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

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 +12,14 @@
 
 package org.eclipse.gmf.runtime.gef.ui.internal.l10n;
 
+import java.lang.reflect.Constructor;
+
+import org.eclipse.jface.resource.ImageDescriptor;
 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;
 
 
 /**
@@ -33,27 +40,33 @@ public class Cursors {
      * Constant define for a cusor used to move an existing line segment
      */
     public static final Cursor CURSOR_SEG_MOVE;
-    
-    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
-	private static int getDeviceZoom() {
-		if (deviceZoom == -1) {
-			deviceZoom = 100; // default value
-			String deviceZoomProperty = System.getProperty("org.eclipse.swt.internal.deviceZoom"); //$NON-NLS-1$
-			if (deviceZoomProperty != null) {
-				try {
-					deviceZoom = Integer.parseInt(deviceZoomProperty);
-				} catch (NumberFormatException ex) {
-					// if the property can not be parsed we keep the default 100% zoom level
-				}
-			}
+	// 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 {
+			// SWT version >= 3.131.0
+			Constructor<Cursor> ctor = Cursor.class.getConstructor(Device.class, ImageDataProvider.class, int.class,
+					int.class);
+			return ctor.newInstance(null, imageDataProvider, hotspotX, hotspotY);
+		} catch (NoSuchMethodException e) {
+			return new Cursor(null, imageDataProvider.getImageData(100), hotspotX, hotspotY);
+		} catch (ReflectiveOperationException e) {
+			throw new RuntimeException("Failed to instantiate Cursor", e); //$NON-NLS-1$
+		}
+	}
+
+	private static ImageData getScaledImageData(ImageDescriptor descriptor, int zoom) {
+		Image image = descriptor.createImage();
+		try {
+			return image.getImageData(zoom);
+		} finally {
+			image.dispose();
 		}
-		return deviceZoom;
 	}
 }