New wireplumber config

.config/wireplumber/scripts/sm-objects.lua

@@ -0,0 +1,103 @@
+-- WirePlumber
+--
+-- Copyright © 2023 Collabora Ltd.
+--    @author George Kiagiadakis <george.kiagiadakis@collabora.com>
+--
+-- SPDX-License-Identifier: MIT
+--
+-- The script exposes a metadata object named "sm-objects" that clients can
+-- use to load objects into the WirePlumber daemon process. The objects are
+-- loaded as soon as the metadata is set and are destroyed when the metadata
+-- is cleared.
+--
+-- To load an object, a client needs to set a metadata entry with:
+--
+--   * subject:
+--  The ID of the owner of the object; you can use 0 here, but the
+--  idea is to be able to restrict which clients can change and/or
+--  delete these objects by using IDs of other objects appropriately
+--
+--   * key: "<UNIQUE-OBJECT-NAME>"
+--  This is the name that will be used to identify the object.
+--  If an object with the same name already exists, it will be destroyed.
+--  Note that the keys are unique per subject, so you can have multiple
+--  objects with the same name as long as they are owned by different subjects.
+--
+--   * type: "Spa:String:JSON"
+--
+--   * value: "{ type = <object-type>,
+--               name = <object-name>,
+--               args = { ...object arguments... } }"
+--  The object type can be one of the following:
+--   - "pw-module": loads a pipewire module: `name` and `args` are interpreted
+--                  just like a module entry in pipewire.conf
+--   - "metadata": loads a metadata object with `metadata.name` = `name`
+--                 and any additional properties provided in `args`
+--
+
+on_demand_objects = {}
+
+object_constructors = {
+  ["pw-module"] = LocalModule,
+  ["metadata"] = function (name, args)
+    local m = ImplMetadata (name, args)
+    m:activate (Features.ALL, function (m, e)
+      if e then
+        Log.warning ("failed to activate on-demand metadata `" .. name .. "`: " .. tostring (e))
+      end
+    end)
+    return m
+  end
+}
+
+function handle_metadata_changed (m, subject, key, type, value)
+  -- destroy all objects when metadata is cleared
+  if not key then
+    on_demand_objects = {}
+    return
+  end
+
+  local object_id = key .. "@" .. tostring(subject)
+
+  -- destroy existing object instance, if needed
+  if on_demand_objects[object_id] then
+    Log.debug("destroy on-demand object: " .. object_id)
+    on_demand_objects[object_id] = nil
+  end
+
+  if value then
+    local json = Json.Raw(value)
+    if not json:is_object() then
+      Log.warning("loading '".. object_id .. "' failed: expected JSON object, got: '" .. value .. "'")
+      return
+    end
+
+    local obj = json:parse(1)
+    if not obj.type then
+      Log.warning("loading '".. object_id .. "' failed: no object type specified")
+      return
+    end
+    if not obj.name then
+      Log.warning("loading '".. object_id .. "' failed: no object name specified")
+      return
+    end
+
+    local constructor = object_constructors[obj.type]
+    if not constructor then
+      Log.warning("loading '".. object_id .. "' failed: unknown object type: " .. obj.type)
+      return
+    end
+
+    Log.info("load on-demand object: " .. object_id .. " -> " .. obj.name)
+    on_demand_objects[object_id] = constructor(obj.name, obj.args)
+  end
+end
+
+objects_metadata = ImplMetadata ("sm-objects")
+objects_metadata:activate (Features.ALL, function (m, e)
+  if e then
+    Log.warning ("failed to activate the sm-objects metadata: " .. tostring (e))
+  else
+    m:connect("changed", handle_metadata_changed)
+  end
+end)