monitors/bluez.lua: Create sink loopback for SCO-A2DP sink nodes

If the BT profile autoswitch setting is enabled, we also want to create a sink
loopback for SCO-A2DP sink nodes. Since BT nodes are removed and created again
when the profile changes, this avoids confusing some apps making them think
that the BT profile has not changed at all, because the loopback nodes are
always present, even when switching profiles.

src/scripts/monitors/bluez.lua

@@ -7,7 +7,9 @@
 
 COMBINE_OFFSET = 64
 LOOPBACK_SOURCE_ID = 128
+LOOPBACK_SINK_ID = 129
 DEVICE_SOURCE_ID = 0
+DEVICE_SINK_ID = 1
 
 cutils = require ("common-utils")
 log = Log.open_topic ("s-monitors")
@@ -23,6 +25,8 @@ config.properties["api.bluez5.connection-info"] = true
 -- Properties used for previously creating a SCO source node. key: SPA device id
 sco_source_node_properties = {}
 
+-- Properties used for previously creating a SCO or A2DP sink node. key: SPA device id
+sco_a2dp_sink_node_properties = {}
 
 devices_om = ObjectManager {
   Interest {
@@ -271,6 +275,16 @@ function createNode(parent, id, type, factory, properties)
     name_prefix = name_prefix .. "_internal"
   end
 
+  -- hide the sink node because we use the loopback sink instead
+  if parent:get_managed_object (LOOPBACK_SINK_ID) ~= nil and
+       (factory == "api.bluez5.sco.sink" or
+           factory == "api.bluez5.a2dp.sink") then
+    properties["bluez5.sink-loopback-target"] = true
+    properties["api.bluez5.internal"] = true
+    -- add 'internal' to name prefix to not be confused with loopback node
+    name_prefix = name_prefix .. "_internal"
+  end
+
   -- set the node name
   local name = name_prefix .. "." ..
       (properties["api.bluez5.address"] or dev_props["device.name"]) .. "." ..
@@ -304,9 +318,12 @@ function createNode(parent, id, type, factory, properties)
     parent:set_managed_pending(id)
   else
     log:info("Create node: " .. properties["node.name"] .. ": " .. factory .. " " .. tostring (id))
-    properties["bluez5.loopback"] = false
     if factory == "api.bluez5.sco.source" then
+      properties["bluez5.loopback"] = false
       sco_source_node_properties[parent_spa_id] = properties
+    elseif factory == "api.bluez5.sco.sink" or factory == "api.bluez5.a2dp.sink" then
+      properties["bluez5.sink-loopback"] = false
+      sco_a2dp_sink_node_properties[parent_spa_id] = properties
     end
     local node = LocalNode("adapter", properties)
     node:activate(Feature.Proxy.BOUND)
@@ -318,14 +335,20 @@ function removeNode(parent, id)
   local dev_props = parent.properties
   local parent_spa_id = tonumber(dev_props["spa.object.id"])
   local src_properties = sco_source_node_properties[parent_spa_id]
+  local sink_properties = sco_a2dp_sink_node_properties[parent_spa_id]
 
   log:debug("Remove node: " .. tostring (id))
 
   if src_properties ~= nil and id == tonumber(src_properties["spa.object.id"]) then
-    log:debug("Clear old SCO properties")
+    log:debug("Clear old SCO source properties")
     sco_source_node_properties[parent_spa_id] = nil
   end
 
+  if sink_properties ~= nil and id == tonumber(sink_properties["spa.object.id"]) then
+    log:debug("Clear old SCO-A2DP sink properties")
+    sco_a2dp_sink_node_properties[parent_spa_id] = nil
+  end
+
   -- Clear also the device set module, if any
   parent:store_managed_object(id + COMBINE_OFFSET, nil)
 end
@@ -400,6 +423,7 @@ end
 
 function removeDevice(parent, id)
   sco_source_node_properties[id] = nil
+  sco_a2dp_sink_node_properties[id] = nil
 end
 
 function createMonitor()
@@ -456,6 +480,42 @@ function CreateDeviceLoopbackSource (dev_name, dec_desc, dev_id)
   return LocalModule("libpipewire-module-loopback", args:get_data(), {})
 end
 
