Panel: support painting background with rounded corners (issue #367)

FlatLineBorder: support rounded corners

CHANGELOG.md

@@ -64,6 +64,7 @@ FlatLaf Change Log
 - MenuItem:
   - Paint the selected icon when the item is selected. (PR #415)
   - Vertically align text if icons have different widths. (issue #437)
+- Panel: Support painting background with rounded corners. (issue #367)
 - Added more color functions to class `ColorFunctions` for easy use in
   applications: `lighten()`, `darken()`, `saturate()`, `desaturate()`, `spin()`,
   `tint()`, `shade()` and `luma()`.

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

@@ -582,17 +582,18 @@ class UIDefaultsLoader
 
 	private static Object parseBorder( String value, Function<String, String> resolver, List<ClassLoader> addonClassLoaders ) {
 		if( value.indexOf( ',' ) >= 0 ) {
-			// top,left,bottom,right[,lineColor[,lineThickness]]
+			// top,left,bottom,right[,lineColor[,lineThickness[,arc]]]
 			List<String> parts = splitFunctionParams( value, ',' );
 			Insets insets = parseInsets( value );
 			ColorUIResource lineColor = (parts.size() >= 5)
 				? (ColorUIResource) parseColorOrFunction( resolver.apply( parts.get( 4 ) ), resolver, true )
 				: null;
-			float lineThickness = (parts.size() >= 6) ? parseFloat( parts.get( 5 ), true ) : 1f;
+			float lineThickness = (parts.size() >= 6 && !parts.get( 5 ).isEmpty()) ? parseFloat( parts.get( 5 ), true ) : 1f;
+			int arc = (parts.size() >= 7) ? parseInteger( parts.get( 6 ), true ) : 0;
 
 			return (LazyValue) t -> {
 				return (lineColor != null)
-					? new FlatLineBorder( insets, lineColor, lineThickness )
+					? new FlatLineBorder( insets, lineColor, lineThickness, arc )
 					: new FlatEmptyBorder( insets );
 			};
 		} else

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

@@ -37,15 +37,18 @@ public class FlatLineBorder
 {
 	private final Color lineColor;
 	private final float lineThickness;
+	/** @since 2 */ private final int arc;
 
 	public FlatLineBorder( Insets insets, Color lineColor ) {
-		this( insets, lineColor, 1f );
+		this( insets, lineColor, 1f, 0 );
 	}
 
-	public FlatLineBorder( Insets insets, Color lineColor, float lineThickness ) {
+	/** @since 2 */
+	public FlatLineBorder( Insets insets, Color lineColor, float lineThickness, int arc ) {
 		super( insets );
 		this.lineColor = lineColor;
 		this.lineThickness = lineThickness;
+		this.arc = arc;
 	}
 
 	public Color getLineColor() {
@@ -56,13 +59,18 @@ public class FlatLineBorder
 		return lineThickness;
 	}
 
+	/** @since 2 */
+	public int getArc() {
+		return arc;
+	}
+
 	@Override
 	public void paintBorder( Component c, Graphics g, int x, int y, int width, int height ) {
 		Graphics2D g2 = (Graphics2D) g.create();
 		try {
 			FlatUIUtils.setRenderingHints( g2 );
 			FlatUIUtils.paintOutlinedComponent( g2, x, y, width, height,
-				0, 0, 0, scale( getLineThickness() ), 0, null, getLineColor(), null );
+				0, 0, 0, scale( getLineThickness() ), scale( getArc() ), null, getLineColor(), null );
 		} finally {
 			g2.dispose();
 		}

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

@@ -16,14 +16,18 @@
 
 package com.formdev.flatlaf.ui;
 
+import java.awt.Graphics;
+import java.awt.Graphics2D;
 import java.beans.PropertyChangeListener;
 import java.util.Map;
 import javax.swing.JComponent;
 import javax.swing.JPanel;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicPanelUI;
+import com.formdev.flatlaf.ui.FlatStylingSupport.Styleable;
 import com.formdev.flatlaf.ui.FlatStylingSupport.StyleableUI;
 import com.formdev.flatlaf.util.LoggingFacade;
+import com.formdev.flatlaf.util.UIScale;
 
