subpictures: move the b_absolute from subpicture to regions
The placement of subpictures is done by regions with x/y coordinates which are either absolute coordinates in the video or margins from the alignment set in the region. It is more logical to move the flag where these values are. It also allows the same subpicture source to provide both absolute and "aligned" regions at the same time, which is not possible at the moment.
This will also allow more improvement on the region placement which should also be allowed to be absolute in the display, rather than in the video area. For example the OSD should be able to use the whole display, it's currently tied to the video area.
We also see a lot of modules that used the absolute flag and still set an alignment to the top/left (it should have the same effect), but that alignment was never used in that case, even in 3.0: https://code.videolan.org/videolan/vlc/-/blob/3.0.x/src/video_output/vout_subpictures.c?ref_type=heads#L458
- libass
- aribcaption
- arib
- avcodec
- ttml
- audiobargraph
- logo
- marq
- rss
- dynamicoverlay
On top of !5157 (merged), only the 8 last commits are new.