Problem with mouse input (touchpad) on X11 while holding a key pressed

The topic already describes it. Whenever I’m pressing a key and holding it pressed, I don’t receive any mouse movement events. I verified that SDL_SendMouseMotion is never executed while having a key pressed. I’ve read that this might be touch pad related while trying to find information about that issue. Does anyone know anything about this? Otherwise I will just fill a bug report.
Thanks a lot.

Oh and if it matters, it was libsdl-2.0.5 from official Debian Repository and self compiled from hg.

I know that windows is currently/was disabling the mouse pad while you type
to prevent inadvertent clicks. Debian might be doing the same thing. I
recommend checking if it works using a non-SDL program before you file a
libSDL bug. If Linux is disabling the touchpad for you, there might be a
way to tell it not to for libSDL’s windows, or you could disable that
option from your mouse settings.

Thanks a lot - that makes sense. Haven’t thought about that issue.