Linux: hide popups when window is moved, resized, maximized, restored, iconified or switched to another window (issue #962)

CHANGELOG.md

@@ -30,6 +30,9 @@ FlatLaf Change Log
 - FlatLaf window decorations: Minimize and maximize icons were not shown for
   custom scale factors less than 100% (e.g. `-Dflatlaf.uiScale=75%`). (issue
   #951)
+- Linux: Popups (menus and combobox lists) were not hidden when window is moved,
+  resized, maximized, restored, iconified or switched to another window. (issue
+  #962)
 
 
 ## 3.5.4

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

@@ -111,6 +111,7 @@ public abstract class FlatLaf
 	private PopupFactory oldPopupFactory;
 	private MnemonicHandler mnemonicHandler;
 	private boolean subMenuUsabilityHelperInstalled;
+	private LinuxPopupMenuCanceler linuxPopupMenuCanceler;
 
 	private Consumer<UIDefaults> postInitialization;
 	private List<Function<Object, Object>> uiDefaultsGetters;
@@ -305,6 +306,10 @@ public abstract class FlatLaf
 		// install submenu usability helper
 		subMenuUsabilityHelperInstalled = SubMenuUsabilityHelper.install();
 
+		// install Linux popup menu canceler
+		if( SystemInfo.isLinux )
+			linuxPopupMenuCanceler = new LinuxPopupMenuCanceler();
+
 		// listen to desktop property changes to update UI if system font or scaling changes
 		if( SystemInfo.isWindows ) {
 			// Windows 10 allows increasing font size independent of scaling:
@@ -397,6 +402,12 @@ public abstract class FlatLaf
 			subMenuUsabilityHelperInstalled = false;
 		}
 
+		// uninstall Linux popup menu canceler
+		if( linuxPopupMenuCanceler != null ) {
+			linuxPopupMenuCanceler.uninstall();
+			linuxPopupMenuCanceler = null;
+		}
+
 		// restore default link color
 		new HTMLEditorKit().getStyleSheet().addRule( "a, address { color: blue; }" );
 		postInitialization = null;

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

@@ -0,0 +1,164 @@
+/*
+ * Copyright 2025 FormDev Software GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.formdev.flatlaf;
+
+import java.awt.Component;
+import java.awt.Window;
+import java.awt.event.ComponentEvent;
+import java.awt.event.ComponentListener;
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
+import javax.swing.JPopupMenu;
+import javax.swing.MenuElement;
+import javax.swing.MenuSelectionManager;
+import javax.swing.SwingUtilities;
+import javax.swing.event.ChangeEvent;
+import javax.swing.event.ChangeListener;
+
+/**
+ * Cancels (hides) popup menus on Linux.
+ * <p>
+ * On Linux, popups are not hidden under following conditions, which results in
+ * misplaced popups:
+ * <ul>
+ *   <li>window moved or resized
+ *   <li>window maximized or restored
+ *   <li>window iconified
+ *   <li>window deactivated (e.g. activated other application)
+ * </ul>
+ *
+ * On Windows and macOS, popups are automatically hidden.
+ * <p>
+ * The implementation is similar to what's done in
+ * {@code javax.swing.plaf.basic.BasicPopupMenuUI.MouseGrabber},
+ * but only hides popup in some conditions.
+ *
+ * @author Karl Tauber
+ */
+class LinuxPopupMenuCanceler
+	extends WindowAdapter
+	implements ChangeListener, ComponentListener
+{
+	private MenuElement[] lastPathSelectedPath;
+	private Window window;
+
+	LinuxPopupMenuCanceler() {
+		MenuSelectionManager msm = MenuSelectionManager.defaultManager();
+		msm.addChangeListener( this );
+
+		lastPathSelectedPath = msm.getSelectedPath();
+		if( lastPathSelectedPath.length > 0 )
+			addWindowListeners( lastPathSelectedPath[0] );
+	}
+
+	void uninstall() {
+		MenuSelectionManager.defaultManager().removeChangeListener( this );
+	}
+
+	private void addWindowListeners( MenuElement selected ) {
+		// see BasicPopupMenuUI.MouseGrabber.grabWindow()
+		Component invoker = selected.getComponent();
+		if( invoker instanceof JPopupMenu )
+			invoker = ((JPopupMenu)invoker).getInvoker();
+		window = (invoker instanceof Window)
+			? (Window) invoker
+			: SwingUtilities.windowForComponent( invoker );
+
+		if( window != null ) {
+			window.addWindowListener( this );
+			window.addComponentListener( this );
+		}
+	}
+
+	private void removeWindowListeners() {
+		if( window != null ) {
+			window.removeWindowListener( this );
+			window.removeComponentListener( this );
+			window = null;
+		}
+	}
+
+	private void cancelPopupMenu() {
+		try {
+			MenuSelectionManager msm = MenuSelectionManager.defaultManager();
+			MenuElement[] selectedPath = msm.getSelectedPath();
+			for( MenuElement e : selectedPath ) {
+				if( e instanceof JPopupMenu )
+					((JPopupMenu)e).putClientProperty( "JPopupMenu.firePopupMenuCanceled", true );
+			}
+			msm.clearSelectedPath();
+		} catch( RuntimeException ex ) {
+			removeWindowListeners();
+			throw ex;
+		} catch( Error ex ) {
+			removeWindowListeners();
+			throw ex;
+		}
+	}
+
+	//---- ChangeListener ----
+
+	@Override
+	public void stateChanged( ChangeEvent e ) {
+		MenuElement[] selectedPath = MenuSelectionManager.defaultManager().getSelectedPath();
+
+		if( selectedPath.length == 0 )
+			removeWindowListeners();
+		else if( lastPathSelectedPath.length == 0 )
+			addWindowListeners( selectedPath[0] );
+
+		lastPathSelectedPath = selectedPath;
+	}
+
+	//---- WindowListener ----
+
+	@Override
+	public void windowIconified( WindowEvent e ) {
+		cancelPopupMenu();
+	}
+
+	@Override
+	public void windowDeactivated( WindowEvent e ) {
+		cancelPopupMenu();
+	}
+
+	@Override
+	public void windowClosing( WindowEvent e ) {
+		cancelPopupMenu();
+	}
+
+	//---- ComponentListener ----
+
+	@Override
+	public void componentResized( ComponentEvent e ) {
+		cancelPopupMenu();
+	}
+
+	@Override
+	public void componentMoved( ComponentEvent e ) {
+		cancelPopupMenu();
+	}
+
+	@Override
+	public void componentShown( ComponentEvent e ) {
+	}
+
+	@Override
+	public void componentHidden( ComponentEvent e ) {
+		cancelPopupMenu();
+	}
+}