Prevent plugin from being loaded twice

Author: WarmUpTill

module/advanced-scene-switcher-module.c

@@ -1,5 +1,16 @@
 #include <obs-module.h>
 #include <obs-frontend-api.h>
+#include <stdlib.h>
+
+#ifdef _WIN32
+#define ADVSS_SETENV(k, v) _putenv_s(k, v)
+#define ADVSS_UNSETENV(k) _putenv_s(k, "")
+#else
+#define ADVSS_SETENV(k, v) setenv(k, v, 1)
+#define ADVSS_UNSETENV(k) unsetenv(k)
+#endif
+
+#define ADVSS_INSTANCE_ENV "ADVSS_INSTANCE_LOADED"
 
 OBS_DECLARE_MODULE()
 OBS_MODULE_USE_DEFAULT_LOCALE("advanced-scene-switcher", "en-US")
@@ -17,6 +28,12 @@ void obs_module_post_load(void)
 
 bool obs_module_load(void)
 {
+	if (getenv(ADVSS_INSTANCE_ENV)) {
+		blog(LOG_WARNING,
+		     "[adv-ss] Another instance is already loaded - skipping.");
+		return false;
+	}
+	ADVSS_SETENV(ADVSS_INSTANCE_ENV, "1");
 	obs_frontend_push_ui_translation(obs_module_get_string);
 	InitSceneSwitcher(obs_current_module(), obs_module_text);
 	return true;
@@ -25,4 +42,5 @@ bool obs_module_load(void)
 void obs_module_unload(void)
 {
 	FreeSceneSwitcher();
+	ADVSS_UNSETENV(ADVSS_INSTANCE_ENV);
 }