3 files changed, 128 insertions, 6 deletions

diff --git a/backend/CMakeLists.txt b/backend/CMakeLists.txt
index 5505e417..23914240 100644
--- a/backend/CMakeLists.txt
+++ b/backend/CMakeLists.txt
@@ -18,6 +18,7 @@ add_library(wlr-backend
     libinput/events.c
     libinput/keyboard.c
 
+    multi/backend.c
     backend.c
     egl.c
     udev.c
diff --git a/backend/backend.c b/backend/backend.c
index 03c662c3..02fd7479 100644
--- a/backend/backend.c
+++ b/backend/backend.c
@@ -8,6 +8,7 @@
 #include <wlr/backend/interface.h>
 #include <wlr/backend/drm.h>
 #include <wlr/backend/libinput.h>
+#include <wlr/backend/multi.h>
 #include "backend/libinput.h"
 #include "backend/udev.h"
 #include "common/log.h"
@@ -46,19 +47,32 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display,
 		wlr_log(L_ERROR, "Failed to start udev");
 		goto error;
 	}
-	struct wlr_backend *wlr;
-	wlr = wlr_libinput_backend_create(display, session, udev);
-	return wlr;
 	int gpu = wlr_udev_find_gpu(udev, session);
 	if (gpu == -1) {
 		wlr_log(L_ERROR, "Failed to open DRM device");
 		goto error_udev;
 	}
-	wlr = wlr_drm_backend_create(display, session, udev, gpu);
-	if (!wlr) {
+	struct wlr_backend *multi = wlr_multi_backend_create();
+	if (!multi) {
 		goto error_gpu;
 	}
-	return wlr;
+	struct wlr_backend *libinput =
+		wlr_libinput_backend_create(display, session, udev);
+	if (!libinput) {
+		goto error_multi;
+	}
+	struct wlr_backend *drm =
+		wlr_drm_backend_create(display, session, udev, gpu);
+	if (!drm) {
+		goto error_libinput;
+	}
+	wlr_multi_backend_add(multi, libinput);
+	wlr_multi_backend_add(multi, drm);
+	return multi;
+error_libinput:
+	wlr_backend_destroy(libinput);
+error_multi:
+	wlr_backend_destroy(multi);
 error_gpu:
 	close(gpu);
 error_udev:
diff --git a/backend/multi/backend.c b/backend/multi/backend.c
new file mode 100644
index 00000000..e3d87ccc
--- /dev/null
+++ b/backend/multi/backend.c
@@ -0,0 +1,107 @@
+#include <stdbool.h>
+#include <stdlib.h>
+#include <wlr/backend/interface.h>
+#include <wlr/common/log.h>
+#include "backend/multi.h"
+#include "common/log.h"
+
+struct subbackend_state {
+	struct wlr_backend *backend;
+	struct wlr_backend *container;
+	struct wl_listener input_add;
+	struct wl_listener input_remove;
+	struct wl_listener output_add;
+	struct wl_listener output_remove;
+};
+
+static bool multi_backend_init(struct wlr_backend_state *state) {
+	for (size_t i = 0; i < state->backends->length; ++i) {
+		struct subbackend_state *sub = state->backends->items[i];
+		if (!wlr_backend_init(sub->backend)) {
+			wlr_log(L_ERROR, "Failed to initialize backend %zd", i);
+			return false;
+		}
+	}
+	return true;
+}
+
+static void multi_backend_destroy(struct wlr_backend_state *state) {
+	for (size_t i = 0; i < state->backends->length; ++i) {
+		struct subbackend_state *sub = state->backends->items[i];
+		wlr_backend_destroy(sub->backend);
+		free(sub);
+	}
+	list_free(state->backends);
+	free(state);
+}
+
+struct wlr_backend_impl backend_impl = {
+	.init = multi_backend_init,
+	.destroy = multi_backend_destroy
+};
+
+struct wlr_backend *wlr_multi_backend_create() {
+	struct wlr_backend_state *state =
+		calloc(1, sizeof(struct wlr_backend_state));
+	if (!state) {
+		wlr_log(L_ERROR, "Backend allocation failed");
+		return NULL;
+	}
+	state->backends = list_create();
+	if (!state->backends) {
+		free(state);
+		wlr_log(L_ERROR, "Backend allocation failed");
+		return NULL;
+	}
+	struct wlr_backend *backend = wlr_backend_create(&backend_impl, state);
+	state->backend = backend;
+	return backend;
+}
+
+static void input_add_reemit(struct wl_listener *listener, void *data) {
+	struct subbackend_state *state = wl_container_of(listener,
+			state, input_add);
+	wl_signal_emit(&state->container->events.input_add, data);
+}
+
+static void input_remove_reemit(struct wl_listener *listener, void *data) {
+	struct subbackend_state *state = wl_container_of(listener,
+			state, input_remove);
+	wl_signal_emit(&state->container->events.input_remove, data);
+}
+
+static void output_add_reemit(struct wl_listener *listener, void *data) {
+	struct subbackend_state *state = wl_container_of(listener,
+			state, output_add);
+	wl_signal_emit(&state->container->events.output_add, data);
+}
+
+static void output_remove_reemit(struct wl_listener *listener, void *data) {
+	struct subbackend_state *state = wl_container_of(listener,
+			state, output_remove);
+	wl_signal_emit(&state->container->events.output_remove, data);
+}
+
+void wlr_multi_backend_add(struct wlr_backend *multi,
+		struct wlr_backend *backend) {
+	struct subbackend_state *sub = calloc(1, sizeof(struct subbackend_state));
+	sub->backend = backend;
+	sub->container = multi;
+
+	sub->input_add.notify = input_add_reemit;
+	sub->input_remove.notify = input_remove_reemit;
+	sub->output_add.notify = output_add_reemit;
+	sub->output_remove.notify = output_remove_reemit;
+
+	wl_list_init(&sub->input_add.link);
+	wl_list_init(&sub->input_remove.link);
+	wl_list_init(&sub->output_add.link);
+	wl_list_init(&sub->output_remove.link);
+
+	wl_signal_add(&backend->events.input_add, &sub->input_add);
+	wl_signal_add(&backend->events.input_remove, &sub->input_remove);
+	wl_signal_add(&backend->events.output_add, &sub->output_add);
+	wl_signal_add(&backend->events.output_remove, &sub->output_remove);
+
+	list_add(multi->state->backends, sub);
+}