From 051a09d2b7da478fd382543c3c4a7229a822279c Mon Sep 17 00:00:00 2001
From: Ted John <ted@brambles.org>
Date: Thu, 8 Apr 2021 21:05:34 +0100
Subject: [PATCH] Update map tile loop to support large maps.

---
 src/openrct2/rct2/S6Importer.cpp |  4 ++--
 src/openrct2/world/Map.cpp       | 33 ++++++++++++++++++--------------
 src/openrct2/world/Map.h         |  3 +--
 3 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/src/openrct2/rct2/S6Importer.cpp b/src/openrct2/rct2/S6Importer.cpp
index 03fd04e4d9..e1d075c976 100644
--- a/src/openrct2/rct2/S6Importer.cpp
+++ b/src/openrct2/rct2/S6Importer.cpp
@@ -459,8 +459,8 @@ public:
 
         // pad_13CE730
         // rct1_scenario_flags
-        gWidePathTileLoopX = _s6.wide_path_tile_loop_x;
-        gWidePathTileLoopY = _s6.wide_path_tile_loop_y;
+        gWidePathTileLoopPosition.x = _s6.wide_path_tile_loop_x;
+        gWidePathTileLoopPosition.y = _s6.wide_path_tile_loop_y;
         // pad_13CE778
 
         // Fix and set dynamic variables
diff --git a/src/openrct2/world/Map.cpp b/src/openrct2/world/Map.cpp
index eb0f789c4f..1d70a4e1e8 100644
--- a/src/openrct2/world/Map.cpp
+++ b/src/openrct2/world/Map.cpp
@@ -90,8 +90,7 @@ uint8_t gMapSelectArrowDirection;
 
 uint8_t gMapGroundFlags;
 
-uint16_t gWidePathTileLoopX;
-uint16_t gWidePathTileLoopY;
+TileCoordsXY gWidePathTileLoopPosition;
 uint16_t gGrassSceneryTileLoopPosition;
 
 int16_t gMapSizeUnits;
@@ -273,8 +272,7 @@ void map_init(int32_t size)
     }
 
     gGrassSceneryTileLoopPosition = 0;
-    gWidePathTileLoopX = 0;
-    gWidePathTileLoopY = 0;
+    gWidePathTileLoopPosition = {};
     gMapSizeUnits = size * 32 - 32;
     gMapSizeMinus2 = size * 32 - 2;
     gMapSize = size;
@@ -599,8 +597,8 @@ void map_update_path_wide_flags()
     // Presumably update_path_wide_flags is too computationally expensive to call for every
     // tile every update, so gWidePathTileLoopX and gWidePathTileLoopY store the x and y
     // progress. A maximum of 128 calls is done per update.
-    uint16_t x = gWidePathTileLoopX;
-    uint16_t y = gWidePathTileLoopY;
+    auto x = gWidePathTileLoopPosition.x;
+    auto y = gWidePathTileLoopPosition.y;
     for (int32_t i = 0; i < 128; i++)
     {
         footpath_update_path_wide_flags({ x, y });
@@ -617,8 +615,8 @@ void map_update_path_wide_flags()
             }
         }
     }
-    gWidePathTileLoopX = x;
-    gWidePathTileLoopY = y;
+    gWidePathTileLoopPosition.x = x;
+    gWidePathTileLoopPosition.y = y;
 }
 
 /**
@@ -1484,7 +1482,7 @@ void map_update_tiles()
     if (gScreenFlags & ignoreScreenFlags)
         return;
 
-    // Update 43 more tiles
+    // Update 43 more tiles (for each 256x256 block)
     for (int32_t j = 0; j < 43; j++)
     {
         int32_t x = 0;
@@ -1499,12 +1497,19 @@ void map_update_tiles()
             interleaved_xy >>= 1;
         }
 
-        auto mapPos = TileCoordsXY{ x, y }.ToCoordsXY();
-        auto* surfaceElement = map_get_surface_element_at(mapPos);
-        if (surfaceElement != nullptr)
+        // Repeat for each 256x256 block on the map
+        for (int32_t blockY = 0; blockY < gMapSize; blockY += 256)
         {
-            surfaceElement->UpdateGrassLength(mapPos);
-            scenery_update_tile(mapPos);
+            for (int32_t blockX = 0; blockX < gMapSize; blockX += 256)
+            {
+                auto mapPos = TileCoordsXY{ blockX + x, blockY + y }.ToCoordsXY();
+                auto* surfaceElement = map_get_surface_element_at(mapPos);
+                if (surfaceElement != nullptr)
+                {
+                    surfaceElement->UpdateGrassLength(mapPos);
+                    scenery_update_tile(mapPos);
+                }
+            }
         }
 
         gGrassSceneryTileLoopPosition++;
diff --git a/src/openrct2/world/Map.h b/src/openrct2/world/Map.h
index c1cf6f6b31..a9dddc5495 100644
--- a/src/openrct2/world/Map.h
+++ b/src/openrct2/world/Map.h
@@ -98,8 +98,7 @@ enum
 extern const std::array<CoordsXY, 8> CoordsDirectionDelta;
 extern const TileCoordsXY TileDirectionDelta[];
 
-extern uint16_t gWidePathTileLoopX;
-extern uint16_t gWidePathTileLoopY;
+extern TileCoordsXY gWidePathTileLoopPosition;
 extern uint16_t gGrassSceneryTileLoopPosition;
 
 extern int16_t gMapSizeUnits;