I thought that I can use a hiImageView and draw with Quarz into it.
Unfortunately I have some trouble in implementing it. For Quarz
drawings, I need a Context. right? In the Quarz2d guide I read that
I need a keventcontolDraw Event to get the context.
Either/Or, not both. Either you draw into a CGImage and display
that in an HIImageView, or you create a custom view and override
kEventControlDraw. If you do both, your CGImage will never be drawn,
because you're doing your own drawing and not letting the
HIImageView's built-in kEventControlDraw draw the image.
The problem is the following: If I want to draw a square into the
imageview, I store the coordinates into a global variable and call
hiviewsetneedsdisplay to get the controlDraw event. Then in the
event handler I get the context with getEventParameters.
This works fine. But if I want to draw a second square, over the
first one. The first one gets lost (because of the redraw of the
hiimageview). How can I draw something new into the imageview
without losing the old content?
That's how kEventControlDraw is supposed to work. It redraws the
view whenever it needs redrawing. What you really want to do is
create a CGBitmapContext, draw into that, and then create a
CGImageRef from that which the HIImageView will draw. Or just do your
*complete* drawing in a custom view's kEventControlDraw.
I tried also to store the context reference globaly an then draw to
it whenever I wan't to draw to it. But then the drawings are not
drawn into the imageview but somwehere else in the window.
No, you don't need to do that. The context ref isn't even
guaranteed to stay the same (or valid, for that matter) after your
kEventControlDraw returns. Create your own bitmap context and draw
into that, then do a setNeedsDisplay to actually cause the redraw.
You might even be able to directly draw the bitmap context's contents
from a custom view, without going through a CGImage, I can't remember
right now.
Cheers,
-- M. Uli Kusterer
"The Witnesses of TeachText are everywhere..."
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