Add FLUID_SEQ_SCALE event type (#723)

doc/recent_changes.txt

@@ -10,6 +10,7 @@
   - The sequencer's queue no longer blocks the synthesizer thread, due to being busy arranging its events internally.
   - Events that share the same tick was given a new, documented order, see fluid_sequencer_send_at().
   - The sequencer's scale can now be used for arbitrary tempo changes. Previously, the scale of the sequencer was limited to 1000. The only limitation now is >0.
+  - There is now a dedicated event type for changing the sequencer's time scale, see fluid_event_scale().
 - The dynamic-sample-loader has learned support to pin samples, see fluid_synth_pin_preset() and fluid_synth_unpin_preset()
 - Added getter and setter functions for individual effect groups
 - Support for UTF-8 filenames under Windows, see fluid_synth_sfload()

include/fluidsynth/event.h

@@ -61,6 +61,7 @@ enum fluid_seq_event_type
     FLUID_SEQ_KEYPRESSURE,        /**< Polyphonic aftertouch event @since 2.0.0 */
     FLUID_SEQ_SYSTEMRESET,        /**< System reset event @since 1.1.0 */
     FLUID_SEQ_UNREGISTERING,      /**< Called when a sequencer client is being unregistered. @since 1.1.0 */
+    FLUID_SEQ_SCALE,              /**< Sets a new time scale for the sequencer @since 2.2.0 */
     FLUID_SEQ_LASTEVENT		/**< @internal Defines the count of events enums @warning This symbol 
                               is not part of the public API and ABI stability guarantee and 
                               may change at any time! */
@@ -115,6 +116,8 @@ FLUIDSYNTH_API void fluid_event_system_reset(fluid_event_t *evt);
 /* Only when unregistering clients */
 FLUIDSYNTH_API void fluid_event_unregistering(fluid_event_t *evt);
 
+FLUIDSYNTH_API void fluid_event_scale(fluid_event_t *evt, double new_scale);
+
 /* Accessing event data */
 FLUIDSYNTH_API int fluid_event_get_type(fluid_event_t *evt);
 FLUIDSYNTH_API fluid_seq_id_t fluid_event_get_source(fluid_event_t *evt);
@@ -129,6 +132,7 @@ FLUIDSYNTH_API void *fluid_event_get_data(fluid_event_t *evt);
 FLUIDSYNTH_API unsigned int fluid_event_get_duration(fluid_event_t *evt);
 FLUIDSYNTH_API short fluid_event_get_bank(fluid_event_t *evt);
 FLUIDSYNTH_API int fluid_event_get_pitch(fluid_event_t *evt);
+FLUIDSYNTH_API double fluid_event_get_scale(fluid_event_t *evt);
 FLUIDSYNTH_API unsigned int fluid_event_get_sfont_id(fluid_event_t *evt);
 /* @} */
 

src/midi/fluid_seqbind.c

@@ -185,7 +185,6 @@ fluid_seq_fluidsynth_callback(unsigned int time, fluid_event_t *evt, fluid_seque
 
     switch(fluid_event_get_type(evt))
     {
-
     case FLUID_SEQ_NOTEON:
         fluid_synth_noteon(synth, fluid_event_get_channel(evt), fluid_event_get_key(evt), fluid_event_get_velocity(evt));
         break;
@@ -326,6 +325,10 @@ fluid_seq_fluidsynth_callback(unsigned int time, fluid_event_t *evt, fluid_seque
         /* nothing in fluidsynth */
         break;
 
+    case FLUID_SEQ_SCALE:
+        fluid_sequencer_set_time_scale(seq, fluid_event_get_scale(evt));
+        break;
+
     default:
         break;
     }

src/synth/fluid_event.c

@@ -479,6 +479,20 @@ fluid_event_unregistering(fluid_event_t *evt)
     evt->type = FLUID_SEQ_UNREGISTERING;
 }
 
+/**
+ * Set a sequencer event to be a scale change event.
+ * Useful for scheduling tempo changes.
+ * @param evt Sequencer event structure
+ * @param new_scale The new time scale to apply to the sequencer, see fluid_sequencer_set_time_scale()
+ * @since 2.2.0
+ */
+void
+fluid_event_scale(fluid_event_t *evt, double new_scale)
+{
+    evt->type = FLUID_SEQ_SCALE;
+    evt->scale = new_scale;
+}
+
 /**
  * Set a sequencer event to be a channel-wide aftertouch event.
  * @param evt Sequencer event structure
@@ -744,3 +758,15 @@ fluid_event_get_sfont_id(fluid_event_t *evt)
 {
     return evt->duration;
 }
+
+/**
+ * Gets time scale field from a sequencer event structure.
+ * @param evt Sequencer event structure
+ * @return SoundFont identifier value.
+ *
+ * Used by the #FLUID_SEQ_SCALE event type.
+ */
+double fluid_event_get_scale(fluid_event_t *evt)
+{
+    return evt->scale;
+}

src/synth/fluid_event.h

@@ -46,6 +46,7 @@ struct _fluid_event_t
     fluid_note_id_t id;
     int pitch;
     unsigned int duration;
+    double scale;
     void *data;
 };