backend/x11: add WLR_X11_OUTPUTS support

backend/backend.c

@@ -61,26 +61,48 @@ struct wlr_renderer *wlr_backend_get_renderer(struct wlr_backend *backend) {
 	return NULL;
 }
 
-static struct wlr_backend *attempt_wl_backend(struct wl_display *display) {
-	struct wlr_backend *backend = wlr_wl_backend_create(display, NULL);
-	if (backend) {
-		int outputs = 1;
-		const char *_outputs = getenv("WLR_WL_OUTPUTS");
-		if (_outputs) {
+static int parse_outputs_env(const char *name) {
+	const char *outputs_str = getenv(name);
+	if (outputs_str == NULL) {
+		return 1;
+	}
+
 	char *end;
-			outputs = (int)strtol(_outputs, &end, 10);
-			if (*end) {
-				wlr_log(L_ERROR, "WLR_WL_OUTPUTS specified with invalid integer, ignoring");
-				outputs = 1;
-			} else if (outputs < 0) {
-				wlr_log(L_ERROR, "WLR_WL_OUTPUTS specified with negative outputs, ignoring");
-				outputs = 1;
+	int outputs = (int)strtol(outputs_str, &end, 10);
+	if (*end || outputs < 0) {
+		wlr_log(L_ERROR, "%s specified with invalid integer, ignoring", name);
+		return 1;
+	}
+
+	return outputs;
 }
+
+static struct wlr_backend *attempt_wl_backend(struct wl_display *display) {
+	struct wlr_backend *backend = wlr_wl_backend_create(display, NULL);
+	if (backend == NULL) {
+		return NULL;
 	}
-		while (outputs--) {
+
+	int outputs = parse_outputs_env("WLR_WL_OUTPUTS");
+	for (int i = 0; i < outputs; ++i) {
 		wlr_wl_output_create(backend);
 	}
+
+	return backend;
+}
+
+static struct wlr_backend *attempt_x11_backend(struct wl_display *display,
+		const char *x11_display) {
+	struct wlr_backend *backend = wlr_x11_backend_create(display, x11_display);
+	if (backend == NULL) {
+		return NULL;
+	}
+
+	int outputs = parse_outputs_env("WLR_X11_OUTPUTS");
+	for (int i = 0; i < outputs; ++i) {
+		wlr_x11_output_create(backend);
 	}
+
 	return backend;
 }
 
@@ -91,7 +113,8 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
 		return NULL;
 	}
 
-	if (getenv("WAYLAND_DISPLAY") || getenv("_WAYLAND_DISPLAY")) {
+	if (getenv("WAYLAND_DISPLAY") || getenv("_WAYLAND_DISPLAY") ||
+			getenv("WAYLAND_SOCKET")) {
 		struct wlr_backend *wl_backend = attempt_wl_backend(display);
 		if (wl_backend) {
 			wlr_multi_backend_add(backend, wl_backend);
@@ -103,10 +126,12 @@ struct wlr_backend *wlr_backend_autocreate(struct wl_display *display) {
 	const char *x11_display = getenv("DISPLAY");
 	if (x11_display) {
 		struct wlr_backend *x11_backend =
-			wlr_x11_backend_create(display, x11_display);
+			attempt_x11_backend(display, x11_display);
+		if (x11_backend) {
 			wlr_multi_backend_add(backend, x11_backend);
 			return backend;
 		}
+	}
 #endif
 
