I am noticing some tearing with some QML 2 animations with Qt 5.4.2 on my Tegra 3 based embedded Linux board. I doubt if this is a complete vsync issue because most of the animations are smooth but there are some animations that involve a lot of parallel motion and clipping that tear consistently. These animation come out torn as opposed to simply stuttering so I don’t think it is completely a performance issue either. Though it might be caused by the system not being able to put out the necessary FPS to sync properly? The exact same application has no such trouble on my Haswell i7 PC.
I have enabled QT_QPA_EGLFS_FORCEVSYNC to no effect and have not yet managed to find anything else that I can try. I should mention though that I am running EGLFS with an X11 backend (http://code.qt.io/cgit/qt/qtbase.git/tree/src/plugins/platforms/eglfs/qeglfshooks_x11.cpp?h=5.4) as a result of the Nvidia drivers dictating the use of X11. I would assume that this means that I can’t really use the FB related settings normally available with EGLFS. Is there anything else that I can try to fix this?
Is there anything that I can do to try and force either vsync or double buffering with the X11 driver?