluginContextProvider {
 
 	UISplitter* getMainSplitter() const;
 
+	UIRightPanel* getRightPanel() const;
+
+	StatusDebuggerController* getStatusDebuggerController() const;
+
 	StatusTerminalController* getStatusTerminalController() const;
 
 	void hideStatusTerminal();
@@ -777,6 +783,7 @@ class App : public UICodeEditorSplitter::Client, public PluginContextProvider {
 	UIThemePtr mTheme;
 	UIStatusBar* mStatusBar{ nullptr };
 	UISplitter* mMainSplitter{ nullptr };
+	std::unique_ptr<UIRightPanel> mRightPanel;
 	UIMessageBox* mCloseMsgBox{ nullptr };
 	UIMenuBar* mMenuBar{ nullptr };
 	std::unique_ptr<SettingsActions> mSettingsActions;

src/tools/ecode/plugins/debugger/debuggerclientlistener.cpp

@@ -140,8 +140,10 @@ void DebuggerClientListener::initUI() {
 	}
 
 	if ( !mStackModel ) {
-		mStackModel = std::make_shared<StackModel>( StackTraceInfo{}, sceneNode );
+		mStackModel =
-	}
+			std::make_shared<StackModel>( StackTraceInfo{}, sceneNode, mPlugin->mProjectPath );
+	} else
+		mStackModel->setProjectPath( mPlugin->mProjectPath );
 
 	UITableView* uiThreads = sdc->getUIThreads();
 	uiThreads->setModel( mThreadsModel );

src/tools/ecode/plugins/debugger/debuggerplugin.cpp

@@ -183,6 +183,11 @@ DebuggerPlugin::~DebuggerPlugin() {
 	}
 }
 
+void DebuggerPlugin::onSaveState( IniFile* state ) {
+	if ( auto controller = getStatusDebuggerController() )
+		state->setValue( "debugger", "panel_layout", controller->saveLayout() );
+}
+
 void DebuggerPlugin::onSaveProject( const std::string& /*projectFolder*/,
 									const std::string& projectStatePath,
 									bool rewriteStateOnlyIfNeeded ) {
@@ -579,11 +584,11 @@ void DebuggerPlugin::loadDAPConfig( const std::string& path, bool updateConfigFi
 		mKeyBindings["debugger-step-over"] = "f10";
 		mKeyBindings["debugger-step-into"] = "f11";
 		mKeyBindings["debugger-step-out"] = "shift+f11";
-		#if EE_PLATFORM == EE_PLATFORM_MACOS
+#if EE_PLATFORM == EE_PLATFORM_MACOS
 		mKeyBindings["toggle-status-app-debugger"] = "mod+6";
-		#else
+#else
 		mKeyBindings["toggle-status-app-debugger"] = "alt+6";
-		#endif
+#endif
 	}
 
 	if ( j.contains( "keybindings" ) ) {
@@ -768,8 +773,9 @@ void DebuggerPlugin::buildSidePanelTab() {
 		if ( mProjectPath.empty() )
 			return;
 		UIIcon* icon = findIcon( "debug" );
-		mTab = mSidePanel->add( i18n( "debugger", "Debugger" ), mTabContents,
+		mTab =
-								icon ? icon->createDrawable( PixelDensity::dpToPx( 12 ) ) : nullptr );
+			mSidePanel->add( i18n( "debugger", "Debugger" ), mTabContents,
+							 icon ? icon->createDrawable( PixelDensity::dpToPx( 12 ) ) : nullptr );
 		mTab->setId( "debugger_tab" );
 		mTab->setTextAsFallback( true );
 
@@ -1217,8 +1223,7 @@ bool DebuggerPlugin::replaceInVal( std::string& val,
 	String::replaceAll( val, KEY_PATH_SEPARATOR, FileSystem::getOSSlash() );
 	String::replaceAll( val, KEY_PATH_SEPARATOR_ABBR, FileSystem::getOSSlash() );
 	String::replaceAll( val, KEY_UUID, UUID().toString() );
-	String::replaceAll( val, KEY_TIMESTAMP,
+	String::replaceAll( val, KEY_TIMESTAMP, std::to_string( Sys::getUnixTimestamp() ) );
-						std::to_string( Sys::getUnixTimestamp() ) );
 
 	auto* editor = getPluginContext()->getSplitter()->getCurEditor();
 	if ( getPluginContext()->getSplitter()->getCurEditor() ) {

src/tools/ecode/plugins/debugger/debuggerplugin.hpp

@@ -67,6 +67,8 @@ class DebuggerPlugin : public PluginBase {
 
 	std::string getDescription() override { return Definition().description; }
 
+	void onSaveState( IniFile* state ) override;
+
 	void onSaveProject( const std::string& projectFolder, const std::string& projectStatePath,
 						bool rewriteStateOnlyIfNeeded ) override;
 

src/tools/ecode/plugins/debugger/models/stackmodel.cpp

@@ -1,10 +1,15 @@
 #include "stackmodel.hpp"
+#include <eepp/system/filesystem.hpp>
 #include <eepp/ui/uiscenenode.hpp>
 
