gpu/backend: move backend interface types to a separate package

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/headless/headless.go

@@ -9,21 +9,22 @@ import (
 	"runtime"
 
 	"gioui.org/gpu"
+	"gioui.org/gpu/backend"
 	"gioui.org/op"
 )
 
 // Window is a headless window.
 type Window struct {
 	size    image.Point
-	ctx     backend
-	backend gpu.Backend
+	ctx     context
+	backend backend.Device
 	gpu     *gpu.GPU
-	fboTex  gpu.Texture
-	fbo     gpu.Framebuffer
+	fboTex  backend.Texture
+	fbo     backend.Framebuffer
 }
 
-type backend interface {
-	Backend() (gpu.Backend, error)
+type context interface {
+	Backend() (backend.Device, error)
 	MakeCurrent() error
 	ReleaseCurrent()
 	Release()
@@ -40,27 +41,27 @@ func NewWindow(width, height int) (*Window, error) {
 		ctx:  ctx,
 	}
 	err = contextDo(ctx, func() error {
-		backend, err := ctx.Backend()
+		dev, err := ctx.Backend()
 		if err != nil {
 			return err
 		}
-		fboTex, err := backend.NewTexture(
-			gpu.TextureFormatSRGB,
+		fboTex, err := dev.NewTexture(
+			backend.TextureFormatSRGB,
 			width, height,
-			gpu.FilterNearest, gpu.FilterNearest,
-			gpu.BufferBindingFramebuffer,
+			backend.FilterNearest, backend.FilterNearest,
+			backend.BufferBindingFramebuffer,
 		)
 		if err != nil {
 			return nil
 		}
 		const depthBits = 16
-		fbo, err := backend.NewFramebuffer(fboTex, depthBits)
+		fbo, err := dev.NewFramebuffer(fboTex, depthBits)
 		if err != nil {
 			fboTex.Release()
 			return err
 		}
-		backend.BindFramebuffer(fbo)
-		gp, err := gpu.New(backend)
+		dev.BindFramebuffer(fbo)
+		gp, err := gpu.New(dev)
 		if err != nil {
 			fbo.Release()
 			fboTex.Release()
@@ -69,7 +70,7 @@ func NewWindow(width, height int) (*Window, error) {
 		w.fboTex = fboTex
 		w.fbo = fbo
 		w.gpu = gp
-		w.backend = backend
+		w.backend = dev
 		return err
 	})
 	if err != nil {
@@ -139,7 +140,7 @@ func (w *Window) Screenshot() (*image.RGBA, error) {
 	return img, nil
 }
 
-func contextDo(ctx backend, f func() error) error {
+func contextDo(ctx context, f func() error) error {
 	errCh := make(chan error)
 	go func() {
 		runtime.LockOSThread()

app/headless/headless_darwin.go

@@ -4,7 +4,7 @@ package headless
 
 import (
 	"gioui.org/app/internal/glimpl"
-	"gioui.org/gpu"
+	"gioui.org/gpu/backend"
 	"gioui.org/gpu/gl"
 )
 
@@ -22,7 +22,7 @@ type nsContext struct {
 	prepared bool
 }
 
-func newGLContext() (backend, error) {
+func newGLContext() (context, error) {
 	ctx := C.gio_headless_newContext()
 	return &nsContext{ctx: ctx, c: new(glimpl.Functions)}, nil
 }
@@ -40,7 +40,7 @@ func (c *nsContext) ReleaseCurrent() {
 	C.gio_headless_clearCurrentContext(c.ctx)
 }
 
-func (c *nsContext) Backend() (gpu.Backend, error) {
+func (c *nsContext) Backend() (backend.Device, error) {
 	return gl.NewBackend(c.c)
 }
 

app/headless/headless_egl.go

@@ -8,6 +8,6 @@ import (
 	"gioui.org/app/internal/egl"
 )
 
-func newGLContext() (backend, error) {
+func newGLContext() (context, error) {
 	return egl.NewContext(egl.EGL_DEFAULT_DISPLAY)
 }

app/headless/headless_gl.go

@@ -2,6 +2,6 @@
 
 package headless
 
-func newContext() (backend, error) {
+func newContext() (context, error) {
 	return newGLContext()
 }

app/headless/headless_js.go

@@ -7,7 +7,7 @@ import (
 	"syscall/js"
 
 	"gioui.org/app/internal/glimpl"
-	"gioui.org/gpu"
+	"gioui.org/gpu/backend"
 	"gioui.org/gpu/gl"
 )
 
@@ -16,7 +16,7 @@ type jsContext struct {
 	f   *glimpl.Functions
 }
 
-func newGLContext() (backend, error) {
+func newGLContext() (context, error) {
 	version := 2
 	doc := js.Global().Get("document")
 	cnv := doc.Call("createElement", "canvas")
@@ -39,7 +39,7 @@ func newGLContext() (backend, error) {
 	return c, nil
 }
 
-func (c *jsContext) Backend() (gpu.Backend, error) {
+func (c *jsContext) Backend() (backend.Device, error) {
 	return gl.NewBackend(c.f)
 }