jerky viewport scrolling performance GTK+

["Lambert Schomaker" <lrb_schomaker hotmail com>]

Hi,

 I am new to GTK+ so the question may be dumb.
We are buidling an image viewer / annotator using glade-2:

glade-2 1.1.3
libgtk-1.2.so.0.9.1
libgtk-x11-2.0.so.0.200.1
libpango-1.0.so.0.200.1
libpangoxft-1.0.so.0.200.1
libgcc_s-3.2.2-20030225.so.1
Hardware: 3 GHz/1 GB.
OS: Linux RH 9.

When using a simple window with one viewport and an embedded gtkimage, 
scrolling is very
jerky (20MB greyscale image), just using out-of-the box glade with very 
little adaptation of
callback.c. The .tif file is loaded in a pixbuf (once),  the pixbuf is set 
into the gtkimage (once).
Horizontal scrolling is reasonable, vertical scrolling is a drama.
Looking at the same image with eog (eye of gnome), scrolling is superbly 
smooth.
Using gtkviewer, scrolling of the same image is somewhat slower but still 
better than our
homebrew thing. I also noticed that event transmission to the window manager 
(e.g. start resize
or drag window) is sluggish. Resident memory of this small application  
(indicated by top): 76 MB.
Idle cpu load is higher than normal. Replacing gtk_main by an event 
iteration loop
with usleep(1000)  (1ms) as a 'yield' did not give noticable improvement or 
deterioration.
No hand-coded event handling has been added on top of the pre-cooked event 
handling.

Where is the trick? Apparently we are missing some point...

Lambert Schomaker

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