Issue #603: [Win32] Shell-TaskItem: overlay text remains after the shell is closed

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Shell.java

@@ -2285,7 +2285,7 @@ long windowProc (long hwnd, int msg, long wParam, long lParam) {
 			if (display.taskBar != null) {
 				for (TaskItem item : display.taskBar.items) {
 					if (item != null && item.shell == this) {
-						item.recreate ();
+						item.onTaskbarButtonCreated();
 						break;
 					}
 				}

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/TaskItem.java

@@ -38,6 +38,7 @@
 public class TaskItem extends Item {
 	TaskBar parent;
 	Shell shell;
+	boolean hasTaskbarButton = false;
 	int progress, progressState = SWT.DEFAULT;
 	Image overlayImage;
 	String overlayText = "";
@@ -89,6 +90,28 @@ protected void checkSubclass () {
 
 @Override
 void destroyWidget () {
+	if (null != parent.mTaskbarList3) { // extra safety just in case
+		// MSDN for 'ITaskbarList3::SetOverlayIcon' says:
+		//   Because a single overlay is applied to the taskbar button instead
+		//   of to the individual window thumbnails, this is a per-group
+		//   feature rather than per-window. Requests for overlay icons can
+		//   be received from individual windows in a taskbar group, but they
+		//   do not queue. The last overlay received is the overlay shown.
+		//   If the last overlay received is removed, the overlay that it
+		//   replaced is restored so long as it is still active. As an example,
+		//   windows 1, 2, and 3 set, in order, overlays A, B, and C.
+		//   Because overlay C was received last, it is shown on the taskbar button.
+		//   Window 2 calls SetOverlayIcon with a NULL value to remove overlay B.
+		//   Window 3 then does the same to remove overlay C.
+		//   Because window 1's overlay A is still active, that overlay is then
+		//   displayed on the taskbar button.
+		// This implies that Shell should pass NULL before closing.
+		//
+		// Issue #603: On Win11 the lack of this actually caused wrong overlay
+		// to show after closing Shell.
+		parent.mTaskbarList3.SetOverlayIcon(shell.handle, 0, 0);
+	}
+
 	parent.destroyItem (this);
 	releaseHandle ();
 }
@@ -188,16 +211,27 @@ public int getProgressState () {
 	return progressState;
 }
 
-void recreate () {
-	if (showingText) {
-		if (overlayText.length () != 0) updateText ();
+void updateImageAndText () {
+	if (showingText && (overlayText.length () != 0)) {
+		updateText ();
+	} else if (overlayImage != null) {
+		updateImage ();
 	} else {
-		if (overlayImage != null) updateImage ();
+		parent.mTaskbarList3.SetOverlayIcon(shell.handle, 0, 0);
 	}
+}
+
+void updateAll () {
+	updateImageAndText ();
 	if (progress != 0) updateProgress ();
 	if (progressState != SWT.DEFAULT) updateProgressState ();
 }
 
+void onTaskbarButtonCreated () {
+	this.hasTaskbarButton = true;
+	updateAll ();
+}
+
 @Override
 void releaseHandle () {
 	super.releaseHandle ();
@@ -287,15 +321,14 @@ public void setOverlayImage (Image overlayImage) {
 	if (overlayImage != null && overlayImage.isDisposed ()) error (SWT.ERROR_INVALID_ARGUMENT);
 	if (shell == null) return;
 	this.overlayImage = overlayImage;
-	if (overlayImage != null) {
-		updateImage ();
-	} else {
-		if (overlayText.length () != 0) {
-			updateText ();
-		} else {
-			parent.mTaskbarList3.SetOverlayIcon(shell.handle, 0, 0);
-		}
-	}
+	this.showingText = (this.overlayImage == null);
+
+	// MSDN for 'ITaskbarList3' says:
+	// TaskbarButtonCreated ... message must be received by your application before it calls any ITaskbarList3 method
+	// #updateAll() will be called later when message is received.
+	if (!hasTaskbarButton) return;
+
+	updateImageAndText ();
 }
 
 /**
@@ -329,15 +362,14 @@ public void setOverlayText (String overlayText) {
 	if (overlayText == null) error (SWT.ERROR_NULL_ARGUMENT);
 	if (shell == null) return;
 	this.overlayText = overlayText;
-	if (overlayText.length () != 0) {
-		updateText ();
-	} else {
-		if (overlayImage != null) {
-			updateImage ();
-		} else {
-			parent.mTaskbarList3.SetOverlayIcon(shell.handle, 0, 0);
-		}
-	}
+	this.showingText = (this.overlayText.length() != 0);
+
+	// MSDN for 'ITaskbarList3' says:
+	// TaskbarButtonCreated ... message must be received by your application before it calls any ITaskbarList3 method
+	// #updateAll() will be called later when message is received.
+	if (!hasTaskbarButton) return;
+
+	updateImageAndText ();
 }
 
 /**
@@ -371,6 +403,12 @@ public void setProgress (int progress) {
 	progress = Math.max (0, Math.min (progress, PROGRESS_MAX));
 	if (this.progress == progress) return;
 	this.progress = progress;
+
+	// MSDN for 'ITaskbarList3' says:
+	// TaskbarButtonCreated ... message must be received by your application before it calls any ITaskbarList3 method
+	// #updateAll() will be called later when message is received.
+	if (!hasTaskbarButton) return;
+
 	updateProgress ();
 }
 
