Don't use C++ callback to notify close request from Qt Figures (bug #54187) * Figure.h/cc (Figure::close_figure_callback): Remove callback. (Figure::eventNotifyBefore): Use gh_manager::post_callback rather than octave_link::post_event to notify that a figure should be closed. * graphics.in.h (graphics_event::create_mcode_event): New static function. * graphics.cc (mcode_event): New class to handle direct mcode evaluation. (gh_manager::do_post_callback): For "closerequestfcn" callback, create an mcode_event and use the "close" function to make the figure current before evaluating the actual closerequestfcn.

--- a/libinterp/corefcn/graphics.in.h	Fri Jan 11 16:57:58 2019 +0100
+++ b/libinterp/corefcn/graphics.in.h	Fri Jan 11 18:14:41 2019 +0100
@@ -6161,6 +6161,10 @@
                          int busyaction = base_graphics_event::QUEUE);
 
   static graphics_event
+  create_mcode_event (const graphics_handle& h, const std::string& cmd,
+                      int busyaction);
+
+  static graphics_event
   create_function_event (event_fcn fcn, void *data = nullptr);
 
   static graphics_event