Re: How to flash two rectangles in a frame?
Re: How to flash two rectangles in a frame?
- Subject: Re: How to flash two rectangles in a frame?
- From: Kyle Sluder <email@hidden>
- Date: Sun, 15 Mar 2009 17:20:30 -0400
On Sun, Mar 15, 2009 at 4:53 PM, Philip Kime <email@hidden> wrote:
> With a minor change, this worked perfectly - many thanks to both people who
> responded. I am simply unaware of a lot of the API here so hadn't looked at
> these functions.
It's worth noting that you're going about this problem a bit
backwards. Typically, one maintains the view's state separate from
its actual window buffer, using this state information inside of
-drawRect:. Relying on your window's backing store to remain
unchanged so that you can reverse the effects of your previous drawing
is perilous, since any code at any time can call -lockFocus on your
view/window and doodle all over your previous drawing. In fact, this
is precisely what the focus ring does.
Your best bet is to instead store a flag and use that flag's value to
change how you draw inside -drawRect:. Use -setNeedsDisplayInRect: to
tell your view to redraw.
--Kyle Sluder
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