internal/graphicsdriver/metal: replace Get with NewGraphics

This is a prepartion to return an error when a graphics driver, especially
DirectX, fails to initialize.

Updates #2142

internal/graphicsdriver/metal/graphics_darwin.go

@@ -19,7 +19,6 @@ import (
 	"math"
 	"sort"
 	"strings"
-	"sync"
 	"unsafe"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
@@ -347,18 +346,11 @@ const (
 	noStencil
 )
 
-var (
-	// isMetalAvailable reports whether Metal is available or not.
-	isMetalAvailable     bool
-	isMetalAvailableOnce sync.Once
-)
-
-var theGraphics Graphics
-
-func Get() *Graphics {
-	isMetalAvailableOnce.Do(func() {
+// NewGraphics creates an implementation of graphicsdriver.Graphcis for Metal.
+// The returned graphics value is nil iff the error is not nil.
+func NewGraphics() (graphicsdriver.Graphics, error) {
 	if !supportsMetal() {
-			return
+		return nil, fmt.Errorf("metal: Metal is not supported in this environment")
 	}
 
 	// Initialize isMetalAvailable on the main thread.
@@ -368,14 +360,10 @@ func Get() *Graphics {
 	// TODO: Is there a better way to check whether Metal is available or not?
 	// It seems OK to call MTLCreateSystemDefaultDevice multiple times, so this should be fine.
 	if _, ok := mtl.CreateSystemDefaultDevice(); !ok {
-			return
+		return nil, fmt.Errorf("metal: mtl.CreateSystemDefaultDevice failed")
 	}
-		isMetalAvailable = true
-	})
-	if !isMetalAvailable {
-		return nil
-	}
-	return &theGraphics
+
+	return &Graphics{}, nil
 }
 
 func (g *Graphics) Begin() error {

internal/ui/graphics.go

@@ -21,19 +21,19 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 )
 
-type graphicsDriverGetter interface {
+type graphicsDriverCreator interface {
 	newAuto() (graphicsdriver.Graphics, error)
 	newOpenGL() (graphicsdriver.Graphics, error)
 	getDirectX() graphicsdriver.Graphics
-	getMetal() graphicsdriver.Graphics
+	newMetal() (graphicsdriver.Graphics, error)
 }
 
-func chooseGraphicsDriver(getter graphicsDriverGetter) (graphicsdriver.Graphics, error) {
+func chooseGraphicsDriver(creator graphicsDriverCreator) (graphicsdriver.Graphics, error) {
 	const envName = "EBITEN_GRAPHICS_LIBRARY"
 
 	switch env := os.Getenv(envName); env {
 	case "", "auto":
-		g, err := getter.newAuto()
+		g, err := creator.newAuto()
 		if err != nil {
 			return nil, err
 		}
@@ -42,7 +42,7 @@ func chooseGraphicsDriver(getter graphicsDriverGetter) (graphicsdriver.Graphics,
 		}
 		return g, nil
 	case "opengl":
-		g, err := getter.newOpenGL()
+		g, err := creator.newOpenGL()
 		if err != nil {
 			return nil, err
 		}
@@ -51,15 +51,19 @@ func chooseGraphicsDriver(getter graphicsDriverGetter) (graphicsdriver.Graphics,
 		}
 		return g, nil
 	case "directx":
-		if g := getter.getDirectX(); g != nil {
+		if g := creator.getDirectX(); g != nil {
 			return g, nil
 		}
 		return nil, fmt.Errorf("ui: %s=%s is specified but DirectX is not available.", envName, env)
 	case "metal":
-		if g := getter.getMetal(); g != nil {
-			return g, nil
+		g, err := creator.newMetal()
+		if err != nil {
+			return nil, err
 		}
+		if g == nil {
 			return nil, fmt.Errorf("ui: %s=%s is specified but Metal is not available", envName, env)
+		}
+		return g, nil
 	default:
 		return nil, fmt.Errorf("ui: an unsupported graphics library is specified: %s", env)
 	}

internal/ui/ui_android.go

@@ -19,22 +19,22 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
 )
 
-type graphicsDriverGetterImpl struct {
+type graphicsDriverCreatorImpl struct {
 	gomobileBuild bool
 }
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
 	return g.newOpenGL()
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (*graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (*graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (*graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	return nil
+func (*graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
+	return nil, nil
 }

internal/ui/ui_cbackend.go

@@ -25,22 +25,22 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
 )
 
-type graphicsDriverGetterImpl struct{}
+type graphicsDriverCreatorImpl struct{}
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
 	return g.newOpenGL()
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (*graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (*graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (*graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	return nil
+func (*graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
+	return nil, nil
 }
 
 const deviceScaleFactor = 1
@@ -58,7 +58,7 @@ type userInterfaceImpl struct {
 
 func (u *userInterfaceImpl) Run(game Game) error {
 	u.context = newContext(game)
-	g, err := chooseGraphicsDriver(&graphicsDriverGetterImpl{})
+	g, err := chooseGraphicsDriver(&graphicsDriverCreatorImpl{})
 	if err != nil {
 		return err
 	}

internal/ui/ui_glfw.go

@@ -834,7 +834,7 @@ func (u *userInterfaceImpl) init() error {
 	}
 	glfw.WindowHint(glfw.TransparentFramebuffer, glfwTransparent)
 
-	g, err := chooseGraphicsDriver(&graphicsDriverGetterImpl{
+	g, err := chooseGraphicsDriver(&graphicsDriverCreatorImpl{
 		transparent: transparent,
 	})
 	if err != nil {

internal/ui/ui_glfw_darwin.go

@@ -248,36 +248,40 @@ package ui
 import "C"
 
 import (
+	"fmt"
+
 	"github.com/hajimehoshi/ebiten/v2/internal/glfw"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/metal"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
 )
 