+function CreateDeviceLoopbackSink (dev_name, dec_desc, dev_id)
+  local args = Json.Object {
+    ["capture.props"] = Json.Object {
+      ["node.name"] = string.format ("bluez_output.%s", dev_name),
+      ["node.description"] = string.format ("%s", dec_desc),
+      ["node.virtual"] = false,
+      ["audio.position"] = "[FL, FR]",
+      ["media.class"] = "Audio/Sink",
+      ["device.id"] = dev_id,
+      ["card.profile.device"] = DEVICE_SINK_ID,
+      ["device.routes"] = "1",
+      ["priority.driver"] = 2010,
+      ["priority.session"] = 2010,
+      ["bluez5.sink-loopback"] = true,
+      ["filter.smart"] = true,
+      ["filter.smart.target"] = Json.Object {
+        ["bluez5.sink-loopback-target"] = true,
+        ["bluez5.sink-loopback"] = false,
+        ["device.id"] = dev_id
+      }
+    },
+    ["playback.props"] = Json.Object {
+      ["node.name"] = string.format ("bluez_playback_internal.%s", dev_name),
+      ["media.class"] = "Stream/Output/Audio/Internal",
+      ["node.description"] =
+          string.format ("Bluetooth internal playback stream for %s", dec_desc),
+      ["bluez5.sink-loopback"] = true,
+      ["node.passive"] = true,
+      ["node.dont-fallback"] = true,
+      ["node.linger"] = true,
+      ["state.restore-props"] = false,
+    }
+  }
+  return LocalModule("libpipewire-module-loopback", args:get_data(), {})
+end
+
 function checkProfiles (dev)
   local device_id = dev["bound-id"]
   local props = dev.properties
@@ -488,19 +548,19 @@ function checkProfiles (dev)
     return
   end
 
-  -- Create the loopback device if never created before
-  local loopback = spa_device:get_managed_object (LOOPBACK_SOURCE_ID)
-  if loopback == nil then
+  -- Create the source loopback device if never created before
+  local source_loopback = spa_device:get_managed_object (LOOPBACK_SOURCE_ID)
+  if source_loopback == nil then
     local dev_name = props["api.bluez5.address"] or props["device.name"]
     local dec_desc = props["device.description"] or props["device.name"]
       or props["device.nick"] or props["device.alias"] or "bluetooth-device"
 
-    log:info("create SCO loopback node: " .. dev_name)
+    log:info("create SCO source loopback node: " .. dev_name)
 
     -- sanitize description, replace ':' with ' '
     dec_desc = dec_desc:gsub("(:)", " ")
-    loopback = CreateDeviceLoopbackSource (dev_name, dec_desc, device_id)
-    spa_device:store_managed_object(LOOPBACK_SOURCE_ID, loopback)
+    source_loopback = CreateDeviceLoopbackSource (dev_name, dec_desc, device_id)
+    spa_device:store_managed_object(LOOPBACK_SOURCE_ID, source_loopback)
 
     -- recreate any sco source node
     local properties = sco_source_node_properties[device_spa_id]
@@ -521,6 +581,39 @@ function checkProfiles (dev)
       end
     end
   end
+
+  local sink_loopback = spa_device:get_managed_object (LOOPBACK_SINK_ID)
+  if sink_loopback == nil then
+    local dev_name = props["api.bluez5.address"] or props["device.name"]
+    local dec_desc = props["device.description"] or props["device.name"]
+      or props["device.nick"] or props["device.alias"] or "bluetooth-device"
+
+    log:info("create SCO-A2DP sink loopback node: " .. dev_name)
+
+    -- sanitize description, replace ':' with ' '
+    dec_desc = dec_desc:gsub("(:)", " ")
+    sink_loopback = CreateDeviceLoopbackSink (dev_name, dec_desc, device_id)
+    spa_device:store_managed_object(LOOPBACK_SINK_ID, sink_loopback)
+
+    -- recreate any sco-a2dp sink node
+    local properties = sco_a2dp_sink_node_properties[device_spa_id]
+    if properties ~= nil then
+      local node_id = tonumber(properties["spa.object.id"])
+      local node = spa_device:get_managed_object (node_id)
+      if node ~= nil then
+        log:info("Recreate node: " .. properties["node.name"] .. ": " ..
+          properties["factory.name"] .. " " .. tostring (node_id))
+
+        spa_device:store_managed_object(node_id, nil)
+
+        properties["bluez5.sink-loopback-target"] = true
+        properties["api.bluez5.internal"] = true
+        node = LocalNode("adapter", properties)
+        node:activate(Feature.Proxy.BOUND)
+        spa_device:store_managed_object(node_id, node)
+      end
+    end
+  end
 end
 
 function onDeviceParamsChanged (dev, param_name)