How is update() supposed to know what region to invalidate? By a list of GdkRegions as a parameters? The dual functionality of draw is just a way of automizing this.
Dov On Tue, Aug 17, 2010 at 18:50, Paul Davis <p...@linuxaudiosystems.com>wrote: > On Tue, Aug 17, 2010 at 9:11 AM, Dov Grobgeld <dov.grobg...@gmail.com> > wrote: > > Sorry, I still don't get it. In my scenario there is initially is no > > external request of a region that should be drawn. The only source of > what > > should be drawn, including what areas should be exposed, are in the > draw() > > routine. The challenge is to translate a set of drawing routines to a set > of > > invalidation areas. > > This is how you described it: > > >Here is a description of my flow, which might e.g. be used to draw a > rubber band box: > > > > 1. motion event calls update() > > 2. update() calls draw() in order to get regions to expose. > > 3. update() calls gdk_invalidate_region() based on output from draw > > 4. exposure-event callback calls draw() to carry out the drawing for > each region > > this is wrong. update() should just call gdk_invalidate_region(). this > will cause expose to be invoked with the region passed in. > the way you've described it above, your draw() method does two > entirely separate tasks. >
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