cachImageInRect and Scrolling Views
cachImageInRect and Scrolling Views
- Subject: cachImageInRect and Scrolling Views
- From: Joseph Jones <email@hidden>
- Date: Fri, 4 Mar 2005 23:44:42 -0800
Hi all,
I was looking around the mail lists for a way to optimize the drawing
of an overlay drag indicator when I cam across cacheImageInRect. Using
this works 100% as intended for static (i.e. non-scrolling) views. What
I need is a way to do the same thing but over a scrolling view. The
graphic area I need to provide access to is much larger than the screen
and is very rich (read expensive to re-draw).
There is one post that mentions a hack someone was trying to implement
to deal with this but it appears to not be working very well. I am
posting in hopes that someone out there has a solution to this
situation since I hate to be stuck with such a non-performant portion
of my application.
The current solution I have (in pseudo code) is as follows:
//Generate Update Rect...
[window restoreCachedImage];
[window discardCached Image];
[superView autoscroll:theEvent];*
[window cacheImageInRect:[self convertRect:updateRect toView:nil]];
[self lockFocus];
[self displayRect:updateRect];
[self unlockFocus];
[window flushWIndow];
When I drag to a point where scrolling occurs, though, garbage is left
behind from my drag indicator. Scrolling back appears to paste old,
incorrect information over the view.
Thanx,
joe
*I have also tried the following to see if the scrolling was just not
being picked up (to no avail):
if ([superView autoscroll:theEvent])
{
[window disableFlushWindow];
[superView lockFocus];
[superView displayRect:[self convertRect:updateRect toView:superView]];
[superView unlockFocus];
[window enableFlushWindow];
}
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