Spread tile loop iterations over all ticks when using day length > 1

See: #545

src/landscape.cpp

@@ -818,18 +818,41 @@ static uint32 GetTileLoopFeedback()
 	return feedbacks[MapLogX() + MapLogY() - 2 * MIN_MAP_SIZE_BITS];
 }
 
+static std::vector<uint> _tile_loop_counts;
+
+void SetupTileLoopCounts()
+{
+	_tile_loop_counts.resize(_settings_game.economy.day_length_factor);
+	if (_settings_game.economy.day_length_factor == 0) return;
+
+	uint64 count_per_tick_fp16 = (static_cast<uint64>(1) << (MapLogX() + MapLogY() + 8)) / _settings_game.economy.day_length_factor;
+	uint64 accumulator = 0;
+	for (uint &count : _tile_loop_counts) {
+		accumulator += count_per_tick_fp16;
+		count = static_cast<uint32>(accumulator >> 16);
+		accumulator &= 0xFFFF;
+	}
+	if (accumulator > 0) _tile_loop_counts[0]++;
+}
+
 /**
  * Gradually iterate over all tiles on the map, calling their TileLoopProcs once every 256 ticks.
  */
-void RunTileLoop()
+void RunTileLoop(bool apply_day_length)
 {
+	/* We update every tile every 256 ticks, so divide the map size by 2^8 = 256 */
+	uint count;
+	if (apply_day_length && _settings_game.economy.day_length_factor > 1) {
+		count = _tile_loop_counts[_tick_skip_counter];
+		if (count == 0) return;
+	} else {
+		count = 1 << (MapLogX() + MapLogY() - 8);
+	}
+
 	PerformanceAccumulator framerate(PFE_GL_LANDSCAPE);
 
 	const uint32 feedback = GetTileLoopFeedback();
 
-	/* We update every tile every 256 ticks, so divide the map size by 2^8 = 256 */
-	uint count = 1 << (MapLogX() + MapLogY() - 8);
-
 	TileIndex tile = _cur_tileloop_tile;
 	/* The LFSR cannot have a zeroed state. */
 	dbg_assert(tile != 0);

src/landscape.h

@@ -166,7 +166,8 @@ bool HasFoundationNW(TileIndex tile, Slope slope_here, uint z_here);
 bool HasFoundationNE(TileIndex tile, Slope slope_here, uint z_here);
 
 void DoClearSquare(TileIndex tile);
-void RunTileLoop();
+void SetupTileLoopCounts();
+void RunTileLoop(bool apply_day_length = false);
 void RunAuxiliaryTileLoop();
 
 void InitializeLandscape();

src/misc.cpp

@@ -116,6 +116,7 @@ void InitializeGame(uint size_x, uint size_y, bool reset_date, bool reset_settin
 	} else {
 		SetScaledTickVariables();
 	}
+	SetupTileLoopCounts();
 	UpdateCachedSnowLine();
 	UpdateCachedSnowLineBounds();
 

src/openttd.cpp

@@ -2050,13 +2050,14 @@ void StateGameLoop()
 		RunAuxiliaryTileLoop();
 		if (_tick_skip_counter < _settings_game.economy.day_length_factor) {
 			AnimateAnimatedTiles();
+			RunTileLoop(true);
 			CallVehicleTicks();
 			OnTick_Companies(false);
 		} else {
 			_tick_skip_counter = 0;
 			IncreaseDate();
 			AnimateAnimatedTiles();
-			RunTileLoop();
+			RunTileLoop(true);
 			CallVehicleTicks();
 			CallLandscapeTick();
 			OnTick_Companies(true);

src/saveload/afterload.cpp

@@ -859,6 +859,7 @@ bool AfterLoadGame()
 	/* Update current year
 	 * must be done before loading sprites as some newgrfs check it */
 	SetDate(_date, _date_fract, false);
+	SetupTileLoopCounts();
 
 	/*
 	 * Force the old behaviour for compatibility reasons with old savegames. As new

src/settings.cpp

@@ -1743,6 +1743,8 @@ static void DayLengthChanged(int32 new_value)
 	extern void VehicleDayLengthChanged(DateTicksScaled old_scaled_date_ticks, DateTicksScaled old_scaled_date_ticks_offset, uint8 old_day_length_factor);
 	VehicleDayLengthChanged(old_scaled_date_ticks, old_scaled_date_ticks_offset, _pre_change_day_length_factor);
 
+	SetupTileLoopCounts();
+
 	MarkWholeScreenDirty();
 }