From 26ec62714c06f061269d42a742bff2713e789068 Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Thu, 5 Jan 2012 00:48:54 +0100 Subject: [PATCH] mixer/alsa: listen for external volume changes Use libasound's polling functions, implement a bridge to GSource / GPollFD and send idle events to clients when an external program changes the ALSA mixer volume. --- NEWS | 2 + src/mixer/alsa_mixer_plugin.c | 181 +++++++++++++++++++++++++++++++++- 2 files changed, 182 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index f5b8fb203..2d3f8f1a4 100644 --- a/NEWS +++ b/NEWS @@ -22,6 +22,8 @@ ver 0.17 (2011/??/??) - shout: add possibility to set url - roar: new output plugin for RoarAudio - winmm: fail if wrong device specified instead of using default device +* mixer: + - alsa: listen for external volume changes * playlist: - allow references to songs outside the music directory * state_file: add option "restore_paused" diff --git a/src/mixer/alsa_mixer_plugin.c b/src/mixer/alsa_mixer_plugin.c index a6e6f364e..22e4e22bd 100644 --- a/src/mixer/alsa_mixer_plugin.c +++ b/src/mixer/alsa_mixer_plugin.c @@ -20,6 +20,7 @@ #include "config.h" #include "mixer_api.h" #include "output_api.h" +#include "event_pipe.h" #include #include @@ -28,6 +29,15 @@ #define VOLUME_MIXER_ALSA_CONTROL_DEFAULT "PCM" #define VOLUME_MIXER_ALSA_INDEX_DEFAULT 0 +struct alsa_mixer_source { + GSource source; + + snd_mixer_t *mixer; + + /** a linked list of all registered GPollFD objects */ + GSList *fds; +}; + struct alsa_mixer { /** the base mixer class */ struct mixer base; @@ -41,6 +51,8 @@ struct alsa_mixer { long volume_min; long volume_max; int volume_set; + + struct alsa_mixer_source *source; }; /** @@ -52,6 +64,161 @@ alsa_mixer_quark(void) return g_quark_from_static_string("alsa_mixer"); } +/* + * GSource helper functions + * + */ + +static GSList ** +find_fd(GSList **list_r, int fd) +{ + while (true) { + GSList *list = *list_r; + if (list == NULL) + return NULL; + + GPollFD *p = list->data; + if (p->fd == fd) + return list_r; + + list_r = &list->next; + } +} + +static void +alsa_mixer_update_fd(struct alsa_mixer_source *source, const struct pollfd *p, + GSList **old_r) +{ + GSList **found_r = find_fd(old_r, p->fd); + if (found_r == NULL) { + /* new fd */ + GPollFD *q = g_new(GPollFD, 1); + q->fd = p->fd; + q->events = p->events; + g_source_add_poll(&source->source, q); + source->fds = g_slist_prepend(source->fds, q); + return; + } + + GSList *found = *found_r; + *found_r = found->next; + + GPollFD *q = found->data; + if (q->events != p->events) { + /* refresh events */ + g_source_remove_poll(&source->source, q); + q->events = p->events; + g_source_add_poll(&source->source, q); + } + + found->next = source->fds; + source->fds = found; +} + +static void +alsa_mixer_update_fds(struct alsa_mixer_source *source) +{ + int count = snd_mixer_poll_descriptors_count(source->mixer); + if (count < 0) + count = 0; + + struct pollfd *pfds = g_new(struct pollfd, count); + count = snd_mixer_poll_descriptors(source->mixer, pfds, count); + if (count < 0) + count = 0; + + GSList *old = source->fds; + source->fds = NULL; + + for (int i = 0; i < count; ++i) + alsa_mixer_update_fd(source, &pfds[i], &old); + g_free(pfds); + + for (; old != NULL; old = old->next) { + GPollFD *q = old->data; + g_source_remove_poll(&source->source, q); + g_free(q); + } + + g_slist_free(old); +} + +/* + * GSource methods + * + */ + +static gboolean +alsa_mixer_source_prepare(GSource *_source, G_GNUC_UNUSED gint *timeout_r) +{ + struct alsa_mixer_source *source = (struct alsa_mixer_source *)_source; + alsa_mixer_update_fds(source); + + return false; +} + +static gboolean +alsa_mixer_source_check(GSource *_source) +{ + struct alsa_mixer_source *source = (struct alsa_mixer_source *)_source; + + for (const GSList *i = source->fds; i != NULL; i = i->next) { + const GPollFD *poll_fd = i->data; + if (poll_fd->revents != 0) + return true; + } + + return false; +} + +static gboolean +alsa_mixer_source_dispatch(GSource *_source, + G_GNUC_UNUSED GSourceFunc callback, + G_GNUC_UNUSED gpointer user_data) +{ + struct alsa_mixer_source *source = (struct alsa_mixer_source *)_source; + + snd_mixer_handle_events(source->mixer); + return true; +} + +static void +alsa_mixer_source_finalize(GSource *_source) +{ + struct alsa_mixer_source *source = (struct alsa_mixer_source *)_source; + + for (GSList *i = source->fds; i != NULL; i = i->next) + g_free(i->data); + + g_slist_free(source->fds); +} + +static GSourceFuncs alsa_mixer_source_funcs = { + .prepare = alsa_mixer_source_prepare, + .check = alsa_mixer_source_check, + .dispatch = alsa_mixer_source_dispatch, + .finalize = alsa_mixer_source_finalize, +}; + +/* + * libasound callbacks + * + */ + +static int +alsa_mixer_elem_callback(G_GNUC_UNUSED snd_mixer_elem_t *elem, unsigned mask) +{ + if (mask & SND_CTL_EVENT_MASK_VALUE) + event_pipe_emit(PIPE_EVENT_MIXER); + + return 0; +} + +/* + * mixer_plugin methods + * + */ + static struct mixer * alsa_mixer_init(G_GNUC_UNUSED void *ao, const struct config_param *param, G_GNUC_UNUSED GError **error_r) @@ -95,7 +262,6 @@ alsa_mixer_lookup_elem(snd_mixer_t *handle, const char *name, unsigned idx) } return NULL; - } static bool @@ -135,6 +301,15 @@ alsa_mixer_setup(struct alsa_mixer *am, GError **error_r) snd_mixer_selem_get_playback_volume_range(am->elem, &am->volume_min, &am->volume_max); + + snd_mixer_elem_set_callback(am->elem, alsa_mixer_elem_callback); + + am->source = (struct alsa_mixer_source *) + g_source_new(&alsa_mixer_source_funcs, sizeof(*am->source)); + am->source->mixer = am->handle; + am->source->fds = NULL; + g_source_attach(&am->source->source, g_main_context_default()); + return true; } @@ -168,6 +343,10 @@ alsa_mixer_close(struct mixer *data) assert(am->handle != NULL); + g_source_destroy(&am->source->source); + g_source_unref(&am->source->source); + + snd_mixer_elem_set_callback(am->elem, NULL); snd_mixer_close(am->handle); }