libobs: Add function to allow custom output drawing

Optionally allows drawing directly to the primary output instead of
having to use a source to draw.

libobs/obs-internal.h

@@ -315,6 +315,8 @@ struct obs_core_data {
 	pthread_mutex_t                 encoders_mutex;
 	pthread_mutex_t                 services_mutex;
 	pthread_mutex_t                 audio_sources_mutex;
+	pthread_mutex_t                 draw_callbacks_mutex;
+	DARRAY(struct draw_callback)    draw_callbacks;
 
 	struct obs_view                 main_view;
 

libobs/obs-video.c

@@ -105,6 +105,19 @@ static inline void render_main_texture(struct obs_core_video *video,
 	gs_clear(GS_CLEAR_COLOR, &clear_color, 1.0f, 0);
 
 	set_render_size(video->base_width, video->base_height);
+
+	pthread_mutex_lock(&obs->data.draw_callbacks_mutex);
+
+	for (size_t i = 0; i < obs->data.draw_callbacks.num; i++) {
+		struct draw_callback *callback;
+		callback = obs->data.draw_callbacks.array+i;
+
+		callback->draw(callback->param,
+				video->base_width, video->base_height);
+	}
+
+	pthread_mutex_unlock(&obs->data.draw_callbacks_mutex);
+
 	obs_view_render(&obs->data.main_view);
 
 	video->textures_rendered[cur_texture] = true;

libobs/obs.c

@@ -542,6 +542,7 @@ static bool obs_init_data(void)
 	assert(data != NULL);
 
 	pthread_mutex_init_value(&obs->data.displays_mutex);
+	pthread_mutex_init_value(&obs->data.draw_callbacks_mutex);
 
 	if (pthread_mutexattr_init(&attr) != 0)
 		return false;
@@ -559,6 +560,8 @@ static bool obs_init_data(void)
 		goto fail;
 	if (pthread_mutex_init(&data->services_mutex, &attr) != 0)
 		goto fail;
+	if (pthread_mutex_init(&obs->data.draw_callbacks_mutex, NULL) != 0)
+		goto fail;
 	if (!obs_view_init(&data->main_view))
 		goto fail;
 
@@ -614,6 +617,8 @@ static void obs_free_data(void)
 	pthread_mutex_destroy(&data->outputs_mutex);
 	pthread_mutex_destroy(&data->encoders_mutex);
 	pthread_mutex_destroy(&data->services_mutex);
+	pthread_mutex_destroy(&data->draw_callbacks_mutex);
+	da_free(data->draw_callbacks);
 }
 
 static const char *obs_signals[] = {
@@ -1919,3 +1924,31 @@ void obs_get_audio_monitoring_device(const char **name, const char **id)
 	if (id)
 		*id = obs->audio.monitoring_device_id;
 }
+
+void obs_add_main_render_callback(
+		void (*draw)(void *param, uint32_t cx, uint32_t cy),
+		void *param)
+{
+	if (!obs)
+		return;
+
+	struct draw_callback data = {draw, param};
+
+	pthread_mutex_lock(&obs->data.draw_callbacks_mutex);
+	da_push_back(obs->data.draw_callbacks, &data);
+	pthread_mutex_unlock(&obs->data.draw_callbacks_mutex);
+}
+
+void obs_remove_main_render_callback(
+		void (*draw)(void *param, uint32_t cx, uint32_t cy),
+		void *param)
+{
+	if (!obs)
+		return;
+
+	struct draw_callback data = {draw, param};
+
+	pthread_mutex_lock(&obs->data.draw_callbacks_mutex);
+	da_erase_item(obs->data.draw_callbacks, &data);
+	pthread_mutex_unlock(&obs->data.draw_callbacks_mutex);
+}

libobs/obs.h

@@ -591,6 +591,13 @@ EXPORT void obs_enum_audio_monitoring_devices(obs_enum_audio_device_cb cb,
 EXPORT bool obs_set_audio_monitoring_device(const char *name, const char *id);
 EXPORT void obs_get_audio_monitoring_device(const char **name, const char **id);
 
+EXPORT void obs_add_main_render_callback(
+		void (*draw)(void *param, uint32_t cx, uint32_t cy),
+		void *param);
+EXPORT void obs_remove_main_render_callback(
+		void (*draw)(void *param, uint32_t cx, uint32_t cy),
+		void *param);
+
 
 /* ------------------------------------------------------------------------- */
 /* View context */