mutter/src/compositor/meta-window-actor-x11.c

/*
 * Copyright (C) 2018 Endless, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 *
 * Written by:
 *     Georges Basile Stavracas Neto <gbsneto@gnome.org>
 */

#include "config.h"

#include "compositor/meta-window-actor-x11.h"

#include "backends/meta-logical-monitor.h"
#include "compositor/compositor-private.h"
#include "compositor/meta-cullable.h"
#include "compositor/meta-shaped-texture-private.h"
#include "compositor/meta-surface-actor.h"
#include "compositor/meta-surface-actor-x11.h"
#include "compositor/region-utils.h"
#include "core/frame.h"
#include "core/window-private.h"
#include "meta/compositor.h"
#include "meta/meta-enum-types.h"
#include "meta/meta-shadow-factory.h"
#include "meta/meta-window-actor.h"
#include "meta/meta-x11-errors.h"
#include "meta/window.h"
#include "x11/meta-x11-display-private.h"

enum
{
  PROP_SHADOW_MODE = 1,
  PROP_SHADOW_CLASS
};

struct _MetaWindowActorX11
{
  MetaWindowActor parent;

  /* List of FrameData for recent frames */
  GList *frames;

  guint send_frame_messages_timer;
  int64_t frame_drawn_time;

  gulong repaint_scheduled_id;
  gulong size_changed_id;

  /* If set, the client needs to be sent a _NET_WM_FRAME_DRAWN
   * client message for one or more messages in ->frames */
  gboolean needs_frame_drawn;
  gboolean repaint_scheduled;

  /*
   * MetaShadowFactory only caches shadows that are actually in use;
   * to avoid unnecessary recomputation we do two things: 1) we store
   * both a focused and unfocused shadow for the window. If the window
   * doesn't have different focused and unfocused shadow parameters,
   * these will be the same. 2) when the shadow potentially changes we
   * don't immediately unreference the old shadow, we just flag it as
   * dirty and recompute it when we next need it (recompute_focused_shadow,
   * recompute_unfocused_shadow.) Because of our extraction of
   * size-invariant window shape, we'll often find that the new shadow
   * is the same as the old shadow.
   */
  MetaShadow *focused_shadow;
  MetaShadow *unfocused_shadow;

  /* A region that matches the shape of the window, including frame bounds */
  cairo_region_t *shape_region;
  /* The region we should clip to when painting the shadow */
  cairo_region_t *shadow_clip;

  /* Extracted size-invariant shape used for shadows */
  MetaWindowShape *shadow_shape;
  char *shadow_class;

  MetaShadowFactory *shadow_factory;
  gulong shadow_factory_changed_handler_id;

  MetaShadowMode shadow_mode;

  gboolean needs_reshape;
  gboolean recompute_focused_shadow;
  gboolean recompute_unfocused_shadow;
};

static MetaCullableInterface *cullable_parent_iface;

static void cullable_iface_init (MetaCullableInterface *iface);

G_DEFINE_TYPE_WITH_CODE (MetaWindowActorX11, meta_window_actor_x11, META_TYPE_WINDOW_ACTOR,
                         G_IMPLEMENT_INTERFACE (META_TYPE_CULLABLE, cullable_iface_init))

/* Each time the application updates the sync request counter to a new even value
 * value, we queue a frame into the windows list of frames. Once we're painting
 * an update "in response" to the window, we fill in frame_counter with the
 * Cogl counter for that frame, and send _NET_WM_FRAME_DRAWN at the end of the
 * frame. _NET_WM_FRAME_TIMINGS is sent when we get a frame_complete callback.
 *
 * As an exception, if a window is completely obscured, we try to throttle drawning
 * to a slower frame rate. In this case, frame_counter stays -1 until
 * send_frame_message_timeout() runs, at which point we send both the
 * _NET_WM_FRAME_DRAWN and _NET_WM_FRAME_TIMINGS messages.
 */
typedef struct
{
  uint64_t sync_request_serial;
  int64_t frame_counter;
  int64_t frame_drawn_time;
} FrameData;

static void
frame_data_free (FrameData *frame)
{
  g_slice_free (FrameData, frame);
}

static void
surface_repaint_scheduled (MetaSurfaceActor *actor,
                           gpointer          user_data)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (user_data);

  actor_x11->repaint_scheduled = TRUE;
}

static void
remove_frame_messages_timer (MetaWindowActorX11 *actor_x11)
{
  g_assert (actor_x11->send_frame_messages_timer != 0);

  g_clear_handle_id (&actor_x11->send_frame_messages_timer, g_source_remove);
}

static void
do_send_frame_drawn (MetaWindowActorX11 *actor_x11,
                     FrameData          *frame)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  MetaDisplay *display = meta_window_get_display (window);
  Display *xdisplay = meta_x11_display_get_xdisplay (display->x11_display);

