app/internal/window: x11 driver

This driver still lacks fling support and dp/sp configuration.

By default, linux builds will try to use the Wayland driver then
fallback to X11 if it fails. Drivers can be disabled by using either the
nowayland or nox11 build tags.

Signed-off-by: Denis Bernard <db047h@gmail.com>

app/internal/window/egl_android.go

@@ -6,6 +6,7 @@ package window
 #include <EGL/egl.h>
 */
 import "C"
+import "gioui.org/app/internal/gl"
 
 func (w *window) eglDestroy() {
 }
@@ -19,4 +20,8 @@ func (w *window) eglWindow(visID int) (_EGLNativeWindowType, int, int, error) {
 	return _EGLNativeWindowType(win), width, height, nil
 }
 
+func (w *window) NewContext() (gl.Context, error) {
+	return newContext(w)
+}
+
 func (w *window) needVSync() bool { return false }