gistfile1.txt

//this is the view i use to show the selection:

_toolbarSelection = [[CPImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, 50.0, 57.0)];
[_toolbarSelection setImage:MediaWindowControllerToolbarSelectionImage];
[_toolbarSelection setAutoresizingMask:CPViewMinXMargin | CPViewMaxXMargin];

// Here comes the hack:
[myWindow._toolbarView addSubview:_toolbarSelection];

// Upon clicking on the button, we do this to position it:

    var selectionFrame = [_toolbarSelection frame],
        toolbarView = [[[self window] toolbar] _toolbarView],
        subviews = [toolbarView subviews],
        index = 0,
        count = [subviews count];
        
    for (; index < count; ++index)
    {
        var toolbarItemView = subviews[index];
        
        if ([toolbarItemView tag] === aTag)
            break;
    }
    
    var frame = [toolbarItemView convertRect:[toolbarItemView bounds] toView:[self window]._toolbarView];
        
    [_toolbarSelection setFrameOrigin:CGPointMake(CGRectGetMinX(frame) + (CGRectGetWidth(frame) - CGRectGetWidth(selectionFrame)) / 2.0, 28.0)];