Added bound helper (#40)

Co-authored-by: Zachary Levy <zachary@sunforge.is>
Reviewed-on: #40

draw/draw.odin

@@ -857,6 +857,15 @@ needs_transform :: #force_inline proc(origin: Vec2, rotation: f32) -> bool {
 // ----- Anchors ------------
 // ---------------------------------------------------------------------------------------------------------------------
 
+// Translate `local` — a point relative to `bounds`'s top-left — into `bounds`'s own coordinate
+// space by offsetting it by the rectangle's origin. Unlike the anchor helpers above (which
+// return size-relative offsets and ignore `bounds.x`/`bounds.y`), this uses the rectangle's
+// position. Handy for drawing inside a sub-region whose rect you were handed — e.g. the
+// `bounds` passed to a `Custom_Draw` callback: `local_to_bounds(bounds, {cx, cy})`.
+bound :: #force_inline proc(bounds: Rectangle, local: Vec2) -> Vec2 {
+	return {bounds.x + local.x, bounds.y + local.y}
+}
+
 // Return Vec2 pixel offsets for use as the `origin` parameter of draw calls.
 // Composable with normal vector +/- arithmetic.
 //