AnimatedBorder:

- support repainting only necessary region while animating
- use AbstractBorder in test app and fixed insets

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

@@ -65,6 +65,7 @@
  * A client property is set on the component to store the animation state.
  *
  * @author Karl Tauber
+ * @since 1.5
  */
 public interface AnimatedBorder
 	extends Border
@@ -89,6 +90,20 @@ default void paintBorder( Component c, Graphics g, int x, int y, int width, int
 	 */
 	void paintBorderAnimated( Component c, Graphics g, int x, int y, int width, int height, float animatedValue );
 
+	/**
+	 * Repaint the animated part of the border.
+	 * <p>
+	 * Useful to limit the repaint region. E.g. if only the bottom border is animated.
+	 * If more than one border side is animated (e.g. bottom and right side), then it
+	 * makes no sense to do separate repaints because the Swing repaint manager unions
+	 * the regions and the whole component is repainted.
+	 * <p>
+	 * The default implementation repaints the whole component.
+	 */
+	default void repaintBorder( Component c, int x, int y, int width, int height ) {
+		c.repaint( x, y, width, height );
+	}
+
 	/**
 	 * Gets the value of the component.
 	 * <p>
@@ -197,7 +212,7 @@ public static void paintBorder( AnimatedBorder border, Component c, Graphics g,
 							as2.fraction = fraction;
 
 							// repaint border
-							c.repaint( as2.x, as2.y, as2.width, as2.height );
+							border.repaintBorder( c, as2.x, as2.y, as2.width, as2.height );
 						}, () -> {
 							as2.startValue = as2.animatedValue = as2.targetValue;
 							as2.animator = null;

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatAnimatedBorderTest.java

@@ -23,7 +23,7 @@
 import java.awt.Insets;
 import java.awt.geom.Rectangle2D;
 import javax.swing.*;
-import com.formdev.flatlaf.ui.FlatMarginBorder;
+import javax.swing.border.AbstractBorder;
 import com.formdev.flatlaf.ui.FlatUIUtils;
 import com.formdev.flatlaf.util.AnimatedBorder;
 import com.formdev.flatlaf.util.ColorFunctions;
@@ -133,7 +133,7 @@ private void initComponents() {
 	 * - animates focus indicator color and border width
 	 */
 	private class AnimatedFocusFadeBorder
-		extends FlatMarginBorder
+		extends AbstractBorder
 		implements AnimatedBorder
 	{
 		// needed because otherwise the empty paint method in superclass
@@ -155,6 +155,13 @@ public void paintBorderAnimated( Component c, Graphics g, int x, int y, int widt
 			FlatUIUtils.paintComponentBorder( (Graphics2D) g, x, y, width, height, 0, lw, 0 );
 		}
 
+		@Override
+		public Insets getBorderInsets( Component c, Insets insets ) {
+			insets.top = insets.bottom = UIScale.scale( 3 );
+			insets.left = insets.right = UIScale.scale( 7 );
+			return insets;
+		}
+
 		@Override
 		public float getValue( Component c ) {
 			return FlatUIUtils.isPermanentFocusOwner( c ) ? 1 : 0;
@@ -174,7 +181,7 @@ public int getAnimationDuration() {
 	 * - animates focus indicator at bottom
 	 */
 	private class AnimatedMaterialBorder
-		extends FlatMarginBorder
+		extends AbstractBorder
 		implements AnimatedBorder
 	{
 		// needed because otherwise the empty paint method in superclass
@@ -206,6 +213,20 @@ public void paintBorderAnimated( Component c, Graphics g, int x, int y, int widt
 				} );
 		}
 
+		@Override
+		public void repaintBorder( Component c, int x, int y, int width, int height ) {
+			// limit repaint to bottom border
+			int lh = UIScale.scale( 2 );
+			c.repaint( x, y + height - lh, width, lh );
+		}
+
+		@Override
+		public Insets getBorderInsets( Component c, Insets insets ) {
+			insets.top = insets.bottom = UIScale.scale( 3 );
+			insets.left = insets.right = UIScale.scale( 7 );
+			return insets;
+		}
+
 		@Override
 		public float getValue( Component c ) {
 			return FlatUIUtils.isPermanentFocusOwner( c ) ? 1 : 0;
@@ -245,7 +266,7 @@ public int getAnimationDuration() {
 
 		@Override
 		public Insets getBorderInsets( Component c ) {
-			return UIScale.scale( new Insets( 4, 4, 4, 4 ) );
+			return UIScale.scale( new Insets( 3, 7, 3, 7 ) );
 		}
 
 		@Override