 namespace ecode {
 
-StackModel::StackModel( StackTraceInfo&& stack, UISceneNode* sceneNode ) :
+StackModel::StackModel( StackTraceInfo&& stack, UISceneNode* sceneNode, std::string projectPath ) :
-	mStack( std::move( stack ) ), mSceneNode( sceneNode ) {}
+	mStack( std::move( stack ) ),
+	mProjectPath( std::move( projectPath ) ),
+	mSceneNode( sceneNode ) {
+	FileSystem::dirAddSlashAtEnd( mProjectPath );
+}
 
 size_t StackModel::rowCount( const ModelIndex& ) const {
 	Lock l( mResourceLock );
@@ -45,7 +50,8 @@ Variant StackModel::data( const ModelIndex& modelIndex, ModelRole role ) const {
 						   : Variant();
 			case Columns::SourcePath:
 				return mStack.stackFrames[modelIndex.row()].source
-						   ? Variant( mStack.stackFrames[modelIndex.row()].source->path )
+						   ? Variant( displaySourcePath(
+								 mStack.stackFrames[modelIndex.row()].source->path ) )
 						   : Variant();
 			case Columns::Line:
 				return Variant( String::toString( mStack.stackFrames[modelIndex.row()].line ) );
@@ -90,4 +96,23 @@ void StackModel::setCurrentScopeId( int scope ) {
 	}
 }
 
+void StackModel::setProjectPath( const std::string& projectPath ) {
+	std::string normalizedProjectPath( projectPath );
+	FileSystem::dirAddSlashAtEnd( normalizedProjectPath );
+	{
+		Lock l( mResourceLock );
+		if ( mProjectPath == normalizedProjectPath )
+			return;
+		mProjectPath = std::move( normalizedProjectPath );
+	}
+	invalidate();
+}
+
+const char* StackModel::displaySourcePath( const std::string& sourcePath ) const {
+	if ( mProjectPath.empty() || sourcePath.size() < mProjectPath.size() ||
+		 0 != sourcePath.compare( 0, mProjectPath.size(), mProjectPath ) )
+		return sourcePath.c_str();
+	return sourcePath.c_str() + mProjectPath.size();
+}
+
 } // namespace ecode

src/tools/ecode/plugins/debugger/models/stackmodel.hpp

@@ -19,7 +19,7 @@ class StackModel : public Model {
   public:
 	enum Columns { ID, Name, SourceName, SourcePath, Line, Column };
 
-	StackModel( StackTraceInfo&& stack, UISceneNode* sceneNode );
+	StackModel( StackTraceInfo&& stack, UISceneNode* sceneNode, std::string projectPath = {} );
 
 	virtual size_t rowCount( const ModelIndex& ) const;
 
@@ -37,10 +37,15 @@ class StackModel : public Model {
 
 	void setCurrentScopeId( int scope );
 
+	void setProjectPath( const std::string& projectPath );
+
   protected:
 	StackTraceInfo mStack;
+	std::string mProjectPath;
 	UISceneNode* mSceneNode{ nullptr };
 	int mCurrentScopeId{ 0 };
+
+	const char* displaySourcePath( const std::string& sourcePath ) const;
 };
 
 } // namespace ecode

src/tools/ecode/plugins/debugger/statusdebuggercontroller.cpp

@@ -1,11 +1,45 @@
 #include "statusdebuggercontroller.hpp"
+#include "../../appconfig.hpp"
+#include "../../uirightpanel.hpp"
 #include "../../widgetcommandexecuter.hpp"
 #include "../plugincontextprovider.hpp"
 #include "eepp/ui/uiwidgetcreator.hpp"
 #include <eepp/ui/uicheckbox.hpp>
+#include <nlohmann/json.hpp>
 
 namespace ecode {
 
+static constexpr size_t DEBUGGER_LAYOUT_MAX_DEPTH = 16;
+static constexpr size_t DEBUGGER_LAYOUT_MAX_NODES = 64;
+static constexpr size_t DEBUGGER_WIDGET_ID_PREFIX_LENGTH = 9;
+
+static bool isValidDebuggerLayoutNode( const nlohmann::json& node,
+									   UnorderedSet<std::string>& widgetTypes, size_t depth,
+									   size_t& nodeCount ) {
+	if ( depth > DEBUGGER_LAYOUT_MAX_DEPTH || ++nodeCount > DEBUGGER_LAYOUT_MAX_NODES )
+		return false;
+	if ( !node.is_object() || !node.contains( "type" ) || !node["type"].is_string() )
+		return false;
+	if ( node["type"] == "splitter" )
+		return node.contains( "first" ) && node.contains( "last" ) &&
+			   isValidDebuggerLayoutNode( node["first"], widgetTypes, depth + 1, nodeCount ) &&
+			   isValidDebuggerLayoutNode( node["last"], widgetTypes, depth + 1, nodeCount );
+	if ( node["type"] != "tabwidget" || !node.contains( "files" ) || !node["files"].is_array() )
+		return false;
+	for ( const auto& file : node["files"] ) {
+		if ( !file.is_object() || !file.contains( "type" ) || !file["type"].is_string() ||
+			 !widgetTypes.emplace( file["type"].get<std::string>() ).second )
+			return false;
+	}
+	return true;
+}
+
+static void restoreColumnWidths( UIAbstractTableView* view, const nlohmann::json& columns,
+								 const char* key ) {
+	if ( view && columns.contains( key ) )
+		view->unserializeColumnWidths( columns[key] );
+}
+
 class UIBreakpointsTableCell : public UITableCell {
   public:
 	static UIBreakpointsTableCell* New( const std::string& tag, const BreakpointsModel* model,
@@ -109,6 +143,37 @@ StatusDebuggerController::StatusDebuggerController( UISplitter* mainSplitter,
 													PluginContextProvider* pluginContext ) :
 	StatusBarElement( mainSplitter, uiSceneNode, pluginContext ) {}
 
