eg-sampler: Send update to UI if gain parameter changes

plugins/eg-sampler.lv2/sampler.c

@@ -82,6 +82,7 @@ typedef struct {
 	sf_count_t frame;
 	bool       play;
 	bool       activated;
+	bool       gain_changed;
 	bool       sample_changed;
 } Sampler;
 
@@ -435,13 +436,21 @@ run(LV2_Handle instance, uint32_t sample_count)
 	// Start a sequence in the notify output port.
 	lv2_atom_forge_sequence_head(&self->forge, &self->notify_frame, 0);
 
-	// Send update to UI if sample has changed due to state restore
-	if (self->sample_changed) {
+	// Send update to UI if gain or sample has changed due to state restore
+	if (self->gain_changed || self->sample_changed) {
 		lv2_atom_forge_frame_time(&self->forge, 0);
-		write_set_file(&self->forge, &self->uris,
-		               self->sample->path,
-		               self->sample->path_len);
-		self->sample_changed = false;
+
+		if (self->gain_changed) {
+			write_set_gain(&self->forge, &self->uris, self->gain_dB);
+			self->gain_changed = false;
+		}
+
+		if (self->sample_changed) {
+			write_set_file(&self->forge, &self->uris,
+			               self->sample->path,
+			               self->sample->path_len);
+			self->sample_changed = false;
+		}
 	}
 
 	// Iterate over incoming events, emitting audio along the way
@@ -587,8 +596,9 @@ restore(LV2_Handle                  instance,
 		return LV2_STATE_ERR_BAD_TYPE;
 	}
 
-	self->gain_dB = *(const float*)value;
-	self->gain    = DB_CO(self->gain_dB);
+	self->gain_dB      = *(const float*)value;
+	self->gain         = DB_CO(self->gain_dB);
+	self->gain_changed = true;
 
 	return LV2_STATE_SUCCESS;
 }

plugins/eg-sampler.lv2/uris.h

@@ -74,6 +74,34 @@ map_sampler_uris(LV2_URID_Map* map, SamplerURIs* uris)
 	uris->patch_value        = map->map(map->handle, LV2_PATCH__value);
 }
 
+/**
+   Write a message like the following to `forge`:
+   [source,turtle]
+   ----
+   []
+   a patch:Set ;
+   patch:property param:gain ;
+   patch:value 0.0f .
+   ----
+*/
+static inline LV2_Atom_Forge_Ref
+write_set_gain(LV2_Atom_Forge*    forge,
+               const SamplerURIs* uris,
+               const float        gain)
+{
+	LV2_Atom_Forge_Frame frame;
+	LV2_Atom_Forge_Ref   set = lv2_atom_forge_object(
+		forge, &frame, 0, uris->patch_Set);
+
+	lv2_atom_forge_key(forge, uris->patch_property);
+	lv2_atom_forge_urid(forge, uris->param_gain);
+	lv2_atom_forge_key(forge, uris->patch_value);
+	lv2_atom_forge_float(forge, gain);
+
+	lv2_atom_forge_pop(forge, &frame);
+	return set;
+}
+
 /**
    Write a message like the following to `forge`:
    [source,turtle]