widget: [API] rename scrollbar update method to update

This matches the convention of other state update methods. While here, remove useless
dimensions return. The update doesn't draw anything, so there are no dimensions involved.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>

widget/list.go

@@ -29,8 +29,8 @@ type Scrollbar struct {
 	oldDragPos float32
 }
 
-// Layout updates the internal state of the scrollbar based on events
-// since the previous call to Layout. The provided axis will be used to
+// Update updates the internal state of the scrollbar based on events
+// since the previous call to Update. The provided axis will be used to
 // normalize input event coordinates and constraints into an axis-
 // independent format. viewportStart is the position of the beginning
 // of the scrollable viewport relative to the underlying content expressed
@@ -39,7 +39,7 @@ type Scrollbar struct {
 // as a value in the range [0,1]. For example, if viewportStart is 0.25
 // and viewportEnd is .5, the viewport described by the scrollbar is
 // currently showing the second quarter of the underlying content.
-func (s *Scrollbar) Layout(gtx layout.Context, axis layout.Axis, viewportStart, viewportEnd float32) layout.Dimensions {
+func (s *Scrollbar) Update(gtx layout.Context, axis layout.Axis, viewportStart, viewportEnd float32) {
 	// Calculate the length of the major axis of the scrollbar. This is
 	// the length of the track within which pointer events occur, and is
 	// used to scale those interactions.
@@ -137,8 +137,6 @@ func (s *Scrollbar) Layout(gtx layout.Context, axis layout.Axis, viewportStart,
 	// Process events from the indicator so that hover is
 	// detected properly.
 	_ = s.indicator.Update(gtx)
-
-	return layout.Dimensions{}
 }
 
 // AddTrack configures the track click listener for the scrollbar to use

widget/material/list.go

@@ -144,7 +144,7 @@ func (s ScrollbarStyle) Layout(gtx layout.Context, axis layout.Axis, viewportSta
 	gtx.Constraints.Min = convert(gtx.Constraints.Min)
 	gtx.Constraints.Max = gtx.Constraints.Min
 
-	s.Scrollbar.Layout(gtx, axis, viewportStart, viewportEnd)
+	s.Scrollbar.Update(gtx, axis, viewportStart, viewportEnd)
 
 	// Darken indicator if hovered.
 	if s.Scrollbar.IndicatorHovered() {