layout: unexport Context.Layout and make it a function

Layout wasn't used outside package layout, so let's not export it.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

layout/flex.go

@@ -67,7 +67,7 @@ func (f *Flex) Rigid(gtx *Context, w Widget) FlexChild {
 	cs = axisConstraints(f.Axis, Constraint{Max: mainMax}, axisCrossConstraint(f.Axis, cs))
 	var m op.MacroOp
 	m.Record(gtx.Ops)
-	dims := gtx.Layout(cs, w)
+	dims := ctxLayout(gtx, cs, w)
 	m.Stop()
 	f.rigidSize += axisMain(f.Axis, dims.Size)
 	f.expand(dims)
@@ -95,7 +95,7 @@ func (f *Flex) Flex(gtx *Context, weight float32, w Widget) FlexChild {
 	cs = axisConstraints(f.Axis, submainc, axisCrossConstraint(f.Axis, cs))
 	var m op.MacroOp
 	m.Record(gtx.Ops)
-	dims := gtx.Layout(cs, w)
+	dims := ctxLayout(gtx, cs, w)
 	m.Stop()
 	f.expand(dims)
 	return FlexChild{m, dims}

layout/layout.go

@@ -82,16 +82,17 @@ const (
 	Vertical
 )
 
-// Layout a widget with a set of constraints and return its
-// dimensions. The previous constraints are restored after layout.
-func (s *Context) Layout(cs Constraints, w Widget) Dimensions {
-	saved := s.Constraints
-	s.Constraints = cs
-	s.Dimensions = Dimensions{}
+// layout a widget with a set of constraints and return its
+// dimensions. The widget dimensions are constrained abd the previous
+// constraints are restored after layout.
+func ctxLayout(gtx *Context, cs Constraints, w Widget) Dimensions {
+	saved := gtx.Constraints
+	gtx.Constraints = cs
+	gtx.Dimensions = Dimensions{}
 	w()
-	s.Dimensions.Size = cs.Constrain(s.Dimensions.Size)
-	s.Constraints = saved
-	return s.Dimensions
+	gtx.Dimensions.Size = cs.Constrain(gtx.Dimensions.Size)
+	gtx.Constraints = saved
+	return gtx.Dimensions
 }
 
 // Reset the context. The constraints' minimum and maximum values are
@@ -166,7 +167,7 @@ func (in Inset) Layout(gtx *Context, w Widget) {
 	var stack op.StackOp
 	stack.Push(gtx.Ops)
 	op.TransformOp{}.Offset(toPointF(image.Point{X: left, Y: top})).Add(gtx.Ops)
-	dims := gtx.Layout(mcs, w)
+	dims := ctxLayout(gtx, mcs, w)
 	stack.Pop()
 	gtx.Dimensions = Dimensions{
 		Size:     dims.Size.Add(image.Point{X: right + left, Y: top + bottom}),
@@ -188,7 +189,7 @@ func (a Align) Layout(gtx *Context, w Widget) {
 	mcs := cs
 	mcs.Width.Min = 0
 	mcs.Height.Min = 0
-	dims := gtx.Layout(mcs, w)
+	dims := ctxLayout(gtx, mcs, w)
 	macro.Stop()
 	sz := dims.Size
 	if sz.X < cs.Width.Min {

layout/list.go

@@ -93,7 +93,7 @@ func (l *List) Layout(gtx *Context, len int, w ListElement) {
 	for l.init(gtx, len); l.more(); l.next() {
 		cs := axisConstraints(l.Axis, Constraint{Max: inf}, axisCrossConstraint(l.Axis, l.ctx.Constraints))
 		i := l.index()
-		l.end(gtx.Layout(cs, func() {
+		l.end(ctxLayout(gtx, cs, func() {
 			w(i)
 		}))
 	}

layout/stack.go

@@ -32,7 +32,7 @@ func (s *Stack) Rigid(gtx *Context, w Widget) StackChild {
 	cs.Height.Min = 0
 	var m op.MacroOp
 	m.Record(gtx.Ops)
-	dims := gtx.Layout(cs, w)
+	dims := ctxLayout(gtx, cs, w)
 	m.Stop()
 	s.expand(dims)
 	return StackChild{m, dims}
@@ -46,7 +46,7 @@ func (s *Stack) Expand(gtx *Context, w Widget) StackChild {
 		Width:  Constraint{Min: s.maxSZ.X, Max: gtx.Constraints.Width.Max},
 		Height: Constraint{Min: s.maxSZ.Y, Max: gtx.Constraints.Height.Max},
 	}
-	dims := gtx.Layout(cs, w)
+	dims := ctxLayout(gtx, cs, w)
 	m.Stop()
 	s.expand(dims)
 	return StackChild{m, dims}