compositor/shell.c

/*
 * Copyright © 2010 Intel Corporation
 * Copyright © 2011 Collabora, Ltd.
 *
 * Permission to use, copy, modify, distribute, and sell this software and
 * its documentation for any purpose is hereby granted without fee, provided
 * that the above copyright notice appear in all copies and that both that
 * copyright notice and this permission notice appear in supporting
 * documentation, and that the name of the copyright holders not be used in
 * advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission.  The copyright holders make
 * no representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
 * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
 * CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <linux/input.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <assert.h>

#include <wayland-server.h>
#include "compositor.h"
#include "desktop-shell-server-protocol.h"

struct wl_shell {
	struct wlsc_compositor *compositor;
	struct wlsc_shell shell;

	struct {
		struct wlsc_process process;
		struct wl_client *client;
		struct wl_resource *desktop_shell;
	} child;

	bool locked;
	bool prepare_event_sent;

	struct wlsc_surface *lock_surface;
	struct wl_listener lock_surface_listener;
	struct wl_list hidden_surface_list;

	struct wl_list backgrounds;
	struct wl_list panels;
};

enum shell_surface_type {
	SHELL_SURFACE_NORMAL,

	SHELL_SURFACE_PANEL,
	SHELL_SURFACE_BACKGROUND,
	SHELL_SURFACE_LOCK,

	SHELL_SURFACE_TOPLEVEL,
	SHELL_SURFACE_TRANSIENT,
	SHELL_SURFACE_FULLSCREEN
};

struct shell_surface {
	struct wlsc_surface *surface;
	struct wl_listener destroy_listener;

	enum shell_surface_type type;
	int32_t saved_x, saved_y;

	struct wlsc_output *output;
	struct wl_list link;
};

struct wlsc_move_grab {
	struct wl_grab grab;
	struct wlsc_surface *surface;
	int32_t dx, dy;
};

static void
destroy_shell_surface(struct shell_surface *priv)
{
	wl_list_remove(&priv->destroy_listener.link);
	wl_list_remove(&priv->link);
	free(priv);
}

static void
handle_shell_surface_destroy(struct wl_listener *listener,
			     struct wl_resource *resource, uint32_t time)
{
	struct shell_surface *priv =
		container_of(listener, struct shell_surface, destroy_listener);
	destroy_shell_surface(priv);
}

static struct shell_surface *
get_shell_surface(struct wlsc_surface *surface)
{
	struct shell_surface *priv;

	if (surface->shell_priv)
		return surface->shell_priv;

	priv = calloc(1, sizeof *priv);
	if (!priv)
		return NULL;

	priv->destroy_listener.func = handle_shell_surface_destroy;
	wl_list_insert(surface->surface.resource.destroy_listener_list.prev,
		       &priv->destroy_listener.link);

	surface->shell_priv = priv;
	priv->surface = surface;
	/* init link so its safe to always remove it in destroy_shell_surface */
	wl_list_init(&priv->link);

	priv->type = SHELL_SURFACE_NORMAL;

	return priv;
}

static void
move_grab_motion(struct wl_grab *grab,
		   uint32_t time, int32_t x, int32_t y)
{
	struct wlsc_move_grab *move = (struct wlsc_move_grab *) grab;
	struct wlsc_surface *es = move->surface;

	wlsc_surface_configure(es, x + move->dx, y + move->dy,
			       es->width, es->height);
}

static void
move_grab_button(struct wl_grab *grab,
		 uint32_t time, int32_t button, int32_t state)
{
}

static void
move_grab_end(struct wl_grab *grab, uint32_t time)
{
	free(grab);
}

static const struct wl_grab_interface move_grab_interface = {
	move_grab_motion,
	move_grab_button,
	move_grab_end
};

static int
wlsc_surface_move(struct wlsc_surface *es,
		  struct wlsc_input_device *wd, uint32_t time)
{
	struct wlsc_move_grab *move;

	move = malloc(sizeof *move);
	if (!move)
		return -1;

