mpv: auto-populate internal playlist with other files in the same directory, on launch

so now i can listen to whole albums by opening any file from within them.
and for shows the next episode will automatically launch.

hosts/common/programs/mpv.nix

@@ -3,6 +3,8 @@
 # mpv docs:
 # - <https://mpv.io/manual/master>
 # - <https://github.com/mpv-player/mpv/wiki>
+# extensions i use:
+# - <https://github.com/jonniek/mpv-playlistmanager>
 # debugging:
 # - enter console by pressing backtick.
 #   > `set volume 50`     -> sets application volume to 50%
@@ -12,6 +14,10 @@
 #   - and then just `print(...)` from lua & it'll show in terminal
 # - invoke mpv with `--no-config` to have it not read ~/.config/mpv/*
 # - press `i` to show decoder info
+#
+# usage tips:
+# - `<` or `>` to navigate prev/next-file-in-folder  (uosc)
+# - shift+enter to view the playlist, then arrow-keys to navigate (mpv-playlistmanager)
 { config, lib, pkgs, ... }:
 
 let
@@ -31,7 +37,8 @@ let
       # `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)
+      # 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()
         local vol = mp.get_property('ao-volume')
@@ -62,6 +69,7 @@ in
     packageUnwrapped = with pkgs; wrapMpv mpv-unwrapped {
       scripts = [
         mpvScripts.mpris
+        mpvScripts.mpv-playlistmanager
         uosc
         # pkgs.mpv-uosc-latest
       ];
@@ -162,8 +170,15 @@ in
       # TODO: unify "Cast" and "Cast (stream)" options above.
     '';
     fs.".config/mpv/mpv.conf".symlink.text = ''
+      # write ~/.local/state/mpv/watch_later on exit, to allow resume
       save-position-on-quit=yes
+      # identify resumed files by filename only, since i use so many symlinks and doubt mpv does well with that.
+      ignore-path-in-watch-later-config
+
+      # keep-open: don't exit on completion of last file in playlist
       keep-open=yes
+      # seeking once at the end of the file causes auto-resume
+      keep-open-pause=no
 
       # force GUI, even for tracks w/o album art
       # see: <https://www.reddit.com/r/mpv/comments/rvrrpt/oscosdgui_and_arch_linux/>
@@ -189,6 +204,11 @@ in
       # if uosc is installed, this file is unused
       visibility=always
     '';
+    fs.".config/mpv/script-opts/console.conf".symlink.text = ''
+      # font size used by mpv's console (`); default 16
+      # font_size=28
+      scale=2
+    '';
     fs.".config/mpv/script-opts/uosc.conf".symlink.text = let
       play_pause_btn = "cycle:play_arrow:pause:no=pause/yes=play_arrow";
       rev_btn = "command:replay_10:seek -10";
@@ -217,6 +237,12 @@ in
 
       ui_scale=1.0
     '';
+    fs.".config/mpv/script-opts/playlistmanager.conf".symlink.text = ''
+      # script docs: <https://github.com/jonniek/mpv-playlistmanager>
+
+      # auto-populate playlist with other files in the same directory, on launch.
+      loadfiles_on_start=yes
+    '';
 
     # mime.priority = 200;  # default = 100; 200 means to yield to other apps
     mime.priority = 50;  # default = 100; 50 in order to take precedence over vlc.