libobs: Add manual transitioning support (T-bar)

Allows the ability to manually specify the transitioning point so the
user can transition at a custom rate, usually done by a device that can
be used as a T-bar
Co-authored-by: NJim <obs.jim@gmail.com>

libobs/obs-internal.h

@@ -700,6 +700,7 @@ struct obs_source {
 	gs_texrender_t *transition_texrender[2];
 	pthread_mutex_t transition_mutex;
 	obs_source_t *transition_sources[2];
+	float transition_manual_val;
 	bool transitioning_video;
 	bool transitioning_audio;
 	bool transition_source_active[2];

libobs/obs-source-transition.c

@@ -351,6 +351,7 @@ bool obs_transition_start(obs_source_t *transition,
 	bool active;
 	bool same_as_source;
 	bool same_as_dest;
+	bool same_mode;
 
 	if (!transition_valid(transition, "obs_transition_start"))
 		return false;
@@ -358,11 +359,20 @@ bool obs_transition_start(obs_source_t *transition,
 	lock_transition(transition);
 	same_as_source = dest == transition->transition_sources[0];
 	same_as_dest = dest == transition->transition_sources[1];
+	same_mode = mode == transition->transition_mode;
 	active = transition_active(transition);
 	unlock_transition(transition);
 
 	if (same_as_source && !active)
 		return false;
+	if (active && mode == OBS_TRANSITION_MODE_MANUAL && same_mode &&
+	    same_as_dest)
+		return true;
+
+	lock_transition(transition);
+	transition->transition_mode = mode;
+	transition->transition_manual_val = 0.0f;
+	unlock_transition(transition);
 
 	if (transition->info.transition_start)
 		transition->info.transition_start(transition->context.data);
@@ -389,11 +399,16 @@ bool obs_transition_start(obs_source_t *transition,
 	recalculate_transition_size(transition);
 	recalculate_transition_matrices(transition);
 
-	/* TODO: Add mode */
-	UNUSED_PARAMETER(mode);
 	return true;
 }
 
+void obs_transition_set_manual_time(obs_source_t *transition, float t)
+{
+	lock_transition(transition);
+	transition->transition_manual_val = t;
+	unlock_transition(transition);
+}
+
 void obs_transition_set(obs_source_t *transition, obs_source_t *source)
 {
 	obs_source_t *s[2];
@@ -429,6 +444,9 @@ void obs_transition_set(obs_source_t *transition, obs_source_t *source)
 
 static float calc_time(obs_source_t *transition, uint64_t ts)
 {
+	if (transition->transition_mode == OBS_TRANSITION_MODE_MANUAL)
+		return transition->transition_manual_val;
+
 	uint64_t end;
 
 	if (ts <= transition->transition_start_time)

libobs/obs.h

@@ -1333,6 +1333,7 @@ EXPORT obs_source_t *obs_transition_get_active_source(obs_source_t *transition);
 
 enum obs_transition_mode {
 	OBS_TRANSITION_MODE_AUTO,
+	OBS_TRANSITION_MODE_MANUAL,
 };
 
 EXPORT bool obs_transition_start(obs_source_t *transition,
@@ -1341,6 +1342,8 @@ EXPORT bool obs_transition_start(obs_source_t *transition,
 
 EXPORT void obs_transition_set(obs_source_t *transition, obs_source_t *source);
 
+EXPORT void obs_transition_set_manual_time(obs_source_t *transition, float t);
+
 enum obs_transition_scale_type {
 	OBS_TRANSITION_SCALE_MAX_ONLY,
 	OBS_TRANSITION_SCALE_ASPECT,