Window between desktop files and background

Window between desktop files and background

My app is a window that sits between the desktop icons and the wallpaper.
To achieve this I used
[self setLevel:kCGDesktopWindowLevel - 1];
However, my window is not interactive, I cannot move it around with my
mouse? Any ideas why?
Mouse events are not firing
- (void)mouseDown:(NSEvent *)theEvent {
NSLog(@"Helloworld");
}
Is something else intercepting the mouse events?