UIDefaultsLoader: added changeHue(), changeSaturation(), changeLightness() and changeAlpha() color functions (inspired by Sass CSS color.change() function)

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

@@ -604,6 +604,10 @@ class UIDefaultsLoader
 				case "fadeout":		return parseColorHSLIncreaseDecrease( 3, false, params, resolver, reportError );
 				case "fade":		return parseColorFade( params, resolver, reportError );
 				case "spin":		return parseColorSpin( params, resolver, reportError );
+				case "changeHue":		return parseColorChange( 0, params, resolver, reportError );
+				case "changeSaturation":return parseColorChange( 1, params, resolver, reportError );
+				case "changeLightness":	return parseColorChange( 2, params, resolver, reportError );
+				case "changeAlpha":		return parseColorChange( 3, params, resolver, reportError );
 			}
 		} finally {
 			parseColorDepth--;
@@ -753,6 +757,36 @@ class UIDefaultsLoader
 		return parseFunctionBaseColor( colorStr, function, derived, resolver, reportError );
 	}
 
+	/**
+	 * Syntax: changeHue(color,value[,options]) or
+	 *         changeSaturation(color,value[,options]) or
+	 *         changeLightness(color,value[,options]) or
+	 *         changeAlpha(color,value[,options])
+	 *   - color: a color (e.g. #f00) or a color function
+	 *   - value: for hue: number of degrees; otherwise: percentage 0-100%
+	 *   - options: [derived]
+	 */
+	private static Object parseColorChange( int hslIndex,
+		List<String> params, Function<String, String> resolver, boolean reportError )
+	{
+		String colorStr = params.get( 0 );
+		int value = (hslIndex == 0)
+			? parseInteger( params.get( 1 ), true )
+			: parsePercentage( params.get( 1 ) );
+		boolean derived = false;
+
+		if( params.size() > 2 ) {
+			String options = params.get( 2 );
+			derived = options.contains( "derived" );
+		}
+
+		// create function
+		ColorFunction function = new ColorFunctions.HSLChange( hslIndex, value );
+
+		// parse base color, apply function and create derived color
+		return parseFunctionBaseColor( colorStr, function, derived, resolver, reportError );
+	}
+
 	private static Object parseFunctionBaseColor( String colorStr, ColorFunction function,
 		boolean derived, Function<String, String> resolver, boolean reportError )
 	{

flatlaf-core/src/main/java/com/formdev/flatlaf/util/ColorFunctions.java

@@ -145,7 +145,46 @@ public class ColorFunctions
 		}
 	}
 
-	//---- class HSLIncreaseDecrease ------------------------------------------
+	//---- class HSLChange ----------------------------------------------------
+
+	/**
+	 * Set the hue, saturation, luminance or alpha of a color.
+	 *
+	 * @since 1.6
+	 */
+	public static class HSLChange
+		implements ColorFunction
+	{
+		public final int hslIndex;
+		public final float value;
+
+		public HSLChange( int hslIndex, float value ) {
+			this.hslIndex = hslIndex;
+			this.value = value;
+		}
+
+		@Override
+		public void apply( float[] hsla ) {
+			hsla[hslIndex] = (hslIndex == 0)
+				? value % 360
+				: clamp( value );
+		}
+
+		@Override
+		public String toString() {
+			String name;
+			switch( hslIndex ) {
+				case 0: name = "changeHue"; break;
+				case 1: name = "changeSaturation"; break;
+				case 2: name = "changeLightness"; break;
+				case 3: name = "changeAlpha"; break;
+				default: throw new IllegalArgumentException();
+			}
+			return String.format( "%s(%.0f%s)", name, value, (hslIndex == 0 ? "" : "%") );
+		}
+	}
+
+	//---- class Fade ---------------------------------------------------------
 
 	/**
 	 * Set the alpha of a color.

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

@@ -355,8 +355,21 @@ class FlatCompletionProvider
 				"options", "(optional) [derived]" );
 			addFunction( "spin",
 				"color", colorParamDesc,
-				"angle", "number of degrees to rotate",
+				"angle", "number of degrees to rotate (0-360)",
 				"options", "(optional) [derived]" );
+
+			addFunction( "changeHue",
+				"color", colorParamDesc,
+				"angle", "number of degrees (0-360)",
+				"options", "(optional) [derived]" );
+			String[] hslChangeParams = {
+				"color", colorParamDesc,
+				"value", "0-100%",
+				"options", "(optional) [derived]"
+			};
+			addFunction( "changeSaturation", hslChangeParams );
+			addFunction( "changeLightness", hslChangeParams );
+			addFunction( "changeAlpha", hslChangeParams );
 		}
 
 		private void addFunction( String name, String... paramNamesAndDescs ) {

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

@@ -60,6 +60,14 @@ public class FlatThemeTokenMaker
 		tokenMap.put( "darken", TOKEN_FUNCTION );
 		tokenMap.put( "saturate", TOKEN_FUNCTION );
 		tokenMap.put( "desaturate", TOKEN_FUNCTION );
+		tokenMap.put( "fadein", TOKEN_FUNCTION );
+		tokenMap.put( "fadeout", TOKEN_FUNCTION );
+		tokenMap.put( "fade", TOKEN_FUNCTION );
+		tokenMap.put( "spin", TOKEN_FUNCTION );
+		tokenMap.put( "changeHue", TOKEN_FUNCTION );
+		tokenMap.put( "changeSaturation", TOKEN_FUNCTION );
+		tokenMap.put( "changeLightness", TOKEN_FUNCTION );
+		tokenMap.put( "changeAlpha", TOKEN_FUNCTION );
 		tokenMap.put( "lazy", TOKEN_FUNCTION );
 
 		// function options

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

@@ -49,3 +49,8 @@ Prop.colorFunc13 = spin($Prop.colorFunc12,40)
 Prop.colorFunc14 = spin($Prop.colorFunc12,-40)
 Prop.colorFunc15 = spin($Prop.colorFunc12,400)
 Prop.colorFunc16 = spin($Prop.colorFunc12,-400)
+
+Prop.colorFunc20 = changeHue(#f00,180)
+Prop.colorFunc21 = changeSaturation(#f00,50%)
+Prop.colorFunc22 = changeLightness(#f00,80%)
+Prop.colorFunc23 = changeAlpha(#f00,50%)