Preserve handles of images when changing zooms #2139

Preserve the handles of images created out of existing image handles and
also from those which are still needed (according to the method
AbstractImageProviderWrapper::getPreservedZoomLevels)

Fixes #2139

Author: fedejeanne

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

@@ -1012,7 +1012,7 @@ private void destroyHandles() {
 
 @Override
 void destroyHandlesExcept(Set<Integer> zoomLevels) {
-	destroyHandles(zoom -> !zoomLevels.contains(zoom) || !this.imageProvider.getPreservedZoomLevels().contains(zoom));
+	destroyHandles(zoom -> !zoomLevels.contains(zoom) && !this.imageProvider.getPreservedZoomLevels().contains(zoom));
 }
 
 private void destroyHandles(Predicate<Integer> filter) {
@@ -1930,6 +1930,11 @@ ImageData newImageData(int zoom) {
 	AbstractImageProviderWrapper createCopy(Image image) {
 		return image.new ExistingImageHandleProviderWrapper(handle, zoomForHandle);
 	}
+
+	@Override
+	public Collection<Integer> getPreservedZoomLevels() {
+		return Collections.singleton(zoomForHandle);
+	}
 }
 
 private abstract class ImageFromImageDataProviderWrapper extends AbstractImageProviderWrapper {