just check intersecting tiles

src/tile.rs

@@ -1,13 +1,20 @@
+use sdl2::rect::Rect;
+
+
 pub struct Layer<T> {
     tiles: Vec<T>,
-    width: i32
+    width: i32,
+    tile_width: i32,
+    tile_height: i32
 }
 
 impl<T> Layer<T> where T: Clone {
-    pub fn new(width: i32, height: i32, tile: T) -> Layer<T> {
+    pub fn new(width: i32, height: i32, tile_width: i32, tile_height: i32, tile: T) -> Layer<T> {
         Layer {
             tiles: Vec::from_elem((width * height) as uint, tile),
-            width: width
+            width: width,
+            tile_width: tile_width,
+            tile_height: tile_height
         }
     }
 
@@ -22,4 +29,14 @@ impl<T> Layer<T> where T: Clone {
 
         *self.tiles.index_mut(&offset) = tile;
     }
+
+    pub fn get_intersecting(&self, rect: &Rect) -> Rect {
+        let x = rect.x / self.tile_width;
+        let w = rect.w / self.tile_width;
+
+        let y = rect.y / self.tile_height;
+        let h = rect.h / self.tile_height;
+
+        Rect::new(x, y, w, h)
+    }
 }