Expose API to notify about variable value change

lib/variables/variable.cpp

@@ -108,16 +108,20 @@ std::optional<int> Variable::IntValue() const
 
 void Variable::SetValue(const std::string &value)
 {
-	std::lock_guard<std::mutex> lock(_mutex);
-	_previousValue = _value;
-	_value = value;
+	{
+		std::lock_guard<std::mutex> lock(_mutex);
+		_previousValue = _value;
+		_value = value;
 
-	UpdateLastUsed();
-	if (_previousValue != _value) {
-		_lastChanged = std::chrono::high_resolution_clock::now();
-		++_valueChangeCount;
+		UpdateLastUsed();
+		if (_previousValue != _value) {
+			_lastChanged =
+				std::chrono::high_resolution_clock::now();
+			++_valueChangeCount;
+		}
+		setLastVariableChangeTime();
 	}
-	setLastVariableChangeTime();
+	_cv.notify_all();
 }
 
 void Variable::SetValue(double value)

lib/variables/variable.hpp

@@ -3,6 +3,7 @@
 #include "item-selection-helpers.hpp"
 #include "resizing-text-edit.hpp"
 
+#include <condition_variable>
 #include <mutex>
 #include <obs-data.h>
 #include <optional>
@@ -43,6 +44,11 @@ public:
 	std::optional<uint64_t> GetSecondsSinceLastUse() const;
 	std::optional<uint64_t> GetSecondsSinceLastChange() const;
 	void MarkAsUsed() const;
+	EXPORT std::condition_variable &GetCV() { return _cv; }
+	EXPORT std::unique_lock<std::mutex> GetCVLock()
+	{
+		return std::unique_lock<std::mutex>(_cvMutex);
+	}
 
 private:
 	SaveAction _saveAction = SaveAction::DONT_SAVE;
@@ -53,6 +59,8 @@ private:
 	mutable std::chrono::high_resolution_clock::time_point _lastUsed;
 	mutable std::chrono::high_resolution_clock::time_point _lastChanged;
 	mutable std::mutex _mutex;
+	std::mutex _cvMutex;
+	std::condition_variable _cv;
 
 	void UpdateLastUsed() const;