Rewrite the algorithm that sets smallIcon/largeIcon in Decorations class

Don't sort, compare and keep the image that is closest to the desired
dimensions, pixel transparency and pixel depth.

The new method "isCloserThan" is based on the (now deleted) "compare"
method and returns true only if "compare" would have returned -1

Reduce visibility of Decorations::setImages

Author: fedejeanne

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Decorations.java

@@ -274,26 +274,6 @@ void closeWidget () {
 	if (event.doit && !isDisposed ()) dispose ();
 }
 
-int compare (ImageData data1, ImageData data2, int width, int height, int depth) {
-	int value1 = Math.abs (data1.width - width), value2 = Math.abs (data2.width - width);
-	if (value1 == value2) {
-		int transparent1 = data1.getTransparencyType ();
-		int transparent2 = data2.getTransparencyType ();
-		if (transparent1 == transparent2) {
-			if (data1.depth == data2.depth) return 0;
-			return data1.depth > data2.depth && data1.depth <= depth ? -1 : 1;
-		}
-		if (transparent1 == SWT.TRANSPARENCY_ALPHA) return -1;
-		if (transparent2 == SWT.TRANSPARENCY_ALPHA) return 1;
-		if (transparent1 == SWT.TRANSPARENCY_MASK) return -1;
-		if (transparent2 == SWT.TRANSPARENCY_MASK) return 1;
-		if (transparent1 == SWT.TRANSPARENCY_PIXEL) return -1;
-		if (transparent2 == SWT.TRANSPARENCY_PIXEL) return 1;
-		return 0;
-	}
-	return value1 < value2 ? -1 : 1;
-}
-
 @Override
 Widget computeTabGroup () {
 	return this;
@@ -882,7 +862,7 @@ public void setImage (Image image) {
 	setImages (image, null);
 }
 
-void setImages (Image image, Image [] images) {
+private void setImages (Image image, Image [] images) {
 	if (smallImage != null) smallImage.dispose ();
 	if (largeImage != null) largeImage.dispose ();
 	smallImage = largeImage = null;
@@ -892,23 +872,17 @@ void setImages (Image image, Image [] images) {
 		smallIcon = largeIcon = image;
 	} else {
 		if (images != null && images.length > 0) {
-			int depth = display.getIconDepth ();
-			ImageData [] datas = null;
-			if (images.length > 1) {
-				Image [] bestImages = new Image [images.length];
-				System.arraycopy (images, 0, bestImages, 0, images.length);
-				datas = new ImageData [images.length];
-				for (int i=0; i<datas.length; i++) {
-					datas [i] = images [i].getImageData ();
-				}
-				images = bestImages;
-				sort (images, datas, getSystemMetrics (OS.SM_CXSMICON), getSystemMetrics (OS.SM_CYSMICON), depth);
-			}
-			smallIcon = images [0];
-			if (images.length > 1) {
-				sort (images, datas, getSystemMetrics (OS.SM_CXICON), getSystemMetrics (OS.SM_CYICON), depth);
-			}
-			largeIcon = images [0];
+			int depth = display.getIconDepth();
+
+			ImageData[] imageData = getImageDataAt100(images);
+
+			int smallIconWidthAt100 = getSystemMetrics(OS.SM_CXSMICON);
+			int smallIconIndex = findIndexOfClosest(imageData, smallIconWidthAt100, depth);
+			smallIcon = images[smallIconIndex];
+
+			int largeIconWidthAt100 = getSystemMetrics(OS.SM_CXICON);
+			int largeIconIndex = findIndexOfClosest(imageData, largeIconWidthAt100, depth);
+			largeIcon = images[largeIconIndex];
 		}
 	}
 	if (smallIcon != null) {
@@ -949,6 +923,64 @@ void setImages (Image image, Image [] images) {
 	}
 }
 
+private static ImageData[] getImageDataAt100(Image[] images) {
+	ImageData[] datas = new ImageData[images.length];
+	for (int i = 0; i < images.length; i++) {
+		datas[i] = images[i].getImageData(100);
+	}
+	return datas;
+}
+
+private static int findIndexOfClosest(ImageData[] imageData, int targetWidth, int targetDepth) {
+	int closestIndex = 0;
+	ImageData closestData = imageData[0];
+	for (int i = 1; i < imageData.length; i++) {
+		if (isCloserThan(imageData[i], closestData, targetWidth, targetDepth)) {
+			closestIndex = i;
+			closestData = imageData[i];
+		}
+	}
+
+	return closestIndex;
+}
+
+private static boolean isCloserThan(ImageData dataToTest, ImageData referenceData, int targetWidth, int targetDepth) {
+	int diffWidthToTest = Math.abs(dataToTest.width - targetWidth);
+	int diffReferenceWidth = Math.abs(referenceData.width - targetWidth);
+
+	// The closer the width the better
+	if (diffWidthToTest != diffReferenceWidth)
+		return diffWidthToTest < diffReferenceWidth;
+
+	int transparencyToTest = dataToTest.getTransparencyType();
+	int referenceTransparency = referenceData.getTransparencyType();
+
+	// If they have the same transparency then the bigger the pixel depth (without
+	// surpassing the target depth) the better
+	if (transparencyToTest == referenceTransparency) {
+		if (dataToTest.depth == referenceData.depth)
+			return false;
+
+		return dataToTest.depth > referenceData.depth && dataToTest.depth <= targetDepth;
+	}
+
+	// If they have different transparency, favor (in this order): the one with
+	// an alpha channel, the one with a mask, the one with a transparency pixel
+	if (transparencyToTest == SWT.TRANSPARENCY_ALPHA)
+		return true;
+	if (referenceTransparency == SWT.TRANSPARENCY_ALPHA)
+		return false;
+	if (transparencyToTest == SWT.TRANSPARENCY_MASK)
+		return true;
+	if (referenceTransparency == SWT.TRANSPARENCY_MASK)
+		return false;
+	if (transparencyToTest == SWT.TRANSPARENCY_PIXEL)
+		return true;
+	if (referenceTransparency == SWT.TRANSPARENCY_PIXEL)
+		return false;
+	return false;
+}
+
 /**
  * Sets the receiver's images to the argument, which may
  * be an empty array. Images are typically displayed by the
@@ -1313,26 +1345,6 @@ public void setVisible (boolean visible) {
 	}
 }
 
-void sort (Image [] images, ImageData [] datas, int width, int height, int depth) {
-	/* Shell Sort from K&R, pg 108 */
-	int length = images.length;
-	if (length <= 1) return;
-	for (int gap=length/2; gap>0; gap/=2) {
-		for (int i=gap; i<length; i++) {
-			for (int j=i-gap; j>=0; j-=gap) {
-				if (compare (datas [j], datas [j + gap], width, height, depth) >= 0) {
-					Image swap = images [j];
-					images [j] = images [j + gap];
-					images [j + gap] = swap;
-					ImageData swapData = datas [j];
-					datas [j] = datas [j + gap];
-					datas [j + gap] = swapData;
-				}
-			}
-		}
-	}
-}
-
 @Override
 boolean translateAccelerator (MSG msg) {
 	if (!isEnabled () || !isActive ()) return false;