From 0f8d930e80b738353ade2c2dbb75bf6660afff15 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mart=C3=ADn=20Lucas=20Golini?= <spartanj@gmail.com>
Date: Mon, 11 May 2026 21:22:49 -0300
Subject: [PATCH] Add support for `--var: var(--other-var)`. Reset global
 definition for body and html elements when new styles are loaded (required
 when these elements have only variable definitions).

---
 include/eepp/ui/css/elementdefinition.hpp     |   2 +
 src/eepp/ui/css/elementdefinition.cpp         |  62 +++++-
 src/eepp/ui/uiscenenode.cpp                   |   8 +
 .../unit_tests/uicss_inheritance_tests.cpp    | 182 ++++++++++++++----
 4 files changed, 219 insertions(+), 35 deletions(-)

diff --git a/include/eepp/ui/css/elementdefinition.hpp b/include/eepp/ui/css/elementdefinition.hpp
index 32c274ee1..a79419c5b 100644
--- a/include/eepp/ui/css/elementdefinition.hpp
+++ b/include/eepp/ui/css/elementdefinition.hpp
@@ -40,6 +40,8 @@ class EE_API ElementDefinition : NonCopyable {
 	bool mStructurallyVolatile;
 
 	void findVariables( const CSS::StyleSheetStyle* style );
+
+	void resolveVariables();
 };
 
 }}} // namespace EE::UI::CSS
diff --git a/src/eepp/ui/css/elementdefinition.cpp b/src/eepp/ui/css/elementdefinition.cpp
index eda4a15b7..4b9f65bcf 100644
--- a/src/eepp/ui/css/elementdefinition.cpp
+++ b/src/eepp/ui/css/elementdefinition.cpp
@@ -1,3 +1,4 @@
+#include <eepp/system/functionstring.hpp>
 #include <eepp/ui/css/elementdefinition.hpp>
 
 namespace EE { namespace UI { namespace CSS {
@@ -70,6 +71,8 @@ void ElementDefinition::refresh() {
 		findVariables( styleSheetStyle );
 	}
 
+	resolveVariables();
+
 	for ( auto& property : mProperties )
 		mPropertyIds.insert( property.first );
 }
@@ -78,11 +81,68 @@ void ElementDefinition::findVariables( const StyleSheetStyle* style ) {
 	for ( const auto& vars : style->getVariables() ) {
 		const StyleSheetVariable& variable = vars.second;
 		const auto& it = mVariables.find( variable.getNameHash() );
-
 		if ( it == mVariables.end() || variable.getSpecificity() >= it->second.getSpecificity() ) {
 			mVariables[variable.getNameHash()] = variable;
 		}
 	}
 }
 
+static void resolveVarValue( std::string& value, const StyleSheetVariables& variables,
+							 UnorderedSet<String::HashType>& visited, int depth = 0 ) {
+	static constexpr int maxDepth = 32;
+	if ( depth > maxDepth )
+		return;
+
+	std::string::size_type tokenStart = 0;
+
+	while ( true ) {
+		tokenStart = value.find( "var(", tokenStart );
+		if ( tokenStart == std::string::npos )
+			return;
+
+		std::string::size_type tokenEnd = String::findCloseBracket( value, tokenStart, '(', ')' );
+		if ( tokenEnd == std::string::npos )
+			return;
+
+		std::string varDef( value, tokenStart, tokenEnd + 1 - tokenStart );
+		System::FunctionString functionType = System::FunctionString::parse( varDef );
+
+		if ( functionType.getParameters().empty() ) {
+			tokenStart = tokenEnd;
+			continue;
+		}
+
+		bool resolved = false;
+		for ( auto& param : functionType.getParameters() ) {
+			if ( String::startsWith( param, "--" ) ) {
+				auto it = variables.find( String::hash( param ) );
+				if ( it != variables.end() &&
+					 visited.find( it->second.getNameHash() ) == visited.end() ) {
+					visited.insert( it->second.getNameHash() );
+					std::string deepValue( it->second.getValue() );
+					resolveVarValue( deepValue, variables, visited, depth + 1 );
+					String::replaceAll( value, varDef, deepValue );
+					resolved = true;
+					break;
+				}
+			}
+		}
+
+		if ( resolved )
+			tokenStart = 0;
+		else
+			tokenStart = tokenEnd;
+	}
+}
+
+void ElementDefinition::resolveVariables() {
+	static UnorderedSet<String::HashType> visited;
+	for ( auto& varPair : mVariables ) {
+		std::string value( varPair.second.getValue() );
+		visited.clear();
+		resolveVarValue( value, mVariables, visited );
+		varPair.second.setValue( value );
+	}
+}
+
 }}} // namespace EE::UI::CSS
diff --git a/src/eepp/ui/uiscenenode.cpp b/src/eepp/ui/uiscenenode.cpp
index a4169c07f..ac8d46d4f 100644
--- a/src/eepp/ui/uiscenenode.cpp
+++ b/src/eepp/ui/uiscenenode.cpp
@@ -422,6 +422,14 @@ void UISceneNode::updateStyleSheet( bool forceReloadStyle ) {
 	if ( mRoot && mRoot->getUIStyle() )
 		mRoot->getUIStyle()->resetGlobalDefinition();
 
