Re: Unclear on NSView's isOpaque concept (and optimization in general)
Re: Unclear on NSView's isOpaque concept (and optimization in general)
- Subject: Re: Unclear on NSView's isOpaque concept (and optimization in general)
- From: Alastair Houghton <email@hidden>
- Date: Thu, 6 Nov 2003 16:12:33 +0000
On 6 Nov 2003, at 15:11, Leon McNeill wrote:
On 6 Nov 2003, at 12:45, Alastair Houghton wrote:
The order in which sibling views are rendered isn't defined and may
even change during a single run of your program due to optimisations
in the frameworks. So if you overlap them, you may find that they
don't always display correctly. Using overlapping sibling views
won't degrade the performance of your app., but it might make it
misbehave.
And on 6 Nov 2003, at 13:05, Clark Cox wrote:
The order in which sibling views are drawn is completely undefined.
You have no way of knowing which of two overlapping views will be
drawn first, and which will be drawn second.
Far from undefined, indeed, I have found nothing in either
documentation nor in real world testing which implies or indicates
that my NSView subclasses will *ever* draw in any order other than the
order in which they were added to their superview (or inserted via
addSubview:positioned:relativeTo:).
Cocoa Programming (Anguish, Buck & Yacktman), p. 200:
"The order in which views with the same superview are drawn is not
defined."
Plus the following threads from this list:
http://cocoa.mamasam.com/COCOADEV/2002/10/2/48305.php
http://cocoa.mamasam.com/COCOADEV/2001/06/1/4750.php
http://cocoa.mamasam.com/COCOADEV/2001/10/2/15717.php
http://cocoa.mamasam.com/COCOADEV/2001/11/2/18827.php
http://cocoa.mamasam.com/COCOADEV/2001/09/1/12120.php
(and doubtless hundreds more).
Most of these comments were probably made some time ago, so it *is*
possible that things have been fixed so that the views aren't actually
drawn in reverse order, but even then, it won't work for views that
dynamically update (as Stephane pointed-out).
I can't find any mention of this in the documentation either, but then
there is a lot of documentation and perhaps I've picked the wrong
search terms.
Kind regards,
Alastair.
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