 	// Attempt DRM+libinput

backend/x11/backend.c

@@ -96,6 +96,7 @@ static int x11_event(int fd, uint32_t mask, void *data) {
 
 static bool wlr_x11_backend_start(struct wlr_backend *backend) {
 	struct wlr_x11_backend *x11 = (struct wlr_x11_backend *)backend;
+	x11->started = true;
 
 	struct {
 		const char *name;
@@ -167,7 +168,7 @@ static bool wlr_x11_backend_start(struct wlr_backend *backend) {
 	wlr_signal_emit_safe(&x11->backend.events.new_input, &x11->pointer_dev);
 
 	for (size_t i = 0; i < x11->requested_outputs; ++i) {
-		x11_output_create(x11);
+		wlr_x11_output_create(&x11->backend);
 	}
 
 	return true;

backend/x11/output.c

@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <stdlib.h>
 #include <wlr/interfaces/wlr_output.h>
 #include <wlr/util/log.h>
@@ -77,18 +78,29 @@ static const struct wlr_output_impl output_impl = {
 	.swap_buffers = output_swap_buffers,
 };
 
-struct wlr_x11_output *x11_output_create(struct wlr_x11_backend *x11) {
+struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
+	assert(wlr_backend_is_x11(backend));
+	struct wlr_x11_backend *x11 = (struct wlr_x11_backend *)backend;
+
+	if (!x11->started) {
+		++x11->requested_outputs;
+		return NULL;
+	}
+
 	struct wlr_x11_output *output = calloc(1, sizeof(struct wlr_x11_output));
 	if (output == NULL) {
 		return NULL;
 	}
 	output->x11 = x11;
-	output->frame_delay = 16; // 60 Hz
 
 	struct wlr_output *wlr_output = &output->wlr_output;
 	wlr_output_init(wlr_output, &x11->backend, &output_impl, x11->wl_display);
 
-	snprintf(wlr_output->name, sizeof(wlr_output->name), "X11-1");
+	wlr_output->refresh = 60 * 1000000;
+	output->frame_delay = 16; // 60 Hz
+
+	snprintf(wlr_output->name, sizeof(wlr_output->name), "X11-%d",
+		wl_list_length(&x11->outputs) + 1);
 	parse_xcb_setup(wlr_output, x11->xcb_conn);
 
 	uint32_t mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
@@ -135,7 +147,7 @@ struct wlr_x11_output *x11_output_create(struct wlr_x11_backend *x11) {
 	wl_list_insert(&x11->outputs, &output->link);
 	wlr_signal_emit_safe(&x11->backend.events.new_output, wlr_output);
 
-	return output;
+	return wlr_output;
 }
 
 void x11_output_handle_configure_notify(struct wlr_x11_output *output,

include/backend/x11.h

@@ -3,11 +3,12 @@
 
 #include <stdbool.h>
 #include <wayland-server.h>
+#include <wlr/backend/x11.h>
+#include <wlr/interfaces/wlr_input_device.h>
+#include <wlr/interfaces/wlr_output.h>
 #include <wlr/render/egl.h>
 #include <X11/Xlib-xcb.h>
 #include <xcb/xcb.h>
-#include <wlr/interfaces/wlr_input_device.h>
-#include <wlr/interfaces/wlr_output.h>
 
 #define XCB_EVENT_RESPONSE_TYPE_MASK 0x7f
 
@@ -28,6 +29,7 @@ struct wlr_x11_output {
 struct wlr_x11_backend {
 	struct wlr_backend backend;
 	struct wl_display *wl_display;
+	bool started;
 
 	Display *xlib_conn;
 	xcb_connection_t *xcb_conn;
@@ -73,7 +75,6 @@ const struct wlr_input_device_impl input_device_impl;
 bool x11_handle_input_event(struct wlr_x11_backend *x11,
 	xcb_generic_event_t *event);
 
-struct wlr_x11_output *x11_output_create(struct wlr_x11_backend *x11);
 void x11_output_handle_configure_notify(struct wlr_x11_output *output,
 	xcb_configure_notify_event_t *event);
 

include/wlr/backend/x11.h

@@ -9,6 +9,7 @@
 
 struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	const char *x11_display);
+struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend);
 
 bool wlr_backend_is_x11(struct wlr_backend *backend);
 bool wlr_input_device_is_x11(struct wlr_input_device *device);