vsync in linux can't be set
sdlayer_checkvsync
does some magic to determine if vsync is locked. Later it prevents videoSetVsync
from change vsync options at all. However if i remove first check with vsync_unsupported
i can have tear-free image.
I suspect that SDL_GL_GetSwapInterval
reports either "adaptive sync" or "no sync" and this most likely breaks sdlayer_checkvsync
magic and disable vsync switching at all.