	move->grab.interface = &move_grab_interface;
	move->dx = es->x - wd->input_device.grab_x;
	move->dy = es->y - wd->input_device.grab_y;
	move->surface = es;

	if (wl_input_device_update_grab(&wd->input_device,
					&move->grab, &es->surface, time) < 0)
		return 0;

	wlsc_input_device_set_pointer_image(wd, WLSC_POINTER_DRAGGING);
	wl_input_device_set_pointer_focus(&wd->input_device,
					  NULL, time, 0, 0, 0, 0);

	return 0;
}

static void
shell_move(struct wl_client *client, struct wl_resource *resource,
	   struct wl_resource *surface_resource,
	   struct wl_resource *input_resource, uint32_t time)
{
	struct wlsc_input_device *wd = input_resource->data;
	struct wlsc_surface *es = surface_resource->data;

	if (wlsc_surface_move(es, wd, time) < 0)
		wl_resource_post_no_memory(resource);
}

struct wlsc_resize_grab {
	struct wl_grab grab;
	uint32_t edges;
	int32_t dx, dy, width, height;
	struct wlsc_surface *surface;
	struct wl_resource *resource;
};

static void
resize_grab_motion(struct wl_grab *grab,
		   uint32_t time, int32_t x, int32_t y)
{
	struct wlsc_resize_grab *resize = (struct wlsc_resize_grab *) grab;
	struct wl_input_device *device = grab->input_device;
	struct wl_surface *surface = &resize->surface->surface;
	int32_t width, height;

	if (resize->edges & WL_SHELL_RESIZE_LEFT) {
		width = device->grab_x - x + resize->width;
	} else if (resize->edges & WL_SHELL_RESIZE_RIGHT) {
		width = x - device->grab_x + resize->width;
	} else {
		width = resize->width;
	}

	if (resize->edges & WL_SHELL_RESIZE_TOP) {
		height = device->grab_y - y + resize->height;
	} else if (resize->edges & WL_SHELL_RESIZE_BOTTOM) {
		height = y - device->grab_y + resize->height;
	} else {
		height = resize->height;
	}

	wl_resource_post_event(resize->resource,
			       WL_SHELL_CONFIGURE, time, resize->edges,
			       surface, width, height);
}

static void
resize_grab_button(struct wl_grab *grab,
		   uint32_t time, int32_t button, int32_t state)
{
}

static void
resize_grab_end(struct wl_grab *grab, uint32_t time)
{
	free(grab);
}

static const struct wl_grab_interface resize_grab_interface = {
	resize_grab_motion,
	resize_grab_button,
	resize_grab_end
};

static int
wlsc_surface_resize(struct wlsc_surface *es,
		    struct wlsc_input_device *wd,
		    uint32_t time, uint32_t edges,
		    struct wl_resource *resource)
{
	struct wlsc_resize_grab *resize;
	enum wlsc_pointer_type pointer = WLSC_POINTER_LEFT_PTR;

	/* FIXME: Reject if fullscreen */

	resize = malloc(sizeof *resize);
	if (!resize)
		return -1;

	resize->grab.interface = &resize_grab_interface;
	resize->edges = edges;
	resize->dx = es->x - wd->input_device.grab_x;
	resize->dy = es->y - wd->input_device.grab_y;
	resize->width = es->width;
	resize->height = es->height;
	resize->surface = es;
	resize->resource = resource;

	if (edges == 0 || edges > 15 ||
	    (edges & 3) == 3 || (edges & 12) == 12)
		return 0;

	switch (edges) {
	case WL_SHELL_RESIZE_TOP:
		pointer = WLSC_POINTER_TOP;
		break;
	case WL_SHELL_RESIZE_BOTTOM:
		pointer = WLSC_POINTER_BOTTOM;
		break;
	case WL_SHELL_RESIZE_LEFT:
		pointer = WLSC_POINTER_LEFT;
		break;
	case WL_SHELL_RESIZE_TOP_LEFT:
		pointer = WLSC_POINTER_TOP_LEFT;
		break;
	case WL_SHELL_RESIZE_BOTTOM_LEFT:
		pointer = WLSC_POINTER_BOTTOM_LEFT;
		break;
	case WL_SHELL_RESIZE_RIGHT:
		pointer = WLSC_POINTER_RIGHT;
		break;
	case WL_SHELL_RESIZE_TOP_RIGHT:
		pointer = WLSC_POINTER_TOP_RIGHT;
		break;
	case WL_SHELL_RESIZE_BOTTOM_RIGHT:
		pointer = WLSC_POINTER_BOTTOM_RIGHT;
		break;
	}

