Fix for Flickering in Embedded Apps

This commit contributes to fixing the flicker issue in SashLayout
whenever an embedded app is present inside it. The fix disallows the
setredraw of the parents if they contains any embedded application as
their descendants.

contributes to #1122

Author: amartya4256

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

@@ -711,8 +711,13 @@ void createWidget () {
 	if ((state & PARENT_BACKGROUND) != 0) {
 		setBackground ();
 	}
+	if((style & SWT.EMBEDDED) != 0) {
+		embeddedContols.add(this);
+	}
 }
 
+private static ArrayList<Control> embeddedContols = new ArrayList<>();
+
 int defaultBackground () {
 	return OS.GetSysColor (OS.COLOR_BTNFACE);
 }
@@ -2494,6 +2499,9 @@ void releaseParent () {
 @Override
 void releaseWidget () {
 	super.releaseWidget ();
+	if((style & SWT.EMBEDDED) != 0) {
+		embeddedContols.remove(this);
+	}
 	if (toolTipText != null) {
 		setToolTipText (getShell (), null);
 	}
@@ -3606,6 +3614,21 @@ boolean setRadioSelection (boolean value) {
 	return false;
 }
 
+private boolean hasEmbeddedChildren() {
+	for (Control current : embeddedContols) {
+		if (!current.isDisposed() && current.isVisible()) {
+			while (current != null) {
+				if (current == this) {
+					return true;
+				} else {
+					current = current.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
@@ -3640,6 +3663,9 @@ public void setRedraw (boolean redraw) {
 	 * drawing is turned off and restore it when drawing is
 	 * turned back on.
 	 */
+	if(hasEmbeddedChildren()) {
+		return;
+	}
 	if (drawCount == 0) {
 		int bits = OS.GetWindowLong (handle, OS.GWL_STYLE);
 		if ((bits & OS.WS_VISIBLE) == 0) state |= HIDDEN;