[GtkGLExt] GtkGlExt and OSMesa

[Stephane Popinet <s popinet niwa co nz>]

Hi all,

I am trying to use OSMesa to do offscreen rendering within a GtkGlExt 
program.

The problem I have is that after I set the current openGL context to 
OSMesa using sthg like:

OSMesaContext ctx = OSMesaCreateContextExt (OSMESA_RGBA, 16, 0, 0, NULL);
OSMesaMakeCurrent (ctx, image, GL_UNSIGNED_BYTE, width, height);
render_image();
save_image();
OSMesaDestroyContext (ctx);

and try to rerender the image in a GtkGlExt window, nothing is rendered.

I suppose it is not very surprising as I expect I have to restore the 
GtkGlExt context in some way. How would you do this?

I have tried calling  gdk_gl_drawable_make_current() after 
OSMesaDestroyContext (ctx), using the saved GdkGlContext and 
GdkGlDrawable but this does not seem to work.

Any help would be much appreciated. A complete example on how to use 
OSMesa within GtkGlExt would be ideal but any other suggestion or option 
for offscreen rendering would be welcome.

cheers,

Stephane