Make DPI_CHANGED event handling async

With this commit, all the widgets scale themselves asynchronously
independent of the order saving the wait time over their children to
scale.

Author: amartya4256

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/internal/DPITestUtil.java

@@ -13,6 +13,9 @@
  *******************************************************************************/
 package org.eclipse.swt.internal;
 
+import java.time.*;
+import java.util.concurrent.atomic.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.widgets.*;
 
@@ -21,14 +24,34 @@ public final class DPITestUtil {
 	private DPITestUtil() {
 	}
 
+	private static int timeoutInMillis = 2000;
+
 	public static void changeDPIZoom (Shell shell, int nativeZoom) {
 		DPIUtil.setDeviceZoom(nativeZoom);
 		Event event = new Event();
 		event.type = SWT.ZoomChanged;
 		event.widget = shell;
 		event.detail = nativeZoom;
 		event.doit = true;
+		AtomicInteger scalingCounter = new AtomicInteger(0);
+		event.data = scalingCounter;
 		shell.notifyListeners(SWT.ZoomChanged, event);
+		waitForDPIChange(shell, timeoutInMillis, scalingCounter);
+	}
+
+	public static void waitForPassCondition(Shell shell, int timeout, AtomicInteger scalingCounter) {
+		final Instant timeOut = Instant.now().plusMillis(timeout);
+		final Display display = shell == null ? Display.getDefault() : shell.getDisplay();
+
+		while (Instant.now().isBefore(timeOut) && scalingCounter.get() != 0) {
+			if (!display.isDisposed()) {
+				display.readAndDispatch();
+			}
+		}
+	}
+
+	public static void waitForDPIChange(Shell shell, int timeout, AtomicInteger scalingCounter) {
+		waitForPassCondition(shell, timeout, scalingCounter);
 	}
 
 }

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

@@ -1977,7 +1977,7 @@ public String toString() {
 void handleDPIChange(Event event, float scalingFactor) {
 	super.handleDPIChange(event, scalingFactor);
 	for (Control child : getChildren()) {
-		child.notifyListeners(SWT.ZoomChanged, event);
+		child.sendZoomChangedEvent(event, getShell());
 	}
 }
 }

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

@@ -16,6 +16,7 @@
 
 
 import java.util.*;
+import java.util.concurrent.atomic.*;
 import java.util.stream.*;
 
 import org.eclipse.swt.*;
@@ -4757,7 +4758,7 @@ public boolean setParent (Composite parent) {
 	if (parent.nativeZoom != nativeZoom) {
 		int newZoom = parent.nativeZoom;
 		Event zoomChangedEvent = createZoomChangedEvent(newZoom);
-		notifyListeners(SWT.ZoomChanged, zoomChangedEvent);
+		sendZoomChangedEvent(zoomChangedEvent, getShell());
 	}
 	int flags = OS.SWP_NOSIZE | OS.SWP_NOMOVE | OS.SWP_NOACTIVATE;
 	OS.SetWindowPos (topHandle, OS.HWND_BOTTOM, 0, 0, 0, 0, flags);
@@ -4953,7 +4954,7 @@ LRESULT WM_DESTROY (long wParam, long lParam) {
 void handleMonitorSpecificDpiChange(int newNativeZoom, Rectangle newBoundsInPixels) {
 	DPIUtil.setDeviceZoom (newNativeZoom);
 	Event zoomChangedEvent = createZoomChangedEvent(newNativeZoom);
-	notifyListeners(SWT.ZoomChanged, zoomChangedEvent);
+	sendZoomChangedEvent(zoomChangedEvent, getShell());
 	this.setBoundsInPixels(newBoundsInPixels.x, newBoundsInPixels.y, newBoundsInPixels.width, newBoundsInPixels.height);
 }
 
@@ -4963,6 +4964,7 @@ private Event createZoomChangedEvent(int zoom) {
 	event.widget = this;
 	event.detail = zoom;
 	event.doit = true;
+	event.data = new AtomicInteger(0);
 	return event;
 }
 

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

@@ -1720,13 +1720,13 @@ void handleDPIChange(Event event, float scalingFactor) {
 
 	Menu menuBar = getMenuBar();
 	if (menuBar != null) {
-		menuBar.notifyListeners(SWT.ZoomChanged, event);
+		menuBar.sendZoomChangedEvent(event, getShell());
 	}
 
 	if (menus != null) {
 		for (Menu menu : menus) {
 			if (menu != null) {
-				menu.notifyListeners(SWT.ZoomChanged, event);
+				menu.sendZoomChangedEvent(event, getShell());
 			}
 		}
 	}

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

@@ -871,7 +871,7 @@ LRESULT wmScroll (ScrollBar bar, boolean update, long hwnd, int msg, long wParam
 void handleDPIChange(Event event, float scalingFactor) {
 	super.handleDPIChange(event, scalingFactor);
 	for (ExpandItem item : getItems()) {
-		item.notifyListeners(SWT.ZoomChanged, event);
+		item.sendZoomChangedEvent(event, getShell());
 	}
 	layoutItems(0, true);
 	redraw();

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

@@ -1366,7 +1366,7 @@ LRESULT wmTimer (long wParam, long lParam) {
 void handleDPIChange(Event event, float scalingFactor) {
 	super.handleDPIChange(event, scalingFactor);
 	for (MenuItem item : getItems()) {
-		item.notifyListeners(SWT.ZoomChanged, event);
+		item.sendZoomChangedEvent(event, getShell());
 	}
 }
 }

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

@@ -1463,7 +1463,7 @@ void handleDPIChange(Event event, float scalingFactor) {
 	// Refresh the sub menu
 	Menu subMenu = getMenu();
 	if (subMenu != null) {
-		subMenu.notifyListeners(SWT.ZoomChanged, event);
+		subMenu.sendZoomChangedEvent(event, subMenu.getShell());
 	}
 }
 }

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

@@ -1136,7 +1136,7 @@ void handleDPIChange(Event event, float scalingFactor) {
 		imageList = null;
 	}
 	for (int i = 0; i < getItemCount(); i++) {
-		items[i].notifyListeners(SWT.ZoomChanged, event);
+		items[i].sendZoomChangedEvent(event, getShell());
 	}
 	layout(true, true);
 }

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

@@ -7363,10 +7363,10 @@ void handleDPIChange(Event event, float scalingFactor) {
 	setItemHeight(-1);
 
 	for (TableItem item : getItems()) {
-		item.notifyListeners(SWT.ZoomChanged, event);
+		item.sendZoomChangedEvent(event, getShell());
 	}
 	for (TableColumn tableColumn : getColumns()) {
-		tableColumn.notifyListeners(SWT.ZoomChanged, event);
+		tableColumn.sendZoomChangedEvent(event, getShell());
 	}
 
 	if (getColumns().length == 0 && scrollWidth != 0) {

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

@@ -1770,7 +1770,7 @@ record ToolItemData(ToolItem toolItem, TBBUTTON button) {
 			// at the end
 			seperatorWidth[i] = item.getWidth();
 		}
-		item.notifyListeners(SWT.ZoomChanged, event);
+		item.sendZoomChangedEvent(event, getShell());
 		buttondata.push(new ToolItemData(item, lpButton));
 		OS.SendMessage(handle, OS.TB_DELETEBUTTON, i, 0);
 	}