[win32] Fix double buffer paint with ImageGcDrawer

This commit fixes a regression introduced with f10721a that did not
properly retain the currently drawn zoom level when an ImageGcDrawer
is used. That leads to issues with zoom != 100.

Author: akoch-yatta

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

@@ -1691,7 +1691,7 @@ private ImageHandle init(ImageData i, int zoom) {
  */
 @Override
 public long internal_new_GC (GCData data) {
-	return configureGC(data, 100);
+	return this.imageProvider.configureGCData(data);
 }
 
 private long configureGC(GCData data, int zoom) {
@@ -1854,6 +1854,10 @@ private abstract class AbstractImageProviderWrapper {
 
 	protected abstract Rectangle getBounds(int zoom);
 
+	protected long configureGCData(GCData data) {
+		return configureGC(data, 100);
+	}
+
 	public Collection<Integer> getPreservedZoomLevels() {
 		return Collections.emptySet();
 	}
@@ -2480,6 +2484,7 @@ private class ImageGcDrawerWrapper extends DynamicImageProviderWrapper {
 	private ImageGcDrawer drawer;
 	private int width;
 	private int height;
+	private int currentZoom = 100;
 
 	ImageGcDrawerWrapper(ImageGcDrawer imageGcDrawer, int width, int height) {
 		checkProvider(imageGcDrawer, ImageGcDrawer.class);
@@ -2494,13 +2499,19 @@ protected Rectangle getBounds(int zoom) {
 		return DPIUtil.scaleBounds(rectangle, zoom, 100);
 	}
 
+	@Override
+	protected long configureGCData(GCData data) {
+		return configureGC(data, currentZoom);
+	}
+
 	@Override
 	ImageData newImageData(int zoom) {
 		return getImageMetadata(zoom).getImageData();
 	}
 
 	@Override
 	protected ImageHandle newImageHandle(int zoom) {
+		currentZoom = zoom;
 		int gcStyle = drawer.getGcStyle();
 		Image image;
 		if ((gcStyle & SWT.TRANSPARENT) != 0) {