Until now, it used only coordinates clipped to the screen for this,
which meant no negative margins were ever reported to libass. This broke
proper rendering of explicitly positioned ASS events (libass simply
could not know the real video size in this case.)
Fix this by reporting margins even if they're negative. This makes it
apparently work correctly with vo_gpu at least.
Note that I'm not really sure if anything in the rendering chain
required non-negative margins. If so, and that code implicitly assumed
it, I suppose crashes and such are possible.
wm4
537f011c6d