+StatusDebuggerController::~StatusDebuggerController() {
+	mEventConnections.clear();
+	mTabWidgetEventConnections.clear();
+	if ( mContainer )
+		mContainer->removeActionsByTag( reinterpret_cast<UintPtr>( this ) );
+	if ( mTabWidgetSplitter ) {
+		mTabWidgetSplitter->setOnTabWidgetCreateCb( nullptr );
+		mTabWidgetSplitter->setOnTabWidgetCloseCb( nullptr );
+		mTabWidgetSplitter->forEachTabWidget( []( UITabWidget* tabWidget ) {
+			tabWidget->setSplitFunction( nullptr );
+			tabWidget->setTabTryCloseCallback( nullptr );
+			tabWidget->setAcceptsDropOfWidgetFn( nullptr );
+		} );
+		eeDelete( mTabWidgetSplitter );
+	}
+	if ( mContext && mContext->getRightPanel() )
+		mContext->getRightPanel()->unregisterPanel( "debugger" );
+	if ( mContainer )
+		mContainer->close();
+}
+
+void StatusDebuggerController::show() {
+	StatusBarElement::show();
+	updateRightPanel();
+}
+
+void StatusDebuggerController::hide() {
+	StatusBarElement::hide();
+	updateRightPanel();
+}
+
 UIWidget* StatusDebuggerController::getWidget() {
 	return mContainer;
 }
@@ -193,6 +258,207 @@ void StatusDebuggerController::clearConsoleBuffer() {
 	} );
 }
 
