JezK
Edit File: sm-objects.lua
-- 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)