[90] Fix cursor initialization when using fractional scaling

Recent Eclipse version support fractional zoom level as opposed to 100%
or 200% zoom. Because no icons exist for those levels, an
IllegalArgumentException is thrown when trying to create the
corresponding cursors.

In order to solve this, one has to consider the following cases:

1) Newer SWT versions provide a Cursor constructor that accepts an
ImageDataProvider. This constructor always creates image data matching
the device zoom.

2) Win32: Older SWT versions automatically upscale the image data to
match the device zoom. Therefore the original image data must be at 100%
zoom.

3) On other operating systems, the image data should be pre-scaled, as
no further scaling is done by SWT.

Author: ptziegler

bundles/org.eclipse.gmf.runtime.gef.ui/src/org/eclipse/gmf/runtime/gef/ui/internal/l10n/Cursors.java

@@ -1,5 +1,5 @@
 /******************************************************************************
- * Copyright (c) 2002, 2003 IBM Corporation and others.
+ * Copyright (c) 2002, 2025 IBM Corporation and others.
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
  * which is available at https://www.eclipse.org/legal/epl-2.0/
@@ -12,7 +12,15 @@
 
 package org.eclipse.gmf.runtime.gef.ui.internal.l10n;
 
+import java.lang.reflect.Constructor;
+
+import org.eclipse.jface.resource.ImageDescriptor;
+import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.Cursor;
+import org.eclipse.swt.graphics.Device;
+import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.graphics.ImageData;
+import org.eclipse.swt.graphics.ImageDataProvider;
 
 
 /**
@@ -37,11 +45,31 @@ public class Cursors {
     private static int deviceZoom = -1;
 
     static {
-		CURSOR_SEG_ADD = new Cursor(null, GefUIPluginImages.DESC_SEG_ADD.getImageData(getDeviceZoom()), 0, 0);
-		CURSOR_SEG_MOVE = new Cursor(null, GefUIPluginImages.DESC_SEG_MOVE.getImageData(getDeviceZoom()), 0, 0);
+		CURSOR_SEG_ADD = createCursor(GefUIPluginImages.DESC_SEG_ADD, 0, 0);
+		CURSOR_SEG_MOVE = createCursor(GefUIPluginImages.DESC_SEG_MOVE, 0, 0);
 	}
 
-    // Taken from org.eclipse.gef.SharedCursors.java
+    // Taken from org.eclipse.gef.internal.InternalGEFPlugin.java
+	private static Cursor createCursor(ImageDescriptor source, int hotspotX, int hotspotY) {
+		ImageDataProvider imageDataProvider = zoom -> getScaledImageData(source, zoom);
+		try {
+			Constructor<Cursor> ctor = Cursor.class.getConstructor(Device.class, ImageDataProvider.class, int.class,
+					int.class);
+			return ctor.newInstance(null, imageDataProvider, hotspotX, hotspotY);
+		} catch (NoSuchMethodException e) {
+			// SWT version < 3.131.0
+		} catch (ReflectiveOperationException e) {
+			throw new RuntimeException("Failed to instantiate Cursor", e); //$NON-NLS-1$
+		}
+		// Note: On Windows, the image data is automatically scaled to match the device zoom
+		int deviceZoom = 100;
+		if (!"win32".equals(SWT.getPlatform())) { //$NON-NLS-1$
+			deviceZoom = getDeviceZoom();
+		}
+		return new Cursor(null, imageDataProvider.getImageData(deviceZoom), hotspotX, hotspotY);
+	}
+	
+	// Taken from org.eclipse.gef.SharedCursors.java
 	private static int getDeviceZoom() {
 		if (deviceZoom == -1) {
 			deviceZoom = 100; // default value
@@ -56,4 +84,13 @@ private static int getDeviceZoom() {
 		}
 		return deviceZoom;
 	}
+
+	private static ImageData getScaledImageData(ImageDescriptor descriptor, int zoom) {
+	    Image image = descriptor.createImage();
+	    try {
+	    	return image.getImageData(zoom);
+	    } finally {
+	        image.dispose();
+	    }
+	}
 }