internal/graphicsdriver/opengl: move initGL to NewGraphics

As restoring from context lost doesn't happen on browsers, initilizing
GL doesn't have to be done at reset.

internal/graphicsdriver/opengl/context_js.go

@@ -17,8 +17,6 @@ package opengl
 import (
 	"errors"
 	"fmt"
-	"os"
-	"strings"
 	"syscall/js"
 	"unsafe"
 
@@ -46,17 +44,6 @@ const (
 	invalidUniform     = -1
 )
 
-func webGL2MightBeAvailable() bool {
-	env := os.Getenv("EBITENGINE_OPENGL")
-	for _, t := range strings.Split(env, ",") {
-		switch strings.TrimSpace(t) {
-		case "webgl1":
-			return false
-		}
-	}
-	return js.Global().Get("WebGL2RenderingContext").Truthy()
-}
-
 type contextImpl struct {
 	ctx    gl.Context
 	canvas js.Value
@@ -66,52 +53,6 @@ type contextImpl struct {
 	fnIsContextLost js.Value
 }
 
-func (c *context) initGL() error {
-	var glContext js.Value
-
-	if doc := js.Global().Get("document"); doc.Truthy() {
-		canvas := c.canvas
-		attr := js.Global().Get("Object").New()
-		attr.Set("alpha", true)
-		attr.Set("premultipliedAlpha", true)
-		attr.Set("stencil", true)
-
-		if webGL2MightBeAvailable() {
-			glContext = canvas.Call("getContext", "webgl2", attr)
-			if glContext.Truthy() {
-				c.webGL2 = true
-			}
-		}
-
-		// Even though WebGL2RenderingContext exists, getting a webgl2 context might fail (#1738).
-		if !glContext.Truthy() {
-			glContext = canvas.Call("getContext", "webgl", attr)
-			if !glContext.Truthy() {
-				glContext = canvas.Call("getContext", "experimental-webgl", attr)
-			}
-			if glContext.Truthy() {
-				c.webGL2 = false
-			}
-		}
-
-		if !glContext.Truthy() {
-			c.webGL2 = false
-			return fmt.Errorf("opengl: getContext failed")
-		}
-	}
-
-	ctx, err := gl.NewDefaultContext(glContext)
-	if err != nil {
-		return err
-	}
-	c.ctx = ctx
-
-	c.fnGetExtension = glContext.Get("getExtension").Call("bind", glContext)
-	c.fnIsContextLost = glContext.Get("isContextLost").Call("bind", glContext)
-
-	return nil
-}
-
 func (c *context) reset() error {
 	c.locationCache = newLocationCache()
 	c.lastTexture = 0
@@ -120,10 +61,6 @@ func (c *context) reset() error {
 	c.lastViewportHeight = 0
 	c.lastBlend = graphicsdriver.Blend{}
 
-	if err := c.initGL(); err != nil {
-		return err
-	}
-
 	if c.fnIsContextLost.Invoke().Bool() {
 		return graphicsdriver.GraphicsNotReady
 	}

internal/graphicsdriver/opengl/graphics_js.go

@@ -15,15 +15,66 @@
 package opengl
 
 import (
+	"fmt"
+	"os"
+	"strings"
 	"syscall/js"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
+	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl/gl"
 )
 
 // NewGraphics creates an implementation of graphicsdriver.Graphics for OpenGL.
 // The returned graphics value is nil iff the error is not nil.
 func NewGraphics(canvas js.Value) (graphicsdriver.Graphics, error) {
+	var glContext js.Value
+
+	attr := js.Global().Get("Object").New()
+	attr.Set("alpha", true)
+	attr.Set("premultipliedAlpha", true)
+	attr.Set("stencil", true)
+
+	var webGL2 bool
+	if webGL2MightBeAvailable() {
+		glContext = canvas.Call("getContext", "webgl2", attr)
+	}
+
+	if glContext.Truthy() {
+		webGL2 = true
+	} else {
+		// Even though WebGL2RenderingContext exists, getting a webgl2 context might fail (#1738).
+		glContext = canvas.Call("getContext", "webgl", attr)
+		if !glContext.Truthy() {
+			glContext = canvas.Call("getContext", "experimental-webgl", attr)
+		}
+	}
+
+	if !glContext.Truthy() {
+		return nil, fmt.Errorf("opengl: getContext failed")
+	}
+
+	ctx, err := gl.NewDefaultContext(glContext)
+	if err != nil {
+		return nil, err
+	}
+
 	g := &Graphics{}
 	g.context.canvas = canvas
+	g.context.ctx = ctx
+	g.context.webGL2 = webGL2
+	g.context.fnGetExtension = glContext.Get("getExtension").Call("bind", glContext)
+	g.context.fnIsContextLost = glContext.Get("isContextLost").Call("bind", glContext)
+
 	return g, nil
 }
+
+func webGL2MightBeAvailable() bool {
+	env := os.Getenv("EBITENGINE_OPENGL")
+	for _, t := range strings.Split(env, ",") {
+		switch strings.TrimSpace(t) {
+		case "webgl1":
+			return false
+		}
+	}
+	return js.Global().Get("WebGL2RenderingContext").Truthy()
+}