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/os_linux.go

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// +build linux,!android
+
+package window
+
+import (
+	"errors"
+)
+
+var mainDone = make(chan struct{})
+
+func Main() {
+	<-mainDone
+}
+
+// instead of creating files with build tags for each combination of wayland +/- x11
+// let each driver initialize these variables with their own version of createWindow.
+var wlDriver, x11Driver func(Callbacks, *Options) error
+
+func NewWindow(window Callbacks, opts *Options) error {
+	var errFirst, err error
+	if wlDriver != nil {
+		if err = wlDriver(window, opts); err == nil {
+			return nil
+		}
+		errFirst = err
+	}
+	if x11Driver != nil {
+		if err = x11Driver(window, opts); err == nil {
+			return nil
+		}
+		if errFirst == nil {
+			errFirst = err
+		}
+	}
+	if errFirst != nil {
+		return errFirst
+	}
+	return errors.New("app: no window driver available")
+}