Il 18/10/19 11:28, Thomas Sevaldrud ha scritto:
I doesn't actually appear to have any negative consequences. Everything works as before, but our users are complaining about the warning :)The reason that these attributes are set after creating the QApplication is that I have a fallback system where I can try for software rendering if the ANGLE setup fails for some reason (crappy drivers, etc). So if my GLContext with AA_UseOpenGLES fails, I try again with AA_UseSoftwareOpenGL. This also appears to work nicely.
The principle is that once Qt "thinks" you are using Desktop GL, setting that attribute may or may not make it switch over to ANGLE, and vice versa. In other words there comes a point in time after which setting the attribute becomes meaningless (in the specific case: typically after the first GL context has been created, but this is undocumented and should not be relied upon).
What Qt is warning about is that you're touching a setting that may or may not have any effect (depending on the OS, what you did so far in the application, which modules of Qt you're using, the day of the week, the moon phase), so don't it.
What you could maybe do is to create a Q(Gui)Application, do your tests to detect which GL way to use, and if you need to switch to ANGLE or software then
1) destroy the QGuiApplication object 2) set all the attributes you need 3) create QGuiApplication again and proceed(Or, similarly: save some settings and restart the application with the new settings)
I don't actually use the QApplication for anything, I'm only using Qt as a GL wrapper with no QML, Gui, Network or anything. So I tried to simply remove the QGuiApplication, but then it crashes during QOpenGLContext::create(), so I guess it needs to exist after all.
Touching any and I mean any GUI class requires a QGuiApplication object, anything else is not supported (and will likely crash).
HTH, -- Giuseppe D'Angelo | giuseppe.dang...@kdab.com | Senior Software Engineer KDAB (France) S.A.S., a KDAB Group company Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com KDAB - The Qt, C++ and OpenGL Experts
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