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

@@ -990,7 +990,7 @@ public void drawImage (Image image, int srcX, int srcY, int srcWidth, int srcHei
 	if (image.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 
 	int gcZoom = getZoom();
-	int srcImageZoom = calculateZoomForImage(gcZoom, srcWidth, srcHeight, destWidth, destHeight);
+	int srcImageZoom = calculateZoomForImage(image, gcZoom, srcWidth, srcHeight, destWidth, destHeight);
 	drawImage(image, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight, gcZoom, srcImageZoom);
 }
 
@@ -1003,25 +1003,30 @@ private Collection<Integer> getAllCurrentMonitorZooms() {
 	return Collections.emptySet();
 }
 
-private int calculateZoomForImage(int gcZoom, int srcWidth, int srcHeight, int destWidth, int destHeight) {
+private int calculateZoomForImage(Image image, int gcZoom, int srcWidth, int srcHeight, int destWidth, int destHeight) {
+	int scaledImageZoom;
 	if (srcWidth == 1 && srcHeight == 1) {
 		// One pixel images can use the GC zoom
-		return gcZoom;
-	}
-	if (destWidth == srcWidth && destHeight == srcHeight) {
+		scaledImageZoom = gcZoom;
+	} else if (destWidth == srcWidth && destHeight == srcHeight) {
 		// unscaled images can use the GC zoom
-		return gcZoom;
+		scaledImageZoom = gcZoom;
 	}
-
 	float imageScaleFactor = 1f * destWidth / srcWidth;
 	int imageZoom = Math.round(gcZoom * imageScaleFactor);
 	if (getAllCurrentMonitorZooms().contains(imageZoom)) {
-		return imageZoom;
-	}
-	if (imageZoom > 150) {
-		return 200;
-	}
-	return 100;
+		scaledImageZoom = imageZoom;
+	} else if (imageZoom > 150) {
+		scaledImageZoom = 200;
+	} else {
+		scaledImageZoom = 100;
+	}
+	Rectangle scaledBounds = image.getBounds(scaledImageZoom);
+	Rectangle unScaledBound = image.getBounds();
+	// validates if the image bounds are scaled up correctly as per required zoom, if it is not zoom is returned as per actual scaling factor.
+	float scalingFactor = (float) scaledBounds.height / unScaledBound.height;
+	scaledImageZoom = (int) (scalingFactor * 100);
+	return scaledImageZoom;
 }
 
 private void drawImage(Image image, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY,