Theme Editor: Preview: support usage of variables in styles

flatlaf-core/src/main/java/com/formdev/flatlaf/UIDefaultsLoader.java

@@ -80,7 +80,7 @@ class UIDefaultsLoader
 	private static final String OPTIONAL_PREFIX = "?";
 	private static final String WILDCARD_PREFIX = "*.";
 
-	private static final String KEY_VARIABLES = "FlatLaf.internal.variables";
+	static final String KEY_VARIABLES = "FlatLaf.internal.variables";
 
 	private static int parseColorDepth;
 

flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/UIDefaultsLoaderAccessor.java

@@ -27,6 +27,8 @@ import com.formdev.flatlaf.UIDefaultsLoader.ValueType;
  */
 public class UIDefaultsLoaderAccessor
 {
+	public static final String KEY_VARIABLES = UIDefaultsLoader.KEY_VARIABLES;
+
 	public static Object UNKNOWN = ValueType.UNKNOWN;
 	public static Object STRING = ValueType.STRING;
 	public static Object BOOLEAN = ValueType.BOOLEAN;

flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatThemePreview.java

@@ -19,6 +19,7 @@ package com.formdev.flatlaf.themeeditor;
 
 import java.awt.*;
 import java.awt.event.HierarchyEvent;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.WeakHashMap;
 import java.util.prefs.Preferences;
@@ -28,6 +29,7 @@ import javax.swing.UIDefaults.LazyValue;
 import javax.swing.event.DocumentEvent;
 import javax.swing.event.DocumentListener;
 import com.formdev.flatlaf.FlatLaf;
+import com.formdev.flatlaf.UIDefaultsLoaderAccessor;
 import com.formdev.flatlaf.extras.components.*;
 
 /**
@@ -51,6 +53,7 @@ class FlatThemePreview
 	private final Map<LazyValue, Object> lazyValueCache = new WeakHashMap<>();
 	private int runWithUIDefaultsGetterLevel;
 	private boolean inGetDefaultFont;
+	private boolean inGetVariables;
 
 	FlatThemePreview( FlatSyntaxTextArea textArea ) {
 		this.textArea = textArea;
@@ -162,6 +165,7 @@ class FlatThemePreview
 		}
 	}
 
+	@SuppressWarnings( "unchecked" )
 	Object getUIDefaultProperty( Object key ) {
 		// avoid StackOverflowError because "defaultFont" value is an active value
 		// that itself uses UIManager.getFont( "defaultFont" ) to get base font
@@ -176,6 +180,19 @@ class FlatThemePreview
 		if( ((String)key).endsWith( "UI" ) )
 			return null;
 
+		// handle access to variables map, which is used in styles
+		if( UIDefaultsLoaderAccessor.KEY_VARIABLES.equals( key ) ) {
+			if( inGetVariables )
+				return null;
+
+			inGetVariables = true;
+			try {
+				return new VariablesDelegateMap( (Map<String, String>) UIManager.get( UIDefaultsLoaderAccessor.KEY_VARIABLES ) );
+			} finally {
+				inGetVariables = false;
+			}
+		}
+
 		Object value = textArea.propertiesSupport.getParsedProperty( (String) key );
 
 		boolean isDefaultFont = "defaultFont".equals( key );
@@ -341,4 +358,31 @@ class FlatThemePreview
 			}
 		}
 	}
+
+	//---- class VariablesDelegateMap -----------------------------------------
+
+	private class VariablesDelegateMap
+		extends HashMap<String, String>
+	{
+		private final Map<String, String> variables;
+
+		public VariablesDelegateMap( Map<String, String> variables ) {
+			this.variables = variables;
+		}
+
+		@Override
+		public String get( Object key ) {
+			String value = textArea.propertiesSupport.getProperty( (String) key );
+			if( value != null )
+				return value;
+
+			if( variables != null ) {
+				value = variables.get( key );
+				if( value != null )
+					return value;
+			}
+
+			return super.get( key );
+		}
+	}
 }

flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatThemePropertiesSupport.java

@@ -179,7 +179,7 @@ class FlatThemePropertiesSupport
 		return getProperty( wildcardKey );
 	}
 
-	private String getProperty( String key ) {
+	String getProperty( String key ) {
 		// look in current text area
 		String value = getProperties().getProperty( key );
 		if( value != null )

flatlaf-theme-editor/theme-editor-test.properties

@@ -117,3 +117,8 @@ Prop.6.selectionForeground = contrast($Prop.6.selectionBackground,#000,#fff)
 
 Prop.7.selectionBackground = #FF9500
 Prop.7.selectionForeground = contrast($Prop.7.selectionBackground,#000,#fff)
+
+
+
+@varStyle1 = #f0f
+[style].style1 = background: @varStyle1