From 33cb234ae16aa6cf6112374f42d808feacabfce2 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Wed, 17 Dec 2014 20:21:27 +0900
Subject: [PATCH] Bug fix: Creating a render target before running

---
 ebitenutil/texture.go |  2 +-
 example/image/main.go |  2 +-
 example/paint/main.go | 29 ++++++++++++++---------------
 graphicscontext.go    |  4 ----
 ui.go                 |  6 ++++++
 5 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/ebitenutil/texture.go b/ebitenutil/texture.go
index f92db2f8e..e07d8c1ac 100644
--- a/ebitenutil/texture.go
+++ b/ebitenutil/texture.go
@@ -22,7 +22,7 @@ import (
 	"os"
 )
 
-func LoadImageAndCreateTexture(path string, filter ebiten.Filter) (ebiten.TextureID, error) {
+func NewTextureIDFromFile(path string, filter ebiten.Filter) (ebiten.TextureID, error) {
 	file, err := os.Open(path)
 	if err != nil {
 		return 0, err
diff --git a/example/image/main.go b/example/image/main.go
index d338f4881..dad2edec7 100644
--- a/example/image/main.go
+++ b/example/image/main.go
@@ -39,7 +39,7 @@ func (g *Game) Update(gr ebiten.GraphicsContext) error {
 
 func main() {
 	g := new(Game)
-	id, err := ebitenutil.LoadImageAndCreateTexture("images/gophers.jpg", ebiten.FilterLinear)
+	id, err := ebitenutil.NewTextureIDFromFile("images/gophers.jpg", ebiten.FilterLinear)
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/example/paint/main.go b/example/paint/main.go
index fb5cf4929..22b029e49 100644
--- a/example/paint/main.go
+++ b/example/paint/main.go
@@ -23,6 +23,7 @@ import (
 	"image/color"
 	"log"
 	"math"
+	"sync"
 )
 
 const (
@@ -31,6 +32,7 @@ const (
 )
 
 type Game struct {
+	init               sync.Once
 	count              int
 	brushRenderTarget  ebiten.RenderTargetID
 	canvasRenderTarget ebiten.RenderTargetID
@@ -40,27 +42,15 @@ func (g *Game) Update(gr ebiten.GraphicsContext) error {
 	if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
 		g.count++
 	}
-	if g.brushRenderTarget.IsNil() {
-		var err error
-		g.brushRenderTarget, err = ebiten.NewRenderTargetID(1, 1, ebiten.FilterNearest)
-		if err != nil {
-			return err
-		}
-
+	g.init.Do(func() {
 		gr.PushRenderTarget(g.brushRenderTarget)
 		gr.Fill(0xff, 0xff, 0xff)
 		gr.PopRenderTarget()
-	}
-	if g.canvasRenderTarget.IsNil() {
-		var err error
-		g.canvasRenderTarget, err = ebiten.NewRenderTargetID(screenWidth, screenHeight, ebiten.FilterNearest)
-		if err != nil {
-			return err
-		}
 		gr.PushRenderTarget(g.canvasRenderTarget)
 		gr.Fill(0xff, 0xff, 0xff)
 		gr.PopRenderTarget()
-	}
+	})
+
 	mx, my := ebiten.CursorPosition()
 
 	if ebiten.IsMouseButtonPressed(ebiten.MouseButtonLeft) {
@@ -81,6 +71,15 @@ func (g *Game) Update(gr ebiten.GraphicsContext) error {
 
 func main() {
 	g := new(Game)
+	var err error
+	g.brushRenderTarget, err = ebiten.NewRenderTargetID(1, 1, ebiten.FilterNearest)
+	if err != nil {
+		log.Fatal(err)
+	}
+	g.canvasRenderTarget, err = ebiten.NewRenderTargetID(screenWidth, screenHeight, ebiten.FilterNearest)
+	if err != nil {
+		log.Fatal(err)
+	}
 	if err := ebiten.Run(g.Update, screenWidth, screenHeight, 2, "Paint (Ebiten Demo)"); err != nil {
 		log.Fatal(err)
 	}
diff --git a/graphicscontext.go b/graphicscontext.go
index 46f09c009..466c50fb5 100644
--- a/graphicscontext.go
+++ b/graphicscontext.go
@@ -22,10 +22,6 @@ import (
 )
 
 func newGraphicsContext(screenWidth, screenHeight, screenScale int) (*graphicsContext, error) {
-	gl.Init()
-	gl.Enable(gl.TEXTURE_2D)
-	gl.Enable(gl.BLEND)
-
 	// The defualt framebuffer should be 0.
 	r := opengl.NewRenderTarget(screenWidth*screenScale, screenHeight*screenScale, true)
 
diff --git a/ui.go b/ui.go
index b96eaa4aa..229453acd 100644
--- a/ui.go
+++ b/ui.go
@@ -18,6 +18,7 @@ package ebiten
 
 import (
 	"fmt"
+	"github.com/go-gl/gl"
 	glfw "github.com/go-gl/glfw3"
 	"image"
 	"runtime"
@@ -47,6 +48,11 @@ func init() {
 		funcs:  make(chan func()),
 	}
 	currentUI.run()
+	currentUI.use(func() {
+		gl.Init()
+		gl.Enable(gl.TEXTURE_2D)
+		gl.Enable(gl.BLEND)
+	})
 }
 
 type ui struct {