 /**
  * Provides the Flat LaF UI delegate for {@link javax.swing.JPanel}.
@@ -32,7 +36,7 @@ import com.formdev.flatlaf.util.LoggingFacade;
  *
  * @uiDefault Panel.font				Font	unused
  * @uiDefault Panel.background			Color	only used if opaque
- * @uiDefault Panel.foreground			Color
+ * @uiDefault Panel.foreground			Color	unused
  * @uiDefault Panel.border				Border
  *
  * @author Karl Tauber
@@ -41,6 +45,9 @@ public class FlatPanelUI
 	extends BasicPanelUI
 	implements StyleableUI
 {
+	// only used via styling (not in UI defaults)
+	/** @since 2 */ @Styleable protected int arc = -1;
+
 	private final boolean shared;
 	private PropertyChangeListener propertyChangeListener;
 	private Map<String, Object> oldStyleValues;
@@ -113,4 +120,34 @@ public class FlatPanelUI
 	public Map<String, Class<?>> getStyleableInfos( JComponent c ) {
 		return FlatStylingSupport.getAnnotatedStyleableInfos( this );
 	}
+
+	@Override
+	public void update( Graphics g, JComponent c ) {
+		// fill background
+		if( c.isOpaque() ) {
+			int width = c.getWidth();
+			int height = c.getHeight();
+			int arc = (this.arc >= 0)
+				? this.arc
+				: ((c.getBorder() instanceof FlatLineBorder)
+					? ((FlatLineBorder)c.getBorder()).getArc()
+					: 0);
+
+			// fill background with parent color to avoid garbage in rounded corners
+			if( arc > 0 )
+				FlatUIUtils.paintParentBackground( g, c );
+
+			g.setColor( c.getBackground() );
+			if( arc > 0 ) {
+				// fill rounded rectangle if having rounded corners
+				Object[] oldRenderingHints = FlatUIUtils.setRenderingHints( g );
+				FlatUIUtils.paintComponentBackground( (Graphics2D) g, 0, 0, width, height,
+					0, UIScale.scale( arc ) );
+				FlatUIUtils.resetRenderingHints( g, oldRenderingHints );
+			} else
+				g.fillRect( 0, 0, width, height );
+		}
+
+		paint( g, c );
+	}
 }

flatlaf-core/src/test/java/com/formdev/flatlaf/TestUIDefaultsLoader.java

@@ -22,8 +22,12 @@ import java.awt.Dimension;
 import java.awt.Font;
 import java.awt.Insets;
 import javax.swing.UIManager;
+import javax.swing.border.Border;
 import javax.swing.UIDefaults.ActiveValue;
+import javax.swing.UIDefaults.LazyValue;
 import org.junit.jupiter.api.Test;
+import com.formdev.flatlaf.ui.FlatEmptyBorder;
+import com.formdev.flatlaf.ui.FlatLineBorder;
 
 /**
  * @author Karl Tauber
@@ -46,8 +50,8 @@ public class TestUIDefaultsLoader
 		assertEquals( 1.23f, UIDefaultsLoader.parseValue( "dummy", "1.23", null ) );
 		assertEquals( 1.23f, UIDefaultsLoader.parseValue( "dummyWidth", "1.23", null ) );
 
-		assertEquals( new Insets( 2,2,2,2 ), UIDefaultsLoader.parseValue( "dummyInsets", "2,2,2,2", null ) );
+		assertEquals( new Insets( 1,2,3,4 ), UIDefaultsLoader.parseValue( "dummyInsets", "1,2,3,4", null ) );
-		assertEquals( new Dimension( 2,2 ), UIDefaultsLoader.parseValue( "dummySize", "2,2", null ) );
+		assertEquals( new Dimension( 1,2 ), UIDefaultsLoader.parseValue( "dummySize", "1,2", null ) );
 		assertEquals( new Color( 0xff0000 ), UIDefaultsLoader.parseValue( "dummy", "#f00", null ) );
 		assertEquals( new Color( 0xff0000 ), UIDefaultsLoader.parseValue( "dummyColor", "#f00", null ) );
 	}
@@ -70,11 +74,35 @@ public class TestUIDefaultsLoader
 		assertEquals( 1.23f, UIDefaultsLoader.parseValue( "dummy", "1.23", float.class ) );
 		assertEquals( 1.23f, UIDefaultsLoader.parseValue( "dummy", "1.23", Float.class ) );
 