+const std::string& StatusDebuggerController::saveLayout() {
+	saveTabLayout();
+	return mSerializedLayout;
+}
+
+void StatusDebuggerController::onTabCreated( UITab* tab, UIWidget* widget ) {
+	tab->setId( "debugger_tab_" + widget->getId().substr( DEBUGGER_WIDGET_ID_PREFIX_LENGTH ) );
+	tab->addClass( "debugger-tab" );
+	tab->setTextAsFallback( true );
+	mEventConnections += tab->connect( Event::OnDragStart,
+									   [this]( const Event* ) { beginRightPanelDropPreview(); } );
+	mEventConnections +=
+		tab->connect( Event::OnDragStop, [this]( const Event* ) { endRightPanelDropPreview(); } );
+}
+
+void StatusDebuggerController::onWidgetFocusChange( UIWidget* ) {}
+
+void StatusDebuggerController::createTabWidgets() {
+	mRightPanelContainer = mContext->getRightPanel()
+							   ? mContext->getRightPanel()->registerPanel( "debugger" )
+							   : nullptr;
+	if ( !mDebuggerTabsContainer || !mRightPanelContainer )
+		return;
+
+	mTabWidgetSplitter = UITabWidgetSplitter::New( this, mUISceneNode );
+	mTabWidgetSplitter->setHideTabBarOnSingleTab( false );
+	mTabWidgetSplitter->setOnTabWidgetCreateCb( [this]( UITabWidget* tabWidget ) {
+		tabWidget->setTabsClosable( false );
+		tabWidget->setAcceptsDropOfWidgetFn(
+			[]( const UIWidget* widget ) { return widget->hasClass( "debugger-tab" ); } );
+		tabWidget->setSplitFunction(
+			[this]( SplitDirection direction, UITabWidget* target ) -> UITabWidget* {
+				Node* dragging = mUISceneNode->getEventDispatcher()->getNodeDragging();
+				if ( dragging && dragging->isType( UI_TYPE_TAB ) ) {
+					auto source = dragging->asType<UITab>()->getTabWidget();
+					bool sourceInRight = source && mRightPanelContainer->isParentOf( source );
+					bool targetInRight = mRightPanelContainer->isParentOf( target );
+					if ( source && sourceInRight != targetInRight )
+						return target;
+				}
+				return mTabWidgetSplitter->splitTabWidget( direction, target );
+			},
+			mTabWidgetSplitter->getVisualSplitEdgePercent() );
+		auto& connections = mTabWidgetEventConnections[tabWidget];
+		connections += tabWidget->connect( Event::OnTabAdded, [this]( const Event* ) {
+			if ( !mRestoringLayout ) {
+				saveTabLayout();
+				updateRightPanel();
+			}
+		} );
+	} );
+	mTabWidgetSplitter->setOnTabWidgetCloseCb(
+		[this]( UITabWidget* tabWidget ) { mTabWidgetEventConnections.erase( tabWidget ); } );
+
+	mUITabWidget = mTabWidgetSplitter->createTabWidget( mDebuggerTabsContainer );
+	mUITabWidget->setId( "app_debugger_tab_widget" );
+	mUIRightTabWidget = mTabWidgetSplitter->createTabWidget( mRightPanelContainer );
+	mUIRightTabWidget->setId( "app_debugger_right_tab_widget" );
+
+	const auto registerWidget = [this]( const std::string& type, UIWidget* widget,
+										const std::string& title ) {
+		widget->addClass( type );
+		mTabWidgetSplitter->registerWidgetType(
+			type, { []( UIWidget* ) { return nlohmann::json::object(); },
+					[widget, title]( const nlohmann::json& ) -> WidgetLoadResult {
+						return { widget, nullptr, title };
+					} } );
+	};
+	registerWidget( "debugger-threads-and-stack", mUIThreadsSplitter,
+					mContext->i18n( "threads_and_stack", "Threads & Stack" ).toUtf8() );
+	registerWidget( "debugger-variables", mUIVariables,
+					mContext->i18n( "variables", "Variables" ).toUtf8() );
+	registerWidget( "debugger-expressions", mUIExpressions,
+					mContext->i18n( "expressions", "Expressions" ).toUtf8() );
+	registerWidget( "debugger-breakpoints", mUIBreakpoints,
+					mContext->i18n( "breakpoints", "Breakpoints" ).toUtf8() );
+	registerWidget( "debugger-console", mUIConsole,
+					mContext->i18n( "console_output", "Console Output" ).toUtf8() );
+
+	restoreTabLayout();
+}
+
+void StatusDebuggerController::restoreTabLayout() {
+	static const UnorderedSet<std::string> expectedWidgetTypes{
+		"debugger-threads-and-stack", "debugger-variables", "debugger-expressions",
+		"debugger-breakpoints", "debugger-console" };
+	mRestoringLayout = true;
+	bool restored = false;
+	mSerializedLayout = mContext->getConfig().iniState.getValue(
+		"debugger", "panel_layout",
+		mContext->getConfig().iniState.getValue( "ui", "debugger_panel_layout", "" ) );
+	const std::string& saved = mSerializedLayout;
+	if ( !saved.empty() ) {
+		auto layout = nlohmann::json::parse( saved, nullptr, false, true );
+		UnorderedSet<std::string> widgetTypes;
+		size_t nodeCount = 0;
+		const int version = layout.is_discarded() ? 0 : layout.value( "version", 0 );
+		if ( !layout.is_discarded() && ( version == 2 || version == 3 ) &&
+			 layout.contains( "bottom" ) && layout.contains( "right" ) &&
+			 isValidDebuggerLayoutNode( layout["bottom"], widgetTypes, 0, nodeCount ) &&
+			 isValidDebuggerLayoutNode( layout["right"], widgetTypes, 0, nodeCount ) &&
+			 widgetTypes == expectedWidgetTypes ) {
+			mTabWidgetSplitter->unserializeNode( layout["bottom"], mUITabWidget );
+			mTabWidgetSplitter->unserializeNode( layout["right"], mUIRightTabWidget );
+			if ( layout.contains( "columns" ) && layout["columns"].is_object() ) {
+				restoreColumnWidths( mUIThreads, layout["columns"], "threads" );
+				restoreColumnWidths( mUIStack, layout["columns"], "stack" );
+				restoreColumnWidths( mUIVariables, layout["columns"], "variables" );
+				restoreColumnWidths( mUIExpressions, layout["columns"], "expressions" );
+				restoreColumnWidths( mUIBreakpoints, layout["columns"], "breakpoints" );
+			}
+			restored = true;
+		}
+	}
+
+	if ( !restored ) {
+		mTabWidgetSplitter->createWidgetInTabWidget(
+			mUITabWidget, mUIThreadsSplitter,
+			mContext->i18n( "threads_and_stack", "Threads & Stack" ).toUtf8(), false );
+		mTabWidgetSplitter->createWidgetInTabWidget(
+			mUITabWidget, mUIBreakpoints, mContext->i18n( "breakpoints", "Breakpoints" ).toUtf8(),
+			false );
+		mTabWidgetSplitter->createWidgetInTabWidget(
