Add preliminary support for multiple layers in ortho maps

1 files changed, 5 insertions, 3 deletions

diff --git a/include/isogfx/asset.h b/include/isogfx/asset.h
index cc70ee3..74063a8 100644
--- a/include/isogfx/asset.h
+++ b/include/isogfx/asset.h
@@ -10,6 +10,7 @@
 #include <isogfx/types.h>
 
 #include <assert.h>
+#include <stddef.h>
 #include <stdint.h>
 
 // Maximum length of path strings in .TS and .TM files.
@@ -177,9 +178,10 @@ static inline const Tm_Layer* tm_map_get_layer(
   assert(map);
   assert(layer >= 0);
   assert(layer < map->num_layers);
-  return (const Tm_Layer*)((const uint8_t*)map->layers +
-                           (layer * map->world_width * map->world_height *
-                            sizeof(Tile)));
+  return (
+      const Tm_Layer*)((const uint8_t*)map->layers +
+                       ((size_t)(layer * map->world_width * map->world_height) *
+                        sizeof(Tile)));
 }
 
 /// Return the ith layer in the tile map.