	if (wl_input_device_update_grab(&wd->input_device,
					&resize->grab, &es->surface, time) < 0)
		return 0;

	wlsc_input_device_set_pointer_image(wd, pointer);
	wl_input_device_set_pointer_focus(&wd->input_device,
					  NULL, time, 0, 0, 0, 0);

	return 0;
}

static void
shell_resize(struct wl_client *client, struct wl_resource *resource,
	     struct wl_resource *surface_resource,
	     struct wl_resource *input_resource, uint32_t time, uint32_t edges)
{
	struct wlsc_input_device *wd = input_resource->data;
	struct wlsc_surface *es = surface_resource->data;

	/* FIXME: Reject if fullscreen */

	if (wlsc_surface_resize(es, wd, time, edges, resource) < 0)
		wl_resource_post_no_memory(resource);
}

static void
shell_set_toplevel(struct wl_client *client,
		   struct wl_resource *resource,
		   struct wl_resource *surface_resource)

{
	struct wlsc_surface *es = surface_resource->data;
	struct shell_surface *priv;

	priv = get_shell_surface(es);
	if (priv->type == SHELL_SURFACE_FULLSCREEN) {
		es->x = priv->saved_x;
		es->y = priv->saved_y;
	}

	wlsc_surface_damage(es);
	priv->type = SHELL_SURFACE_TOPLEVEL;
	es->fullscreen_output = NULL;
}

static void
shell_set_transient(struct wl_client *client,
		    struct wl_resource *resource,
		    struct wl_resource *surface_resource,
		    struct wl_resource *parent_resource,
		    int x, int y, uint32_t flags)
{
	struct wlsc_surface *es = surface_resource->data;
	struct wlsc_surface *pes = parent_resource->data;
	struct shell_surface *priv;

	priv = get_shell_surface(es);

	/* assign to parents output  */
	es->output = pes->output;
 
	es->x = pes->x + x;
	es->y = pes->y + y;

	wlsc_surface_damage(es);
	priv->type = SHELL_SURFACE_TRANSIENT;
}

static void
shell_set_fullscreen(struct wl_client *client,
		     struct wl_resource *resource,
		     struct wl_resource *surface_resource)

{
	struct wlsc_surface *es = surface_resource->data;
	struct wlsc_output *output;
	struct shell_surface *priv;

	priv = get_shell_surface(es);

	/* FIXME: Fullscreen on first output */
	/* FIXME: Handle output going away */
	output = container_of(es->compositor->output_list.next,
			      struct wlsc_output, link);
	es->output = output;

	priv->saved_x = es->x;
	priv->saved_y = es->y;
	es->x = (output->current->width - es->width) / 2;
	es->y = (output->current->height - es->height) / 2;
	es->fullscreen_output = output;
	wlsc_surface_damage(es);
	priv->type = SHELL_SURFACE_FULLSCREEN;
}

static const struct wl_shell_interface shell_interface = {
	shell_move,
	shell_resize,
	shell_set_toplevel,
	shell_set_transient,
	shell_set_fullscreen
};

static void
desktop_shell_set_background(struct wl_client *client,
			     struct wl_resource *resource,
			     struct wl_resource *output_resource,
			     struct wl_resource *surface_resource)
{
	struct wl_shell *shell = resource->data;
	struct wlsc_surface *surface = surface_resource->data;
	struct shell_surface *priv;

	wl_list_for_each(priv, &shell->backgrounds, link) {
		if (priv->output == output_resource->data) {
			priv->surface->output = NULL;
			wl_list_remove(&priv->surface->link);
			wl_list_remove(&priv->link);
			break;
		}
	}

