find-selected-default-node.lua: add a new default node hook

Hook accords higher priority to the currently selected device over and on top of
the previously selected devices.

src/config/wireplumber.conf

@@ -219,6 +219,7 @@ wireplumber.components = [
   { name = default-nodes/find-echo-cancel-default-node.lua, type = script/lua, priority = 120 }
   { name = default-nodes/state-default-nodes.lua, type = script/lua, priority = 120 }
   { name = default-nodes/find-best-default-node.lua, type = script/lua, priority = 120 }
+  { name = default-nodes/find-selected-default-node.lua, type = script/lua, priority = 120 }
   { name = default-nodes/select-default-nodes.lua, type = script/lua, priority = 120 }
 
   { name = linking/find-virtual-target.lua, type = script/lua, priority = 100 }

src/scripts/default-nodes/apply-default-node.lua

@@ -8,6 +8,7 @@ SimpleEventHook {
   name = "default-nodes/apply-default-node",
   after = { "default-nodes/find-best-default-node",
             "default-nodes/find-echo-cancel-default-node",
+            "default-nodes/find-selected-default-node",
             "default-nodes/find-stored-default-node" },
   interests = {
     EventInterest {

src/scripts/default-nodes/find-selected-default-node.lua

@@ -0,0 +1,63 @@
+-- WirePlumber
+--
+-- Copyright © 2022 Collabora Ltd.
+--
+-- SPDX-License-Identifier: MIT
+
+-- hook to make sure the user prefered device(default.configured.*) is higher
+-- priority.
+
+SimpleEventHook {
+  name = "default-nodes/find-selected-default-node",
+  interests = {
+    EventInterest {
+      Constraint { "event.type", "=", "select-default-node" },
+    },
+  },
+  execute = function (event)
+    local available_nodes = event:get_data ("available-nodes")
+
+    available_nodes = available_nodes and available_nodes:parse ()
+    if not available_nodes then
+      return
+    end
+
+    local selected_prio = event:get_data ("selected-node-priority") or 0
+    local selected_node = event:get_data ("selected-node")
+
+    local source = event:get_source ()
+    local props = event:get_properties ()
+    local def_node_type = props ["default-node.type"]
+    local metadata_om = source:call ("get-object-manager", "metadata")
+    local metadata = metadata_om:lookup { Constraint { "metadata.name", "=", "default" } }
+    local obj = metadata:find (0, "default.configured." .. def_node_type)
+
+    if not obj then
+      return
+    end
+
+    local json = Json.Raw (obj)
+    local current_configured_node = json:parse ().name
+
+    for _, node_props in ipairs (available_nodes) do
+      local name = node_props ["node.name"]
+      local priority = node_props ["priority.session"]
+      priority = math.tointeger (priority) or 0
+
+      if current_configured_node == name then
+        priority = 30000 + priority
+
+        if priority > selected_prio then
+
+          selected_prio = priority
+          selected_node = name
+
+          event:set_data ("selected-node-priority", selected_prio)
+          event:set_data ("selected-node", selected_node)
+        end
+
+        break
+      end
+    end
+  end
+}:register ()