Re: Drawing over a transparent background
Re: Drawing over a transparent background
- Subject: Re: Drawing over a transparent background
- From: Ron Fleckner <email@hidden>
- Date: Tue, 1 Sep 2009 20:04:05 +1000
Well despite some good replies to my original query below, and many
thanks for your interest to those who did reply, I'm still no nearer
to being able to fix the problem. So I've made a relatively
lightweight project that demonstrates what happens:
<http://members.ozemail.com.au/~ronfleckner/DrawingProblemDemo.zip>
Just build and run to see what's happening. There's a window with a
transparency slider on it that also describes the problem.
I'm beginning to think that either quartz drawing isn't up to the task
(unlikely...) or there's something I'm doing or not doing that I
should/shouldn't.
Thanks in advance to anyone with the time to look at it.
Ron Fleckner
On 24/08/2009, at 9:33 AM, Ron Fleckner wrote:
Hi,
I asked about this on quartz-dev but go no reply after a few days so
I'm asking here.
My borderless window has a semi-transparent background. When the
drawing in a subview changes, the background retains a ghost of the
original drawing in the subview. I don't want that ghost image!
The app is a resizeable analog clock. (Yes, I'm a dilettante
recreational coder.)
I've tried various -display methods, but none of them, so far, have
fixed the problem. So -setNeedsDisplay:, -setNeedsDisplayInRect:, -
displayRect, -displayRectIgnoringOpacity and others don't affect the
ghosting problem.
Here's an image of what I'm seeing:
<http://members.ozemail.com.au/~ronfleckner/DrawingWithTransProb.png>
If the background is a solid colour, the drawing looks fine. It
only appears when the background has opacity < 1.0 The opacity and
colours of the window are set in the interface by the user.
Thanks for any help
Ron
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