[Octave-bug-tracker] [bug #55225] building doc figures in .eps or .pdf format occasionally silently fails

[Pantxo Diribarne]

Follow-up Comment #62, bug #55225 (project octave):

@jwe: bug #58678 suggests that using BlockingQueuedConnection to initialize
and finalize objects is not safe. Could the copy-on-write approach you talked
about in https://savannah.gnu.org/bugs/index.php#comment44 help solving this?

For reminder, the reason why I chose to synchronize threads this way are:
* qt_graphics_toolkit::print_figure: we want to be sure the printout file is
ready when drawnow returns. This is necessary e.g. for:


plot (1:10)
print -dpdflatexstandalone toto
system "pdflatex toto"


* qt_graphics_toolkit::get_pixels: this function must return pixels from the
GUI thread where they are drawn

* qt_graphics_toolkit::finalize: we want to make sure that the reference to
the graphics objects held by the GUI Object is released when we return. This
way we can use the graphics destructor of the graphics_object to trigger some
cleanup actions like with uicontextmenu (see bug #58403)

* qt_graphics_toolkit::initialize: we want to be sure the GUI Object has been
created when one of the above functions is called otherwise this bug can
happen (invokeMethod fails).

I think first and second points can be circumvented by drawing on an FBO in
the interpreter thread.

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