Commit e2664f1d authored by Jehan's avatar Jehan

devel-docs: add a new file "debugging-tips.txt".

This will be a neat reminder for some of the hidden environment
variables helpful to debug GIMP in some cases, as well as some other
tricks, which we often have to tell people or even which we forget (or
don't even know sometimes) ourselves.
This will be less annoying to just remember to check this file if we
forget the name of some environment variable than to try and grep the
git log or the code.
If someone adds another environment variable which changes some behavior
of the code, please add it here. Also if you know some other helpful
tricks, share with all. Thanks.
parent 6bd43d73
There are a few environment variables, options or other more-or-less
known tricks to debug GIMP. Let's try to add them here for reminder and
newcomers.
## Basics ##
The basic thing is to build babl, GEGL and GIMP with `--enable-debug`.
Note that if you also built glib from source with `--enable-debug`,
every GObject destroyed are apparently overwritten with values invalid
as pointers, so dereferencing one after destruction usually leads to a
crash, which is a good way to find some more vicious bugs.
## Debug logs ##
You can see various GIMP_LOG() calls in the code. These will only be
outputted when you set GIMP_DEBUG environment variable to a
comma-separated list of domain.
For instance, for `GIMP_LOG (XCF, "some string")` to be outputted,
run GIMP like this:
> GIMP_DEBUG=xcf gimp-2.9
Special flags are:
- "all" to output all domain logs;
- "list-all" to get a list of available domains.
## Debugging a warning ##
If you encounter a CRITICAL or WARNING message on console, you can make
so that GIMP crashes on it, which will make it very easy to be tracked
down in a debugger (for instance GDB), by running GIMP with:
> gimp-2.9 --g-fatal-warnings
## Debugging GEGL code ##
You may encounter this kind of warning upon exiting GIMP:
> EEEEeEeek! 2 GeglBuffers leaked
To debug GeglBuffer leaks, set the environment variable GEGL_DEBUG to
"buffer-alloc".
## Debugging babl ##
Profile conversion is done with babl by default when possible, which is
much faster.
Setting GIMP_COLOR_TRANSFORM_DISABLE_BABL environment variable switch
back to the old lcms implementation, which can be useful for comparison.
## Debugging X Window System error ##
Make X calls synchronous so that your crashs happen immediately with:
> gimp-2.9 --sync
You can also break on `gdk_x_error()`.
## Debugging icons ##
See file `devel-docs/icons.txt` to learn more about our icons, and in
particular the environment variable GIMP_ICONS_LIKE_A_BOSS.
## Debugging plug-ins ##
See file `devel-docs/debug-plug-ins.txt` for usage of environment
variable GIMP_PLUGIN_DEBUG.
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