feat: Implement #to_grid_coordinates and #cell_rect for Tilemap

lib/dragon_skeleton/tilemap.rb

@@ -59,6 +59,24 @@ def render(outputs)
       outputs.primitives << @primitive
     end
 
+    # Converts a position to grid coordinates.
+    def to_grid_coordinates(position)
+      {
+        x: (position.x - @x).idiv(@cell_w),
+        y: (position.y - @y).idiv(@cell_h)
+      }
+    end
+
+    # Returns the rectangle of the cell at the given grid coordinates.
+    def cell_rect(grid_coordinates)
+      {
+        x: @x + (grid_coordinates.x * @cell_w),
+        y: @y + (grid_coordinates.y * @cell_h),
+        w: @cell_w,
+        h: @cell_h
+      }
+    end
+
     class RenderedPrimitive # :nodoc: Internal class responsible for rendering the tilemap.
       def initialize(cells, tilemap)
         @cells = cells

tests/lib/dragon_skeleton/tilemap.rb

@@ -54,6 +54,18 @@ def test_tilemap_render(args, assert)
   # rubocop:enable all
 end
 
+def test_tilemap_to_grid_coordinates(_args, assert)
+  tilemap = Tilemap.new(x: 50, y: 50, cell_w: 100, cell_h: 100, grid_w: 2, grid_h: 3)
+
+  assert.equal! tilemap.to_grid_coordinates({ x: 55, y: 55 }), { x: 0, y: 0 }
+end
+
+def test_tilemap_cell_rect(_args, assert)
+  tilemap = Tilemap.new(x: 50, y: 50, cell_w: 100, cell_h: 100, grid_w: 2, grid_h: 3)
+
+  assert.equal! tilemap.cell_rect({ x: 1, y: 2 }), { x: 150, y: 250, w: 100, h: 100 }
+end
+
 def test_tilemap_tileset_assigns_default_tile(_args, assert)
   tileset = TestTileset.new(
     default_tile: { tile_w: 50, tile_h: 50 },