+			mUITabWidget, mUIConsole, mContext->i18n( "console_output", "Console Output" ).toUtf8(),
+			false );
+		mTabWidgetSplitter->createWidgetInTabWidget(
+			mUIRightTabWidget, mUIVariables, mContext->i18n( "variables", "Variables" ).toUtf8(),
+			false );
+		mTabWidgetSplitter->createWidgetInTabWidget(
+			mUIRightTabWidget, mUIExpressions,
+			mContext->i18n( "expressions", "Expressions" ).toUtf8(), false );
+		mUITabWidget->setTabSelected( Uint32{ 0 } );
+		mUIRightTabWidget->setTabSelected( Uint32{ 0 } );
+	}
+	if ( mUITabWidget->getTabCount() )
+		mTabWidgetSplitter->setCurrentWidget(
+			mUITabWidget->getTabSelected()->getOwnedWidget()->asType<UIWidget>() );
+	mRestoringLayout = false;
+	saveTabLayout();
+	updateRightPanel();
+}
+
+void StatusDebuggerController::saveTabLayout() {
+	if ( mRestoringLayout || !mTabWidgetSplitter || !mDebuggerTabsContainer ||
+		 !mRightPanelContainer || !mDebuggerTabsContainer->getFirstChild() ||
+		 !mRightPanelContainer->getFirstChild() )
+		return;
+	nlohmann::json layout;
+	layout["version"] = 3;
+	layout["bottom"] = mTabWidgetSplitter->serializeNode( mDebuggerTabsContainer->getFirstChild() );
+	layout["right"] = mTabWidgetSplitter->serializeNode( mRightPanelContainer->getFirstChild() );
+	layout["columns"]["threads"] = mUIThreads->serializeColumnWidths();
+	layout["columns"]["stack"] = mUIStack->serializeColumnWidths();
+	layout["columns"]["variables"] = mUIVariables->serializeColumnWidths();
+	layout["columns"]["expressions"] = mUIExpressions->serializeColumnWidths();
+	layout["columns"]["breakpoints"] = mUIBreakpoints->serializeColumnWidths();
+	mSerializedLayout = layout.dump();
+}
+
+bool StatusDebuggerController::rightPanelHasTabs() const {
+	bool hasTabs = false;
+	if ( !mTabWidgetSplitter || !mRightPanelContainer )
+		return false;
+	mTabWidgetSplitter->forEachTabWidgetStoppable( [this, &hasTabs]( UITabWidget* tabWidget ) {
+		hasTabs = mRightPanelContainer->isParentOf( tabWidget ) && tabWidget->getTabCount() > 0;
+		return hasTabs;
+	} );
+	return hasTabs;
+}
+
+void StatusDebuggerController::beginRightPanelDropPreview() {
+	if ( !mRightPanelDropPreview && mContainer && mContainer->isVisible() &&
+		 !rightPanelHasTabs() ) {
+		mRightPanelDropPreview = true;
+		updateRightPanel();
+	}
+}
+
+void StatusDebuggerController::endRightPanelDropPreview() {
+	if ( !mRightPanelDropPreview || !mContainer )
+		return;
+	// The drop target is resolved after OnDragStop. Keep the empty panel alive until the next
+	// update so it can receive the drop, then collapse it if the drag was canceled or rejected.
+	mContainer->removeActionsByTag( reinterpret_cast<UintPtr>( this ) );
+	mContainer->runOnMainThread(
+		[this] {
+			mRightPanelDropPreview = false;
+			updateRightPanel();
+		},
+		Time::Zero, reinterpret_cast<UintPtr>( this ) );
+}
+
+void StatusDebuggerController::updateRightPanel() {
+	auto rightPanel = mContext->getRightPanel();
+	if ( !rightPanel || !mRightPanelContainer || !mTabWidgetSplitter )
+		return;
+	rightPanel->setPanelVisible( "debugger",
+								 mContainer && mContainer->isVisible() &&
+									 ( mRightPanelDropPreview || rightPanelHasTabs() ) );
+}
+
 void StatusDebuggerController::createContainer() {
 	if ( mContainer )
 		return;
@@ -206,21 +472,16 @@ void StatusDebuggerController::createContainer() {
 	}
 	</style>
 	<hboxce id="app_debugger" lw="mp" lh="mp" visible="false">
-		<TabWidget id="app_debugger_tab_widget" lw="0" lw8="1" lh="mp">
+		<vbox id="app_debugger_tabs" lw="0" lw8="1" lh="mp">
 			<Splitter id="debugger_threads_and_stack" layout_width="mp" lh="mp" splitter-partition="15%">
-				<TableView id="debugger_threads" layout_width="mp" layout_height="mp" />
+			<TableView id="debugger_threads" layout_width="mp" layout_height="mp" column-width-mode="percentage" column-width-mode-menu="true" />
-				<TableView id="debugger_stack" layout_width="mp" layout_height="mp" />
+			<TableView id="debugger_stack" layout_width="mp" layout_height="mp" column-width-mode="percentage" column-width-mode-menu="true" />
-			</Splitter>
+		</Splitter>
-			<TreeView id="debugger_variables" layout_width="mp" layout_height="mp" />
+		<TreeView id="debugger_variables" layout_width="mp" layout_height="mp" column-width-mode="percentage" column-width-mode-menu="true" />
-			<TreeView id="debugger_expressions" layout_width="mp" layout_height="mp" />
+		<TreeView id="debugger_expressions" layout_width="mp" layout_height="mp" column-width-mode="percentage" column-width-mode-menu="true" />
-			<BreakpointsTableView id="debugger_breakpoints" layout_width="mp" layout_height="mp" />
+		<BreakpointsTableView id="debugger_breakpoints" layout_width="mp" layout_height="mp" column-width-mode="percentage" column-width-mode-menu="true" />
 			<CodeEditor id="debugger_console" layout_width="mp" layout_height="mp" />
-			<Tab id="debugger_tab_threads_and_stack" text="@string(threads_and_stack, Threads & Stack)" owns="debugger_threads_and_stack" />
+		</vbox>
-			<Tab id="debugger_tab_variables" text="@string(variables, Variables)" owns="debugger_variables" />
-			<Tab id="debugger_tab_expressions" text="@string(expressions, Expressions)" owns="debugger_expressions" />
-			<Tab id="debugger_tab_breakpoints" text="@string(breakpoints, Breakpoints)" owns="debugger_breakpoints" />
-			<Tab id="debugger_tab_console" text="@string(console_output, Console Output)" owns="debugger_console" />
-		</TabWidget>
 		<vbox id="app_debugger_buttons" class="vertical_bar" lw="16dp" lh="mp">
 			<PushButton class="expand_status_bar_panel" lw="mp" tooltip="@string(expand_panel, Expand Panel)" />
 			<PushButton id="app_debugger_start" class="debugger_start" lw="mp" icon="icon(debug-start, 12dp)" tooltip="@string(start, Start)" />
@@ -248,7 +509,7 @@ void StatusDebuggerController::createContainer() {
 
