Support play/pause toggling

src/audio/audio_fsm.cpp

@@ -133,6 +133,12 @@ void Standby::react(const QueueUpdate& ev) {
   sFileSource->SetPath(db->GetTrackPath(*current_track));
 }
 
+void Standby::react(const TogglePlayPause& ev) {
+  if (sCurrentTrack) {
+    transit<Playback>();
+  }
+}
+
 void Playback::entry() {
   ESP_LOGI(kTag, "beginning playback");
   sOutput->SetInUse(true);
@@ -142,7 +148,7 @@ void Playback::exit() {
   ESP_LOGI(kTag, "finishing playback");
   // TODO(jacqueline): Second case where it's useful to wait for the i2s buffer
   // to drain.
-  vTaskDelay(pdMS_TO_TICKS(250));
+  vTaskDelay(pdMS_TO_TICKS(10));
   sOutput->SetInUse(false);
 
   events::System().Dispatch(PlaybackFinished{});
@@ -170,6 +176,10 @@ void Playback::react(const QueueUpdate& ev) {
   sFileSource->SetPath(db->GetTrackPath(*current_track));
 }
 
+void Playback::react(const TogglePlayPause& ev) {
+  transit<Standby>();
+}
+
 void Playback::react(const PlaybackUpdate& ev) {
   ESP_LOGI(kTag, "elapsed: %lu, total: %lu", ev.seconds_elapsed,
            ev.seconds_total);

src/audio/include/audio_events.hpp

@@ -37,6 +37,8 @@ struct PlayFile : tinyfsm::Event {
 
 struct VolumeChanged : tinyfsm::Event {};
 
+struct TogglePlayPause : tinyfsm::Event {};
+
 namespace internal {
 
 struct InputFileOpened : tinyfsm::Event {};

src/audio/include/audio_fsm.hpp

@@ -57,6 +57,7 @@ class AudioState : public tinyfsm::Fsm<AudioState> {
   virtual void react(const PlayFile&) {}
   virtual void react(const QueueUpdate&) {}
   virtual void react(const PlaybackUpdate&) {}
+  virtual void react(const TogglePlayPause&) {}
 
   virtual void react(const internal::InputFileOpened&) {}
   virtual void react(const internal::InputFileClosed&) {}
@@ -90,6 +91,7 @@ class Standby : public AudioState {
   void react(const PlayFile&) override;
   void react(const internal::InputFileOpened&) override;
   void react(const QueueUpdate&) override;
+  void react(const TogglePlayPause&) override;
 
   using AudioState::react;
 };
@@ -102,6 +104,7 @@ class Playback : public AudioState {
   void react(const PlayFile&) override;
   void react(const QueueUpdate&) override;
   void react(const PlaybackUpdate&) override;
+  void react(const TogglePlayPause&) override;
 
   void react(const internal::InputFileOpened&) override;
   void react(const internal::InputFileClosed&) override;

src/ui/screen_playing.cpp

@@ -8,6 +8,7 @@
 #include <sys/_stdint.h>
 #include <memory>
 
+#include "audio_events.hpp"
 #include "core/lv_event.h"
 #include "core/lv_obj.h"
 #include "core/lv_obj_scroll.h"
@@ -63,6 +64,10 @@ static void below_fold_focus_cb(lv_event_t* ev) {
   instance->OnFocusBelowFold();
 }
 
+static void play_pause_cb(lv_event_t* ev) {
+  events::Audio().Dispatch(audio::TogglePlayPause{});
+}
+
 static lv_style_t scrubber_style;
 
 auto info_label(lv_obj_t* parent) -> lv_obj_t* {
@@ -159,7 +164,10 @@ Playing::Playing(std::weak_ptr<database::Database> db, audio::TrackQueue* queue)
                         LV_FLEX_ALIGN_CENTER, LV_FLEX_ALIGN_CENTER);
 
   play_pause_control_ = control_button(controls_container, LV_SYMBOL_PLAY);
+  lv_obj_add_event_cb(play_pause_control_, play_pause_cb, LV_EVENT_CLICKED,
+                      NULL);
   lv_group_add_obj(group_, play_pause_control_);
+
   lv_group_add_obj(group_, control_button(controls_container, LV_SYMBOL_PREV));
   lv_group_add_obj(group_, control_button(controls_container, LV_SYMBOL_NEXT));
   lv_group_add_obj(group_,