Re: [gtk-list] list speed

[Raph Levien <raph acm org>]

On Fri, 24 Oct 1997, Sascha Ziemann wrote:

> Hi,
> 
> I wrote a program that shows the X11 colors from rgb.txt. My rgb.txt is
> 750 lines long and so the list contains 750 items. The resize of that
> window takes 2 secs on a AMD K6 200. I think that is really slow. Is
> that normal for a GTK program? I use the Guile-GTK bindings and I am
> wondering weather it is GTK or because of the Guile-GTK layer that makes
> it so slow.
> 
> You can get the program here:
> http://www.ping.de/sites/aibon/Programme/GNOME/Colorbrowser/

I haven't downloaded this program, but I have also noticed a performance 
problem with lists in GTK.

I believe (without having done the relevant experiments, admittedly), that
the fundamental problem is the use of a separate X window for each list
entry. Gtk currently requires that children of a container must own their
own window if they are to recieve mouse events. If you look a the 
scrolledwindow test in testgtk, it has the same problem - on my machine 
(a 133 Mhz P5), it takes just under 2 seconds to map 400 buttons, almost 
exactly the same performance as yours after you factor in the difference 
in machine speeds. I've also noticed a similar problem in the file 
selection window when there are lots of files.

So it seems likely that the problem is in Gtk rather than the Guile
bindings. 

Also, you're lucky your database only contains 750 items. If it contained 
more than about 2200, then the list would be more than 32767 pixels tall, 
which would cause overflows in both Gtk and X, causing the list not to be 
displayed properly.

I'm not sure what's the best solution to these problems. One possibility 
to consider is to redo the list widget in the Gzw (Gzilla widget) 
framework. This framework does propagate mouse events from containers to 
their children, and also handles scrolling of 32 bit pixel dimensions 
rather than 16 bit. I believe it would offer a dramatic performance 
advantage in specific situations including large scrolling lists. On the 
downside, it's not ready yet (I've got it partially working, but not 
ready for release), and it's not clear to me that it's worth loading down 
Gtk with an alternate widget framework.

Raph