 	mContext->getStatusBar()->registerStatusBarPanel( mContainer, mContainer );
 
-	mContainer->bind( "app_debugger_tab_widget", mUITabWidget );
+	mContainer->bind( "app_debugger_tabs", mDebuggerTabsContainer );
 	mContainer->bind( "debugger_threads_and_stack", mUIThreadsSplitter );
 	mContainer->bind( "debugger_threads", mUIThreads );
 	mContainer->bind( "debugger_stack", mUIStack );
@@ -256,6 +517,8 @@ void StatusDebuggerController::createContainer() {
 	mContainer->bind( "debugger_variables", mUIVariables );
 	mContainer->bind( "debugger_expressions", mUIExpressions );
 	mContainer->bind( "debugger_console", mUIConsole );
+	mEventConnections += mContainer->connect( Event::OnVisibleChange,
+											  [this]( const Event* ) { updateRightPanel(); } );
 	mContainer->bind( "app_debugger_start", mUIButStart );
 	mContainer->bind( "app_debugger_stop", mUIButStop );
 	mContainer->bind( "app_debugger_pause", mUIButPause );
@@ -264,25 +527,34 @@ void StatusDebuggerController::createContainer() {
 	mContainer->bind( "app_debugger_step_into", mUIButStepInto );
 	mContainer->bind( "app_debugger_step_out", mUIButStepOut );
 
+	createTabWidgets();
+
 	mContainer->setCommand( "next-tab", [this] {
-		if ( mUITabWidget )
+		if ( mTabWidgetSplitter && mTabWidgetSplitter->getCurWidget() ) {
-			mUITabWidget->focusNextTab();
+			auto tabWidget =
+				mTabWidgetSplitter->tabWidgetFromWidget( mTabWidgetSplitter->getCurWidget() );
+			if ( tabWidget )
+				tabWidget->focusNextTab();
+		}
 	} );
 
 	mContainer->setCommand( "previous-tab", [this] {
-		if ( mUITabWidget )
+		if ( mTabWidgetSplitter && mTabWidgetSplitter->getCurWidget() ) {
-			mUITabWidget->focusPreviousTab();
+			auto tabWidget =
+				mTabWidgetSplitter->tabWidgetFromWidget( mTabWidgetSplitter->getCurWidget() );
+			if ( tabWidget )
+				tabWidget->focusPreviousTab();
+		}
 	} );
 
 	for ( int i = 1; i <= 5; i++ ) {
 		mContainer->setCommand( String::format( "switch-to-tab-%d", i ), [this, i] {
-			if ( mUITabWidget )
+			if ( mTabWidgetSplitter )
-				mUITabWidget->setTabSelected(
+				mTabWidgetSplitter->switchToTab( i - 1 );
-					eeclamp<Int32>( i - 1, 0, mUITabWidget->getTabCount() - 1 ) );
 		} );
 	}
 
-	mContainer->on( Event::KeyDown, [this]( const Event* event ) {
+	mEventConnections += mContainer->connect( Event::KeyDown, [this]( const Event* event ) {
 		auto ke = event->asKeyEvent();
 		if ( ke->getSanitizedMod() == 0 && ke->getKeyCode() == EE::Window::KEY_ESCAPE &&
 			 mSplitter->getCurEditor() ) {
@@ -313,19 +585,12 @@ void StatusDebuggerController::createContainer() {
 
 	mUIThreads->setAutoExpandOnSingleColumn( true );
 
-	mUIStack->setAutoColumnsWidth( true );
-	mUIStack->setFitAllColumnsToWidget( true );
 	mUIStack->setMainColumn( 1 );
 
-	mUIVariables->setAutoColumnsWidth( true );
+	mUIVariables->setMainColumn( 1 );
-	mUIVariables->setFitAllColumnsToWidget( true );
 
-	mUIBreakpoints->setAutoColumnsWidth( true );
-	mUIBreakpoints->setFitAllColumnsToWidget( true );
 	mUIBreakpoints->setMainColumn( 1 );
 
