layout: replace NewContext with a Queue argument to Context.Reset

We're about to reduce the scope of the Window.Queue by moving it
to FrameEvent. As a consequence, Context can no longer rely on a
Queue constant over its lifetime.

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

layout/context.go

@@ -29,13 +29,6 @@ type Context struct {
 	*op.Ops
 }
 
-// NewContext returns a Context for an event queue.
-func NewContext(q event.Queue) *Context {
-	return &Context{
-		queue: q,
-	}
-}
-
 // layout a widget with a set of constraints and return its
 // dimensions. The widget dimensions are constrained and the previous
 // constraints are restored after layout.
@@ -51,10 +44,11 @@ func ctxLayout(gtx *Context, cs Constraints, w Widget) Dimensions {
 
 // Reset the context. The constraints' minimum and maximum values are
 // set to the size.
-func (c *Context) Reset(cfg system.Config, size image.Point) {
+func (c *Context) Reset(q event.Queue, cfg system.Config, size image.Point) {
 	c.Constraints = RigidConstraints(size)
 	c.Dimensions = Dimensions{}
 	c.cfg = cfg
+	c.queue = q
 	if c.Ops == nil {
 		c.Ops = new(op.Ops)
 	}

layout/example_test.go

@@ -10,7 +10,7 @@ import (
 
 func ExampleInset() {
 	gtx := new(layout.Context)
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
+	gtx.Reset(nil, nil, image.Point{X: 100, Y: 100})
 	// Loose constraints with no minimal size.
 	gtx.Constraints.Width.Min = 0
 	gtx.Constraints.Height.Min = 0
@@ -33,7 +33,7 @@ func ExampleInset() {
 func ExampleDirection() {
 	gtx := new(layout.Context)
 	// Rigid constraints with both minimum and maximum set.
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
+	gtx.Reset(nil, nil, image.Point{X: 100, Y: 100})
 
 	layout.Center.Layout(gtx, func() {
 		// Lay out a 50x50 sized widget.
@@ -50,7 +50,7 @@ func ExampleDirection() {
 
 func ExampleFlex() {
 	gtx := new(layout.Context)
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
+	gtx.Reset(nil, nil, image.Point{X: 100, Y: 100})
 
 	layout.Flex{}.Layout(gtx,
 		// Rigid 10x10 widget.
@@ -72,7 +72,7 @@ func ExampleFlex() {
 
 func ExampleStack() {
 	gtx := new(layout.Context)
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
+	gtx.Reset(nil, nil, image.Point{X: 100, Y: 100})
 	gtx.Constraints.Width.Min = 0
 	gtx.Constraints.Height.Min = 0
 
@@ -94,7 +94,7 @@ func ExampleStack() {
 
 func ExampleList() {
 	gtx := new(layout.Context)
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
+	gtx.Reset(nil, nil, image.Point{X: 100, Y: 100})
 
 	// The list is 1e6 elements, but only 5 fit the constraints.
 	const listLen = 1e6

layout/stack_test.go

@@ -9,7 +9,7 @@ import (
 
 func TestStack(t *testing.T) {
 	var gtx Context
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
+	gtx.Reset(nil, nil, image.Point{X: 100, Y: 100})
 	gtx.Constraints.Width.Min = 0
 	gtx.Constraints.Height.Min = 0
 	exp := image.Point{X: 60, Y: 70}