	priv = get_shell_surface(surface);
	priv->type = SHELL_SURFACE_BACKGROUND;
	priv->output = output_resource->data;

	wl_list_insert(&shell->backgrounds, &priv->link);

	surface->x = priv->output->x;
	surface->y = priv->output->y;

	wl_resource_post_event(resource,
			       DESKTOP_SHELL_CONFIGURE,
			       wlsc_compositor_get_time(), 0, surface,
			       priv->output->current->width,
			       priv->output->current->height);
}

static void
desktop_shell_set_panel(struct wl_client *client,
			struct wl_resource *resource,
			struct wl_resource *output_resource,
			struct wl_resource *surface_resource)
{
	struct wl_shell *shell = resource->data;
	struct wlsc_surface *surface = surface_resource->data;
	struct shell_surface *priv;

	wl_list_for_each(priv, &shell->panels, link) {
		if (priv->output == output_resource->data) {
			priv->surface->output = NULL;
			wl_list_remove(&priv->surface->link);
			wl_list_remove(&priv->link);
			break;
		}
	}

	priv = get_shell_surface(surface);
	priv->type = SHELL_SURFACE_PANEL;
	priv->output = output_resource->data;

	wl_list_insert(&shell->panels, &priv->link);

	surface->x = priv->output->x;
	surface->y = priv->output->y;

	wl_resource_post_event(resource,
			       DESKTOP_SHELL_CONFIGURE,
			       wlsc_compositor_get_time(), 0, surface_resource,
			       priv->output->current->width,
			       priv->output->current->height);
}

static void
handle_lock_surface_destroy(struct wl_listener *listener,
			    struct wl_resource *resource, uint32_t time)
{
	struct wl_shell *shell =
		container_of(listener, struct wl_shell, lock_surface_listener);

	fprintf(stderr, "lock surface gone\n");
	shell->lock_surface = NULL;
}

static void
desktop_shell_set_lock_surface(struct wl_client *client,
			       struct wl_resource *resource,
			       struct wl_resource *surface_resource)
{
	struct wl_shell *shell = resource->data;
	struct shell_surface *priv;

	shell->prepare_event_sent = false;

	if (!shell->locked)
		return;

	shell->lock_surface = surface_resource->data;

	shell->lock_surface_listener.func = handle_lock_surface_destroy;
	wl_list_insert(&surface_resource->destroy_listener_list,
		       &shell->lock_surface_listener.link);

	priv = get_shell_surface(shell->lock_surface);
	priv->type = SHELL_SURFACE_LOCK;
}

static void
resume_desktop(struct wl_shell *shell)
{
	struct wlsc_surface *surface;
	struct wl_list *list;

	wl_list_for_each(surface, &shell->hidden_surface_list, link)
		wlsc_surface_configure(surface, surface->x, surface->y,
				       surface->width, surface->height);

	if (wl_list_empty(&shell->backgrounds)) {
		list = &shell->compositor->surface_list;
	} else {
		struct shell_surface *background;
		background = container_of(shell->backgrounds.prev,
					  struct shell_surface, link);
		list = background->surface->link.prev;
	}

	if (!wl_list_empty(&shell->hidden_surface_list))
		wl_list_insert_list(list, &shell->hidden_surface_list);
	wl_list_init(&shell->hidden_surface_list);

	shell->locked = false;
	wlsc_compositor_repick(shell->compositor);
	wlsc_compositor_wake(shell->compositor);
}

static void
desktop_shell_unlock(struct wl_client *client,
		     struct wl_resource *resource)
{
	struct wl_shell *shell = resource->data;

	shell->prepare_event_sent = false;

	if (shell->locked)
		resume_desktop(shell);
}

static const struct desktop_shell_interface desktop_shell_implementation = {
	desktop_shell_set_background,
	desktop_shell_set_panel,
	desktop_shell_set_lock_surface,
	desktop_shell_unlock
};

