Minor nit: improve dropdown list scrolling.

include/eepp/scene/event.hpp

@@ -130,6 +130,7 @@ class EE_API Event {
 		OnToggle,
 		OnFocusWithin,
 		OnFocusWithinLoss,
+		OnItemsCountChange,
 		NoEvent = eeINDEX_NOT_FOUND
 	};
 

include/eepp/ui/uidropdownlist.hpp

@@ -18,6 +18,7 @@ class EE_API UIDropDownList : public UIDropDown {
 	virtual ~UIDropDownList();
 
 	virtual Uint32 getType() const;
+
 	virtual bool isType( const Uint32& type ) const;
 
 	UIListBox* getListBox() const;
@@ -27,17 +28,24 @@ class EE_API UIDropDownList : public UIDropDown {
 	virtual UIDropDownList* setMaxNumVisibleItems( const Uint32& maxNumVisibleItems );
 
 	virtual bool applyProperty( const StyleSheetProperty& attribute );
+
 	virtual std::string getPropertyString( const PropertyDefinition* propertyDef,
 										   const Uint32& propertyIndex = 0 ) const;
+
 	virtual std::vector<PropertyId> getPropertiesImplemented() const;
 
 	virtual void loadFromXmlNode( const pugi::xml_node& node );
 
+	void setClickStepItems( Uint32 num );
+
+	Uint32 getClickStepItems() const { return mClickStepItems; }
+
   protected:
 	friend class UIComboBox;
 
 	UIListBox* mListBox;
 	Uint32 mListBoxCloseCb{ 0 };
+	Uint32 mClickStepItems{ 3 };
 
 	UIDropDownList( const std::string& tag = "dropdownlist" );
 
@@ -52,6 +60,8 @@ class EE_API UIDropDownList : public UIDropDown {
 	virtual void onClassChange();
 
 	void destroyListBox();
+
+	void updateClickStep();
 };
 
 }} // namespace EE::UI

include/eepp/ui/uilistbox.hpp

@@ -63,6 +63,8 @@ class EE_API UIListBox : public UITouchDraggableWidget {
 
 	std::vector<UIListBoxItem*> getItemsSelected();
 
+	Uint32 getVisibleItemsCount() const;
+
 	Rectf getContainerPadding() const;
 
 	void setSmoothScroll( const bool& soft );
@@ -195,6 +197,8 @@ class EE_API UIListBox : public UITouchDraggableWidget {
 	virtual void onTouchDragValueChange( Vector2f diff );
 
 	virtual bool isTouchOverAllowedChildren();
+
+	void onItemsCountChange();
 };
 
 }} // namespace EE::UI

src/eepp/ui/uidropdownlist.cpp

@@ -37,6 +37,7 @@ UIDropDownList::UIDropDownList( const std::string& tag ) : UIDropDown( tag ), mL
 	mListBox->on( Event::OnItemKeyDown, [this]( auto event ) { onItemKeyDown( event ); } );
 	mListBox->on( Event::KeyDown, [this]( auto event ) { onItemKeyDown( event ); } );
 	mListBox->on( Event::OnClear, [this]( auto event ) { onWidgetClear( event ); } );
+	mListBox->on( Event::OnItemsCountChange, [this]( auto event ) { updateClickStep(); } );
 	mListBoxCloseCb =
 		mListBox->on( Event::OnClose, [this]( const Event* ) { mListBox = nullptr; } );
 	mListBox->on( Event::OnSelectionChanged, [this]( auto ) {
@@ -139,10 +140,12 @@ UIDropDownList* UIDropDownList::setMaxNumVisibleItems( const Uint32& maxNumVisib
 	if ( maxNumVisibleItems != mStyleConfig.MaxNumVisibleItems ) {
 		mStyleConfig.MaxNumVisibleItems = maxNumVisibleItems;
 
-		if ( NULL != mListBox )
+		if ( NULL != mListBox ) {
 			mListBox->setSize( getSize().getWidth(), std::min( mStyleConfig.MaxNumVisibleItems,
 															   getListBox()->getItemsCount() ) *
 														 mListBox->getRowHeight() );
+			updateClickStep();
+		}
 	}
 	return this;
 }
@@ -232,4 +235,20 @@ void UIDropDownList::onClassChange() {
 		mListBox->setClasses( getClasses() );
 }
 
