Intercepting NSMenu key events

Question

I am making a search field, which opens a NSMenu similar to Finder and Mail

The only problem, which drives me crazy, is that i cannot intercept the key events, once the menu is open

• I even subclassed the NSApplication sendEvent, but was surprised to find out, that during menu, there is no call to Applications sendAction:

• I subclassed performKeyEquivalent: NSMenu but it is not called

 - (BOOL)performKeyEquivalent:(NSEvent *)theEvent

• I am listening for the delegate call on menuHasKeyEquivalent: but it doesn't get called

 - (BOOL)menuHasKeyEquivalent:(NSMenu*)menu forEvent:(NSEvent*)event target:(id*)target action:(SEL*)action

How to intercept the keyboard input during NSMenu

Answer 1

It is possible with a usage of Carbon event handlers. These functions allow interception of keyboard events while menu is open: GetEventDispatcherTarget() and InstallEventHandler(). This is a hack, but in fact, it works reliably across all MacOSX versions starting from 10.7. Here's the source code that could be used as a reference implementation: https://github.com/mikekazakov/MGKMenuWithFilter

Answer 2

KeyEquivalent is for menu shortcuts not intercepting all the keys. There is no need to intercept the NSMenu events and it is not possible to be used for that purpose. To make a suggestion box you basically need to make a custom NSWindow and make it look like a menu.

Apple provides a Sample Code and they explained it in WWDC 2010 session 145 at some point.