command: make audio device list available to the client API

DOCS/man/input.rst

@@ -1334,6 +1334,27 @@ Property list
     Note that you need to escape the ``\`` character, because the string is
     processed for C escape sequences before passing it to the OSD code.
 
+``audio-device-list``
+    Return the list of discovered audio devices. This is mostly for use with
+    the client API, and reflects what ``--audio-device=help`` with the command
+    line player returns.
+
+    When querying the property with the client API using ``MPV_FORMAT_NODE``,
+    or with Lua ``mp.get_property_native``, this will return a mpv_node with
+    the following contents:
+
+    ::
+
+        MPV_FORMAT_NODE_ARRAY
+            MPV_FORMAT_NODE_MAP (for each device entry)
+                "name"          MPV_FORMAT_STRING
+                "description"   MPV_FORMAT_STRING
+
+    The ``name`` is what is to be passed to the ``--audio-device`` option (and
+    often a rather cryptic audio API-specific ID), while ``description`` is
+    human readable free form text. The description is an empty string if none
+    was received.
+
 ``options/<name>`` (RW)
     Read-only access to value of option ``--<name>``. Most options can be
     changed at runtime by writing to this property. Note that many options

player/command.c

@@ -84,6 +84,8 @@ struct command_ctx {
     // bitmap list can be manipulated without additional synchronization.
     struct sub_bitmaps overlay_osd[2];
     struct sub_bitmaps *overlay_osd_current;
+
+    struct ao_device_list *cached_ao_devices;
 };
 
 struct overlay {
@@ -1308,6 +1310,35 @@ static int mp_property_volrestore(void *ctx, struct m_property *prop,
     return mp_property_generic_option(mpctx, prop, action, arg);
 }
 
+static int get_device_entry(int item, int action, void *arg, void *ctx)
+{
+    struct ao_device_list *list = ctx;
+    struct ao_device_desc *entry = &list->devices[item];
+
+    struct m_sub_property props[] = {
+        {"name",        SUB_PROP_STR(entry->name)},
+        {"description", SUB_PROP_STR(entry->desc)},
+        {0}
+    };
+
+    return m_property_read_sub(props, action, arg);
+}
+
+static int mp_property_audio_devices(void *ctx, struct m_property *prop,
+                                     int action, void *arg)
+{
+    struct MPContext *mpctx = ctx;
+    struct command_ctx *cmd = mpctx->command_ctx;
+    if (!cmd->cached_ao_devices)
+        cmd->cached_ao_devices = ao_get_device_list(mpctx->global);
+    if (!cmd->cached_ao_devices)
+        return M_PROPERTY_ERROR;
+    talloc_steal(cmd, cmd->cached_ao_devices);
+
+    return m_property_read_list(action, arg, cmd->cached_ao_devices->num_devices,
+                                get_device_entry, cmd->cached_ao_devices);
+}
+
 /// Audio delay (RW)
 static int mp_property_audio_delay(void *ctx, struct m_property *prop,
                                    int action, void *arg)
@@ -2794,6 +2825,7 @@ static const struct m_property mp_properties[] = {
     {"aid", mp_property_audio},
     {"balance", mp_property_balance},
     {"volume-restore-data", mp_property_volrestore},
+    {"audio-device-list", mp_property_audio_devices},
 
     // Video
     {"fullscreen", mp_property_fullscreen},