Prevent activating the application when clicking on NSWindow/NSView

Question

I'm working on a screenshot Mac app. I'm trying to rebuilt what happens when you press Cmd-Ctrl-Shift-4: the cross hair cursor and the selection rectangle for the screenshot.

I'm using a custom borderless NSWindow on top of all other windows. I disabled the cursor to draw my own along with the selection rectangle.

My problem is that as soon as I click & drag to capture a screenshot, my app gets activated (because the click is intercepted by my shielding window).

Is there a way how I can receive the click in my custom view/window without having my app get activated?

I tried using an NSPanel with the NSNonactivatingPanelMask flag, but in this case, I have a problem with the cursor: I can't draw my own when another app is active, because I can't hide the cursor for other apps...

Answer 1

Actually, I have a new, better answer to this question involving more undocumented goodies. Here it is for future posterity:

There is an undocumented method on NSWindow that does exactly what you want:

@interface NSWindow (Private)
- (void )_setPreventsActivation:(bool)preventsActivation;
@end

[myWindow _setPreventsActivation:true];

This stops the window from activating both itself and its application when the user clicks on it.

The standard warnings about using undocumented APIs of course apply: Apple may change this at some point (although it's been around for many OS X versions so there's a good chance they won't) and using this may get your app rejected from the Mac app store.