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Re: drawRect troubles
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Re: drawRect troubles


  • Subject: Re: drawRect troubles
  • From: Ivan Kourtev <email@hidden>
  • Date: Sat, 28 Oct 2006 23:33:36 -0400

On Oct 28, 2006, at 11:11 PM, Scott Stevenson wrote:

On Oct 28, 2006, at 8:05 PM, Ivan Kourtev wrote:

For performance reasons I am trying to do incremental drawing -- draw/erase only small amounts of stuff that has changed -- but it seems that the view contents is "erased" between successive calls to drawRect. After each drawRect, I only see the incremental drawing -- the small stuff added/removed -- but not what was there before.

Have you tried playing with Quartz Debug's "flash updates" checkbox?
Should show you which areas are considered invalid at which points. Might help.


    - Scott


Yes, I've been doing this. All the update areas seem to be correct. The problem is that the drawing I see in the view contains only what was done explicitly in drawRect.


I was under the impression that what's been drawn in the view so far is there, and if I don't want it, I have to erase it. So I am only adding small pieces of stuff in drawRect -- and they do appear on screen. All of the previous drawing is gone.

Since I am issuing the [self setNeedsDisplay:YES] is there any way to also specify which particular parts of the view should be invalidated? Right now, the argument to drawRect is always the entire view area.

-- ivan

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  • Follow-Ups:
    • Re: drawRect troubles
      • From: Uli Kusterer <email@hidden>
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References: 
 >drawRect troubles (From: Ivan Kourtev <email@hidden>)
 >Re: drawRect troubles (From: Scott Stevenson <email@hidden>)

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