mpv: sane-sysvol script: init

it's a one-way volume control, but that's a start

hosts/common/programs/mpv/default.nix

@@ -91,48 +91,23 @@ let
            local last_up = cursor.last_event['primary_up'] or { time = 0 }
            if cursor.hover_raw or last_down.time >= last_up.time then cursor:move(mouse.x, mouse.y) end"
 
-      ### patch so that the volume control corresponds to `ao-volume`, i.e. the system-wide volume.
+      ### patch so that uosc volume control is routed to sane-sysvol.
       ### this is particularly nice for moby, because it avoids the awkwardness that system volume
       ### is hard to adjust while screen is on.
-      ### note that only under alsa (`-ao=alsa`) does `ao-volume` actually correspond to system volume.
+      ### previously i used ao-volume instead of sane-sysvol: but that forced `ao=alsa`
+      ### and came with heavy perf penalties (especially when adjusting the volume)
       substituteInPlace src/uosc/main.lua \
         --replace-fail \
-          "mp.observe_property('volume', 'number', create_state_setter('volume'))" \
-          "mp.observe_property('volume', 'number', update_ao_volume)"
+          "mp.observe_property('volume'" \
+          "mp.observe_property('user-data/sane-sysvol/volume'" \
+        --replace-fail 'volume = nil' 'volume = 0'
       substituteInPlace src/uosc/elements/Volume.lua \
-        --replace-fail "mp.commandv('set', 'volume'" "mp.commandv('set', 'ao-volume'" \
-        --replace-fail "mp.set_property_native('volume'" "mp.set_property('ao-volume'"
-
-      # `ao-volume` isn't actually an observable property.
-      # as of 2024/03/02, they *may* be working on that:
-      # - <https://github.com/mpv-player/mpv/pull/13604#issuecomment-1971665736>
-      # in the meantime, just query the volume every tick (i.e. frame).
-      # alternative is mpv's JSON IPC feature, where i could notify its socket whenever pipewire volume changes.
-      cat <<EOF >> src/uosc/main.lua
-      function update_ao_volume(_, vol)
-        if vol == nil then
-          -- vol will be nil if called manually, instead of via observe_property
-          vol = mp.get_property('ao-volume')
-        end
-        if vol == nil then
-          vol = 0
-        else
-          vol = tonumber(vol)
-        end
-
-        if vol ~= state.volume then
-          set_state('volume', vol)
-          request_render()
-        end
-      end
-      -- tick seems to occur on every redraw (even when volume is hidden).
-      -- in practice: for every new frame of the source, or whenever the cursor is moved.
-      mp.register_event('tick', update_ao_volume)
-      -- if paused and cursor isn't moving, then `tick` isn't called. fallback to a timer.
-      mp.add_periodic_timer(2, update_ao_volume)
-      -- invoke immediately to ensure state.volume is non-nil
-      update_ao_volume()
-      EOF
+        --replace-fail \
+          "mp.commandv('set', 'volume'" \
+          "mp.set_property_native('user-data/sane-sysvol/volume'" \
+        --replace-fail \
+          "mp.set_property_native('volume'" \
+          "mp.set_property_native('user-data/sane-sysvol/volume'"
     '';
   });
   mpv-unwrapped = pkgs.mpv-unwrapped.overrideAttrs (upstream: {
@@ -217,6 +192,7 @@ in
       ".local/state/mpv"
     ];
     fs.".config/mpv/scripts/sane-cast/main.lua".symlink.target = ./sane-cast-main.lua;
+    fs.".config/mpv/scripts/sane-sysvol/main.lua".symlink.target = ./sane-sysvol-main.lua;
     fs.".config/mpv/input.conf".symlink.target = ./input.conf;
     fs.".config/mpv/mpv.conf".symlink.target = ./mpv.conf;
     fs.".config/mpv/script-opts/osc.conf".symlink.target = ./osc.conf;

hosts/common/programs/mpv/sane-sysvol-main.lua

@@ -0,0 +1,37 @@
+msg = require('mp.msg')
+msg.trace('sane-sysvol: load: begin')
+
+function subprocess(args)
+  mp.command_native({
+    name = "subprocess",
+    args = args,
+    -- these arguments below probably don't matter: copied from sane-cast
+    detach = false,
+    capture_stdout = false,
+    capture_stderr = false,
+    passthrough_stdin = false,
+    playback_only = false,
+  })
+end
+
+function translate_out(vol)
+  -- called when mpv wants to set the system-wide volume
+  local volstr = tostring(vol) .. "%"
+  msg.trace("setting system-wide volume:", volstr)
+  if vol == nil then
+    return
+  end
+  subprocess({
+    "wpctl",
+    "set-volume",
+    "@DEFAULT_AUDIO_SINK@",
+    volstr
+  })
+end
+
+mp.set_property_native('user-data/sane-sysvol/volume', 0)
+mp.observe_property('user-data/sane-sysvol/volume', 'native', function(_, val)
+  translate_out(val)
+end)
+
+msg.trace('sane-sysvol: load: complete')