[Win32] Remove obsolete zoom parameter for refreshing GC handle

When refreshing a GC with another zoom, that zoom is unnecessarily
duplicated in the DrawableWrapper of the Image and as a parameter of the
refresh method of the GC. This refresh method than unnecessarily uses
that zoom to initialize the GCData's native zoom with it, even though
that's overwritten with the proper zoom by initializing the GC with the
DrawableWrapper afterwards.

This change removes the zoom duplication by removing the parameter in
the refresh method of the GC. It removes the unnecessary assignment of
the GCData's native zoom and moves the check for whether a refresh is
necessary because of a zoom change from the GC to the image. In
addition, it ensures that the memGC of an image is not accidentally set
to null in case the memGC's zoom does already fit to the requested zoom.

Author: HeikoKlare

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/GC.java

@@ -5833,15 +5833,12 @@ Point textExtentInPixels(String string, int flags) {
 	return new Point(rect.right, rect.bottom);
 }
 
-void refreshFor(Drawable drawable, int zoom) {
+void refreshFor(Drawable drawable) {
 	if (drawable == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
-	if (zoom == getZoom()) {
-		return;
-	}
 	destroy();
 	GCData newData = new GCData();
 	originalData.copyTo(newData);
-	createGcHandle(drawable, newData, zoom);
+	createGcHandle(drawable, newData);
 }
 
 /**
@@ -5947,8 +5944,7 @@ private void storeAndApplyOperationForExistingHandle(Operation operation) {
 	operation.apply();
 }
 
-private void createGcHandle(Drawable drawable, GCData newData, int nativeZoom) {
-	newData.nativeZoom = nativeZoom;
+private void createGcHandle(Drawable drawable, GCData newData) {
 	long newHandle = drawable.internal_new_GC(newData);
 	if (newHandle == 0) SWT.error(SWT.ERROR_NO_HANDLES);
 	init(drawable, newData, newHandle);

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Image.java

@@ -2177,10 +2177,12 @@ protected ImageHandle newImageHandle(int zoom) {
 			return createBaseHandle(zoom);
 		}
 		if (memGC != null) {
-			GC currentGC = memGC;
-			memGC = null;
-			createHandle(zoom);
-			currentGC.refreshFor(new DrawableWrapper(Image.this, zoom), zoom);
+			if (memGC.getZoom() != zoom) {
+				GC currentGC = memGC;
+				memGC = null;
+				createHandle(zoom);
+				currentGC.refreshFor(new DrawableWrapper(Image.this, zoom));
+			}
 			return zoomLevelToImageHandle.get(zoom);
 		}
 		return super.newImageHandle(zoom);