On Jan 13, 2015, at 10:55 PM, Quincey Morris <quinceymor...@rivergatesoftware.com> wrote:
> On Jan 13, 2015, at 21:25 , N!K <pu56ucl...@alumni.purdue.edu> wrote: >> >> I have not been able to find a reason for this behavior. . I don’t know how >> to reveal the point between passes where bounds is actually changed. It does >> not happen in any other NSView projects of mine; drawRect runs only once in >> them > > The immediate reason is probably that the view’s size changed, which is not > unlikely when the window is in the process of being displayed. The view may > be resized for a “local” reason, such as the application of auto layout > constraints, or for a “global” reason, such as the containing being resized > and the change filtering down to subviews. > > Another possibility is that the view didn’t change size, but that (as an > implementation detail of the Cocoa drawing system) it received two partial > invalidations, and these weren’t coalesced in this case. > >> I would like to prevent the second pass, or at least prevent the bounds >> change between passes. > > I don’t see any practical way to prevent ‘drawRect’ from being called again. > Redundant ‘drawRect’ calls can occur any time during the view’s lifetime. This I didn’t realize, until you and Jens are explaining to me now. > > Are you implying that one bounds rect is “right” and one is “wrong”? No. The system draws the view correctly, as long as I don’t interfere by adding my attempt at initialization and scaling. > If so, how do you know that, and why can’t you just make your code do nothing > if the bounds are “wrong”? > > If the only criterion is that the *last* bounds rect is “right”, you’ve got a > big problem, because there’s no such concept in the drawing system. > > If you’re hoping that someone can suggest a solution, you probably need to be > more specific about what “right” and “wrong” mean. > >> I’m reluctant to try restoring bounds to its first value. I appreciate Ken >> Thomases’ warning in a previous subject not to change bounds in drawRect. > > > I’d say it wasn’t a warning, but rather an injunction to never, ever do that. > Doing so is Wile E. Coyote stuff. > I wish this had appeared in the Cocoa books I’ve read. On a lighter note, the Roadrunner cartoons are my favorites. Every blunder presents a classic engineering failure. :) _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