static void
move_binding(struct wl_input_device *device, uint32_t time,
	     uint32_t key, uint32_t button, uint32_t state, void *data)
{
	struct wlsc_surface *surface =
		(struct wlsc_surface *) device->pointer_focus;
	struct shell_surface *priv;

	if (surface == NULL)
		return;

	priv = get_shell_surface(surface);
	switch (priv->type) {
		case SHELL_SURFACE_PANEL:
		case SHELL_SURFACE_BACKGROUND:
		case SHELL_SURFACE_FULLSCREEN:
			return;
		default:
			break;
	}

	wlsc_surface_move(surface, (struct wlsc_input_device *) device, time);
}

static void
resize_binding(struct wl_input_device *device, uint32_t time,
	       uint32_t key, uint32_t button, uint32_t state, void *data)
{
	struct wlsc_surface *surface =
		(struct wlsc_surface *) device->pointer_focus;
	struct wl_resource *resource;
	uint32_t edges = 0;
	int32_t x, y;
	struct shell_surface *priv;

	if (surface == NULL)
		return;
	
	priv = get_shell_surface(surface);
	switch (priv->type) {
		case SHELL_SURFACE_PANEL:
		case SHELL_SURFACE_BACKGROUND:
		case SHELL_SURFACE_FULLSCREEN:
			return;
		default:
			break;
	}

	x = device->grab_x - surface->x;
	y = device->grab_y - surface->y;

	if (x < surface->width / 3)
		edges |= WL_SHELL_RESIZE_LEFT;
	else if (x < 2 * surface->width / 3)
		edges |= 0;
	else
		edges |= WL_SHELL_RESIZE_RIGHT;

	if (y < surface->height / 3)
		edges |= WL_SHELL_RESIZE_TOP;
	else if (y < 2 * surface->height / 3)
		edges |= 0;
	else
		edges |= WL_SHELL_RESIZE_BOTTOM;

	resource = /* Find shell resource for surface client */ 0;

	/* ... or use wl_shell_surface */

	wlsc_surface_resize(surface, (struct wlsc_input_device *) device,
			    time, edges, resource);
}

static void
activate(struct wlsc_shell *base, struct wlsc_surface *es,
	 struct wlsc_input_device *device, uint32_t time)
{
	struct wl_shell *shell = container_of(base, struct wl_shell, shell);
	struct wlsc_compositor *compositor = shell->compositor;
	struct shell_surface *priv;

	priv = get_shell_surface(es);

	wlsc_surface_activate(es, device, time);

	if (compositor->wxs)
		wlsc_xserver_surface_activate(es);

	switch (priv->type) {
	case SHELL_SURFACE_BACKGROUND:
		/* put background back to bottom */
		wl_list_remove(&es->link);
		wl_list_insert(compositor->surface_list.prev, &es->link);
		break;
	case SHELL_SURFACE_PANEL:
		/* already put on top */
		break;
	default:
		if (!shell->locked) {
			/* bring panel back to top */
			struct shell_surface *panel;
			wl_list_for_each(panel, &shell->panels, link) {
				wl_list_remove(&panel->surface->link);
				wl_list_insert(&compositor->surface_list,
					       &panel->surface->link);
			}
		}
	}
}

static void
lock(struct wlsc_shell *base)
{
	struct wl_shell *shell = container_of(base, struct wl_shell, shell);
	struct wl_list *surface_list = &shell->compositor->surface_list;
	struct wlsc_surface *cur;
	struct wlsc_surface *tmp;
	struct shell_surface *priv;
	struct wlsc_input_device *device;
	uint32_t time;

	if (shell->locked)
		return;

	shell->locked = true;

	/* Move all surfaces from compositor's list to our hidden list,
	 * except the background. This way nothing else can show or
	 * receive input events while we are locked. */

	if (!wl_list_empty(&shell->hidden_surface_list)) {
		fprintf(stderr,
		"%s: Assertion failed: hidden_surface_list is not empty.\n",
								__func__);
	}

	wl_list_for_each_safe(cur, tmp, surface_list, link) {
		/* skip input device sprites, cur->surface is uninitialised */
		if (cur->surface.resource.client == NULL)
			continue;

		priv = get_shell_surface(cur);
		if (priv->type == SHELL_SURFACE_BACKGROUND)
			continue;

		cur->output = NULL;
		wl_list_remove(&cur->link);
		wl_list_insert(shell->hidden_surface_list.prev, &cur->link);
	}

