SWT TrayItem.setImage does not scale properly in Mac status bar

Question

On my cross-platform SWT Java application, I'm using TrayItem's setImages() function to set the dock and status bar icon. The icon is a 128x128 transparent PNG. The status and tray icons are appropriately clipped on both Windows and Linux distributions, but on the Mac I have problems that make the status bar icon appear with strange padding on both sides like this:

It's strange to me that this is working on all other platforms but the Mac. For instance, here is the same status bar icon without the problem on my Linux box:

Does anyone have any idea how to prevent this extra padding on the Mac?

Answer 1

I found the problem in SWT Cocoa sources.

public void setImage (Image image) {
    checkWidget ();
    if (image != null && image.isDisposed ()) error (SWT.ERROR_INVALID_ARGUMENT);
    super.setImage (image);
    double /*float*/ width = 0;
    if (image == null) {
        view.setImage (null);
    } else {
        /*
         * Feature in Cocoa.  If the NSImage object being set into the view is
         * the same NSImage object that is already there then the new image is
         * not taken.  This results in the view's image not changing even if the
         * NSImage object's content has changed since it was last set into the
         * view.  The workaround is to temporarily set the view's image to null
         * so that the new image will then be taken.
         */
        NSImage current = view.image ();
        if (current != null && current.id == image.handle.id) {
            view.setImage (null);
        }
        view.setImage (image.handle);
        if (visible) {
            width = image.handle.size ().width + BORDER;
        }
    }
    item.setLength (width);
}

The problem is on the line width = image.handle.size ().width + BORDER; which just takes pure size of image (in your case it's 128 px). I didn't found any suitable workaround (I saw you post bug report on SWT bugzilla).

So only way to avoid this bug (for now) is to make your tray image smaller.