Changes between Initial Version and Version 2 of Ticket #8900

Timestamp:

May 9, 2023, 10:47:27 PM (3 years ago)

Author:

Tom Goddard

Comment:

Duplicate of #2729.

This has been reported a few dozen times, always on Linux. It appears the OpenGL connection has been dropped. In ticket #2729 the user was switched (so the console belonged to a different user) then when they switched back to the original user ChimeraX gave this error. Maybe the trouble is just that ChimeraX tries to render after a new user has the console and it does not detect that it does not have a valid window. The drawing code calls QWindow.isExposed() to check if the graphics should be drawn. This may be incorrectly claiming that the window is exposed. The drawing code in these reports does make the OpenGL context current on the graphics window. I think that would give an error if the window could not be rendered, but not certain about that.

The errors in is invalid operation in glDrawBuffer(GL_BACK). Docs say that means the framebuffer does not have a back buffer.

It may be worth testing switching users while ChimeraX is running on Ubuntu to see if this error can be produced. If it can maybe I can find a more reliable way to tell if the QOpenGLContext can render. The QOpenGLContext.isValid() call says the context can be lost on some operating systems. But it also suggests that makeCurrent() should then fail, and it has not failed in these reports. So maybe the context is not lost but the QWindow cannot be rendered since the console no longer belongs to the user. I have not seen any OpenGL documentation about the behavior in this case.