Fix cursors double-size on Mac and Linux 11 (#356)

See #354

On Mac and Linux X11 device zoom should always be 100% when creating the ImageData for the cursor.

org.eclipse.gef/src/org/eclipse/gef/SharedCursors.java

@@ -15,7 +15,7 @@
 import org.eclipse.swt.graphics.Cursor;
 
 import org.eclipse.jface.resource.ImageDescriptor;
-
+import org.eclipse.core.runtime.Platform;
 import org.eclipse.draw2d.Cursors;
 
 import org.eclipse.gef.internal.Internal;
@@ -70,7 +70,11 @@ private static int getDeviceZoom() {
 				}
 			}
 		}
-		return deviceZoom;
+		// On Mac and Linux X11 ImageData for cursors should always be created with 100% device zoom 
+		return Platform.getOS().equals(Platform.OS_MACOSX) ||
+				(Platform.getOS().equals(Platform.OS_LINUX) && "x11".equalsIgnoreCase(System.getenv("XDG_SESSION_TYPE"))) //$NON-NLS-1$ //$NON-NLS-2$
+				? 100 
+				: deviceZoom;
 	}
 
 }