[Gimp-developer] How to debug rendering problems in master?

[Omari Stephens <xsdg xsdg org>]

I just compiled master today to play around with the high bit depth 
support.  As has been mentioned, it's broken :o)

I seem to be running into two problems:

1) It seems like the rendering has some variety of race conditions and 
mipmap-looking caching problems.  Any suggestions for how to debug 
these, things to try, or files to look at?  One issue I've seen 
repeatedly is that the image looks mostly-ok at <= 50% zoom.  The 
top-left tile will be wrong.  When I move above 50% zoom, it looks like 
the entire image is rendered as a zoomed-in version of that incorrect 
top-left tile.

2) It's horrifically slow :o)  I've never actually gotten a profiler to 
work on my machine.  Anyone have any suggestions for bits that could use 
some optimization?  Especially bits that someone who is good at C but 
unfamiliar with the new codebase could take a look at?

In particular, is there anything I can do to make GIMP/GEGL take 
advantage of the multiple cores on my machine?  It only ever seems to 
use one, which is a waste, because I've got 7 other cores I paid money 
for just for GIMP (and other image processing).


In sum, I already have images that could benefit from >8bit processing, 
so I'd like the future to be here sooner rather than later.  Please tell 
me how to help make that happen.  Maslow's triangle dictates that I must 
work on problems 1 or 2, if at all possible.

--xsdg