-	mUIExpressions->setAutoColumnsWidth( true );
-	mUIExpressions->setFitAllColumnsToWidget( true );
 	mUIExpressions->setMainColumn( 1 );
 
 	mUIConsole->setLocked( true );
@@ -333,7 +598,7 @@ void StatusDebuggerController::createContainer() {
 	mUIConsole->setShowLineNumber( false );
 	mUIConsole->getDocument().reset();
 	mUIConsole->setScrollY( mUIConsole->getMaxScroll().y );
-	mUIConsole->on( Event::OnScrollChange, [this]( auto ) {
+	mEventConnections += mUIConsole->connect( Event::OnScrollChange, [this]( const Event* ) {
 		mScrollLocked = mUIConsole->getMaxScroll().y == mUIConsole->getScroll().y;
 	} );
 }

src/tools/ecode/plugins/debugger/statusdebuggercontroller.hpp

@@ -3,8 +3,11 @@
 
 #include "../../uistatusbar.hpp"
 #include "models/breakpointsmodel.hpp"
+#include <eepp/core/containers.hpp>
+#include <eepp/scene/eventconnection.hpp>
 #include <eepp/system/luapattern.hpp>
 #include <eepp/ui/tools/uicodeeditorsplitter.hpp>
+#include <eepp/ui/tools/uitabwidgetsplitter.hpp>
 #include <eepp/ui/uicodeeditor.hpp>
 #include <eepp/ui/uirelativelayout.hpp>
 #include <eepp/ui/uiscenenode.hpp>
@@ -34,7 +37,7 @@ class UIBreakpointsTableView : public UITableView {
 	UIWidget* createCell( UIWidget* rowWidget, const ModelIndex& index );
 };
 
-class StatusDebuggerController : public StatusBarElement {
+class StatusDebuggerController : public StatusBarElement, public UITabWidgetSplitter::Client {
   public:
 	enum class State { NotStarted, Running, Paused };
 
@@ -43,7 +46,11 @@ class StatusDebuggerController : public StatusBarElement {
 	StatusDebuggerController( UISplitter* mainSplitter, UISceneNode* uiSceneNode,
 							  PluginContextProvider* pluginContext );
 
-	virtual ~StatusDebuggerController() {};
+	virtual ~StatusDebuggerController();
+
+	virtual void show();
+
+	virtual void hide();
 
 	UIWidget* getWidget();
 
@@ -71,8 +78,14 @@ class StatusDebuggerController : public StatusBarElement {
 
 	void setDebuggingState( State state );
 
+	const std::string& saveLayout();
+
 	std::function<void( StatusDebuggerController*, UIWidget* )> onWidgetCreated{ nullptr };
 
+	void onTabCreated( UITab* tab, UIWidget* widget );
+
+	void onWidgetFocusChange( UIWidget* widget );
+
   protected:
 	UIHLinearLayoutCommandExecuter* mContainer{ nullptr };
 	UITableView* mUIThreads{ nullptr };
@@ -90,9 +103,32 @@ class StatusDebuggerController : public StatusBarElement {
 	UIPushButton* mUIButStepOver{ nullptr };
 	UIPushButton* mUIButStepOut{ nullptr };
 	UITabWidget* mUITabWidget{ nullptr };
+	UITabWidget* mUIRightTabWidget{ nullptr };
+	UITabWidgetSplitter* mTabWidgetSplitter{ nullptr };
+	UILayout* mDebuggerTabsContainer{ nullptr };
+	UILayout* mRightPanelContainer{ nullptr };
+	Scene::EventConnectionList mEventConnections;
+	UnorderedMap<UITabWidget*, Scene::EventConnectionList> mTabWidgetEventConnections;
 	bool mScrollLocked{ true };
+	bool mRestoringLayout{ false };
+	bool mRightPanelDropPreview{ false };
+	std::string mSerializedLayout;
 
 	void createContainer();
+
+	void createTabWidgets();
+
+	void restoreTabLayout();
+
+	void saveTabLayout();
+
+	bool rightPanelHasTabs() const;
+
+	void beginRightPanelDropPreview();
+
+	void endRightPanelDropPreview();
+
+	void updateRightPanel();
 };
 
 } // namespace ecode

src/tools/ecode/plugins/plugincontextprovider.hpp

@@ -19,6 +19,7 @@ class Font;
 namespace UI {
 
 class UISplitter;
+class UILayout;
 class UITabWidget;
 class UISceneNode;
 class UICodeEditor;
@@ -58,6 +59,8 @@ class ProjectDirectoryTree;
 struct TerminalConfig;
 class UIMainLayout;
 class UITreeViewFS;
+class StatusDebuggerController;
+class UIRightPanel;
 
 class PluginContextProvider {
   public:
@@ -65,6 +68,10 @@ class PluginContextProvider {
 
 	virtual UISplitter* getMainSplitter() const = 0;
 
