CheckBox and RadioButton:

- fixed styling of custom icon
- fixed focus width (and preferred size) if using custom icon
- added unit tests

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

@@ -203,16 +203,12 @@ public class FlatRadioButtonUI
 	protected Object applyStyleProperty( AbstractButton b, String key, Object value ) {
 		// style icon
 		if( key.startsWith( "icon." ) ) {
-			Icon styleIcon = b.getIcon();
+			Icon icon = getRealIcon( b );
-
+			if( !(icon instanceof FlatCheckBoxIcon) )
-			if (styleIcon == null)
-				styleIcon = icon;
-
-			if( !(styleIcon instanceof FlatCheckBoxIcon) )
 				return new UnknownStyleException( key );
 
-            if( styleIcon == icon && iconShared ) {
+			if( icon == this.icon && iconShared ) {
-				icon = FlatStylingSupport.cloneIcon( icon );
+				this.icon = icon = FlatStylingSupport.cloneIcon( icon );
 				iconShared = false;
 			}
 
@@ -230,6 +226,7 @@ public class FlatRadioButtonUI
 	@Override
 	public Map<String, Class<?>> getStyleableInfos( JComponent c ) {
 		Map<String, Class<?>> infos = FlatStylingSupport.getAnnotatedStyleableInfos( this );
+		Icon icon = getRealIcon( c );
 		if( icon instanceof FlatCheckBoxIcon ) {
 			for( Map.Entry<String, Class<?>> e : ((FlatCheckBoxIcon)icon).getStyleableInfos().entrySet() )
 				infos.put( "icon.".concat( e.getKey() ), e.getValue() );
@@ -242,6 +239,7 @@ public class FlatRadioButtonUI
 	public Object getStyleableValue( JComponent c, String key ) {
 		// style icon
 		if( key.startsWith( "icon." ) ) {
+			Icon icon = getRealIcon( c );
 			return (icon instanceof FlatCheckBoxIcon)
 				? ((FlatCheckBoxIcon)icon).getStyleableValue( key.substring( "icon.".length() ) )
 				: null;
@@ -337,16 +335,18 @@ public class FlatRadioButtonUI
 	}
 
 	private int getIconFocusWidth( JComponent c ) {
-		AbstractButton b = (AbstractButton) c;
+		Icon icon = getRealIcon( c );
-		Icon icon = b.getIcon();
-		if( icon == null )
-			icon = getDefaultIcon();
-
 		return (icon instanceof FlatCheckBoxIcon)
 			? Math.round( UIScale.scale( ((FlatCheckBoxIcon)icon).getFocusWidth() ) )
 			: 0;
 	}
 
+	private Icon getRealIcon( JComponent c ) {
+		AbstractButton b = (AbstractButton) c;
+		Icon icon = b.getIcon();
+		return (icon != null) ? icon : getDefaultIcon();
+	}
+
 	@Override
 	public int getBaseline( JComponent c, int width, int height ) {
 		return FlatButtonUI.getBaselineImpl( c, width, height );

flatlaf-core/src/test/java/com/formdev/flatlaf/ui/TestFlatStyleableInfo.java

@@ -30,6 +30,9 @@ import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 import com.formdev.flatlaf.icons.*;
+import com.formdev.flatlaf.ui.TestFlatStyling.CustomCheckBoxIcon;
+import com.formdev.flatlaf.ui.TestFlatStyling.CustomIcon;
+import com.formdev.flatlaf.ui.TestFlatStyling.CustomRadioButtonIcon;
 
 /**
  * @author Karl Tauber
@@ -144,7 +147,12 @@ public class TestFlatStyleableInfo
 
 	@Test
 	void checkBox() {
-		JCheckBox c = new JCheckBox();
+		checkBox( new JCheckBox() );
+		checkBox( new JCheckBox( new CustomIcon() ) );
+		checkBox( new JCheckBox( new CustomCheckBoxIcon() ) );
+	}
+
+	private void checkBox( JCheckBox c ) {
 		FlatCheckBoxUI ui = (FlatCheckBoxUI) c.getUI();
 
 		assertTrue( ui.getDefaultIcon() instanceof FlatCheckBoxIcon );
@@ -153,6 +161,11 @@ public class TestFlatStyleableInfo
 		Map<String, Class<?>> expected = new LinkedHashMap<>();
 		radioButton( expected );
 
