From b85f5edee0f00d27934ab24c72db592d160b7ce0 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 5 Aug 2017 21:24:04 +0900
Subject: [PATCH] loop: Simplify logic

---
 internal/loop/run.go | 13 ++++++-------
 run.go               | 32 ++++++++++++++++++++------------
 2 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/internal/loop/run.go b/internal/loop/run.go
index ac2b9ca91..3218cfbd0 100644
--- a/internal/loop/run.go
+++ b/internal/loop/run.go
@@ -80,25 +80,24 @@ func (c *runContext) updateFPS(fps float64) {
 	c.m.Unlock()
 }
 
-type Runner interface {
-	Run(width, height int, scale float64, title string) error
-}
-
-func Run(runner Runner, width, height int, scale float64, title string) (err error) {
+func Start() error {
 	if currentRunContext != nil {
 		return errors.New("loop: The game is already running")
 	}
 	currentRunContext = &runContext{}
 	currentRunContext.startRunning()
-	defer currentRunContext.endRunning()
 
 	n := now()
 	currentRunContext.lastUpdated = n
 	currentRunContext.lastFPSUpdated = n
 
 	close(contextInitCh)
+	return nil
+}
 
-	return runner.Run(width, height, scale, title)
+func End() {
+	currentRunContext.endRunning()
+	currentRunContext = nil
 }
 
 func (c *runContext) updateCount(now int64) int {
diff --git a/run.go b/run.go
index 3cf96853b..c62e3a311 100644
--- a/run.go
+++ b/run.go
@@ -60,12 +60,8 @@ func IsRunningSlowly() bool {
 
 var theGraphicsContext atomic.Value
 
-type runner struct {
-	g *graphicsContext
-}
-
-func (r *runner) Run(width, height int, scale float64, title string) error {
-	if err := ui.Run(width, height, scale, title, &updater{r.g}); err != nil {
+func run(width, height int, scale float64, title string, g *graphicsContext) error {
+	if err := ui.Run(width, height, scale, title, &updater{g}); err != nil {
 		if _, ok := err.(*ui.RegularTermination); ok {
 			return nil
 		}
@@ -110,13 +106,19 @@ func (u *updater) Invalidate() {
 func Run(f func(*Image) error, width, height int, scale float64, title string) error {
 	ch := make(chan error)
 	go func() {
+		defer close(ch)
+
 		g := newGraphicsContext(f)
 		theGraphicsContext.Store(g)
-		r := &runner{g}
-		if err := loop.Run(r, width, height, scale, title); err != nil {
+		if err := loop.Start(); err != nil {
 			ch <- err
+			return
 		}
-		close(ch)
+		if err := run(width, height, scale, title, g); err != nil {
+			ch <- err
+			return
+		}
+		loop.End()
 	}()
 	// TODO: Use context in Go 1.7?
 	if err := ui.RunMainThreadLoop(ch); err != nil {
@@ -135,13 +137,19 @@ func Run(f func(*Image) error, width, height int, scale float64, title string) e
 func RunWithoutMainLoop(f func(*Image) error, width, height int, scale float64, title string) <-chan error {
 	ch := make(chan error)
 	go func() {
+		defer close(ch)
+
 		g := newGraphicsContext(f)
 		theGraphicsContext.Store(g)
-		r := &runner{g}
-		if err := loop.Run(r, width, height, scale, title); err != nil {
+		if err := loop.Start(); err != nil {
 			ch <- err
+			return
 		}
-		close(ch)
+		if err := run(width, height, scale, title, g); err != nil {
+			ch <- err
+			return
+		}
+		loop.End()
 	}()
 	return ch
 }