JBR-6145 Wayland: synthetic focus for popups

Author: mkartashev

src/java.desktop/unix/classes/sun/awt/wl/WLKeyboardFocusManagerPeer.java

@@ -1,5 +1,6 @@
 package sun.awt.wl;
 
+import sun.awt.AWTAccessor;
 import sun.awt.KeyboardFocusManagerPeerImpl;
 import sun.util.logging.PlatformLogger;
 
@@ -35,10 +36,25 @@ public Window getCurrentFocusedWindow() {
 
     @Override
     public void setCurrentFocusOwner(Component comp) {
+        Window cur = getCurrentFocusedWindow();
         if (comp != null && (!(comp instanceof Window window) ||
-                WLComponentPeer.getNativelyFocusableOwnerOrSelf(window) != currentFocusedWindow)) {
+                WLComponentPeer.getNativelyFocusableOwnerOrSelf(window) != cur)) {
             // In Wayland, only Window can be focused, not any widget in it.
             focusLog.severe("Unexpected focus owner set in a Window: " + comp);
+            return;
+        }
+
+        if (comp != null) {
+            Window nativeFocusable = WLComponentPeer.getNativelyFocusableOwnerOrSelf(comp);
+            AWTAccessor.ComponentAccessor acc = AWTAccessor.getComponentAccessor();
+            WLComponentPeer nativeFocusablePeer = acc.getPeer(nativeFocusable);
+            if (nativeFocusablePeer instanceof WLWindowPeer windowPeer) {
+                // May have to transfer the keyboard focus to a child popup window
+                // when this 'windowPeer' receives focus from Wayland again because popups
+                // aren't natively focusable under Wayland.
+                Component synthFocusOwner = nativeFocusable != comp ? comp : null;
+                windowPeer.setSyntheticFocusOwner(synthFocusOwner);
+            }
         }
     }
 

src/java.desktop/unix/classes/sun/awt/wl/WLToolkit.java

@@ -402,9 +402,19 @@ private static void dispatchKeyboardEnterEvent(long serial, long surfacePtr) {
 
         final WLInputState newInputState = inputState.updatedFromKeyboardEnterEvent(serial, surfacePtr);
         final WLWindowPeer peer = peerFromSurface(surfacePtr);
-        if (peer != null && peer.getTarget() instanceof Window window) {
+        if (peer != null) {
+            Window window = (Window) peer.getTarget();
+            Window winToFocus = window;
+
+            Component s = peer.getSyntheticFocusOwner();
+            if (s instanceof Window synthWindow) {
+                if (synthWindow.isVisible() && synthWindow.isFocusableWindow()) {
+                    winToFocus = synthWindow;
+                }
+            }
+
             WLKeyboardFocusManagerPeer.getInstance().setCurrentFocusedWindow(window);
-            final WindowEvent windowEnterEvent = new WindowEvent(window, WindowEvent.WINDOW_GAINED_FOCUS);
+            WindowEvent windowEnterEvent = new WindowEvent(winToFocus, WindowEvent.WINDOW_GAINED_FOCUS);
             postPriorityEvent(windowEnterEvent);
         }
         inputState = newInputState;

src/java.desktop/unix/classes/sun/awt/wl/WLWindowPeer.java

@@ -43,11 +43,15 @@
 import java.awt.geom.Path2D;
 import java.awt.peer.ComponentPeer;
 import java.awt.peer.WindowPeer;
+import java.lang.ref.WeakReference;
 
 public class WLWindowPeer extends WLComponentPeer implements WindowPeer {
     private static Font defaultFont;
     private Dialog blocker;
 
+    // If this window gets focus from Wayland, we need to transfer focus synthFocusOwner, if any
+    private WeakReference<Component> synthFocusOwner = new WeakReference<>(null);
+
     public static final String WINDOW_CORNER_RADIUS = "apple.awt.windowCornerRadius";
 
     private WLRoundedCornersManager.RoundedCornerKind roundedCornerKind = WLRoundedCornersManager.RoundedCornerKind.DEFAULT; // guarded by stateLock
@@ -224,6 +228,14 @@ private void requestWindowFocus() {
         }
     }
 
+    public Component getSyntheticFocusOwner() {
+        return synthFocusOwner.get();
+    }
+
+    public void setSyntheticFocusOwner(Component c) {
+        synthFocusOwner = new WeakReference<>(c);
+    }
+
     private boolean canPaintRoundedCorners() {
         int roundedCornerSize = WLRoundedCornersManager.roundCornerRadiusFor(roundedCornerKind);
         // Note: You would normally get a transparency-capable color model when using