Ensure DrawImage deals with scenario ImageData not linearly scaled

This change makes sure DrawImage handles the scenario where ImageData
may not be linearly scaled across zooms.

Author: arunjose696

bundles/org.eclipse.swt/Eclipse SWT Tests/win32/org/eclipse/swt/graphics/ImagesWin32Tests.java

@@ -25,6 +25,90 @@
 @ExtendWith(WithMonitorSpecificScalingExtension.class)
 class ImagesWin32Tests {
 
+	@Test
+	public void test_imageScaledFrom150_when125PercentImageUnavailable() {
+		Display display = Display.getDefault();
+		GC gc = new GC(display);
+		GCData gcData = gc.getGCData();
+		gcData.nativeZoom = 125;
+		ImageDataProvider imageDataProviderReturnsNullAt125 = zoom -> {
+			if (zoom == 125) {
+				return null;
+			}
+			float scaleFactor = zoom / 100f;
+			int scaledWidth = Math.round(16 * scaleFactor);
+			int scaledHeight = Math.round(16 * scaleFactor);
+			return new ImageData(scaledWidth, scaledHeight, 1, new PaletteData(new RGB(255, 0, 0)));
+		};
+		Image image = new Image(display, imageDataProviderReturnsNullAt125);
+		gc.drawImage(image, 0, 0, 16, 16, 0, 0, 16, 16);
+		gc.dispose();
+		image.dispose();
+	}
+
+	@Test
+	public void test_imageScaledFrom100_when125And150PercentImagesUnavailable() {
+		Display display = Display.getDefault();
+		GC gc = new GC(display);
+		GCData gcData = gc.getGCData();
+		gcData.nativeZoom = 125;
+		ImageDataProvider imageDataProviderReturnsNullAt125and150 = zoom -> {
+			if (zoom == 125) {
+				return null;
+			}
+			if (zoom == 150) {
+				return null;
+			}
+			float scaleFactor = zoom / 100f;
+			int scaledWidth = Math.round(16 * scaleFactor);
+			int scaledHeight = Math.round(16 * scaleFactor);
+			return new ImageData(scaledWidth, scaledHeight, 1, new PaletteData(new RGB(255, 0, 0)));
+		};
+		Image image = new Image(display, imageDataProviderReturnsNullAt125and150);
+		gc.drawImage(image, 0, 0, 16, 16, 0, 0, 16, 16);
+		gc.dispose();
+		image.dispose();
+	}
+
+	@Test
+	public void test_drawImage_when130PercentImageUnavailable() {
+		Display display = Display.getDefault();
+		GC gc = new GC(display);
+		GCData gcData = gc.getGCData();
+		gcData.nativeZoom = 130;
+		ImageDataProvider imageDataProviderReturnsNullAt125 = zoom -> {
+			if (zoom == 130){
+				return null;
+			}
+			float scaleFactor = zoom / 100f;
+			int scaledWidth = Math.round(16 * scaleFactor);
+			int scaledHeight = Math.round(16 * scaleFactor);
+			return new ImageData(scaledWidth, scaledHeight, 1, new PaletteData(new RGB(255, 0, 0)));
+		};
+		Image image = new Image(display, imageDataProviderReturnsNullAt125);
+		gc.drawImage(image, 0, 0, 16, 16, 0, 0, 16, 16);
+		gc.dispose();
+		image.dispose();
+	}
+
+	@Test
+	public void test_drawImageUsesWronglyScaledImageDataProvider() {
+		Display display = Display.getDefault();
+		GC gc = new GC(display);
+		GCData gcData = gc.getGCData();
+		gcData.nativeZoom = 125;
+		ImageDataProvider incorrectlyScaledimageDataProvider = zoom -> {
+			int scaleFactor = zoom / 100;
+			int scaledWidth = Math.round(16 * scaleFactor);
+			int scaledHeight = Math.round(16 * scaleFactor);
+			return new ImageData(scaledWidth, scaledHeight, 1, new PaletteData(new RGB(255, 0, 0)));
+		};
+		Image image = new Image(display, incorrectlyScaledimageDataProvider);
+		gc.drawImage(image, 0, 0, 16, 16, 0, 0, 16, 16);
+		gc.dispose();
+		image.dispose();
+	}
+
 	@Test
 	public void testImageIconTypeShouldNotChangeAfterCallingGetHandleForDifferentZoom() {
 		Image icon = Display.getDefault().getSystemImage(SWT.ICON_ERROR);

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

@@ -1026,20 +1026,22 @@ private int calculateZoomForImage(int gcZoom, int srcWidth, int srcHeight, int d
 
 private void drawImage(Image image, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY,
 		int destWidth, int destHeight, int imageZoom, int scaledImageZoom) {
-	Rectangle src = DPIUtil.scaleUp(drawable, new Rectangle(srcX, srcY, srcWidth, srcHeight), scaledImageZoom);
+	Rectangle scaledBounds = image.getBounds(scaledImageZoom);
+	Rectangle unScaledBound = image.getBounds();
+	float scalingFactor = (float) scaledBounds.height / unScaledBound.height;
+	Rectangle src = DPIUtil.scaleUp(drawable, new Rectangle(srcX, srcY, srcWidth, srcHeight),(int) (scalingFactor * 100));
 	Rectangle dest = DPIUtil.scaleUp(drawable, new Rectangle(destX, destY, destWidth, destHeight), imageZoom);
 	if (scaledImageZoom != 100) {
 		/*
 		 * This is a HACK! Due to rounding errors at fractional scale factors,
 		 * the coordinates may be slightly off. The workaround is to restrict
 		 * coordinates to the allowed bounds.
 		 */
-		Rectangle b = image.getBounds(scaledImageZoom);
-		int errX = src.x + src.width - b.width;
-		int errY = src.y + src.height - b.height;
+		int errX = src.x + src.width - scaledBounds.width;
+		int errY = src.y + src.height - scaledBounds.height;
 		if (errX != 0 || errY != 0) {
 			if (errX <= scaledImageZoom / 100 && errY <= scaledImageZoom / 100) {
-				src.intersect(b);
+				src.intersect(scaledBounds);
 			} else {
 				SWT.error (SWT.ERROR_INVALID_ARGUMENT);
 			}