Add X11 backend skeleton

backend/backend.c

@@ -10,6 +10,7 @@
 #include <wlr/backend/drm.h>
 #include <wlr/backend/libinput.h>
 #include <wlr/backend/wayland.h>
+#include <wlr/backend/x11.h>
 #include <wlr/backend/multi.h>
 #include <wlr/util/log.h>
 
@@ -77,9 +78,9 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
 		}
 	}
 
-	if (getenv("DISPLAY")) {
+	const char *x11_display = getenv("DISPLAY");
-		wlr_log(L_ERROR, "X11 backend is not implemented"); // TODO
+	if (x11_display) {
-		return NULL;
+		return wlr_x11_backend_create(x11_display);
 	}
 
 	// Attempt DRM+libinput

backend/meson.build

@@ -22,6 +22,7 @@ backend_files = files(
 	'wayland/registry.c',
 	'wayland/wl_seat.c',
 	'wayland/os-compatibility.c',
+	'x11/backend.c',
 )
 
 if systemd.found()

backend/x11/backend.c

@@ -0,0 +1,30 @@
+#include <stdbool.h>
+#include <wlr/backend/interface.h>
+#include <wlr/backend/x11.h>
+#include <wlr/egl.h>
+#include "backend/x11.h"
+
+struct wlr_backend *wlr_x11_backend_create(const char *display) {
+	return NULL;
+}
+
+static bool wlr_x11_backend_start(struct wlr_backend *backend) {
+	return false;
+}
+
+static void wlr_x11_backend_destroy(struct wlr_backend *backend) {
+}
+
+struct wlr_egl *wlr_x11_backend_get_egl(struct wlr_backend *backend) {
+	return NULL;
+}
+
+static struct wlr_backend_impl backend_impl = {
+	.start = wlr_x11_backend_start,
+	.destroy = wlr_x11_backend_destroy,
+	.get_egl = wlr_x11_backend_get_egl,
+};
+
+bool wlr_backend_is_x11(struct wlr_backend *backend) {
+	return backend->impl == &backend_impl;
+}

include/backend/x11.h

@@ -0,0 +1,8 @@
+#ifndef WLR_X11_H
+#define WLR_X11_H
+
+struct wlr_x11_backend {
+	struct wlr_backend backend;
+};
+
+#endif

include/wlr/backend/x11.h

@@ -0,0 +1,11 @@
+#ifndef WLR_BACKEND_X11_H
+#define WLR_BACKEND_X11_H
+
+#include <wlr/backend.h>
+#include <stdbool.h>
+
+struct wlr_backend *wlr_x11_backend_create(const char *display);
+
+bool wlr_backend_is_x11(struct wlr_backend *backend);
+
+#endif