+void UIDropDownList::setClickStepItems( Uint32 num ) {
+	if ( num != mClickStepItems ) {
+		mClickStepItems = num;
+		updateClickStep();
+	}
+}
+
+void UIDropDownList::updateClickStep() {
+	if ( mListBox == nullptr )
+		return;
+	Float totalScrollableItems = (Float)mListBox->getItemsCount() - getMaxNumVisibleItems();
+	mListBox->getVerticalScrollBar()->setClickStep(
+		totalScrollableItems > mClickStepItems ? mClickStepItems / totalScrollableItems
+											   : mListBox->getVerticalScrollBar()->getMaxValue() );
+}
+
 }} // namespace EE::UI

src/eepp/ui/uilistbox.cpp

@@ -135,6 +135,7 @@ void UIListBox::addListBoxItems( const std::vector<String>& texts ) {
 	findMaxWidth();
 	updatePageStep();
 	updateScroll();
+	onItemsCountChange();
 }
 
 Uint32 UIListBox::addListBoxItem( const String& text ) {
@@ -143,6 +144,7 @@ Uint32 UIListBox::addListBoxItem( const String& text ) {
 
 	updatePageStep();
 	updateScroll();
+	onItemsCountChange();
 
 	return (Uint32)( mItems.size() - 1 );
 }
@@ -190,6 +192,8 @@ void UIListBox::removeListBoxItems( const std::vector<Uint32>& ItemsIndex ) {
 
 	if ( mTexts.empty() )
 		sendCommonEvent( Event::OnClear );
+
+	onItemsCountChange();
 }
 
 void UIListBox::clear() {
@@ -204,11 +208,12 @@ void UIListBox::clear() {
 
 	sendCommonEvent( Event::OnClear );
 	sendCommonEvent( Event::OnSelectionChanged );
+	onItemsCountChange();
 }
 
 Uint32 UIListBox::removeListBoxItem( Uint32 ItemIndex ) {
 	removeListBoxItems( { ItemIndex } );
-
+	onItemsCountChange();
 	return ItemIndex;
 }
 
@@ -415,7 +420,7 @@ void UIListBox::createItemIndex( const Uint32& i ) {
 void UIListBox::updateScrollBarState() {
 	bool clipped = 0 != mContainer->isClipped();
 
-	Uint32 visibleItems = mContainer->getSize().getHeight() / mRowHeight;
+	Uint32 visibleItems = getVisibleItemsCount();
 	mItemsNotVisible = (Int32)mItems.size() - visibleItems;
 
 	if ( mItemsNotVisible <= 0 ) {
@@ -488,7 +493,7 @@ void UIListBox::updateScroll( bool fromScrollChange ) {
 
 	updateScrollBarState();
 
-	Uint32 visibleItems = mContainer->getSize().getHeight() / mRowHeight;
+	Uint32 visibleItems = getVisibleItemsCount();
 	mItemsNotVisible = (Uint32)mItems.size() - visibleItems;
 	Int32 scrolleable = (Int32)mItems.size() * mRowHeight - mContainer->getSize().getHeight();
 	bool isScrollVisible = mVScrollBar->isVisible();
@@ -729,6 +734,10 @@ std::vector<UIListBoxItem*> UIListBox::getItemsSelected() {
 	return tItems;
 }
 
+Uint32 UIListBox::getVisibleItemsCount() const {
+	return mContainer->getSize().getHeight() / mRowHeight;
+}
+
 Uint32 UIListBox::getItemIndex( UIListBoxItem* Item ) {
 	for ( Uint32 i = 0; i < mItems.size(); i++ ) {
 		if ( Item == mItems[i] )
@@ -1138,4 +1147,8 @@ void UIListBox::loadItemsFromXmlNode( const pugi::xml_node& node ) {
 	endAttributesTransaction();
 }
 
+void UIListBox::onItemsCountChange() {
+	sendCommonEvent( Event::OnItemsCountChange );
+}
+
 }} // namespace EE::UI