Only redraw once after scaling every widget #62

This commit contributes to reducing the number of redraws and only draw
once all the widgets have performed scaling using their
Widget:handleDpiChange handlers.

contributes to
#62 and
#128

Author: amartya4256

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

@@ -1984,6 +1984,5 @@ private static void handleDPIChange(Widget widget, int newZoom, float scalingFac
 	for (Control child : composite.getChildren()) {
 		DPIZoomChangeRegistry.applyChange(child, newZoom, scalingFactor);
 	}
-	composite.redrawInPixels (null, true);
 }
 }

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

@@ -4764,6 +4764,7 @@ public boolean setParent (Composite parent) {
 		int newZoom = parent.nativeZoom;
 		float scalingFactor = 1f * newZoom / oldZoom;
 		DPIZoomChangeRegistry.applyChange(this, newZoom, scalingFactor);
+		getShell().WM_SIZE(0, 0);
 	}
 	int flags = OS.SWP_NOSIZE | OS.SWP_NOMOVE | OS.SWP_NOACTIVATE;
 	OS.SetWindowPos (topHandle, OS.HWND_BOTTOM, 0, 0, 0, 0, flags);
@@ -4961,6 +4962,7 @@ void handleMonitorSpecificDpiChange(int newNativeZoom, Rectangle newBoundsInPixe
 	DPIUtil.setDeviceZoom (newNativeZoom);
 	DPIZoomChangeRegistry.applyChange(this, newNativeZoom, scalingFactor);
 	this.setBoundsInPixels(newBoundsInPixels.x, newBoundsInPixels.y, newBoundsInPixels.width, newBoundsInPixels.height);
+	getShell().WM_SIZE(0, 0);
 }
 
 LRESULT WM_DPICHANGED (long wParam, long lParam) {