eliminate static wrapper functions in gh_manager class This is a large but straightforward change to eliminate the remains of the singleton pattern that was used for the gh_manager class. All static functions in the gh_manager class that previously used the "instance" function to access the gh_manager object stored in the global interpreter object and then called the corresponding "do_" functions have been eliminated. The "do_" prefix has been removed from the normal member functions and all uses of the static functions (calls of the form gh_manager::X) have been replaced with a call to the member function. The gh_manager object is accessed through the interpreter object and there is a new __get_gh_manager__ convenience function defined in the intepreter-private.cc file. Additionally, instead of using the gh_manager::auto_lock class, we access the mutex variable associated with the gh_manager object and pass it to the octave::autolock constructor to manage scoped locks for the gh_manager class. The following interpreter functions are now "methods" and require the interpreter as the first argument: F__calc_dimensions__, F__fltk_check__, F__get__, F__get_frame__, F__go_axes__, F__go_delete__, F__go_execute_callback__, F__go_figure__, F__go_figure_handles__, F__go_handles__, F__go_hggroup__, F__go_image__, F__go_light__, F__go_line__, F__go_patch__, F__go_post_callback__, F__go_surface__, F__go_text__, F__go_uibuttongroup__, F__go_uicontextmenu__, F__go_uicontrol__, F__go_uimenu__, F__go_uipanel__, F__go_uipushtool__, F__go_uitable__, F__go_uitoggletool__, F__go_uitoolbar__, F__image_pixel_size__, F__show_figure__, F__shutdown_qt__, F__update_normals__, F__zoom__, Faddlistener, Faddproperty, Fdellistener, Fdrawnow, Fget, Fishghandle, Fkbhit, Fpause, Freset, Fset, and Fwaitfor. Files affected: BaseControl.cc, ButtonControl.cc, ButtonGroup.cc, Canvas.cc, Container.cc, ContextMenu.cc, Figure.cc, GLCanvas.cc, Object.cc, Panel.cc, QtHandlesUtils.h, SliderControl.cc, Table.cc, __init_qt__.cc, qt-graphics-toolkit.cc, main-window.cc, gl-render.cc, gl-render.h, gl2ps-print.cc, graphics-toolkit.cc, graphics.cc, graphics.in.h, input.cc, interpreter.cc, sysdep.cc, utils.cc, __init_fltk__.cc.

--- a/libgui/graphics/GLCanvas.cc	Wed Aug 07 12:57:25 2019 -0700
+++ b/libgui/graphics/GLCanvas.cc	Fri Aug 09 10:36:08 2019 -0400
@@ -68,8 +68,11 @@
   void
   GLCanvas::draw (const graphics_handle& gh)
   {
-    gh_manager::auto_lock lock;
-    graphics_object go = gh_manager::get_object (gh);
+    gh_manager& gh_mgr = octave::__get_gh_manager__ ("GLCanvas::draw");
+
+    octave::autolock guard  (gh_mgr.graphics_lock ());
+
+    graphics_object go = gh_mgr.get_object (gh);
 
     if (go)
       {
@@ -85,7 +88,10 @@
   GLCanvas::do_getPixels (const graphics_handle& gh)
   {
     uint8NDArray retval;
-    graphics_object go = gh_manager::get_object (gh);
+
+    gh_manager& gh_mgr = octave::__get_gh_manager__ ("GLCanvas::do_getPixels");
+
+    graphics_object go = gh_mgr.get_object (gh);
 
     if (go && go.isa ("figure"))
       {
@@ -135,8 +141,11 @@
   GLCanvas::do_print (const QString& file_cmd, const QString& term,
                       const graphics_handle& handle)
   {
-    gh_manager::auto_lock lock;
-    graphics_object go = gh_manager::get_object (handle);
+    gh_manager& gh_mgr = octave::__get_gh_manager__ ("GLCanvas::do_print");
+
+    octave::autolock guard  (gh_mgr.graphics_lock ());
+
+    graphics_object go = gh_mgr.get_object (handle);
 
     if (go.valid_object ())
       {