Borderless NSButton turns gray when clicked

Question

I am making a little application with three NSButtons with an image set. These buttons have no border nor background. However, when I click a button it turns into a gray rec

Answer 1

You should be able to adjust this by changing the state mask. To do so, check out the highlightsBy: and showsStateBy: properties of NSButtonCell - they are for setting the press effect and displaying the effect respectively. The applicable constants for these methods are in the NSCell reference page.