gtk3-demo OpenGL Area triangle is different colour in GLES than with GL
Steps to reproduce
- Install the gtk3-demo application on a system that supports both GL and GLES (Debian 10, x86-64, AMD graphics card, Wayland/GNOME environment)
- Run the gtk3-demo and inside run the "OpenGL Area" example
- Exit the application
- Run the gtk3-demo again with the
GDK_GL=glesenvironment variable set
- Run the "OpenGL Area" example
The colour of the triangle in the GL mode is yellow while the colour of the triangle in the GLES mode is blue.
It is expected that the triangle colour is the same in both modes, just with different shader logic, API, etc.
- libgtk-3-0 3.24.5-1 (Debian Package)
- gtk-3-examples 3.24.5-1 (Debian Package)
The triangle appears to be blue in other GLES environments on other graphics processors and processors, such as the pinephone. It is unclear if the demo is meant to be that way or there is some problem with the colour channels when using GLES with GTK.