player: make various commands for managing external tracks abortable

Until now, they could be aborted only by ending playback, and calling
mpv_abort_async_command didn't do anything.

This requires furthering the mess how playback abort is done. The main
reason why mp_cancel exists at all is to avoid that a "frozen" demuxer
(blocked on network I/O or whatever) cannot freeze the core. The core
should always get its way. Previously, there was a single mp_cancel
handle, that could be signaled, and all demuxers would unfreeze. With
external files, we might want to abort loading of a certain external
file, which automatically means they need a separate mp_cancel. So give
every demuxer its own mp_cancel, and "slave" it to whatever parent
mp_cancel handles aborting.

Since the mpv demuxer API conflates creating the demuxer and reading the
file headers, mp_cancel strictly need to be created before the demuxer
is created (or we couldn't abort loading). Although we give every
demuxer its own mp_cancel (as "enforced" by cancel_and_free_demuxer),
it's still rather messy to create/destroy it along with the demuxer.

1 files changed, 12 insertions, 0 deletions

diff --git a/TOOLS/lua/command-test.lua b/TOOLS/lua/command-test.lua
index 79c1127cbf..dd384818cc 100644
--- a/TOOLS/lua/command-test.lua
+++ b/TOOLS/lua/command-test.lua
@@ -65,6 +65,18 @@ mp.observe_property("vo-configured", "bool", function(_, v)
         mp.abort_async_command(x)
     end)
 
+    -- (assuming this "freezes")
+    local y = mp.command_native_async({name = "sub-add", url = "-"},
+        function(res, val, err)
+            print("done sub-add stdin: " .. join(" ", {res, val, err}))
+        end)
+    mp.add_timeout(20, function()
+        print("aborting sub-add stdin after timeout")
+        mp.abort_async_command(y)
+    end)
+
+
+
     -- This should get killed on script exit.
     mp.command_native_async({name = "subprocess", playback_only = false,
                              args = {"sleep", "inf"}}, function()end)