+	virtual UIRightPanel* getRightPanel() const = 0;
+
+	virtual StatusDebuggerController* getStatusDebuggerController() const = 0;
+
 	virtual UITreeViewFS* getProjectTreeView() const = 0;
 
 	virtual void hideGlobalSearchBar() = 0;

src/tools/ecode/uirightpanel.cpp

@@ -0,0 +1,101 @@
+#include "uirightpanel.hpp"
+#include "appconfig.hpp"
+
+namespace ecode {
+
+using namespace EE;
+using namespace EE::UI;
+
+UIRightPanel::UIRightPanel( UISplitter* splitter, UILayout* container, AppConfig* config ) :
+	mSplitter( splitter ), mContainer( container ), mConfig( config ) {}
+
+UILayout* UIRightPanel::registerPanel( const std::string& id ) {
+	auto found = mPanels.find( id );
+	if ( found != mPanels.end() )
+		return found->second.layout;
+	if ( !mContainer )
+		return nullptr;
+	auto layout = UIRelativeLayout::New();
+	layout->setId( id );
+	layout->setLayoutSizePolicy( SizePolicy::MatchParent, SizePolicy::MatchParent );
+	layout->setVisible( false )->setEnabled( false )->setParent( mContainer );
+	mPanels.emplace( id, Panel{ layout, false } );
+	return layout;
+}
+
+void UIRightPanel::unregisterPanel( const std::string& id ) {
+	auto found = mPanels.find( id );
+	if ( found == mPanels.end() )
+		return;
+	if ( found->second.layout )
+		found->second.layout->close();
+	mPanels.erase( found );
+	updateVisibility();
+}
+
+void UIRightPanel::setPanelVisible( const std::string& id, bool visible ) {
+	auto found = mPanels.find( id );
+	if ( found == mPanels.end() )
+		return;
+	if ( visible ) {
+		for ( auto& panel : mPanels ) {
+			if ( panel.first != id && panel.second.visible ) {
+				panel.second.visible = false;
+				if ( panel.second.layout )
+					panel.second.layout->setVisible( false )->setEnabled( false );
+			}
+		}
+	}
+	if ( found->second.visible == visible )
+		return;
+	found->second.visible = visible;
+	if ( found->second.layout )
+		found->second.layout->setVisible( visible )->setEnabled( visible );
+	updateVisibility();
+}
+
+bool UIRightPanel::isPanelVisible( const std::string& id ) const {
+	auto found = mPanels.find( id );
+	return found != mPanels.end() && found->second.visible;
+}
+
+void UIRightPanel::saveState() {
+	if ( mSplitter && mConfig &&
+		 mSplitter->getSplitPartition().getUnit() == StyleSheetLength::Percentage &&
+		 mSplitter->getSplitPartition().getValue() < 100.f )
+		mConfig->windowState.rightPanelPartition = mSplitter->getSplitPartition().toString();
+}
+
+UISplitter* UIRightPanel::getSplitter() const {
+	return mSplitter;
+}
+
+UILayout* UIRightPanel::getContainer() const {
+	return mContainer;
+}
+
+void UIRightPanel::updateVisibility() {
+	if ( !mSplitter || !mConfig )
+		return;
+	bool visible = false;
+	for ( const auto& panel : mPanels ) {
+		if ( panel.second.visible ) {
+			visible = true;
+			break;
+		}
+	}
+	if ( visible == mVisible )
+		return;
+	mVisible = visible;
+	if ( visible ) {
+		auto partition = mConfig->windowState.rightPanelPartition;
+		if ( partition.empty() || partition == "100%" )
+			partition = "75%";
+		mSplitter->setSplitPartition( StyleSheetLength( partition ) );
+	} else {
+		saveState();
+		mSplitter->setSplitPartition( StyleSheetLength( "100%" ) );
+	}
+}
+
+} // namespace ecode

src/tools/ecode/uirightpanel.hpp

@@ -0,0 +1,50 @@
+#ifndef ECODE_UIRIGHTPANEL_HPP
+#define ECODE_UIRIGHTPANEL_HPP
+
+#include <eepp/core/containers.hpp>
+#include <eepp/ui/uirelativelayout.hpp>
+#include <eepp/ui/uisplitter.hpp>
+
+using namespace EE;
+using namespace EE::UI;
+
+namespace ecode {
+
+class AppConfig;
+
+class UIRightPanel {
+  public:
+	UIRightPanel( UISplitter* splitter, UILayout* container, AppConfig* config );
+
+	UILayout* registerPanel( const std::string& id );
+
+	void unregisterPanel( const std::string& id );
+
+	void setPanelVisible( const std::string& id, bool visible );
+
+	bool isPanelVisible( const std::string& id ) const;
+
+	void saveState();
+
+	UISplitter* getSplitter() const;
+
+	UILayout* getContainer() const;
+
+  protected:
+	struct Panel {
+		UILayout* layout{ nullptr };
+		bool visible{ false };
+	};
+
+	UISplitter* mSplitter{ nullptr };
+	UILayout* mContainer{ nullptr };
+	AppConfig* mConfig{ nullptr };
+	UnorderedMap<std::string, Panel> mPanels;
+	bool mVisible{ false };
+
+	void updateVisibility();
+};
+
+} // namespace ecode
+
+#endif // ECODE_UIRIGHTPANEL_HPP