Styling: support using java.util.Map as style

e.g. `mySlider.putClientProperty( "JComponent.style", Collections.singletonMap( "thumbSize", new Dimension( 8, 24 ) ) );`

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

@@ -130,7 +130,7 @@ public interface FlatClientProperties
 	 * Specifies the style of a component in CSS syntax ("key1: value1; key2: value2; ...").
 	 * <p>
 	 * <strong>Components</strong> {@link javax.swing.JComponent}<br>
-	 * <strong>Value type</strong> {@link java.lang.String}<br>
+	 * <strong>Value type</strong> {@link java.lang.String} or {@link java.util.Map}&lt;String, Object&gt;<br>
 	 *
 	 * @since TODO
 	 */

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatSliderUI.java

@@ -190,7 +190,7 @@ public class FlatSliderUI
 
 			switch( e.getPropertyName() ) {
 				case FlatClientProperties.COMPONENT_STYLE:
-					applyStyle( FlatStyleSupport.toString( e.getNewValue() ) );
+					applyStyle( e.getNewValue() );
 					slider.revalidate();
 					slider.repaint();
 					break;
@@ -201,8 +201,8 @@ public class FlatSliderUI
 	/**
 	 * @since TODO
 	 */
-	protected void applyStyle( String style ) {
+	protected void applyStyle( Object style ) {
-		oldStyleValues = FlatStyleSupport.parse( oldStyleValues, style, this::applyStyleProperty );
+		oldStyleValues = FlatStyleSupport.parseAndApply( oldStyleValues, style, this::applyStyleProperty );
 	}
 
 	/**

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatStyleSupport.java

@@ -17,8 +17,8 @@
 package com.formdev.flatlaf.ui;
 
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.function.BiFunction;
 import javax.swing.JComponent;
 import javax.swing.UIManager;
@@ -40,7 +40,7 @@ public class FlatStyleSupport
 	 * to apply the properties.
 	 *
 	 * @param oldStyleValues map of old values modified by the previous invocation, or {@code null}
-	 * @param style the style in CSS syntax
+	 * @param style the style in CSS syntax as string, or a Map, or {@code null}
 	 * @param applyProperty function that is invoked to apply the properties;
 	 *                      first parameter is the key, second the binary value;
 	 *                      the function must return the old value
@@ -48,20 +48,67 @@ public class FlatStyleSupport
 	 * @throws IllegalArgumentException on syntax errors
 	 * @throws ClassCastException if value type does not fit to expected type 
 	 */
-	public static Map<String, Object> parse( Map<String, Object> oldStyleValues,
+	public static Map<String, Object> parseAndApply( Map<String, Object> oldStyleValues,
-		String style, BiFunction<String, Object, Object> applyProperty ) throws IllegalArgumentException
+		Object style, BiFunction<String, Object, Object> applyProperty ) throws IllegalArgumentException
 	{
 		// restore previous values
 		if( oldStyleValues != null ) {
-			for( Entry<String, Object> e : oldStyleValues.entrySet() )
+			for( Map.Entry<String, Object> e : oldStyleValues.entrySet() )
 				applyProperty.apply( e.getKey(), e.getValue() );
 		}
 
 		// ignore empty style
+		if( style == null )
+			return null;
+
+		if( style instanceof String ) {
+			// handle style in CSS syntax
+			String str = (String) style;
+			if( str.trim().isEmpty() )
+				return null;
+
+			return applyStyle( parse( str ), applyProperty );
+		} else if( style instanceof Map ) {
+			// handle style of type Map
+			@SuppressWarnings( "unchecked" )
+			Map<String, Object> map = (Map<String, Object>) style;
+			return applyStyle( map, applyProperty );
+		} else
+			return null;
+	}
+
+	private static Map<String, Object> applyStyle( Map<String, Object> style,
+		BiFunction<String, Object, Object> applyProperty )
+	{
+		if( style.isEmpty() )
+			return null;
+
+		Map<String, Object> oldValues = new HashMap<>();
+		for( Map.Entry<String, Object> e : style.entrySet() ) {
+			String key = e.getKey();
+			Object newValue = e.getValue();
+
+			Object oldValue = applyProperty.apply( key, newValue );
+			oldValues.put( key, oldValue );
+		}
+		return oldValues;
+	}
+
+	/**
+	 * Parses styles in CSS syntax ("key1: value1; key2: value2; ..."),
+	 * converts the value strings into binary and returns all key/value pairs as map.
+	 *
+	 * @param style the style in CSS syntax, or {@code null}
+	 * @return map of parsed styles, or {@code null}
+	 * @throws IllegalArgumentException on syntax errors
+	 */
+	public static Map<String, Object> parse( String style )
+		throws IllegalArgumentException
+	{
 		if( style == null || style.trim().isEmpty() )
 			return null;
 
-		Map<String, Object> oldValues = null;
+		Map<String, Object> map = new LinkedHashMap<>();
 
 		// split style into parts and process them
 		for( String part : StringUtils.split( style, ';' ) ) {
@@ -84,16 +131,10 @@ public class FlatStyleSupport
 				throw new IllegalArgumentException( "missing value in '" + part + "'" );
 
 			// parse value string and convert it into binary value
-			Object newValue = parseValue( key, value );
+			map.put( key, parseValue( key, value ) );
-			Object oldValue = applyProperty.apply( key, newValue );
-
-			// remember previous value
-			if( oldValues == null )
-				oldValues = new HashMap<>();
-			oldValues.put( key, oldValue );
 		}
 
-		return oldValues;
+		return map;
 	}
 
 	private static Object parseValue( String key, String value ) {
@@ -107,11 +148,7 @@ public class FlatStyleSupport
 		return getStyle( c ) != null;
 	}
 
-	public static String getStyle( JComponent c ) {
+	public static Object getStyle( JComponent c ) {
-		return toString( c.getClientProperty( FlatClientProperties.COMPONENT_STYLE ) );
+		return c.getClientProperty( FlatClientProperties.COMPONENT_STYLE );
-	}
-
-	static String toString( Object style ) {
-		return (style instanceof String) ? (String) style : null;
 	}
 }