Re: Deferring a selector until later, but before painting

FROM : Ken Ferry
DATE : Thu Mar 06 23:13:31 2008

On Thu, Mar 6, 2008 at 2:06 PM, John Stiles <<email_removed>> wrote:
>
>  Ken Ferry wrote:
>  On Thu, Mar 6, 2008 at 9:59 AM, John Stiles <<email_removed>> wrote:
>
>
>  On Leopard, this solution works perfectly. I get a chance to update my
>  view right before it draws, which is exactly what the doctor ordered.
>
>  Any way to get this on Tiger or am I just out of luck?
>
>  Out of luck. Well, you can do the work in -drawRect:, but if any of
> the work you do invalidates display, it'll be delicate code (meaning
> it may be hard to get it to work right, or relatively fragile between
> releases). It might be good to implement a -resolveInvalidatedStuff
> method, then call it from both -viewWillDraw and -drawRect:. Then, on
> Leopard, you'll never actually be doing any work in drawRect: because
> you will have already resolved all state. If it works on Tiger at
> that point, great, and if not, any further tricky work you do is
> targeting an unchanging OS. Make sense?
>
>
>  Hmm. What I'm doing is almost certainly going to invalidate display, so I
> am probably just out of luck for Tiger.
>
>  If there was some bulletproof solution that could be made to work under
> Tiger, that would have been nice, but it's not a big deal. I don't currently
> anticipate this code being used under Tiger. I just like to write things so
> that we could use them as far back as reasonably possible, in case plans
> change. I guess if that does happen, I can bring back the old code and Tiger
> users can live with the controls-changing-after-display behavior that we had
> before.


Note that implementing -viewWillDraw won't keep your code from running
on Tiger, the method just won't get called.  That's what I was getting
at with the hybrid drawRect:/viewWillDraw approach.

-Ken