[win32] Adjust wrong size after DPI fix in Shell

This commit addresses an issue with the logic fixing a missing DPI
change event from windows in the Shell#WM_WINDOWPOSCHANGED callback. It
adapts the calculation to properly calculate the new size taking
previous and new zoom into account and executes the logic asynchronously.

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/DPIUtil.java

@@ -235,6 +235,15 @@ public static Point scaleDown(Point point, int zoom) {
 	return scaledPoint;
 }
 
+public static Point scalePoint(Point point, int targetZoom, int currentZoom) {
+	if (point == null || targetZoom == currentZoom) return point;
+	float scaleFactor = (float) targetZoom / (float) currentZoom;
+	Point scaledPoint = new Point (0,0);
+	scaledPoint.x = Math.round (point.x / scaleFactor);
+	scaledPoint.y = Math.round (point.y / scaleFactor);
+	return scaledPoint;
+}
+
 /**
  * Returns a new scaled down Point if enabled for Drawable class.
  */

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

@@ -2738,12 +2738,18 @@ LRESULT WM_WINDOWPOSCHANGED (long wParam, long lParam) {
 	// this check is added to trigger a dpi change event if an unexpected DPI value is
 	// detected.
 	if (display.isRescalingAtRuntime()) {
-		int dpiForWindow = DPIUtil.mapDPIToZoom(OS.GetDpiForWindow(getShell().handle));
-		if (dpiForWindow != nativeZoom) {
-			WINDOWPOS lpwp = new WINDOWPOS ();
-			OS.MoveMemory (lpwp, lParam, WINDOWPOS.sizeof);
-			handleMonitorSpecificDpiChange(dpiForWindow, new Rectangle(lpwp.x, lpwp.y, lpwp.cx, lpwp.cy));
-		}
+		display.asyncExec(() -> {
+			int dpiForWindow = DPIUtil.mapDPIToZoom(OS.GetDpiForWindow(getShell().handle));
+			if (dpiForWindow != nativeZoom) {
+				int dpiForWindowAutoscale = DPIUtil.getZoomForAutoscaleProperty(dpiForWindow);
+				int nativeZoomAutoscale = DPIUtil.getZoomForAutoscaleProperty(nativeZoom);
+				WINDOWPOS lpwp = new WINDOWPOS ();
+				OS.MoveMemory (lpwp, lParam, WINDOWPOS.sizeof);
+				Point sizeInNativeZoom = new Point(lpwp.cx, lpwp.cy);
+				Point sizeInDpiForWindow = DPIUtil.scalePoint(sizeInNativeZoom, dpiForWindowAutoscale, nativeZoomAutoscale);
+				handleMonitorSpecificDpiChange(dpiForWindow, new Rectangle(lpwp.x, lpwp.y, sizeInDpiForWindow.x, sizeInDpiForWindow.y));
+			}
+		});
 	}
 	return result;
 }