Create Borderless Transparent Window:

nswindow.m

- (id) initWithContentRect: (NSRect) contentRect
                 styleMask: (unsigned int) aStyle
                   backing: (NSBackingStoreType) bufferingType
                     defer: (BOOL) flag
{
    if (![super initWithContentRect: contentRect 
                             styleMask: NSBorderlessWindowMask 
                          backing: bufferingType 
                         defer: flag]){
        return nil;
    }
    [self setBackgroundColor: [NSColor clearColor]];
    [self setOpaque:NO];
 
    return self;
}