Fixed drawing glitch with overwide tiles

The layer rendering code was not prepared to handle tiles that were
wider than the tile width of the map.

This commit also fixes the initialization of the maximum tile height,
which was based on the map height rather than the tile height. This
could slightly reduce overdraw for some maps.

Reviewed-by: Stefan Beller <stefanbeller@googlemail.com>

2 files changed, 10 insertions, 5 deletions

diff --git a/src/map.cpp b/src/map.cpp
index f845f2ff..9e6d865d 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -120,8 +120,10 @@ Image* MapLayer::getTile(int x, int y) const
     return mTiles[x + y * mWidth];
 }
 
-void MapLayer::draw(Graphics *graphics, int startX, int startY,
-                    int endX, int endY, int scrollX, int scrollY,
+void MapLayer::draw(Graphics *graphics,
+                    int startX, int startY,
+                    int endX, int endY,
+                    int scrollX, int scrollY,
                     const MapSprites &sprites, int debugFlags) const
 {
     startX -= mX;
@@ -178,7 +180,8 @@ void MapLayer::draw(Graphics *graphics, int startX, int startY,
 Map::Map(int width, int height, int tileWidth, int tileHeight):
     mWidth(width), mHeight(height),
     mTileWidth(tileWidth), mTileHeight(tileHeight),
-    mMaxTileHeight(height),
+    mMaxTileHeight(tileHeight),
+    mMaxTileWidth(tileWidth),
     mDebugFlags(MAP_NORMAL),
     mOnClosedList(1), mOnOpenList(2),
     mLastScrollX(0.0f), mLastScrollY(0.0f)
@@ -281,6 +284,8 @@ void Map::addTileset(Tileset *tileset)
 
     if (tileset->getHeight() > mMaxTileHeight)
         mMaxTileHeight = tileset->getHeight();
+    if (tileset->getWidth() > mMaxTileWidth)
+        mMaxTileWidth = tileset->getWidth();
 }
 
 bool spriteCompare(const Sprite *a, const Sprite *b)
@@ -304,7 +309,7 @@ void Map::draw(Graphics *graphics, int scrollX, int scrollY)
     // Calculate range of tiles which are on-screen
     int endPixelY = graphics->getHeight() + scrollY + mTileHeight - 1;
     endPixelY += mMaxTileHeight - mTileHeight;
-    int startX = scrollX / mTileWidth;
+    int startX = (scrollX - mMaxTileWidth + mTileWidth) / mTileWidth;
     int startY = scrollY / mTileHeight;
     int endX = (graphics->getWidth() + scrollX + mTileWidth - 1) / mTileWidth;
     int endY = endPixelY / mTileHeight;
diff --git a/src/map.h b/src/map.h
index 9fc32232..2e0eb614 100644
--- a/src/map.h
+++ b/src/map.h
@@ -360,7 +360,7 @@ class Map : public Properties
 
         int mWidth, mHeight;
         int mTileWidth, mTileHeight;
-        int mMaxTileHeight;
+        int mMaxTileHeight, mMaxTileWidth;
         MetaTile *mMetaTiles;
         Layers mLayers;
         Tilesets mTilesets;