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Subject: Re: [geda-user] gschem sometimes takes a nap
From: Peter Clifton <pcjc2 AT cam DOT ac DOT uk>
To: geda-user AT delorie DOT com
Date: Sat, 06 Sep 2014 23:10:34 +0100
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On Fri, 2014-09-05 at 21:38 -0700, Edward Hennessy wrote:
> A potential fix is checked into source control. Hopefully, it isn't just tuned to execute faster on my machine.
> 
> Something not intuitive is going on under the hood:
> 
> - The change in x_event.c reduces the number of invalid rectangles to one - yields a speed improvement
> - The change in x_grid.c moves the cairo_stroke() into the for loop - performance actually gets WORSE
> - When both changes are combined - performance is much faster than the changes in x_event.c alone


Presumably you are seeing a trade-off between painting lots of small
pieces of the screen, and painting the whole screen in one hit. Gschem
isn't very efficient at mapping the small regions into a list of objects
to paint.

I'd suggest looking at whether there is a heuristic you can apply for
the operations which cause a certain amount of redraw, to force a redraw
of the whole screen rather than the individual areas.

It might be worth looking at whether invalidating the whole screen for
_every_ update is actually a pragmatic way to proceed.

If you invalidate the whole screen area, GDK _should_ subsume the small
regions into the larger one.

Now most X11 desktops have moved away from a model where you get
individual small expose events, so painting exposed regions uncovered by
moving other windows is not really a concern nowadays. All the drawing
is triggered by us.


-- 
Peter Clifton <peter DOT clifton AT clifton-electronics DOT co DOT uk>

Clifton Electronics