[cairo] Program logic for interactive usage
dogusanh at tr.net
Thu Mar 20 04:22:56 PDT 2008
Thanks for reply.
Carl Worth wrote:
> On Wed, 19 Mar 2008 13:25:39 +0200, Hakki Dogusan wrote:
>> - create a stationary context in program startup
>> mastersurface = cairo_image_surface_create(CAIRO.FORMAT_ARGB32,
>> width, height)
>> mastercontext = cairo_create(mastersurface)
> From your description it doesn't sound like you need mastersurface to
> be an *image* surface. So your program may be more efficient if you
> instead use cairo_surface_create_similar here, (and pass to it a
> surface that's targeting your window system---perhaps by calling
> cairo_get_target after your "create a context for paint DC").
I read efficieny warning about image surfaces before. So, was tried
creating a similar surface upon program entrance without success; I was
getting "Gdk-CRITICAL **: gdk_cairo_create: assertion `GDK_IS_DRAWABLE
(drawable)' failed" messages.
I was thought something similar with your "perhaps by calling
cairo_get_target after your "create a context for paint DC"" comment,
but creating something on a temporary surface/context was scared me.
Now, using your hint, I'm delaying creation of master surface & context
till first OnPaint event. My current skeleton is as follows:
-- frame creation: mastercontext=NULL, mastersurface=NULL
-- All drawing routines checks mastercontext for NULL
-- create temp context cr for DC
-- if mastercontext == NULL
tempsurface = cairo_get_target(cr)
mastersurface = cairo_surface_create_similar(tempsurface, ..)
mastercontext = cairo_create(mastersurface)
-- do initial(delayed) master drawings
-- put masterdrawings
cairo_set_source_surface(cr, mastersurface, 0, 0)
--paint temporary drawings
>> - HitTest in Mouse events
>> for each master-shape's path:
>> cairo_append_path(mastercontext, path)
>> result = cairo_in_fill(mastercontext, x, y)
> The cairo_in_fill call is correct, but fairly expensive. As an
> optimization, you might want to add some bounding-box based bailouts
> to avoid having to call cairo_in_fill when it will obviously return
There are mostly rectangle paths (ie.selection indicator) involved for
cairo_in_fill test. Will it still be expensive for them? (Sorry, I
didn't read Cairo sources.)
>> Is my logic reasonable?
> Seems fine to me. Is everything working well for you?
Yes! Was working, and still working fine after changing to new skeleton.
> I hope you're having fun with cairo,
I am :)
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