From b331d3f7870bc4e56ebf22d5bb2ac192008dc5dd Mon Sep 17 00:00:00 2001
From: SamuXarick <43006711+SamuXarick@users.noreply.github.com>
Date: Sun, 5 Jan 2025 21:05:34 +0000
Subject: [PATCH] Codechange: Speed up ground density transition during river
 generation

This in turn avoids running the tile loop.
---
 src/clear_cmd.cpp |  2 +-
 src/clear_func.h  |  2 ++
 src/landscape.cpp |  8 +-------
 src/water_cmd.cpp | 19 ++++++++++++++++++-
 4 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/clear_cmd.cpp b/src/clear_cmd.cpp
index c40904e0fd..00e67d7640 100644
--- a/src/clear_cmd.cpp
+++ b/src/clear_cmd.cpp
@@ -202,7 +202,7 @@ static inline bool NeighbourIsNormal(TileIndex tile)
 	return false;
 }
 
-static void TileLoopClearDesert(TileIndex tile)
+void TileLoopClearDesert(TileIndex tile)
 {
 	/* Current desert level - 0 if it is not desert */
 	uint current = 0;
diff --git a/src/clear_func.h b/src/clear_func.h
index 28fd7d4a85..cdc6c9b74a 100644
--- a/src/clear_func.h
+++ b/src/clear_func.h
@@ -15,4 +15,6 @@
 void DrawHillyLandTile(const TileInfo *ti);
 void DrawClearLandTile(const TileInfo *ti, uint8_t set);
 
+void TileLoopClearDesert(TileIndex tile);
+
 #endif /* CLEAR_FUNC_H */
diff --git a/src/landscape.cpp b/src/landscape.cpp
index 544a41876b..056a939c6c 100644
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -1400,7 +1400,7 @@ static void CreateRivers()
 
 	uint wells = Map::ScaleBySize(4 << _settings_game.game_creation.amount_of_rivers);
 	const uint num_short_rivers = wells - std::max(1u, wells / 10);
-	SetGeneratingWorldProgress(GWP_RIVER, wells + TILE_UPDATE_FREQUENCY / 64); // Include the tile loop calls below.
+	SetGeneratingWorldProgress(GWP_RIVER, wells);
 
 	/* Try to create long rivers. */
 	for (; wells > num_short_rivers; wells--) {
@@ -1424,12 +1424,6 @@ static void CreateRivers()
 
 	/* Widening rivers may have left some tiles requiring to be watered. */
 	ConvertGroundTilesIntoWaterTiles();
-
-	/* Run tile loop to update the ground density. */
-	for (uint i = 0; i != TILE_UPDATE_FREQUENCY; i++) {
-		if (i % 64 == 0) IncreaseGeneratingWorldProgress(GWP_RIVER);
-		RunTileLoop();
-	}
 }
 
 /**
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
index f15c15666b..fe60bca1e5 100644
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -40,6 +40,7 @@
 #include "water_cmd.h"
 #include "landscape_cmd.h"
 #include "pathfinder/water_regions.h"
+#include "clear_func.h"
 
 #include "table/strings.h"
 
@@ -443,7 +444,23 @@ CommandCost CmdBuildLock(DoCommandFlag flags, TileIndex tile)
 /** Callback to create non-desert around a river tile. */
 static bool RiverModifyDesertZone(TileIndex tile, void *)
 {
-	if (GetTropicZone(tile) == TROPICZONE_DESERT) SetTropicZone(tile, TROPICZONE_NORMAL);
+	if (GetTropicZone(tile) == TROPICZONE_DESERT) {
+		SetTropicZone(tile, TROPICZONE_NORMAL);
+
+		/* Speed up the transition from desert to grass. */
+		if (IsTileType(tile, MP_CLEAR)) TileLoopClearDesert(tile);
+
+		for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
+			const TileIndex t = tile + TileOffsByDiagDir(dir);
+
+			if (!IsValidTile(t)) continue;
+			if (!IsTileType(t, MP_CLEAR)) continue;
+
+			/* Speed up the transition of adjacent desert tile density. */
+			TileLoopClearDesert(t);
+		}
+	}
+
 	return false;
 }