+		// remove "icon." keys if check box has custom icon
+		Icon icon = c.getIcon();
+		if( icon != null && !(icon instanceof FlatCheckBoxIcon) )
+			expected.keySet().removeIf( key -> key.startsWith( "icon." ) );
+
 		assertMapEquals( expected, ui.getStyleableInfos( c ) );
 	}
 
@@ -492,7 +505,12 @@ public class TestFlatStyleableInfo
 
 	@Test
 	void radioButton() {
-		JRadioButton c = new JRadioButton();
+		radioButton( new JRadioButton() );
+		radioButton( new JRadioButton( new CustomIcon() ) );
+		radioButton( new JRadioButton( new CustomRadioButtonIcon() ) );
+	}
+
+	private void radioButton( JRadioButton c ) {
 		FlatRadioButtonUI ui = (FlatRadioButtonUI) c.getUI();
 
 		assertTrue( ui.getDefaultIcon() instanceof FlatRadioButtonIcon );
@@ -504,6 +522,11 @@ public class TestFlatStyleableInfo
 			"icon.centerDiameter", float.class
 		);
 
+		// remove "icon." keys if radio button has custom icon
+		Icon icon = c.getIcon();
+		if( icon != null && !(icon instanceof FlatRadioButtonIcon) )
+			expected.keySet().removeIf( key -> key.startsWith( "icon." ) );
+
 		assertMapEquals( expected, ui.getStyleableInfos( c ) );
 	}
 

flatlaf-core/src/test/java/com/formdev/flatlaf/ui/TestFlatStyleableValue.java

@@ -77,6 +77,9 @@ import com.formdev.flatlaf.icons.FlatRadioButtonMenuItemIcon;
 import com.formdev.flatlaf.icons.FlatSearchIcon;
 import com.formdev.flatlaf.icons.FlatSearchWithHistoryIcon;
 import com.formdev.flatlaf.ui.FlatStylingSupport.StyleableUI;
+import com.formdev.flatlaf.ui.TestFlatStyling.CustomCheckBoxIcon;
+import com.formdev.flatlaf.ui.TestFlatStyling.CustomIcon;
+import com.formdev.flatlaf.ui.TestFlatStyling.CustomRadioButtonIcon;
 
 /**
  * @author Karl Tauber
@@ -269,11 +272,20 @@ public class TestFlatStyleableValue
 
 	@Test
 	void checkBox() {
-		JCheckBox c = new JCheckBox();
+		checkBox( new JCheckBox() );
+		checkBox( new JCheckBox( new CustomCheckBoxIcon() ) );
+		checkBox( new JCheckBox( new CustomIcon() ) );
+	}
+
+	private void checkBox( JCheckBox c ) {
 		FlatCheckBoxUI ui = (FlatCheckBoxUI) c.getUI();
 
 		// FlatCheckBoxUI extends FlatRadioButtonUI
 		radioButton( ui, c );
+
+		// necessary to clear FlatRadioButtonUI.oldStyleValues because
+		// ui.applyStyle(...) operates on shared instance
+		ui.uninstallUI( c );
 	}
 
 	@Test
@@ -536,14 +548,24 @@ public class TestFlatStyleableValue
 
 	@Test
 	void radioButton() {
-		JRadioButton c = new JRadioButton();
+		radioButton( new JRadioButton() );
+		radioButton( new JRadioButton( new CustomRadioButtonIcon() ) );
+		radioButton( new JRadioButton( new CustomIcon() ) );
+	}
+
+	private void radioButton( JRadioButton c ) {
 		FlatRadioButtonUI ui = (FlatRadioButtonUI) c.getUI();
 
 		assertTrue( ui.getDefaultIcon() instanceof FlatRadioButtonIcon );
 
 		radioButton( ui, c );
 
-		testFloat( c, ui, "icon.centerDiameter", 1.23f );
+		if( !(c.getIcon() instanceof CustomIcon) )
+			testFloat( c, ui, "icon.centerDiameter", 1.23f );
+
+		// necessary to clear FlatRadioButtonUI.oldStyleValues because
+		// ui.applyStyle(...) operates on shared instance
+		ui.uninstallUI( c );
 	}
 
 	private void radioButton( FlatRadioButtonUI ui, AbstractButton b ) {
@@ -551,6 +573,11 @@ public class TestFlatStyleableValue
 
