app/internal/d3d11: add Direct3D backend

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

app/internal/window/d3d11_windows.go

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package window
+
+import (
+	"gioui.org/app/internal/d3d11"
+	"gioui.org/gpu/backend"
+)
+
+type d3d11Context struct {
+	win     *window
+	swchain *d3d11.SwapChain
+	fbo     *d3d11.Framebuffer
+	backend backend.Device
+	*d3d11.Device
+	width, height int
+}
+
+func init() {
+	backends = append(backends, gpuAPI{
+		priority: 1,
+		initializer: func(w *window) (Context, error) {
+			hwnd, _, _ := w.HWND()
+			dev, err := d3d11.NewDevice()
+			if err != nil {
+				return nil, err
+			}
+			swchain, err := dev.CreateSwapChain(hwnd)
+			if err != nil {
+				dev.Release()
+				return nil, err
+			}
+			return &d3d11Context{win: w, Device: dev, swchain: swchain}, nil
+		},
+	})
+}
+
+func (c *d3d11Context) Backend() (backend.Device, error) {
+	backend, err := d3d11.NewBackend(c.Device)
+	if err != nil {
+		return nil, err
+	}
+	c.backend = backend
+	c.backend.BindFramebuffer(c.fbo)
+	return backend, nil
+}
+
+func (c *d3d11Context) Present() error {
+	if err := c.swchain.Present(); err != nil {
+		if err, ok := err.(d3d11.ErrorCode); ok {
+			switch err.Code {
+			case d3d11.DXGI_STATUS_OCCLUDED:
+				// Ignore
+				return nil
+			case d3d11.DXGI_ERROR_DEVICE_RESET, d3d11.DXGI_ERROR_DEVICE_REMOVED, d3d11.D3DDDIERR_DEVICEREMOVED:
+				return ErrDeviceLost
+			}
+		}
+	}
+	return nil
+}
+
+func (c *d3d11Context) MakeCurrent() error {
+	_, width, height := c.win.HWND()
+	if c.fbo != nil && width == c.width && height == c.height {
+		c.backend.BindFramebuffer(c.fbo)
+		return nil
+	}
+	if c.fbo != nil {
+		c.fbo.Release()
+		c.fbo = nil
+	}
+	if err := c.swchain.Resize(); err != nil {
+		return err
+	}
+	c.width = width
+	c.height = height
+	fbo, err := c.swchain.Framebuffer(c.Device)
+	if err != nil {
+		return err
+	}
+	c.fbo = fbo
+	if c.backend != nil {
+		c.backend.BindFramebuffer(c.fbo)
+	}
+	return nil
+}
+
+func (c *d3d11Context) Lock() {}
+
+func (c *d3d11Context) Unlock() {}
+
+func (c *d3d11Context) Release() {
+	if c.fbo != nil {
+		c.fbo.Release()
+	}
+	c.swchain.Release()
+	c.Device.Release()
+	c.fbo = nil
+	c.swchain = nil
+	c.Device = nil
+}

app/internal/window/egl_windows.go

@@ -6,28 +6,33 @@ import (
 	"gioui.org/app/internal/egl"
 )
 
-type context struct {
+type glContext struct {
 	win *window
 	*egl.Context
 }
 
-func (w *window) NewContext() (Context, error) {
-	disp := egl.NativeDisplayType(w.HDC())
-	ctx, err := egl.NewContext(disp)
-	if err != nil {
-		return nil, err
-	}
-	return &context{win: w, Context: ctx}, nil
+func init() {
+	backends = append(backends, gpuAPI{
+		priority: 2,
+		initializer: func(w *window) (Context, error) {
+			disp := egl.NativeDisplayType(w.HDC())
+			ctx, err := egl.NewContext(disp)
+			if err != nil {
+				return nil, err
+			}
+			return &glContext{win: w, Context: ctx}, nil
+		},
+	})
 }
 
-func (c *context) Release() {
+func (c *glContext) Release() {
 	if c.Context != nil {
 		c.Context.Release()
 		c.Context = nil
 	}
 }
 
-func (c *context) MakeCurrent() error {
+func (c *glContext) MakeCurrent() error {
 	c.Context.ReleaseSurface()
 	win, width, height := c.win.HWND()
 	eglSurf := egl.NativeWindowType(win)
@@ -41,6 +46,6 @@ func (c *context) MakeCurrent() error {
 	return nil
 }
 
-func (c *context) Lock() {}
+func (c *glContext) Lock() {}
 
-func (c *context) Unlock() {}
+func (c *glContext) Unlock() {}

app/internal/window/os_windows.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"image"
 	"runtime"
+	"sort"
 	"sync"
 	"time"
 	"unicode"
@@ -42,6 +43,15 @@ const _WM_REDRAW = windows.WM_USER + 0
 var onceMu sync.Mutex
 var mainDone = make(chan struct{})
 
+// backends is the list of potential Context
+// implementations.
+var backends []gpuAPI
+
+type gpuAPI struct {
+	priority    int
+	initializer func(w *window) (Context, error)
+}
+
 func Main() {
 	<-mainDone
 }
@@ -345,6 +355,26 @@ func (w *window) destroy() {
 	}
 }
 
+func (w *window) NewContext() (Context, error) {
+	sort.Slice(backends, func(i, j int) bool {
+		return backends[i].priority < backends[j].priority
+	})
+	var cerr error
+	for _, b := range backends {
+		ctx, err := b.initializer(w)
+		if err == nil {
+			return ctx, nil
+		}
+		if cerr == nil {
+			cerr = err
+		}
+	}
+	if cerr != nil {
+		return nil, cerr
+	}
+	return nil, errors.New("NewContext: no available backends")
+}
+
 func (w *window) ShowTextInput(show bool) {}
 
 func (w *window) HDC() syscall.Handle {