KEY_DOWN event not sent for TAB while holding LEFT_CONTROL on OSX

[keenanwoodall]

In the app event callback I'm not receiving a key down event for the Tab key on my m1 macbook while the Control key is held. The KEY_UP event does fire, just not the KEY_DOWN. Is this just an OSX quirk?

case .KEY_DOWN: {
   log.debug("DOWN", event.key_code)
}
case .KEY_UP: {
   log.debug("UP", event.key_code)
}

Steps:

1. Press Left Control down
2. Press Tab down
3. Release Tab
4. Release Left Control
   Logs:

DOWN LEFT_CONTROL
UP TAB
UP LEFT_CONTROL

[floooh]

My guess is that macOS intercepts Ctrl-Tab because it's the system hotkey to switch between windows of an application.

Don't know if this can be deactivated via Cocoa APIs though.

[keenanwoodall]

I found the same problem mentioned on a flutter issue. It seems some key events, such as Control+Tab, are notified by calling performKeyEvent instead of keyDown. Docs

[floooh]

Thanks for digging up that Flutter PR. I guess this is the important part:

- (BOOL)performKeyEquivalent:(NSEvent*)event {
  if ([_controller isDispatchingKeyEvent:event]) {
    // When NSWindow is nextResponder, keyboard manager will send to it
    // unhandled events (through [NSWindow keyDown:]). If event has both
    // control and cmd modifiers set (i.e. cmd+control+space - emoji picker)
    // NSWindow will then send this event as performKeyEquivalent: to first
    // responder, which might be FlutterTextInputPlugin. If that's the case, the
    // plugin must not handle the event, otherwise the emoji picker would not
    // work (due to first responder returning YES from performKeyEquivalent:)
    // and there would be an infinite loop, because FlutterViewController will
    // send the event back to [keyboardManager handleEvent:].
    return NO;
  }
  [event markAsKeyEquivalent];
  [_flutterView keyDown:event];
  return YES;
}

I'll need to play around with that in sokol_app.h, for now I'll put the ticket into my todo list, but no ETA when I'll get around to looking into it :)

(PS: or if you want to experiment with it: PR welcome... we'll just need to check that we don't accidentially disable any important system-functionality, but disabling Ctrl-Tab in sokol_app.h is fine as long as there's no multi-window feature I guess - otherwise we could also add more config-booleans to sapp_desc like I did for the HTML5 event bubbling configuration)

[keenanwoodall]

Thanks, sounds good! I can just use the key up event for now, so definitely no rush :)

[floooh]

So I just played around a bit and tried this, and it works at least for the Ctrl-Tab case (interestingly this opens a Dear ImGui popup to switch between windows, I never saw that before heh).

I'll put it into a branch and try to figure out if this simple function breaks anything else. Might take a few days.

- (BOOL)performKeyEquivalent:(NSEvent*)event {
    [_sapp.macos.view keyDown:event];
    return YES;
}

[floooh]

Ah ok, first problem with this simple approach is that performKeyEquivalent is called for each key pressed together with Ctrl or Cmd, so I'll probably need to filter out specific key combos (like Ctrl+Tab).

[floooh]

Ok, fixed via #1228

[keenanwoodall]

Thanks! you rock 🤘