[win32] Choose best Image handle drawing with GC

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

@@ -14,10 +14,14 @@
 package org.eclipse.swt.graphics;
 
 
+import java.util.*;
+import java.util.stream.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.internal.*;
 import org.eclipse.swt.internal.gdip.*;
 import org.eclipse.swt.internal.win32.*;
+import org.eclipse.swt.widgets.*;
 
 /**
  * Class <code>GC</code> is where all of the drawing capabilities that are
@@ -985,31 +989,70 @@ public void drawImage (Image image, int srcX, int srcY, int srcWidth, int srcHei
 	if (image == null) SWT.error (SWT.ERROR_NULL_ARGUMENT);
 	if (image.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 
-	int imageZoom = getZoom();
-	Rectangle src = DPIUtil.scaleUp(drawable, new Rectangle(srcX, srcY, srcWidth, srcHeight), imageZoom);
+	int gcZoom = getZoom();
+	int srcImageZoom = calculateZoomForImage(gcZoom, srcWidth, srcHeight, destWidth, destHeight);
+	drawImage(image, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight, gcZoom, srcImageZoom);
+}
+
+private Collection<Integer> getAllCurrentMonitorZooms() {
+	if (device instanceof Display display) {
+		return Arrays.stream(display.getMonitors())
+			.map(Monitor::getZoom)
+			.collect(Collectors.toSet());
+	}
+	return Collections.emptySet();
+}
+
+private int calculateZoomForImage(int gcZoom, int srcWidth, int srcHeight, int destWidth, int destHeight) {
+	if (srcWidth == 1 && srcHeight == 1) {
+		// One pixel images can use the GC zoom
+		return gcZoom;
+	}
+	if (destWidth == srcWidth && destHeight == srcHeight) {
+		// unscaled images can use the GC zoom
+		return 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;
+}
+
+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 dest = DPIUtil.scaleUp(drawable, new Rectangle(destX, destY, destWidth, destHeight), imageZoom);
-	if (imageZoom != 100) {
+	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(imageZoom);
+		Rectangle b = image.getBounds(scaledImageZoom);
 		int errX = src.x + src.width - b.width;
 		int errY = src.y + src.height - b.height;
 		if (errX != 0 || errY != 0) {
-			if (errX <= imageZoom / 100 && errY <= imageZoom / 100) {
+			if (errX <= scaledImageZoom / 100 && errY <= scaledImageZoom / 100) {
 				src.intersect(b);
 			} else {
 				SWT.error (SWT.ERROR_INVALID_ARGUMENT);
 			}
 		}
 	}
-	drawImage(image, src.x, src.y, src.width, src.height, dest.x, dest.y, dest.width, dest.height, false);
+	drawImage(image, src.x, src.y, src.width, src.height, dest.x, dest.y, dest.width, dest.height, false, scaledImageZoom);
 }
 
 void drawImage(Image srcImage, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight, boolean simple) {
-	int imageZoom = getZoom();
+	drawImage(srcImage, srcX, srcY, srcWidth, srcHeight, destX, destY, destWidth, destHeight, simple, getZoom());
+}
+
+void drawImage(Image srcImage, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight, boolean simple, int imageZoom) {
 	if (data.gdipGraphics != 0) {
 		//TODO - cache bitmap
 		long [] gdipImage = srcImage.createGdipImage(imageZoom);