+	auto bodies = mRoot->findAllByType( UI_TYPE_HTML_BODY );
+	for ( auto body : bodies )
+		body->asType<UIWidget>()->getUIStyle()->resetGlobalDefinition();
+
+	auto htmls = mRoot->findAllByType( UI_TYPE_HTML_HTML );
+	for ( auto html : htmls )
+		html->asType<UIWidget>()->getUIStyle()->resetGlobalDefinition();
+
 	if ( mRoot && mediaChanged )
 		mRoot->reportStyleStateChangeRecursive( false, false );
 
diff --git a/src/tests/unit_tests/uicss_inheritance_tests.cpp b/src/tests/unit_tests/uicss_inheritance_tests.cpp
index 8355d9241..780d7e4de 100644
--- a/src/tests/unit_tests/uicss_inheritance_tests.cpp
+++ b/src/tests/unit_tests/uicss_inheritance_tests.cpp
@@ -1,6 +1,7 @@
 #include "utest.hpp"
 #include <eepp/graphics/font.hpp>
 #include <eepp/graphics/fontmanager.hpp>
+#include <eepp/graphics/pixeldensity.hpp>
 #include <eepp/scene/node.hpp>
 #include <eepp/system/filesystem.hpp>
 #include <eepp/ui/css/stylesheet.hpp>
@@ -354,8 +355,7 @@ UTEST( CSSUnits, ExChWithFont ) {
 						WindowBackend::Default, 32 ),
 		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash() ), 1.f );
 
-	Graphics::Font* font =
-		app.getUI()->getUIThemeManager()->getDefaultFont();
+	Graphics::Font* font = app.getUI()->getUIThemeManager()->getDefaultFont();
 	EXPECT_TRUE( font != nullptr );
 
 	Float elFontSize = 24.f;
@@ -374,49 +374,163 @@ UTEST( CSSUnits, ExChWithFont ) {
 	EXPECT_NE( fallback, resultCh );
 }
 
-UTEST( CSSUnits, Integration ) {
-	for ( Float scale : { 1.f, 1.5f, 2.f } ) {
-		UTEST_PRINT_STEP( String::format( "SCALE %.1f", scale ).c_str() );
-		UIApplication app( WindowSettings( 800, 600, "eepp - CSS Units Ex/Ch Integration Test",
-										   WindowStyle::Default, WindowBackend::Default, 32 ),
-						   UIApplication::Settings(
-							   Sys::getProcessPath() + ".." + FileSystem::getOSSlash(), scale ) );
+UTEST( CSSVariables, VariableReferencesSimple ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - CSS Var Ref Test 1", WindowStyle::Default,
+						WindowBackend::Default, 32 ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash() ), 1 );
 
-		std::string xml = R"(
+	std::string xml = R"(
 <html>
 	<head>
 		<style>
-		.text {
-			font-size: 20px;
-		}
-		#exbox {
-			width: 10ex;
-			height: 2ex;
-		}
-		#chbox {
-			width: 10ch;
-			height: 2ch;
+		body {
+			--primary: #FF0000;
+			--text-color: var(--primary);
+			color: var(--text-color);
 		}
 		</style>
 	</head>
 <body>
-	<div id="exbox" class="text">x</div>
-	<div id="chbox" class="text">0</div>
+	<div id="testdiv">Test text</div>
 </body>
 </html>
-		)";
+    )";
 
-		UIWidget* root = app.getUI()->loadLayoutFromString( xml );
-		EXPECT_TRUE( root != nullptr );
+	UIWidget* root = app.getUI()->loadLayoutFromString( xml );
+	EXPECT_TRUE( root != nullptr );
 
