[Octave-bug-tracker] [bug #49083] demo camlight fails using qt graphics_toolkit

[Markus Mützel]

Follow-up Comment #4, bug #49083 (project octave):

After reading the code again, I guess that for some reason a GL error occured
before "get_maxlight" is called.
Atm, I am cross-building with the following change in gl-render.cc:

@@ -603,6 +603,8 @@
 
   static int max_lights = 0;
 
+  std::cout << "GL error: " << glGetError () << std::endl;
+
   // Check actual maximum number of lights possible
   if (max_lights == 0)
     {


That should reset a possible GL error and print the error number. Maybe that
could give a hint as to what is going on here.

However, it might take some time before I have any results because
cross-building is just so tedious...

@Rik: I guess something is wrong with how we are initializing OpenGL for
Windows or we cause an error very early after initialization. We do not call
glGetError as often as we probably should. I have also seen problems with
"texturemap" on Windows on my system (see bug #46997). As far as I can see,
that is the only place that glGetError was called before. That error in
texturemaps disappeared for me. I guess that is because the GL error is now
reset earlier in "get_maxlights" (causing problems here).

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