libobs: Add "monitoring by default" source cap

(This also modifies the UI module)

Adds the ability for a source to monitor by default.  This is mainly
aimed at browser sources, so that they do not stop outputting audio by
default like they used to.

UI/window-basic-source-select.cpp

@@ -197,6 +197,14 @@ bool AddNew(QWidget *parent, const char *id, const char *name,
 
 			newSource = source;
 
+			/* set monitoring if source monitors by default */
+			uint32_t flags = obs_source_get_output_flags(source);
+			if ((flags & OBS_SOURCE_MONITOR_BY_DEFAULT) != 0) {
+				obs_source_set_monitoring_type(
+					source,
+					OBS_MONITORING_TYPE_MONITOR_ONLY);
+			}
+
 			success = true;
 		}
 	}

libobs/obs-source.h

@@ -139,6 +139,12 @@ enum obs_balance_type {
  */
 #define OBS_SOURCE_CAP_DISABLED (1 << 10)
 
+/**
+ * Source should enable monitoring by default.  Monitoring should be set by the
+ * frontend if this flag is set.
+ */
+#define OBS_SOURCE_MONITOR_BY_DEFAULT (1 << 11)
+
 /** @} */
 
 typedef void (*obs_source_enum_proc_t)(obs_source_t *parent,

libobs/obs.c

@@ -1733,6 +1733,8 @@ static obs_source_t *obs_load_source_type(obs_data_t *source_data)
 	double volume;
 	double balance;
 	int64_t sync;
+	uint32_t prev_ver;
+	uint32_t caps;
 	uint32_t flags;
 	uint32_t mixers;
 	int di_order;
@@ -1743,6 +1745,9 @@ static obs_source_t *obs_load_source_type(obs_data_t *source_data)
 
 	obs_data_release(hotkeys);
 
+	prev_ver = (uint32_t)obs_data_get_int(source_data, "prev_ver");
+	caps = obs_source_get_output_flags(source);
+
 	obs_data_set_default_double(source_data, "volume", 1.0);
 	volume = obs_data_get_double(source_data, "volume");
 	obs_source_set_volume(source, (float)volume);
@@ -1795,6 +1800,14 @@ static obs_source_t *obs_load_source_type(obs_data_t *source_data)
 		source, (enum obs_deinterlace_field_order)di_order);
 
 	monitoring_type = (int)obs_data_get_int(source_data, "monitoring_type");
+	if (prev_ver < MAKE_SEMANTIC_VERSION(24, 0, 0)) {
+		if ((caps & OBS_SOURCE_MONITOR_BY_DEFAULT) != 0) {
+			/* updates older sources to enable monitoring
+			 * automatically if they added monitoring by default in
+			 * version 24 */
+			monitoring_type = OBS_MONITORING_TYPE_MONITOR_ONLY;
+		}
+	}
 	obs_source_set_monitoring_type(
 		source, (enum obs_monitoring_type)monitoring_type);
 
@@ -1921,6 +1934,8 @@ obs_data_t *obs_save_source(obs_source_t *source)
 		hotkey_data = hotkeys;
 	}
 
+	obs_data_set_int(source_data, "prev_ver", LIBOBS_API_VER);
+
 	obs_data_set_string(source_data, "name", name);
 	obs_data_set_string(source_data, "id", id);
 	obs_data_set_obj(source_data, "settings", settings);