Destroying unnecessary zoom level handles

Add display change event triggered by display zoom changes, regardless
of window presence on the monitor

Author: ShahzaibIbrahim

bundles/org.eclipse.swt/Eclipse SWT PI/win32/org/eclipse/swt/internal/win32/OS.java

@@ -1752,6 +1752,7 @@ public class OS extends C {
 	public static final int WM_DEADCHAR = 0x103;
 	public static final int WM_DESTROY = 0x2;
 	public static final int WM_DPICHANGED = 0x02E0;
+	public static final int WM_DISPLAYCHANGE = 0x7E;
 	public static final int WM_DRAWITEM = 0x2b;
 	public static final int WM_ENDSESSION = 0x16;
 	public static final int WM_ENTERIDLE = 0x121;

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

@@ -4856,6 +4856,7 @@ long windowProc (long hwnd, int msg, long wParam, long lParam) {
 		case OS.WM_XBUTTONDOWN:			result = WM_XBUTTONDOWN (wParam, lParam); break;
 		case OS.WM_XBUTTONUP:			result = WM_XBUTTONUP (wParam, lParam); break;
 		case OS.WM_DPICHANGED:			result = WM_DPICHANGED (wParam, lParam); break;
+		case OS.WM_DISPLAYCHANGE:		result = WM_DISPLAYCHANGE(wParam, lParam); break;
 	}
 	if (result != null) return result.value;
 	// widget could be disposed at this point
@@ -4967,6 +4968,14 @@ LRESULT WM_DPICHANGED (long wParam, long lParam) {
 	return LRESULT.ONE;
 }
 
+LRESULT WM_DISPLAYCHANGE (long wParam, long lParam) {
+	if (getDisplay().isRescalingAtRuntime()) {
+		Device.win32_destroyUnusedHandles(getDisplay());
+		return LRESULT.ZERO;
+	}
+	return LRESULT.ONE;
+}
+
 LRESULT WM_DRAWITEM (long wParam, long lParam) {
 	DRAWITEMSTRUCT struct = new DRAWITEMSTRUCT ();
 	OS.MoveMemory (struct, lParam, DRAWITEMSTRUCT.sizeof);