io/pointer: clarify the documentation for Event.Position

Signed-off-by: Elias Naur <[email protected]>

io/pointer/pointer.go

@@ -32,8 +32,10 @@ type Event struct {
  Time time.Duration
  // Buttons are the set of pressed mouse buttons for this event.
  Buttons Buttons
- // Position is the position of the event, relative to
- // the current transformation, as set by op.TransformOp.
+ // Position is the coordinates of the event in the local coordinate
+ // system of the receiving tag. The transformation from global window
+ // coordinates to local coordinates is performed by the inverse of
+ // the [gioui.org/op.TransformOp]s applied to the [InputOp].
  Position f32.Point
  // Scroll is the scroll amount, if any.
  Scroll f32.Point