Event queue(s) between the GUI and the interpreter

[Jordi Gutiérrez Hermoso]

While patching bug #42307 to use Fsource directly without attempting
to invoke the interpreter on a filename (thus getting rid of the
problem of even considering what characters are in the filename), I
came to the conclusion that this could be easily done by directly
passing Fsource with the right parameters to the octave_link class.

However, I'm now confused. It looks like there are two queues, one in
the interpreter called gui_event_queue and another in the GUI called
_cmd_processing, each with its own mutex and/or semaphore. It looks
like the gui_event_queue gets fed with functions from the GUI (i.e.
defined in libgui), and that _cmd_queue gets fed with actual commands
stored as QStrings that get called from
main_window::execute_command_callback (btw, exactly which line in this
last function is responsible for actually executing the command?
command_editor::replace_line?)

So where exactly would I do something like call Fsource directly?
Should I create another queue-mutex-semaphore triplet in the GUI for
DEFUNs and feed gui_event_queue with function calls to a function like
main_window::execute_defun_callback?

This seems a bit convoluted, but par for the course for Octave code.
:-)

- Jordi G. H.