Editor prerequisites [part 2] (#889)

lib/LoadProgress.h

@@ -0,0 +1,71 @@
+/*
+ * LoadProgress.h, part of VCMI engine
+ *
+ * Authors: listed in file AUTHORS in main folder
+ *
+ * License: GNU General Public License v2.0 or later
+ * Full text of license available in license.txt file, in main folder
+ *
+ */
+
+#pragma once
+
+#include "StdInc.h"
+#include <atomic>
+
+namespace Load
+{
+
+using Type = unsigned char;
+
+/*
+ * Purpose of that class is to track progress of computations
+ * Derive from this class if you want to translate user or system
+ * remaining amount of work needed.
+ * Tracking of the progress should be from another thread.
+ */
+class DLL_LINKAGE Progress
+{
+public:
+	
+	//Sets current state to 0.
+	//Amount of steps to finish progress will be equal to 100
+	Progress();
+	virtual ~Progress() = default;
+
+	//Returns current state of the progress
+	//To translate it into percentage (to float, for example):
+	//float progress = <>.get() / std::numeric_limits<Load::Type>::max();
+	Type get() const;
+	
+	//Returns true if current state equal to final state, false otherwise
+	bool finished() const;
+	
+	//Sets current state equal to the argument
+	void set(Type);
+	
+	//Sets current state to 0
+	//steps - amount of steps needed to reach final state
+	void reset(int steps = 100);
+	
+	//Immediately sets state to final
+	//finished() will return true after calling this method
+	void finish();
+	
+	//Sets amount of steps needed to reach final state
+	//doesn't modify current state
+	void setupSteps(int steps);
+	
+	//Sets amount of steps needed to reach state specified
+	//doesn't modify current state
+	void setupStepsTill(int steps, Type state);
+	
+	//Increases current state by steps count
+	//if current state reaches final state, returns immediately
+	void step(int count = 1);
+
+private:
+	std::atomic<Type> _progress, _target;
+	std::atomic<int> _step, _maxSteps;
+};
+}