	/* reset pointer foci */
	wlsc_compositor_repick(shell->compositor);

	/* reset keyboard foci */
	time = wlsc_compositor_get_time();
	wl_list_for_each(device, &shell->compositor->input_device_list, link) {
		wl_input_device_set_keyboard_focus(&device->input_device,
						   NULL, time);
	}

	/* TODO: disable bindings that should not work while locked. */

	/* All this must be undone in resume_desktop(). */
}

static void
unlock(struct wlsc_shell *base)
{
	struct wl_shell *shell = container_of(base, struct wl_shell, shell);

	if (!shell->locked || shell->lock_surface) {
		wlsc_compositor_wake(shell->compositor);
		return;
	}

	/* If desktop-shell client has gone away, unlock immediately. */
	if (!shell->child.desktop_shell) {
		resume_desktop(shell);
		return;
	}

	if (shell->prepare_event_sent)
		return;

	wl_resource_post_event(shell->child.desktop_shell,
			       DESKTOP_SHELL_PREPARE_LOCK_SURFACE);
	shell->prepare_event_sent = true;
}

static void
map(struct wlsc_shell *base,
    struct wlsc_surface *surface, int32_t width, int32_t height)
{
	struct wl_shell *shell = container_of(base, struct wl_shell, shell);
	struct wlsc_compositor *compositor = shell->compositor;
	struct wl_list *list;
	struct shell_surface *priv;

	priv = get_shell_surface(surface);

	if (shell->locked)
		list = &shell->hidden_surface_list;
	else
		list = &compositor->surface_list;

	/* surface stacking order, see also activate() */
	switch (priv->type) {
	case SHELL_SURFACE_BACKGROUND:
		/* background always visible, at the bottom */
		wl_list_insert(compositor->surface_list.prev, &surface->link);
		break;
	case SHELL_SURFACE_PANEL:
		/* panel always on top, hidden while locked */
		wl_list_insert(list, &surface->link);
		break;
	case SHELL_SURFACE_LOCK:
		/* lock surface always visible, on top */
		wl_list_insert(&compositor->surface_list, &surface->link);

		wlsc_compositor_repick(compositor);
		wlsc_compositor_wake(compositor);
		break;
	default:
		/* everything else just below the panel */
		if (!wl_list_empty(&shell->panels)) {
			struct shell_surface *panel =
				container_of(shell->panels.prev,
					     struct shell_surface, link);
			wl_list_insert(&panel->surface->link, &surface->link);
		} else {
			wl_list_insert(list, &surface->link);
		}
	}

	if (priv->type == SHELL_SURFACE_TOPLEVEL) {
		surface->x = 10 + random() % 400;
		surface->y = 10 + random() % 400;
	}

	surface->width = width;
	surface->height = height;
	if (!shell->locked || priv->type == SHELL_SURFACE_LOCK)
		wlsc_surface_configure(surface,
				       surface->x, surface->y, width, height);
}

static void
configure(struct wlsc_shell *shell, struct wlsc_surface *surface,
	  int32_t x, int32_t y, int32_t width, int32_t height)
{
	struct wlsc_mode *current;
	struct shell_surface *priv;

	priv = get_shell_surface(surface);
	switch (priv->type) {
	case SHELL_SURFACE_FULLSCREEN:
		current = surface->fullscreen_output->current;
		x = (current->width - surface->width) / 2;
		y = (current->height - surface->height) / 2;
		break;
	default:
		break;
	}

	wlsc_surface_configure(surface, x, y, width, height);
}

static void
desktop_shell_sigchld(struct wlsc_process *process, int status)
{
	struct wl_shell *shell =
		container_of(process, struct wl_shell, child.process);

