graphics: Add InitializeIfNeeded function (preparing for Android)

internal/graphics/draw.go

@@ -33,21 +33,11 @@ type Matrix interface {
 	Element(i, j int) float64
 }
 
-var shadersInitialized = false
-
 func drawTexture(c *opengl.Context, texture opengl.Texture, projectionMatrix *[4][4]float64, vertices []int16, geo Matrix, color Matrix, mode opengl.CompositeMode) error {
 	c.BlendFunc(mode)
 
 	// NOTE: WebGL doesn't seem to have Check gl.MAX_ELEMENTS_VERTICES or gl.MAX_ELEMENTS_INDICES so far.
 	// Let's use them to compare to len(quads) in the future.
-
-	if !shadersInitialized {
-		if err := theOpenGLState.initialize(c); err != nil {
-			return err
-		}
-		shadersInitialized = true
-	}
-
 	n := len(vertices) / 16
 	if n == 0 {
 		return nil

internal/graphics/program.go

@@ -21,6 +21,7 @@ import (
 )
 
 type openGLState struct {
+	initialized          bool
 	indexBufferLines     opengl.Buffer
 	indexBufferQuads     opengl.Buffer
 	programTexture       opengl.Program
@@ -43,7 +44,21 @@ const (
 	float32Size = 4
 )
 
-func (s *openGLState) initialize(c *opengl.Context) error {
+func InitializeIfNeeded(c *opengl.Context) error {
+	return theOpenGLState.initializeIfNeeded(c)
+}
+
+func (s *openGLState) initializeIfNeeded(c *opengl.Context) error {
+	if s.initialized {
+		return nil
+	}
+
+	var zeroProgram opengl.Program
+	s.lastProgram = zeroProgram
+	s.lastProjectionMatrix = nil
+	s.lastModelviewMatrix = nil
+	s.lastColorMatrix = nil
+
 	shaderVertexModelviewNative, err := c.NewShader(c.VertexShader, shader(c, shaderVertexModelview))
 	if err != nil {
 		panic(fmt.Sprintf("graphics: shader compiling error:\n%s", err))
@@ -85,6 +100,7 @@ func (s *openGLState) initialize(c *opengl.Context) error {
 	}
 	s.indexBufferLines = c.NewBuffer(c.ElementArrayBuffer, indices, c.StaticDraw)
 
+	s.initialized = true
 	return nil
 }
 

internal/ui/ui_glfw.go

@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/go-gl/glfw/v3.1/glfw"
+	"github.com/hajimehoshi/ebiten/internal/graphics"
 	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 )
 
@@ -87,6 +88,9 @@ func Init() (*opengl.Context, error) {
 	if err := u.context.Init(); err != nil {
 		return nil, err
 	}
+	if err := graphics.InitializeIfNeeded(u.context); err != nil {
+		return nil, err
+	}
 
 	return u.context, nil
 }

internal/ui/ui_js.go

@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"github.com/gopherjs/gopherjs/js"
+	"github.com/hajimehoshi/ebiten/internal/graphics"
 	"github.com/hajimehoshi/ebiten/internal/graphics/opengl"
 )
 
@@ -105,7 +106,14 @@ func (u *UserInterface) SwapBuffers() {
 func Init() (*opengl.Context, error) {
 	// Do nothing in node.js.
 	if js.Global.Get("require") != js.Undefined {
-		return opengl.NewContext()
+		c, err := opengl.NewContext()
+		if err != nil {
+			return nil, err
+		}
+		if err := graphics.InitializeIfNeeded(c); err != nil {
+			return nil, err
+		}
+		return c, nil
 	}
 
 	doc := js.Global.Get("document")
@@ -208,7 +216,14 @@ func Init() (*opengl.Context, error) {
 		// Do nothing.
 	})
 
-	return opengl.NewContext()
+	c, err := opengl.NewContext()
+	if err != nil {
+		return nil, err
+	}
+	if err := graphics.InitializeIfNeeded(c); err != nil {
+		return nil, err
+	}
+	return c, nil
 }
 
 func setMouseCursorFromEvent(e *js.Object) {