-		UIRichText* exbox = root->querySelector( "#exbox" )->asType<UIRichText>();
-		EXPECT_TRUE( exbox != nullptr );
-		EXPECT_GT( exbox->getPixelsSize().getWidth(), 0.f );
-		EXPECT_GT( exbox->getPixelsSize().getHeight(), 0.f );
+	UIRichText* div = root->querySelector( "#testdiv" )->asType<UIRichText>();
+	EXPECT_TRUE( div != nullptr );
 
-		UIRichText* chbox = root->querySelector( "#chbox" )->asType<UIRichText>();
-		EXPECT_TRUE( chbox != nullptr );
-		EXPECT_GT( chbox->getPixelsSize().getWidth(), 0.f );
-		EXPECT_GT( chbox->getPixelsSize().getHeight(), 0.f );
-	}
+	EXPECT_TRUE( Color( "#FF0000" ) == div->getFontColor() );
+}
+
+UTEST( CSSVariables, VariableReferencesChain ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - CSS Var Ref Test 2", WindowStyle::Default,
+						WindowBackend::Default, 32 ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash() ), 1 );
+
+	std::string xml = R"(
+<html>
+	<head>
+		<style>
+		body {
+			--a: #00FF00;
+			--b: var(--a);
+			--c: var(--b);
+			color: var(--c);
+		}
+		</style>
+	</head>
+<body>
+	<div id="testdiv">Test text</div>
+</body>
+</html>
+    )";
+
+	UIWidget* root = app.getUI()->loadLayoutFromString( xml );
+	EXPECT_TRUE( root != nullptr );
+
+	UIRichText* div = root->querySelector( "#testdiv" )->asType<UIRichText>();
+	EXPECT_TRUE( div != nullptr );
+
+	EXPECT_TRUE( Color( "#00FF00" ) == div->getFontColor() );
+}
+
+UTEST( CSSVariables, VariableReferencesWithPadding ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - CSS Var Ref Test 3", WindowStyle::Default,
+						WindowBackend::Default, 32 ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash() ), 1 );
+
+	std::string xml = R"(
+<html>
+	<head>
+		<style>
+		#testdiv {
+			--base: 20px;
+			--spacing: var(--base);
+			padding: var(--spacing);
+		}
+		</style>
+	</head>
+<body>
+	<div id="testdiv">Test text</div>
+</body>
+</html>
+    )";
+
+	UIWidget* root = app.getUI()->loadLayoutFromString( xml );
+	EXPECT_TRUE( root != nullptr );
+
+	UIWidget* div = root->querySelector( "#testdiv" );
+	EXPECT_TRUE( div != nullptr );
+
+	Float padding = PixelDensity::dpToPx( div->getPadding().Left );
+	EXPECT_NEAR( 20.f, padding, 1.f );
+}
+
+UTEST( CSSVariables, VariableReferencesMultiple ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - CSS Var Ref Test 4", WindowStyle::Default,
+						WindowBackend::Default, 32 ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash() ), 1 );
+
+	std::string xml = R"(
+<html>
+	<head>
+		<style>
+		#testdiv {
+			--color1: #0000FF;
+			--color2: var(--color1);
+			--color3: var(--color2);
+			color: var(--color3);
+		}
+		</style>
+	</head>
+<body>
+	<div id="testdiv">Test text</div>
+</body>
+</html>
+    )";
+
+	UIWidget* root = app.getUI()->loadLayoutFromString( xml );
+	EXPECT_TRUE( root != nullptr );
+
+	UIRichText* div = root->querySelector( "#testdiv" )->asType<UIRichText>();
+	EXPECT_TRUE( div != nullptr );
+
+	EXPECT_TRUE( Color( "#0000FF" ) == div->getFontColor() );
+}
+
+UTEST( CSSVariables, VariableReferencesCircular ) {
+	UIApplication app(
+		WindowSettings( 800, 600, "eepp - CSS Var Ref Test 5", WindowStyle::Default,
+						WindowBackend::Default, 32 ),
+		UIApplication::Settings( Sys::getProcessPath() + ".." + FileSystem::getOSSlash() ), 1 );
+
+	std::string xml = R"(
+<html>
+	<head>
+		<style>
+		body {
+			--x: var(--y);
+			--y: var(--x);
+			color: var(--x, #FF0000);
+		}
+		</style>
+	</head>
+<body>
+	<div id="testdiv">Test text</div>
+</body>
+</html>
+    )";
+
+	UIWidget* root = app.getUI()->loadLayoutFromString( xml );
+	EXPECT_TRUE( root != nullptr );
+
+	UIRichText* div = root->querySelector( "#testdiv" )->asType<UIRichText>();
+	EXPECT_TRUE( div != nullptr );
 }