app/internal/d3d11: add Direct3D backend

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

app/headless/headless_windows.go

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package headless
+
+import (
+	"gioui.org/app/internal/d3d11"
+	"gioui.org/gpu/backend"
+)
+
+type d3d11Context struct {
+	*d3d11.Device
+}
+
+func newContext() (context, error) {
+	dev, err := d3d11.NewDevice()
+	if err != nil {
+		return nil, err
+	}
+	return &d3d11Context{Device: dev}, nil
+}
+
+func (c *d3d11Context) Backend() (backend.Device, error) {
+	backend, err := d3d11.NewBackend(c.Device)
+	if err != nil {
+		return nil, err
+	}
+	return backend, nil
+}
+
+func (c *d3d11Context) MakeCurrent() error {
+	return nil
+}
+
+func (c *d3d11Context) ReleaseCurrent() {
+}
+
+func (c *d3d11Context) Release() {
+	c.Device.Release()
+	c.Device = nil
+}