Re: scrolling and drawing porblems
Re: scrolling and drawing porblems
- Subject: Re: scrolling and drawing porblems
- From: Ivan Kourtev <email@hidden>
- Date: Tue, 7 Nov 2006 15:52:18 -0500
On Nov 7, 2006, at 3:43 PM, m wrote:
On Nov 7, 2006, at 12:25 PM, Ivan Kourtev wrote:
I want to have a certain object drawn at a constant position
relative to the visible rectangle of my custom view (so that it's
always visible). The problem was that the my custom view was in a
scroll view that by default copies view content on scroll. As
both you and Eric suggested one way to accomplish what I wanted
was to disable the copying. Indeed, something like [[self
enclosingScrollView] setCopiesOnScroll:NO]; in my custom view did
the job.
The side effect of this is that since there is no copying anymore,
the argument to drawRect in my custom view after scrolling is the
entire visible rectangle (rather than just a small strip exposed
after scrolling).
Is this a problem in fact or in theory? Put another way, are you
noticing (as a user) a performance impact as a result of having to
redraw the while view instead of just a bit? Depending on how
complex and expensive your drawing is, you might find the code
complexity required (time spent coding, fixing, maintaining) to
optimize drawing doesn't pay off in substantial user perceived
responsiveness.
I absolutely agree but in this particular case performance is
impacted significantly indeed. I am drawing some fairly complex
diagrams in a near full screen sizes. So, for example, going from 5
x 1,000 redraw area after scrolling to 1,600 x 1,000 (entire visible
rectangle) degrades the application performance noticeably and
unacceptably.
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