-type graphicsDriverGetterImpl struct {
+type graphicsDriverCreatorImpl struct {
 	transparent bool
 }
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
-	if m := g.getMetal(); m != nil {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
+	m, err1 := g.newMetal()
+	if err1 == nil {
 		return m, nil
 	}
-	return g.newOpenGL()
+	o, err2 := g.newOpenGL()
+	if err2 == nil {
+		return o, nil
+	}
+	return nil, fmt.Errorf("ui: failed to choose graphics drivers: Metal: %v, OpenGL: %v", err1, err2)
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (*graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (*graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (*graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	if m := metal.Get(); m != nil {
-		return m
-	}
-	return nil
+func (*graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
+	return metal.NewGraphics()
 }
 
 // clearVideoModeScaleCache must be called from the main thread.

internal/ui/ui_glfw_unix.go

@@ -31,24 +31,24 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
 )
 
-type graphicsDriverGetterImpl struct {
+type graphicsDriverCreatorImpl struct {
 	transparent bool
 }
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
 	return g.newOpenGL()
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (*graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (*graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (*graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	return nil
+func (*graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
+	return nil, nil
 }
 
 type videoModeScaleCacheKey struct{ X, Y int }

internal/ui/ui_glfw_windows.go

@@ -31,22 +31,22 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/microsoftgdk"
 )
 
-type graphicsDriverGetterImpl struct {
+type graphicsDriverCreatorImpl struct {
 	transparent bool
 }
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
 	if d := g.getDirectX(); d != nil {
 		return d, nil
 	}
 	return g.newOpenGL()
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (g *graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (g *graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	if g.transparent {
 		return nil
 	}
@@ -56,8 +56,8 @@ func (g *graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (*graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	return nil
+func (*graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
+	return nil, nil
 }
 
 const (

internal/ui/ui_ios.go

@@ -18,40 +18,42 @@
 package ui
 
 import (
+	"fmt"
+
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/metal"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
 )
 
-type graphicsDriverGetterImpl struct {
+type graphicsDriverCreatorImpl struct {
 	gomobileBuild bool
 }
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
-	if m := g.getMetal(); m != nil {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
+	m, err1 := g.newMetal()
+	if err1 == nil {
 		return m, nil
 	}
-	return g.newOpenGL()
+	o, err2 := g.newOpenGL()
+	if err2 == nil {
+		return o, nil
+	}
+	return nil, fmt.Errorf("ui: failed to choose graphics drivers: Metal: %v, OpenGL: %v", err1, err2)
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (*graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (*graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (g *graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	// When gomobile-build is used, GL functions must be called via
-	// gl.Context so that they are called on the appropriate thread.
+func (g *graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
 	if g.gomobileBuild {
-		return nil
+		return nil, fmt.Errorf("ui: Metal is not available with gomobile-build")
 	}
-	if m := metal.Get(); m != nil {
-		return m
-	}
-	return nil
+	return metal.NewGraphics()
 }
 
 func SetUIView(uiview uintptr) {

internal/ui/ui_js.go

@@ -25,22 +25,22 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/internal/hooks"
 )
 
-type graphicsDriverGetterImpl struct{}
+type graphicsDriverCreatorImpl struct{}
 
-func (g *graphicsDriverGetterImpl) newAuto() (graphicsdriver.Graphics, error) {
+func (g *graphicsDriverCreatorImpl) newAuto() (graphicsdriver.Graphics, error) {
 	return g.newOpenGL()
 }
 
-func (*graphicsDriverGetterImpl) newOpenGL() (graphicsdriver.Graphics, error) {
+func (*graphicsDriverCreatorImpl) newOpenGL() (graphicsdriver.Graphics, error) {
 	return opengl.NewGraphics()
 }
 
-func (*graphicsDriverGetterImpl) getDirectX() graphicsdriver.Graphics {
+func (*graphicsDriverCreatorImpl) getDirectX() graphicsdriver.Graphics {
 	return nil
 }
 
-func (*graphicsDriverGetterImpl) getMetal() graphicsdriver.Graphics {
-	return nil
+func (*graphicsDriverCreatorImpl) newMetal() (graphicsdriver.Graphics, error) {
+	return nil, nil
 }
 
 var (
@@ -609,7 +609,7 @@ func (u *userInterfaceImpl) Run(game Game) error {
 		}
 	}
 	u.running = true
-	g, err := chooseGraphicsDriver(&graphicsDriverGetterImpl{})
+	g, err := chooseGraphicsDriver(&graphicsDriverCreatorImpl{})
 	if err != nil {
 		return err
 	}

internal/ui/ui_mobile.go

@@ -270,7 +270,7 @@ func (u *userInterfaceImpl) run(game Game, mainloop bool) (err error) {
 	}()
 
 	u.context = newContext(game)
-	g, err := chooseGraphicsDriver(&graphicsDriverGetterImpl{
+	g, err := chooseGraphicsDriver(&graphicsDriverCreatorImpl{
 		gomobileBuild: mainloop,
 	})
 	if err != nil {
@@ -279,6 +279,8 @@ func (u *userInterfaceImpl) run(game Game, mainloop bool) (err error) {
 	u.graphicsDriver = g
 
 	if mainloop {
+		// When gomobile-build is used, GL functions must be called via
+		// gl.Context so that they are called on the appropriate thread.
 		ctx := <-glContextCh
 		g.(*opengl.Graphics).SetGomobileGLContext(ctx)
 	} else {