[Win32] Consider transformation scale in GC.drawImage(image, x, y) #2919

The GC.drawImage(image, x, y) does not consider a potential
transformation applied to the GC when retrieving the best-fitting image
handle. The other GC.drawImage() methods are already updated
accordingly.

The GC.drawImage(image, x, y) method has a special use case of drawing
an image that is currently being rendered by another GC (like used in
double-buffering scenarios for rulers), which also requires potentially
different native and autoscale zooms to be used be applied when
retrieving a handle.

For that reason, this change only delegates a call for
GC.drawImage(image, x, y) to the existing scaling GC.drawImage() method
in case the transformation currently applied to the GC is not the
identity, as that's not the use case for rendering an image currently
generated by another GC.

Fixes #2919

Author: HeikoKlare

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

@@ -522,19 +522,6 @@ void disposeAll() {
 		super.disposeAll();
 	}
 
-	protected float calculateTransformationScale() {
-		Transform current = new Transform(device);
-		getTransform(current);
-		float[] m = new float[6];
-		current.getElements(m);
-		// this calculates the effective length in x and y
-		// direction without being affected by the rotation
-		// of the transformation
-		float scaleWidth = (float) Math.hypot(m[0], m[2]);
-		float scaleHeight = (float) Math.hypot(m[1], m[3]);
-		current.dispose();
-		return Math.max(scaleWidth, scaleHeight);
-	}
 }
 
 private class CopyAreaToImageOperation extends ImageOperation {
@@ -1055,7 +1042,32 @@ public void drawImage (Image image, int x, int y) {
 	checkNonDisposed();
 	if (image == null) SWT.error (SWT.ERROR_NULL_ARGUMENT);
 	if (image.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
-	storeAndApplyOperationForExistingHandle(new DrawImageOperation(image, new Point(x, y)));
+	Transform transform = new Transform(device);
+	try {
+		getTransform(transform);
+		if (transform.isIdentity()) {
+			storeAndApplyOperationForExistingHandle(new DrawImageOperation(image, new Point(x, y)));
+		} else {
+			Rectangle imageBounds = image.getBounds();
+			drawImage(image, x, y, imageBounds.width, imageBounds.height);
+		}
+	} finally {
+		transform.dispose();
+	}
+}
+
+private float calculateTransformationScale() {
+	Transform current = new Transform(device);
+	getTransform(current);
+	float[] m = new float[6];
+	current.getElements(m);
+	// this calculates the effective length in x and y
+	// direction without being affected by the rotation
+	// of the transformation
+	float scaleWidth = (float) Math.hypot(m[0], m[2]);
+	float scaleHeight = (float) Math.hypot(m[1], m[3]);
+	current.dispose();
+	return Math.max(scaleWidth, scaleHeight);
 }
 
 private class DrawImageOperation extends ImageOperation {