So it turns out that the "notify::src-drawables" property signal in
particular can happen during gimp_paint_tool_paint_interpolate() called
from gimp_paint_tool_paint_thread(). Though the function
gimp_clone_options_gui_update_src_label() was run in the main thread in
simple cases, being called this way through a paint thread happens when
very quickly changing the source while painting, which is what Aryeom
does (when I see her using the clone tool, she would sometimes change
the source very quickly several times in barely a few seconds).
Yet GTK and GDK calls must not happen in non-main threads. It used to be
acceptable when protected with gdk_threads_enter|leave() calls but doing
this is deprecated. The now sanctioned method is to call the GTK code in
an idle function since these are guaranteed to run in the main thread.
This was most likely explaining why crashes could quite randomly happen,
though I'm not sure why I never had those (even though I could reproduce
the GTK calls happening in non-main threads, but without crashing GIMP)
and why Aryeom gets these much more often suddenly. Maybe some recent
dependency change which would trigger these more easily or other
context-dependant changes (as most non thread-safe code, bugs and crash
often happen in race conditions, so are harder to reproduce reliably)?
c06083158a