Re: [Gtk2hs-users] Poor performance for large repaints

[Axel S. <Axe...@en...>]

On Fri, 2009-01-30 at 16:03 +0100, Peter Verswyvelen wrote:
> Yes I am using Cairo. Does an alternative exists for doing vector
> graphics and bitmap painting?

Well, for vector graphics there's probably only Cairo. If you're always
taking a bitmap and draw something on it with vector graphics afterwards
(rather than alternating one after the other) then there are some magic
functions in Graphics.UI.Gtk.Cairo that allow you to take a Pixbuf and
turn it into a cairo surface.

Thus, each time your image is changing you could
- draw the bitmap parts into a new Pixbuf pb using one of the following:
  - manipulate the pixels using pixbufGetPixels
  - load a pixbuf from file
  - draw into a Pixmap using the old-style drawing functions in
Graphics.UI.Gtk.Gdk.Drawable
- draw the Cairo parts onto a surface you get from
cairoImageSurfaceFromPixbuf pb

Then, each time the expose handler is run, you need to
- draw the exposed region/rectangle using drawPixbuf in
Graphics.UI.Gtk.Gdk.Drawable

> What has become of Glitz, the OpenGL backend? Is this dead?

I don't think anybody has started on that...

Cheers,
Axel.


> On Fri, Jan 30, 2009 at 2:33 PM, Axel Simon <Axe...@en...> wrote:
> > On Fri, 2009-01-30 at 14:26 +0100, Peter Verswyvelen wrote:
> >> When double buffering is turned on, repainting even a single rectangle
> >> becomes rather slow when the windows gets large.
> >>
> >> The overhead does not seem the number of shapes being painted, but the
> >> pixel area they cover.
> >>
> >> Is this a known issue?
> >>
> >> Maybe this is just a GTK issue and I should ask in the GTK list?
> >
> > Are you using Cairo? It seems that Cairo is rather slow, especially
> > earlier versions. We had questions from other people who said redrawing
> > was very slow. It's probably not the Haskell side but more of a way the
> > API is used. For instance, our example SVG viewer in /demos/svg/ takes
> > minutes with older Cairo versions to draw more complex images whereas it
> > takes two seconds on with Cairo 1.4.1.
> >
> > Axel.
> >
> >