Re: cairo drawing commands to gdk_invalidate_region

[Dov Grobgeld <dov grobgeld gmail com>]

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 <paul linuxaudiosystems com> wrote:

On Tue, Aug 17, 2010 at 9:11 AM, Dov Grobgeld <dov grobgeld 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.