@@ -414,6 +452,12 @@ public void setProgressState (int progressState) {
 	if (shell == null) return;
 	if (this.progressState == progressState) return;
 	this.progressState = progressState;
+
+	// MSDN for 'ITaskbarList3' says:
+	// TaskbarButtonCreated ... message must be received by your application before it calls any ITaskbarList3 method
+	// #updateAll() will be called later when message is received.
+	if (!hasTaskbarButton) return;
+
 	updateProgressState ();
 }
 
@@ -429,7 +473,6 @@ public void handleEvent (Event event) {
 }
 
 void updateImage () {
-	showingText = false;
 	Image image2 = null;
 	long hIcon = 0;
 	switch (overlayImage.type) {
@@ -463,8 +506,7 @@ void updateProgressState () {
 	parent.mTaskbarList3.SetProgressState(shell.handle, tbpFlags);
 }
 
-void updateText () {
-	showingText = true;
+long renderTextIcon () {
 	/* Create resources */
 	int width = 16, height = 16;
 	long hdc = OS.GetDC (0);
@@ -547,6 +589,11 @@ void updateText () {
 	OS.DeleteObject (hBitmap);
 	OS.DeleteObject (hMask);
 
+	return hIcon;
+}
+
+void updateText () {
+	long hIcon = renderTextIcon();
 	parent.mTaskbarList3.SetOverlayIcon(shell.handle, hIcon, 0);
 	OS.DestroyIcon (hIcon);
 }

tests/org.eclipse.swt.tests/ManualTests/org/eclipse/swt/tests/manual/Issue0603_WrongTaskBarOverlays.java

@@ -0,0 +1,111 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Syntevo and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Syntevo - initial API and implementation
+ *******************************************************************************/
+
+package org.eclipse.swt.tests.manual;
+
+import org.eclipse.swt.*;
+import org.eclipse.swt.graphics.GC;
+import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.layout.*;
+import org.eclipse.swt.widgets.*;
+
+public final class Issue0603_WrongTaskBarOverlays {
+	public static void main(String[] args) {
+		final Display display = new Display();
+
+		final Shell shell = new Shell(display);
+		shell.setLayout(new GridLayout(1, true));
+
+		final Label hint = new Label(shell, 0);
+		hint.setText(
+			"1. Use Win11; Win10 is not enough\n" +
+			"2. Start the program and pin its icon on TaskBar\n" +
+			"3. Press the button below to open a few Shells with overlays\n" +
+			"4. Issue #603: when one of them is closed, it doesn't restore previous overlay correctly\n" +
+			"   Note that Windows is documented to restore the overlay that was set last, contrary to\n" +
+			"   overlay of currently active Shell\n" +
+			"5. Issue #603: when all of them is closed, there should be no overlay\n" +
+			"6. The checkboxes below are to test that patch didn't break setting text/image overlays"
+		);
+
+		Button button = new Button(shell, SWT.PUSH);
+		button.setText("Test");
+		button.addListener(SWT.Selection, e -> {
+			for (int iShell = 0; iShell < 3; iShell++) {
+				Shell shell2 = new Shell(display);
+				shell2.setText("Shell #" + iShell);
+				shell2.setSize(250, 100);
+				shell2.open();
+
+				final TaskItem taskItem2 = display.getSystemTaskBar().getItem(shell2);
+				taskItem2.setOverlayText("#" + iShell);
+
+				// Windows Explorer seems to get confused when multiple overlays are set quickly
+				// It will then sometimes put them in wrong order.
+				// The workaround is to wait and process display events after each shell
+				{
+					try {
+						Thread.sleep(500);
+					} catch (InterruptedException ex) {
+					}
+
+					while (display.readAndDispatch()) {
+					}
+				}
+			}
+		});
+
+		final TaskItem taskItem = display.getSystemTaskBar().getItem(shell);
+
+		Button chkText = new Button(shell, SWT.CHECK);
+		chkText.setText("Set Text overlay for me");
+		chkText.addListener(SWT.Selection, e -> {
+			if (chkText.getSelection()) {
+				taskItem.setOverlayText("Main");
+			} else {
+				taskItem.setOverlayText("");
+			}
+		});
+
+		Image image = new Image(display, 16, 16);
+		{
+			GC gc = new GC(image);
+			gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
+			gc.setForeground(display.getSystemColor(SWT.COLOR_RED));
+			gc.fillRectangle(0, 0, 16, 16);
+			gc.dispose();
+		}
+
+		Button chkImage = new Button(shell, SWT.CHECK);
+		chkImage.setText("Set Image overlay for me");
+		chkImage.addListener(SWT.Selection, e -> {
+			if (chkImage.getSelection()) {
+				taskItem.setOverlayImage(image);
+			} else {
+				taskItem.setOverlayImage(null);
+			}
+		});
+
+		shell.pack();
+		shell.open();
+
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+
+		image.dispose();
+	}
+}