Add a priority field to TimerGameTick::TPeriod

Use this as the primary sort key for TimerGameTick::TPeriod,
to avoid container sort order changes on timer period saveload.

src/timer/timer_game_tick.cpp

@@ -19,13 +19,13 @@
 template<>
 void IntervalTimer<TimerGameTick>::Elapsed(TimerGameTick::TElapsed delta)
 {
-	if (this->period == 0) return;
+	if (this->period.value == 0) return;
 
 	this->storage.elapsed += delta;
 
 	uint count = 0;
-	while (this->storage.elapsed >= this->period) {
-		this->storage.elapsed -= this->period;
+	while (this->storage.elapsed >= this->period.value) {
+		this->storage.elapsed -= this->period.value;
 		count++;
 	}
 
@@ -38,11 +38,11 @@ template<>
 void TimeoutTimer<TimerGameTick>::Elapsed(TimerGameTick::TElapsed delta)
 {
 	if (this->fired) return;
-	if (this->period == 0) return;
+	if (this->period.value == 0) return;
 
 	this->storage.elapsed += delta;
 
-	if (this->storage.elapsed >= this->period) {
+	if (this->storage.elapsed >= this->period.value) {
 		this->callback();
 		this->fired = true;
 	}
@@ -58,7 +58,16 @@ void TimerManager<TimerGameTick>::Elapsed(TimerGameTick::TElapsed delta)
 
 #ifdef WITH_ASSERT
 template<>
-void TimerManager<TimerGameTick>::Validate(TimerGameTick::TPeriod)
+void TimerManager<TimerGameTick>::Validate(TimerGameTick::TPeriod period)
 {
+	if (period.priority == TimerGameTick::Priority::NONE) return;
+
+	/* Validate we didn't make a developer error and scheduled more than one
+	 * entry on the same priority. There can only be one timer on
+	 * a specific priority, to ensure we are deterministic, and to avoid
+	 * container sort order invariant issues with timer period saveload. */
+	for (const auto &timer : TimerManager<TimerGameTick>::GetTimers()) {
+		assert(timer->period.priority != period.priority);
+	}
 }
 #endif /* WITH_ASSERT */

src/timer/timer_game_tick.h

@@ -21,7 +21,34 @@
  */
 class TimerGameTick {
 public:
-	using TPeriod = uint;
+	enum Priority {
+		NONE, ///< These timers can be executed in any order; the order is not relevant.
+
+		/* For all other priorities, the order is important.
+		 * For safety, you can only setup a single timer on a single priority. */
+		COMPETITOR_TIMEOUT,
+	};
+
+	struct TPeriod {
+		Priority priority;
+		uint value;
+
+		TPeriod(Priority priority, uint value) : priority(priority), value(value)
+		{}
+
+		bool operator < (const TPeriod &other) const
+		{
+			/* Sort by priority before value, such that changes in value for priorities other than NONE do not change the container order */
+			if (this->priority != other.priority) return this->priority < other.priority;
+			return this->value < other.value;
+		}
+
+		bool operator == (const TPeriod &other) const
+		{
+			return this->priority == other.priority && this->value == other.value;
+		}
+	};
+
 	using TElapsed = uint;
 	struct TStorage {
 		uint elapsed;