-		assertEquals( new Insets( 2,2,2,2 ), UIDefaultsLoader.parseValue( "dummy", "2,2,2,2", Insets.class ) );
+		assertEquals( new Insets( 1,2,3,4 ), UIDefaultsLoader.parseValue( "dummy", "1,2,3,4", Insets.class ) );
-		assertEquals( new Dimension( 2,2 ), UIDefaultsLoader.parseValue( "dummy", "2,2", Dimension.class ) );
+		assertEquals( new Dimension( 1,2 ), UIDefaultsLoader.parseValue( "dummy", "1,2", Dimension.class ) );
 		assertEquals( new Color( 0xff0000 ), UIDefaultsLoader.parseValue( "dummy", "#f00", Color.class ) );
 	}
 
+	@Test
+	void parseBorders() {
+		Insets insets = new Insets( 1,2,3,4 );
+		assertBorderEquals( new FlatEmptyBorder( insets ), "1,2,3,4" );
+		assertBorderEquals( new FlatLineBorder( insets, Color.red ), "1,2,3,4,#f00" );
+		assertBorderEquals( new FlatLineBorder( insets, Color.red, 2.5f, 0 ), "1,2,3,4,#f00,2.5" );
+		assertBorderEquals( new FlatLineBorder( insets, Color.red, 2.5f, 6 ), "1,2,3,4,#f00,2.5,6" );
+		assertBorderEquals( new FlatLineBorder( insets, Color.red, 1, 6 ), "1,2,3,4,#f00,,6" );
+	}
+
+	private void assertBorderEquals( Border expected, String actualStyle ) {
+		Border actual = (Border) ((LazyValue)UIDefaultsLoader.parseValue( "dummyBorder", actualStyle, null )).createValue( null );
+		assertEquals( expected.getClass(), actual.getClass() );
+		if( expected instanceof FlatEmptyBorder )
+			assertEquals( ((FlatEmptyBorder)actual).getBorderInsets(), ((FlatEmptyBorder)expected).getBorderInsets() );
+		if( expected instanceof FlatLineBorder ) {
+			FlatLineBorder a = (FlatLineBorder) actual;
+			FlatLineBorder e = (FlatLineBorder) expected;
+			assertEquals( a.getLineColor(), e.getLineColor() );
+			assertEquals( a.getLineThickness(), e.getLineThickness() );
+			assertEquals( a.getArc(), e.getArc() );
+		}
+	}
+
 	@Test
 	void parseFonts() {
 		// style

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

@@ -386,6 +386,7 @@ public class TestFlatStyleableInfo
 		FlatPanelUI ui = (FlatPanelUI) c.getUI();
 
 		Map<String, Class<?>> expected = expectedMap(
+			"arc", int.class
 		);
 
 		assertMapEquals( expected, ui.getStyleableInfos( c ) );

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

@@ -529,6 +529,8 @@ public class TestFlatStyling
 		JPanel c = new JPanel();
 		FlatPanelUI ui = (FlatPanelUI) c.getUI();
 
+		ui.applyStyle( c, "arc: 8" );
+
 		// JComponent properties
 		ui.applyStyle( c, "background: #fff" );
 		ui.applyStyle( c, "foreground: #fff" );

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

@@ -194,7 +194,7 @@ class FlatColorPipette
 
 			zoom = UIScale.scale( 16 );
 
-			getRootPane().setBorder( new FlatLineBorder( new Insets( 2, 2, 2, 2 ), Color.red, 2 ) );
+			getRootPane().setBorder( new FlatLineBorder( new Insets( 2, 2, 2, 2 ), Color.red, 2, 0 ) );
 
 			view = new MagnifierView();
 			view.setPreferredSize( new Dimension( pixels * zoom, pixels * zoom ) );