Marks the currently rendered data (if any) as invalid, and queues
a redraw of the widget, ensuring that the #GtkGLArea::render signal
is emitted during the draw.
This is only needed when the gtk_gl_area_set_auto_render() has
been called with a %FALSE value. The default behaviour is to
emit #GtkGLArea::render on each draw.
Marks the currently rendered data (if any) as invalid, and queues a redraw of the widget, ensuring that the #GtkGLArea::render signal is emitted during the draw.
This is only needed when the gtk_gl_area_set_auto_render() has been called with a %FALSE value. The default behaviour is to emit #GtkGLArea::render on each draw.