vo_dmabuf_wayland: add osd support

This adds osd support via shm buffers using a similar approach that the
normal buffers do, but it differs in a few key areas. One thing to note
is that sway and weston actually handle this extremely differently which
required all the abstractions here. In particular, weston does not cope
well with destroying the wl_buffer from shm outside of the release
handler at all (i.e. it segfaults). The workaround here is to simply
attach a NULL to the osd surface and do a surface commit before we
destroy the buffers. This is reasonable enough and seems to work well
although it's pretty weird. Sway is more straightforward although it
actually releases the osd buffer when the window goes out of sight.
Also, I found that it doesn't always release every buffer before you
close it unlike weston seems to do which is part of the reason all this
bookkeeping is required. I don't know if there's any other compositor
out there that can possibly handle vo_dmabuf_wayland right now, but
suffering through these two is good enough for now I think.

1 files changed, 1 insertions, 2 deletions

diff --git a/DOCS/man/vo.rst b/DOCS/man/vo.rst
index 1c3d18a5e2..dccfa62a7c 100644
--- a/DOCS/man/vo.rst
+++ b/DOCS/man/vo.rst
@@ -292,8 +292,7 @@ Available video output drivers are:
     and to perform scaling and color space conversion using fixed-function hardware,
     if available, rather than GPU shaders. This frees up GPU resources for other tasks.
     Currently this driver is experimental and only works with the ``--hwdec=vaapi``
-    or ``hwdec=drm`` drivers;
-    OSD is also not supported. Supported compositors : Weston and Sway.
+    or ``hwdec=drm`` drivers. Supported compositors : Weston and Sway.
 
 ``vaapi``
     Intel VA API video output driver with support for hardware decoding. Note