diff --git a/gesture/gesture.go b/gesture/gesture.go
index aa3585b5..2d63963c 100644
--- a/gesture/gesture.go
+++ b/gesture/gesture.go
@@ -244,6 +244,8 @@ func (c *Click) Events(q event.Queue) []ClickEvent {
 func (ClickEvent) ImplementsEvent() {}
 
 // Add the handler to the operation list to receive scroll events.
+// The bounds variable refers to the scrolling boundaries
+// as defined in io/pointer.InputOp.
 func (s *Scroll) Add(ops *op.Ops, bounds image.Rectangle) {
 	oph := pointer.InputOp{
 		Tag:          s,