app: move glctx into app.App

Also move the initialization of glctx to an init function, removing
the data race mentioned in golang/go#12718. (Unfortunately the data
race is not the cause of the bug.)

Change-Id: If5f1fd7755d5645cf25ccc780ee8d138011c8f10
Reviewed-on: https://go-review.googlesource.com/15460
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

app/android.go

@@ -64,7 +64,6 @@ import (
 	"golang.org/x/mobile/event/size"
 	"golang.org/x/mobile/event/touch"
 	"golang.org/x/mobile/geom"
-	"golang.org/x/mobile/gl"
 	"golang.org/x/mobile/internal/mobileinit"
 )
 
@@ -268,9 +267,7 @@ func main(f func(App)) {
 var mainUserFn func(App)
 
 func mainUI(vm, jniEnv, ctx uintptr) error {
-	var worker gl.Worker
-	glctx, worker = gl.NewContext()
-	workAvailable := worker.WorkAvailable()
+	workAvailable := theApp.worker.WorkAvailable()
 
 	donec := make(chan struct{})
 	go func() {
@@ -331,7 +328,7 @@ func mainUI(vm, jniEnv, ctx uintptr) error {
 			C.surface = nil
 			theApp.sendLifecycle(lifecycle.StageAlive)
 		case <-workAvailable:
-			worker.DoWork()
+			theApp.worker.DoWork()
 		case <-theApp.publish:
 			// TODO: compare a generation number to redrawGen for stale paints?
 			if C.surface != nil {

app/app.go

@@ -67,10 +67,9 @@ var theApp = &app{
 	publishResult:  make(chan PublishResult),
 }
 
-var glctx gl.Context // TODO: move into theApp
-
 func init() {
 	theApp.eventsIn = pump(theApp.eventsOut)
+	theApp.glctx, theApp.worker = gl.NewContext()
 }
 
 func (a *app) sendLifecycle(to lifecycle.Stage) {
@@ -80,7 +79,7 @@ func (a *app) sendLifecycle(to lifecycle.Stage) {
 	a.eventsIn <- lifecycle.Event{
 		From:        a.lifecycleStage,
 		To:          to,
-		DrawContext: glctx,
+		DrawContext: a.glctx,
 	}
 	a.lifecycleStage = to
 }
@@ -93,6 +92,9 @@ type app struct {
 	lifecycleStage lifecycle.Stage
 	publish        chan struct{}
 	publishResult  chan PublishResult
+
+	glctx  gl.Context
+	worker gl.Worker
 }
 
 func (a *app) Events() <-chan interface{} {
@@ -111,7 +113,7 @@ func (a *app) Publish() PublishResult {
 	//
 	// This enforces that the final receive (for this paint cycle) on
 	// gl.WorkAvailable happens before the send on endPaint.
-	glctx.Flush()
+	a.glctx.Flush()
 	a.publish <- struct{}{}
 	return <-a.publishResult
 }
@@ -199,7 +201,7 @@ func pump(dst chan interface{}) (src chan interface{}) {
 func (a *app) registerGLViewportFilter() {
 	a.RegisterFilter(func(e interface{}) interface{} {
 		if e, ok := e.(size.Event); ok {
-			glctx.Viewport(0, 0, e.WidthPx, e.HeightPx)
+			a.glctx.Viewport(0, 0, e.WidthPx, e.HeightPx)
 		}
 		return e
 	})

app/darwin_amd64.go

@@ -34,7 +34,6 @@ import (
 	"golang.org/x/mobile/event/size"
 	"golang.org/x/mobile/event/touch"
 	"golang.org/x/mobile/geom"
-	"golang.org/x/mobile/gl"
 )
 
 var initThreadID uint64
@@ -75,23 +74,21 @@ func main(f func(App)) {
 // draw events is the CVDisplayLink timer, which is tied to the display
 // vsync. Secondary draw events come from [NSView drawRect:] when the
 // window is resized.
-func loop(ctx C.GLintptr) {
+func (a *app) loop(ctx C.GLintptr) {
 	runtime.LockOSThread()
 	C.makeCurrentContext(ctx)
-	var worker gl.Worker
-	glctx, worker = gl.NewContext()
 
-	workAvailable := worker.WorkAvailable()
+	workAvailable := a.worker.WorkAvailable()
 	for {
 		select {
 		case <-workAvailable:
-			worker.DoWork()
+			a.worker.DoWork()
 		case <-draw:
 		loop1:
 			for {
 				select {
 				case <-workAvailable:
-					worker.DoWork()
+					a.worker.DoWork()
 				case <-theApp.publish:
 					C.CGLFlushDrawable(C.CGLGetCurrentContext())
 					theApp.publishResult <- PublishResult{}
@@ -116,7 +113,7 @@ func drawgl() {
 
 //export startloop
 func startloop(ctx C.GLintptr) {
-	go loop(ctx)
+	go theApp.loop(ctx)
 }
 
 var windowHeightPx float32

app/darwin_armx.go

@@ -34,7 +34,6 @@ import (
 	"golang.org/x/mobile/event/size"
 	"golang.org/x/mobile/event/touch"
 	"golang.org/x/mobile/geom"
-	"golang.org/x/mobile/gl"
 )
 
 var initThreadID uint64
@@ -166,19 +165,13 @@ func sendTouch(cTouch, cTouchType uintptr, x, y float32) {
 	}
 }
 
-var (
-	worker        gl.Worker
-	workAvailable <-chan struct{}
-)
+var workAvailable <-chan struct{}
 
 //export drawgl
 func drawgl(ctx uintptr) {
-	if glctx == nil {
+	if workAvailable == nil {
 		C.setContext(unsafe.Pointer(ctx))
-
-		glctx, worker = gl.NewContext()
-		workAvailable = worker.WorkAvailable()
-
+		workAvailable = theApp.worker.WorkAvailable()
 		// TODO(crawshaw): not just on process start.
 		theApp.sendLifecycle(lifecycle.StageFocused)
 	}
@@ -190,7 +183,7 @@ func drawgl(ctx uintptr) {
 	for {
 		select {
 		case <-workAvailable:
-			worker.DoWork()
+			theApp.worker.DoWork()
 		case <-theApp.publish:
 			theApp.publishResult <- PublishResult{}
 			return