 		//---- icon ----
 
+		if( b.getIcon() instanceof CustomIcon ) {
+			assertEquals( null, ui.getStyleableValue( b, "icon.focusWidth" ) );
+			return;
+		}
+
 		testFloat( b, ui, "icon.focusWidth", 1.23f );
 		testColor( b, ui, "icon.focusColor", 0x123456 );
 		testFloat( b, ui, "icon.borderWidth", 1.23f );

flatlaf-core/src/test/java/com/formdev/flatlaf/ui/TestFlatStyling.java

@@ -19,7 +19,9 @@ package com.formdev.flatlaf.ui;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import java.awt.Color;
+import java.awt.Component;
 import java.awt.Dimension;
+import java.awt.Graphics;
 import java.awt.Insets;
 import java.util.HashMap;
 import java.util.Map;
@@ -294,13 +296,22 @@ public class TestFlatStyling
 
 	@Test
 	void checkBox() {
-		JCheckBox c = new JCheckBox();
+		checkBox( new JCheckBox() );
+		checkBox( new JCheckBox( new CustomIcon() ) );
+		checkBox( new JCheckBox( new CustomCheckBoxIcon() ) );
+	}
+
+	private void checkBox( JCheckBox c ) {
 		FlatCheckBoxUI ui = (FlatCheckBoxUI) c.getUI();
 
 		assertTrue( ui.getDefaultIcon() instanceof FlatCheckBoxIcon );
 
 		// FlatCheckBoxUI extends FlatRadioButtonUI
 		radioButton( ui, c );
+
+		// necessary to clear FlatRadioButtonUI.oldStyleValues because
+		// ui.applyStyle(...) operates on shared instance
+		ui.uninstallUI( c );
 	}
 
 	@Test
@@ -651,14 +662,24 @@ public class TestFlatStyling
 
 	@Test
 	void radioButton() {
-		JRadioButton c = new JRadioButton();
+		radioButton( new JRadioButton() );
+		radioButton( new JRadioButton( new CustomIcon() ) );
+		radioButton( new JRadioButton( new CustomRadioButtonIcon() ) );
+	}
+
+	private void radioButton( JRadioButton c ) {
 		FlatRadioButtonUI ui = (FlatRadioButtonUI) c.getUI();
 
 		assertTrue( ui.getDefaultIcon() instanceof FlatRadioButtonIcon );
 
 		radioButton( ui, c );
 
-		ui.applyStyle( c, "icon.centerDiameter: 8" );
+		if( !(c.getIcon() instanceof CustomIcon) )
+			ui.applyStyle( c, "icon.centerDiameter: 8" );
+
+		// necessary to clear FlatRadioButtonUI.oldStyleValues because
+		// ui.applyStyle(...) operates on shared instance
+		ui.uninstallUI( c );
 	}
 
 	private void radioButton( FlatRadioButtonUI ui, AbstractButton b ) {
@@ -676,6 +697,9 @@ public class TestFlatStyling
 
 		//---- icon ----
 
+		if( b.getIcon() instanceof CustomIcon )
+			return;
+
 		ui.applyStyle( b, "icon.focusWidth: 1.5" );
 		ui.applyStyle( b, "icon.focusColor: #fff" );
 		ui.applyStyle( b, "icon.borderWidth: 1.5" );
@@ -1565,4 +1589,34 @@ public class TestFlatStyling
 		UIManager.put( "test.enum", null );
 		assertEquals( SomeEnum.enumValue1, FlatUIUtils.getUIEnum( "test.enum", SomeEnum.class, SomeEnum.enumValue1 ) );
 	}
+
+	//---- class CustomIcon ---------------------------------------------------
+
+	static class CustomIcon
+		implements Icon
+	{
+		@Override public void paintIcon( Component c, Graphics g, int x, int y ) {}
+		@Override public int getIconWidth() { return 1; }
+		@Override public int getIconHeight() { return 1; }
+	}
+
+	//---- class CustomCheckBoxIcon ----------------------------------------
+
+	static class CustomCheckBoxIcon
+		extends FlatCheckBoxIcon
+	{
+		CustomCheckBoxIcon() {
+			background = Color.green;
+		}
+	}
+
+	//---- class CustomRadioButtonIcon ----------------------------------------
+
+	static class CustomRadioButtonIcon
+		extends FlatRadioButtonIcon
+	{
+		CustomRadioButtonIcon() {
+			background = Color.green;
+		}
+	}
 }