As of OS X 10.10 most of NSStatusItem has been deprecated in favour of the button property, which consists of an NSStatusBarButton. It should work like a normal button but unfortunately the cell and setCell methods in NSStatusButton have also been deprecated. As a result of this I'm struggling to find a way to keep the button highlighted after it's clicked (Normally the button is highlighted on mouse down, and unhighlighted on mouse up. I want to keep it highlighted after mouse up).
Calling [NSStatusButton setHighlighted:] in its action doesn't work because it seems to unhighlight itself once the mouse is up. On the other hand, using a delay to call it on the next loop i.e. [self performSelector: withDelay:] causes the highlight to flash in a rather unsightly way. It works, but doesn't look nice.
Setting the button type to NSToggleButton removes the highlight entirely and instead highlights the template image which was odd.
Those were the only methods I could think of. Is there anyway to override this NSButtonCell mouseUp behaviour?
I added a subview to the status item, and inside that view I added event handlers for mouseDown etc. which called [[statusItem button] highlight:true]. As it turns out setHighlighted: doesn't do the same thing as highlight:.
NSArray *array = [NSArray arrayWithObjects:[statusItem button], [self statusItemView], nil];
[[[statusItem button] superview] setSubviews:array];
//Highlight like so:
[[statusItem button] highlight:true];
EDIT: As of El Capitan this method no longer works, and neither does statusItem.button.highlight = true either 😀🔫