	shell->child.process.pid = 0;
	shell->child.client = NULL; /* already destroyed by wayland */
}

static int
launch_desktop_shell_process(struct wl_shell *shell)
{
	const char *shell_exe = LIBEXECDIR "/wayland-desktop-shell";
	struct wlsc_compositor *compositor = shell->compositor;
	char s[32];
	int sv[2], flags;

	if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, sv) < 0) {
		fprintf(stderr, "socketpair failed\n");
		return -1;
	}

	shell->child.process.pid = fork();
	shell->child.process.cleanup = desktop_shell_sigchld;

	switch (shell->child.process.pid) {
	case 0:
		/* SOCK_CLOEXEC closes both ends, so we need to unset
		 * the flag on the client fd. */
		flags = fcntl(sv[1], F_GETFD);
		if (flags != -1)
			fcntl(sv[1], F_SETFD, flags & ~FD_CLOEXEC);

		snprintf(s, sizeof s, "%d", sv[1]);
		setenv("WAYLAND_SOCKET", s, 1);
		if (execl(shell_exe, shell_exe, NULL) < 0)
			fprintf(stderr, "%s: running '%s' failed: %m\n",
				__func__, shell_exe);
		exit(-1);

	default:
		close(sv[1]);
		shell->child.client =
			wl_client_create(compositor->wl_display, sv[0]);
		wlsc_watch_process(&shell->child.process);
		break;

	case -1:
		fprintf(stderr, "%s: fork failed: %m\n", __func__);
		return -1;
	}
	return 0;
}

static void
bind_shell(struct wl_client *client, void *data, uint32_t version, uint32_t id)
{
	struct wl_shell *shell = data;

	wl_client_add_object(client, &wl_shell_interface,
			     &shell_interface, id, shell);
}

static void
unbind_desktop_shell(struct wl_resource *resource)
{
	struct wl_shell *shell = resource->data;

	if (shell->locked)
		resume_desktop(shell);

	shell->child.desktop_shell = NULL;
	shell->prepare_event_sent = false;
	free(resource);
}

static void
bind_desktop_shell(struct wl_client *client,
		   void *data, uint32_t version, uint32_t id)
{
	struct wl_shell *shell = data;
	struct wl_resource *resource;

	resource = wl_client_add_object(client, &desktop_shell_interface,
					&desktop_shell_implementation,
					id, shell);

	if (client == shell->child.client) {
		resource->destroy = unbind_desktop_shell;
		shell->child.desktop_shell = resource;
		return;
	}

	wl_resource_post_error(resource, WL_DISPLAY_ERROR_INVALID_OBJECT,
			       "permission to bind desktop_shell denied");
	wl_resource_destroy(resource, 0);
}

int
shell_init(struct wlsc_compositor *ec);

WL_EXPORT int
shell_init(struct wlsc_compositor *ec)
{
	struct wl_shell *shell;

	shell = malloc(sizeof *shell);
	if (shell == NULL)
		return -1;

	memset(shell, 0, sizeof *shell);
	shell->compositor = ec;
	shell->shell.activate = activate;
	shell->shell.lock = lock;
	shell->shell.unlock = unlock;
	shell->shell.map = map;
	shell->shell.configure = configure;

	wl_list_init(&shell->hidden_surface_list);
	wl_list_init(&shell->backgrounds);
	wl_list_init(&shell->panels);

	if (wl_display_add_global(ec->wl_display, &wl_shell_interface,
				  shell, bind_shell) == NULL)
		return -1;

	if (wl_display_add_global(ec->wl_display,
				  &desktop_shell_interface,
				  shell, bind_desktop_shell) == NULL)
		return -1;

	if (launch_desktop_shell_process(shell) != 0)
		return -1;

	wlsc_compositor_add_binding(ec, 0, BTN_LEFT, MODIFIER_SUPER,
				    move_binding, shell);
	wlsc_compositor_add_binding(ec, 0, BTN_MIDDLE, MODIFIER_SUPER,
				    resize_binding, shell);

	ec->shell = &shell->shell;

	return 0;
}