From 212ae90401be3f4c8cef5c97c6ae596d4048c864 Mon Sep 17 00:00:00 2001
From: Karl Tauber <karl@jformdesigner.com>
Date: Sat, 30 Jan 2021 17:54:47 +0100
Subject: [PATCH] client property "JComponent.focusOwner" added to allow
 customizing detection of focused state (issue #185)

---
 .../formdev/flatlaf/FlatClientProperties.java | 19 +++++++++++++++++++
 .../com/formdev/flatlaf/ui/FlatUIUtils.java   | 11 +++++++++++
 2 files changed, 30 insertions(+)

diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java
index 17d16c40..d03e5ae2 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java
@@ -172,6 +172,25 @@ public interface FlatClientProperties
 	 */
 	String OUTLINE_WARNING = "warning";
 
+	/**
+	 * Specifies a callback that is invoked to check whether a component is permanent focus owner.
+	 * Used to paint focus indicators.
+	 * <p>
+	 * May be useful in special cases for custom components.
+	 * <p>
+	 * Use a {@link java.util.function.Predicate} that receives the component as parameter:
+	 * <pre>{@code
+	 * myComponent.putClientProperty( "JComponent.focusOwner",
+	 *     (Predicate) c -> {
+	 *         return ...; // check here
+	 *     } );
+	 * }</pre>
+	 * <p>
+	 * <strong>Component</strong> {@link javax.swing.JComponent}<br>
+	 * <strong>Value type</strong> {@link java.util.function.Predicate&lt;javax.swing.JComponent&gt;
+	 */
+	String COMPONENT_FOCUS_OWNER = "JComponent.focusOwner";
+
 	//---- Popup --------------------------------------------------------------
 
 	/**
diff --git a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatUIUtils.java b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatUIUtils.java
index 58693238..1f49eb93 100644
--- a/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatUIUtils.java
+++ b/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatUIUtils.java
@@ -39,6 +39,7 @@ import java.awt.geom.Rectangle2D;
 import java.awt.geom.RoundRectangle2D;
 import java.util.IdentityHashMap;
 import java.util.WeakHashMap;
+import java.util.function.Predicate;
 import java.util.function.Supplier;
 import javax.swing.JComponent;
 import javax.swing.JTable;
@@ -175,8 +176,18 @@ public class FlatUIUtils
 	 * Returns whether the given component is the permanent focus owner and
 	 * is in the active window. Used to paint focus indicators.
 	 */
+	@SuppressWarnings( "unchecked" )
 	public static boolean isPermanentFocusOwner( Component c ) {
 		KeyboardFocusManager keyboardFocusManager = KeyboardFocusManager.getCurrentKeyboardFocusManager();
+
+		if( c instanceof JComponent ) {
+			Object value = ((JComponent)c).getClientProperty( FlatClientProperties.COMPONENT_FOCUS_OWNER );
+			if( value instanceof Predicate ) {
+				return ((Predicate<JComponent>)value).test( (JComponent) c ) &&
+					keyboardFocusManager.getActiveWindow() == SwingUtilities.windowForComponent( c );
+			}
+		}
+
 		return keyboardFocusManager.getPermanentFocusOwner() == c &&
 			keyboardFocusManager.getActiveWindow() == SwingUtilities.windowForComponent( c );
 	}