JBR-6145 [Wayland toolkit] Popup windows aren't focusable

A partial solution. Cases not still covered:
* Alt+tab from the app and back should keep popup focused if it was focused initially
* Mouse clicks between popup and owner should transfer focus as expected

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

@@ -206,20 +206,17 @@ public boolean isFocusable() {
     public boolean requestFocus(Component lightweightChild, boolean temporary,
                                 boolean focusedWindowChangeAllowed, long time,
                                 FocusEvent.Cause cause) {
-        final Component currentlyFocused = WLKeyboardFocusManagerPeer.getInstance().getCurrentFocusOwner();
-        if (currentlyFocused == null)
+        final Window currentlyFocusedWindow = WLKeyboardFocusManagerPeer.getInstance().getCurrentFocusedWindow();
+        if (currentlyFocusedWindow == null)
             return false;
 
-        WLComponentPeer peer = AWTAccessor.getComponentAccessor().getPeer(currentlyFocused);
-        if (peer == null)
-            return false;
-
-        if (this == peer) {
+        Window targetDecoratedWindow = getNativelyFocusableOwnerOrSelf(target);
+        if (currentlyFocusedWindow == targetDecoratedWindow) {
             WLKeyboardFocusManagerPeer.deliverFocus(lightweightChild,
-                    target,
+                    null,
                     true,
                     cause,
-                    WLKeyboardFocusManagerPeer.getInstance().getCurrentFocusOwner());
+                    null);
         } else {
             return false;
         }
@@ -286,9 +283,12 @@ protected void wlSetVisible(boolean v) {
      * Returns true if our target should be treated as a popup in Wayland's sense,
      * i.e. it has to have a parent to position relative to.
      */
-    private boolean targetIsWlPopup() {
-        return target instanceof Window window
-                && window.getType() == Window.Type.POPUP
+    protected boolean targetIsWlPopup() {
+        return target instanceof Window window && isWlPopup(window);
+    }
+
+    static boolean isWlPopup(Window window) {
+        return window.getType() == Window.Type.POPUP
                 && AWTAccessor.getWindowAccessor().getPopupParent(window) != null;
     }
 
@@ -1173,4 +1173,23 @@ static void performUnlocked(Runnable task) {
             WLToolkit.awtLock();
         }
     }
+
+    private static void startMovingWindowTogetherWithMouse(Window window, int mouseButton)
+    {
+        final AWTAccessor.ComponentAccessor acc = AWTAccessor.getComponentAccessor();
+        ComponentPeer peer = acc.getPeer(window);
+        if (peer instanceof WLComponentPeer wlComponentPeer) {
+            wlComponentPeer.startDrag();
+        } else {
+            throw new IllegalArgumentException("AWT window must have WLComponentPeer as its peer");
+        }
+    }
+
+    static Window getNativelyFocusableOwnerOrSelf(Component component) {
+        Window result = component instanceof Window window ? window : SwingUtilities.getWindowAncestor(component);
+        while (result != null && isWlPopup(result)) {
+            result = result.getOwner();
+        }
+        return result;
+    }
 }

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

@@ -35,7 +35,8 @@ public Window getCurrentFocusedWindow() {
 
     @Override
     public void setCurrentFocusOwner(Component comp) {
-        if (comp != null && comp != currentFocusedWindow) {
+        if (comp != null && (!(comp instanceof Window window) ||
+                WLComponentPeer.getNativelyFocusableOwnerOrSelf(window) != currentFocusedWindow)) {
             // In Wayland, only Window can be focused, not any widget in it.
             focusLog.severe("Unexpected focus owner set in a Window: " + comp);
         }

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

@@ -26,11 +26,13 @@
 
 import sun.awt.AWTAccessor;
 import java.awt.*;
+import java.awt.event.WindowEvent;
 import java.awt.peer.ComponentPeer;
 import java.awt.peer.WindowPeer;
 
 public class WLWindowPeer extends WLComponentPeer implements WindowPeer {
     private static Font defaultFont;
+    private Dialog blocker;
 
     static synchronized Font getDefaultFont() {
         if (null == defaultFont) {
@@ -55,14 +57,29 @@ public WLWindowPeer(Window target) {
 
     @Override
     protected void wlSetVisible(boolean v) {
+        if (v && targetIsWlPopup() && shouldBeFocusedOnShowing()) {
+            requestWindowFocus();
+        }
         super.wlSetVisible(v);
         final AWTAccessor.ComponentAccessor acc = AWTAccessor.getComponentAccessor();
-        for (Component c : ((Window)target).getComponents()) {
+        for (Component c : getWindow().getComponents()) {
             ComponentPeer cPeer = acc.getPeer(c);
             if (cPeer instanceof WLComponentPeer) {
                 ((WLComponentPeer) cPeer).wlSetVisible(v);
             }
         }
+        if (!v && targetIsWlPopup() && getWindow().isFocused()) {
+            Window targetOwner = getWindow().getOwner();
+            while (targetOwner != null && (targetOwner.getOwner() != null && !targetOwner.isFocusableWindow())) {
+                targetOwner = targetOwner.getOwner();
+            }
+            if (targetOwner != null) {
+                WLWindowPeer wndpeer = AWTAccessor.getComponentAccessor().getPeer(targetOwner);
+                if (wndpeer != null) {
+                    wndpeer.requestWindowFocus();
+                }
+            }
+        }
     }
 
     @Override
@@ -109,7 +126,7 @@ public void updateFocusableWindowState() {
 
     @Override
     public void setModalBlocked(Dialog blocker, boolean blocked) {
-
+        this.blocker = blocked ? blocker : null;
     }
 
     @Override
@@ -153,8 +170,28 @@ public void repositionSecurityWarning() {
 
     @Override
     public GraphicsConfiguration getAppropriateGraphicsConfiguration(
-            GraphicsConfiguration gc)
-    {
+            GraphicsConfiguration gc) {
         return gc;
     }
+
+    private Window getWindow() {
+        return (Window) target;
+    }
+
+    private boolean shouldBeFocusedOnShowing() {
+        Window window = getWindow();
+        return window.isFocusableWindow() &&
+                window.isAutoRequestFocus() &&
+                blocker == null;
+    }
+
+    // supporting only 'synthetic' focus transfers for now (when natively focused window stays the same)
+    private void requestWindowFocus() {
+        Window window = getWindow();
+        Window nativeFocusTarget = getNativelyFocusableOwnerOrSelf(window);
+        if (nativeFocusTarget != null &&
+                WLKeyboardFocusManagerPeer.getInstance().getCurrentFocusedWindow() == nativeFocusTarget) {
+            WLToolkit.postEvent(new WindowEvent(window, WindowEvent.WINDOW_GAINED_FOCUS));
+        }
+    }
 }