[macOS] Initialize image data from ImageGcDrawer at device zoom only

An Image based on an ImageGcDrawer currently initializes two image
representations for 100% and 200% zoom, so that an appropriate
representation for each of the two zoom levels can be retrieved. This,
however, leads to issues when creating a GC on an Image created in that
way, as only one of the two representations (the one fitting to the
current device zoom) will be modified by the GC. If later the
representation with the other zoom is used, it will not contain the
changes performed by the GC.

One such scenario is starting an application at a monitor with one zoom
(used as the device zoom throughout the application lifecycle then) and
moving the shell to a monitor with a different zoom. An image will then
be modified only for the zoom of the first monitor, thus if using it
inside a control, it will yield the unmodified version on the second
monitor.

To avoid this issue, this change ensures that an Image based on an
ImageGcDrawer is only initialized for the device zoom.

Fixes eclipse-platform/eclipse.platform.ui#3039

Author: HeikoKlare

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

@@ -572,7 +572,7 @@ public Image(Device device, ImageData data) {
 	NSAutoreleasePool pool = null;
 	if (!NSThread.isMainThread()) pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
 	try {
-		init(data);
+		init(data, 100);
 		init();
 	} finally {
 		if (pool != null) pool.release();
@@ -623,7 +623,7 @@ public Image(Device device, ImageData source, ImageData mask) {
 		ImageData image = new ImageData(source.width, source.height, source.depth, source.palette, source.scanlinePad, source.data);
 		image.maskPad = mask.scanlinePad;
 		image.maskData = mask.data;
-		init(image);
+		init(image, 100);
 	} finally {
 		if (pool != null) pool.release();
 	}
@@ -789,7 +789,7 @@ public Image(Device device, ImageFileNameProvider imageFileNameProvider) {
 	if (!NSThread.isMainThread()) pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
 	try {
 		initNative(filename);
-		if (this.handle == null) init(ImageDataLoader.load(filename, 100, 100).element());
+		if (this.handle == null) init(ImageDataLoader.load(filename, 100, 100).element(), 100);
 		init();
 		String filename2x = imageFileNameProvider.getImagePath(200);
 		if (filename2x != null) {
@@ -848,7 +848,7 @@ public Image(Device device, ImageDataProvider imageDataProvider) {
 	NSAutoreleasePool pool = null;
 	if (!NSThread.isMainThread()) pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
 	try {
-		init (data);
+		init (data, 100);
 		init ();
 		ImageData data2x = imageDataProvider.getImageData (200);
 		if (data2x != null) {
@@ -886,20 +886,13 @@ public Image(Device device, ImageGcDrawer imageGcDrawer, int width, int height)
 	this.imageGcDrawer = imageGcDrawer;
 	this.width = width;
 	this.height = height;
-	ImageData data = drawWithImageGcDrawer(imageGcDrawer, width, height, 100);
+	ImageData data = drawWithImageGcDrawer(imageGcDrawer, width, height, DPIUtil.getDeviceZoom());
 	if (data == null) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 	NSAutoreleasePool pool = null;
 	if (!NSThread.isMainThread()) pool = (NSAutoreleasePool) new NSAutoreleasePool().alloc().init();
 	try {
-		init (data);
+		init (data, DPIUtil.getDeviceZoom());
 		init ();
-		ImageData data2x = drawWithImageGcDrawer(imageGcDrawer, width, height, 200);
-		if (data2x != null) {
-			alphaInfo_200 = new AlphaInfo();
-			NSBitmapImageRep rep = createRepresentation (data2x, alphaInfo_200);
-			handle.addRepresentation(rep);
-			rep.release();
-		}
 	} finally {
 		if (pool != null) pool.release();
 	}
@@ -1474,7 +1467,7 @@ void init(int width, int height) {
 	if (alphaInfo_100 == null) alphaInfo_100 = new AlphaInfo();
 }
 
-void init(ImageData image) {
+void init(ImageData image, int imageZoom) {
 	if (image == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 
 	if (handle != null) handle.release();
@@ -1484,8 +1477,8 @@ void init(ImageData image) {
 	size.width = width;
 	size.height = height;
 	handle = handle.initWithSize(size);
-	this.width = image.width;
-	this.height = image.height;
+	this.width = image.width * 100 / imageZoom;
+	this.height = image.height * 100 / imageZoom;
 	if (alphaInfo_100 == null) alphaInfo_100 = new AlphaInfo();
 	NSBitmapImageRep rep = createRepresentation(image, alphaInfo_100);
 	handle.addRepresentation(rep);
@@ -1495,7 +1488,7 @@ void init(ImageData image) {
 
 private void initWithSupplier(Function<Integer, Boolean> canLoadAtZoom, Function<Integer, ImageData> zoomToImageData) {
 	ImageData imageData = zoomToImageData.apply(100);
-	init(imageData);
+	init(imageData, 100);
 	if (canLoadAtZoom.apply(200)) {
 		ImageData imageData2x = zoomToImageData.apply(200);
 		alphaInfo_200 = new AlphaInfo();

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_graphics_Image.java

@@ -25,6 +25,7 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.assumeFalse;
 import static org.junit.Assume.assumeTrue;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
@@ -1075,6 +1076,34 @@ public void test_imageDataSameViaProviderAndSimpleData() {
 	dataImage.dispose();
 }
 
+/**
+ * See https://github.com/eclipse-platform/eclipse.platform.ui/issues/3039
+ */
+@Test
+public void test_gcOnImageGcDrawer_imageDataAtNonDeviceZoom() {
+	int originalDeviceZoom = DPIUtil.getDeviceZoom();
+	int deviceZoom = 200;
+	int nonDeviceZoom = 100;
+	DPIUtil.setDeviceZoom(deviceZoom);
+
+	ImageGcDrawer blueDrawer = (gc, width, height) -> {
+		gc.setBackground(display.getSystemColor(SWT.COLOR_BLUE));
+		gc.fillRectangle(0, 0, width, height);
+	};
+	Image image = new Image(display, blueDrawer, 1, 1);
+	int bluePixelValue = image.getImageData(nonDeviceZoom).getPixel(0, 0);
+
+	GC redOverwritingGc = new GC(image);
+	try {
+		redOverwritingGc.setBackground(display.getSystemColor(SWT.COLOR_RED));
+		redOverwritingGc.fillRectangle(0, 0, 1, 1);
+		assertNotEquals(bluePixelValue, image.getImageData(nonDeviceZoom).getPixel(0, 0));
+	} finally {
+		redOverwritingGc.dispose();
+		image.dispose();
+		DPIUtil.setDeviceZoom(originalDeviceZoom);
+	}
+}
 
 private Comparator<ImageData> imageDataComparator() {
 	return Comparator.<ImageData>comparingInt(d -> d.width) //
@@ -1095,3 +1124,4 @@ private Comparator<ImageData> imageDataComparator() {
 }
 
 }
+