Thanks for the pointers. I actually figured out a way to do it. If
you [NSView setWantsLayer:NO] and render the layer yourself like
so.....
- (void)drawRect:(NSRect)dirty {
CGContextRef ctx = [[NSGraphicsContext currentContext] graphicsPort];
CGContextClipToRect(ctx, NSRectToCGRect(dirty));
[[self layer] renderInContext:ctx];
}
...then the transparent pixels end up being transparent to clicks too!
Can't say I understand what's going on here exactly and I'm guess I'm
using twice as much graphics memory as I need to now but it works.
Rowan
On Sun, Apr 26, 2009 at 12:37 PM, Bill Cheeseman <b...@cheeseman.name> wrote:
> On Apr 26, 2009, at 2:09 PM, Rowan Nairn wrote:
>
>> So the little detail is this: I
>> don't want to make my whole window transparent to mouse events. There
>> are bits of my window on which I want to detect clicks. Those are the
>> bits that I've drawn on. I want the bits I haven't drawn on, the
>> visually transparent bits, to ignore clicks.
>>
>> When I use [NSView drawRect:] this works as expected - any pixel that
>> is visually transparent is also transparent to clicks. However when I
>> use a layer (either hosted or backed) the whole area intercepts
>> clicks, whether visually transparent or not. I'm starting to think
>> there's no way around this so I might just go back to [NSView
>> drawRect:] even though it makes the animation slower.
>
> As far as I know, there is no simple way to do that without drawing (and I
> didn't know you could do it with drawing).
>
> It occurred to me, however, that you could use Quartz event taps to do this.
> Event taps let you intercept clicks globally, in any application, and modify
> them or take other action before you pass them along. You could intercept
> every mouse event at the global session level (before it is assigned to an
> application); determine whether its screen location is in your application's
> window, and which part of that window; set clickthrough on or off in your
> window depending on whether that area is transparent; and then send the
> click along. It would automatically go to your application or the
> application under it, depending on your window's clickthrough setting. I
> believe this could be made to work with mouse dragged events as well as
> click events.
>
> You can read about event taps in Apple's "Quartz Event Services Reference"
> document, and play with them using my free utility, Event Taps Testbench, at
> <http://prefabsoftware.eventtapstestbench>.
>
> Event taps are complicated if you aren't familiar with them, so if you
> already have a drawing solution maybe that's the best bet.
>
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