Reduce flickering in embedded controls

Ignore calls to Control::setRedraw(boolean) if the control contains any
embedded application as a child.

This change does not completely get rid of the flickering but it reduces
it drastically.

Contributes to
#1122

Author: amartya4256

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

@@ -55,6 +55,8 @@ public abstract class Control extends Widget implements Drawable {
 		DPIZoomChangeRegistry.registerHandler(Control::handleDPIChange, Control.class);
 	}
 
+	private static Set<Control> embeddedControls = new HashSet<>();
+
 	/**
 	 * the handle to the OS resource
 	 * (Warning: This field is platform dependent)
@@ -711,6 +713,9 @@ void createWidget () {
 	if ((state & PARENT_BACKGROUND) != 0) {
 		setBackground ();
 	}
+	if((style & SWT.EMBEDDED) != 0) {
+		embeddedControls.add(this);
+	}
 }
 
 int defaultBackground () {
@@ -2494,6 +2499,9 @@ void releaseParent () {
 @Override
 void releaseWidget () {
 	super.releaseWidget ();
+	if((style & SWT.EMBEDDED) != 0) {
+		embeddedControls.remove(this);
+	}
 	if (toolTipText != null) {
 		setToolTipText (getShell (), null);
 	}
@@ -3606,6 +3614,23 @@ boolean setRadioSelection (boolean value) {
 	return false;
 }
 
+private boolean hasEmbeddedChildren() {
+	for (Control ec : embeddedControls) {
+		if (!ec.isDisposed() && ec.isVisible() && ec.isChildOf(this)) return true;
+	}
+	return false;
+}
+
+private boolean isChildOf(Control parent) {
+	Control c = this;
+	while (c != null) {
+		if (c == parent) return true;
+
+		c = c.getParent();
+	}
+	return false;
+}
+
 /**
  * If the argument is <code>false</code>, causes subsequent drawing
  * operations in the receiver to be ignored. No drawing of any kind
@@ -3631,6 +3656,20 @@ boolean setRadioSelection (boolean value) {
  */
 public void setRedraw (boolean redraw) {
 	checkWidget ();
+
+	/*
+	 * Some embedded applications like webview2 (Edge), Excel, etc
+	 * have a renderer that will draw the whole application white
+	 * when setting redraw to false and will repaint it completely
+	 * when setting it to true. This causes flickering, which is why
+	 * turning redraw on/off is disabled in these cases.
+	 *
+	 * https://github.com/eclipse-platform/eclipse.platform.swt/issues/1122
+	 */
+	if(hasEmbeddedChildren()) {
+		return;
+	}
+
 	/*
 	 * Feature in Windows.  When WM_SETREDRAW is used to turn
 	 * off drawing in a widget, it clears the WS_VISIBLE bits