Implement image surfaces

src/gfx/geom.rs

@@ -5,6 +5,12 @@ type rect<A> = { mut origin: point<A>, mut size: size<A> };
 
 enum au = int;
 
+impl size for size<int> {
+    fn area() -> int {
+        self.width * self.height
+    }
+}
+
 fn point<A:copy>(x: A, y: A) -> point<A> {
     {mut x: x, mut y: y}
 }

src/gfx/surface.rs

@@ -1,9 +1,30 @@
+import gfx::geom;
+import gfx::geom::size;
+
 enum format {
     fo_rgba_8888
     // TODO: RGB 565, others?
 }
 
-type surface = {
-    format: format
+type image_surface = {
+    size: geom::size<int>,
+    format: format,
+    buffer: [u8]
 };
 
+impl format for format {
+    fn bpp() -> uint {
+        alt self {
+            fo_rgba_8888 { 32u }
+        }
+    }
+}
+
+fn image_surface(size: geom::size<int>, format: format) -> image_surface {
+    {
+        size: size,
+        format: format,
+        buffer: vec::from_elem((size.area() as uint) * format.bpp(), 0u8)
+    }
+}
+