  XClientMessageEvent ev = { 0, };

  frame->frame_drawn_time =
    meta_compositor_monotonic_time_to_server_time (display,
                                                   g_get_monotonic_time ());
  actor_x11->frame_drawn_time = frame->frame_drawn_time;

  ev.type = ClientMessage;
  ev.window = meta_window_get_xwindow (window);
  ev.message_type = display->x11_display->atom__NET_WM_FRAME_DRAWN;
  ev.format = 32;
  ev.data.l[0] = frame->sync_request_serial & G_GUINT64_CONSTANT (0xffffffff);
  ev.data.l[1] = frame->sync_request_serial >> 32;
  ev.data.l[2] = frame->frame_drawn_time & G_GUINT64_CONSTANT (0xffffffff);
  ev.data.l[3] = frame->frame_drawn_time >> 32;

  meta_x11_error_trap_push (display->x11_display);
  XSendEvent (xdisplay, ev.window, False, 0, (XEvent *) &ev);
  XFlush (xdisplay);
  meta_x11_error_trap_pop (display->x11_display);
}

static void
do_send_frame_timings (MetaWindowActorX11 *actor_x11,
                       FrameData          *frame,
                       int                 refresh_interval,
                       int64_t             presentation_time)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  MetaDisplay *display = meta_window_get_display (window);
  Display *xdisplay = meta_x11_display_get_xdisplay (display->x11_display);

  XClientMessageEvent ev = { 0, };

  ev.type = ClientMessage;
  ev.window = meta_window_get_xwindow (window);
  ev.message_type = display->x11_display->atom__NET_WM_FRAME_TIMINGS;
  ev.format = 32;
  ev.data.l[0] = frame->sync_request_serial & G_GUINT64_CONSTANT (0xffffffff);
  ev.data.l[1] = frame->sync_request_serial >> 32;

  if (presentation_time != 0)
    {
      int64_t presentation_time_server =
        meta_compositor_monotonic_time_to_server_time (display,
                                                       presentation_time);
      int64_t presentation_time_offset = presentation_time_server - frame->frame_drawn_time;
      if (presentation_time_offset == 0)
        presentation_time_offset = 1;

      if ((int32_t)presentation_time_offset == presentation_time_offset)
        ev.data.l[2] = presentation_time_offset;
    }

  ev.data.l[3] = refresh_interval;
  ev.data.l[4] = 1000 * META_SYNC_DELAY;

  meta_x11_error_trap_push (display->x11_display);
  XSendEvent (xdisplay, ev.window, False, 0, (XEvent *) &ev);
  XFlush (xdisplay);
  meta_x11_error_trap_pop (display->x11_display);
}

static void
send_frame_timings (MetaWindowActorX11 *actor_x11,
                    FrameData          *frame,
                    ClutterFrameInfo   *frame_info,
                    int64_t             presentation_time)
{
  float refresh_rate;
  int refresh_interval;

  refresh_rate = frame_info->refresh_rate;
  /* 0.0 is a flag for not known, but sanity-check against other odd numbers */
  if (refresh_rate >= 1.0)
    refresh_interval = (int) (0.5 + 1000000 / refresh_rate);
  else
    refresh_interval = 0;

  do_send_frame_timings (actor_x11, frame, refresh_interval, presentation_time);
}

static gboolean
send_frame_messages_timeout (gpointer data)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (data);
  GList *l;

  for (l = actor_x11->frames; l;)
    {
      GList *l_next = l->next;
      FrameData *frame = l->data;

      if (frame->frame_counter == -1)
        {
          do_send_frame_drawn (actor_x11, frame);
          do_send_frame_timings (actor_x11, frame, 0, 0);

          actor_x11->frames = g_list_delete_link (actor_x11->frames, l);
          frame_data_free (frame);
        }

      l = l_next;
    }

  actor_x11->needs_frame_drawn = FALSE;
  actor_x11->send_frame_messages_timer = 0;

  return G_SOURCE_REMOVE;
}

static void
queue_send_frame_messages_timeout (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  MetaDisplay *display = meta_window_get_display (window);
  MetaLogicalMonitor *logical_monitor;
  int64_t current_time;
  float refresh_rate;
  int interval, offset;

  if (actor_x11->send_frame_messages_timer != 0)
    return;

  logical_monitor = meta_window_get_main_logical_monitor (window);
  if (logical_monitor)
    {
      GList *monitors = meta_logical_monitor_get_monitors (logical_monitor);
      MetaMonitor *monitor;
      MetaMonitorMode *mode;

      monitor = g_list_first (monitors)->data;
      mode = meta_monitor_get_current_mode (monitor);

      refresh_rate = meta_monitor_mode_get_refresh_rate (mode);
    }
  else
    {
      refresh_rate = 60.0f;
    }

  current_time =
    meta_compositor_monotonic_time_to_server_time (display,
                                                   g_get_monotonic_time ());
  interval = (int) (1000000 / refresh_rate) * 6;
  offset = MAX (0, actor_x11->frame_drawn_time + interval - current_time) / 1000;

 /* The clutter master clock source has already been added with META_PRIORITY_REDRAW,
  * so the timer will run *after* the clutter frame handling, if a frame is ready
  * to be drawn when the timer expires.
  */
  actor_x11->send_frame_messages_timer =
    g_timeout_add_full (META_PRIORITY_REDRAW, offset,
                        send_frame_messages_timeout,
                        actor_x11, NULL);
  g_source_set_name_by_id (actor_x11->send_frame_messages_timer,
                           "[mutter] send_frame_messages_timeout");
}

static void
assign_frame_counter_to_frames (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  MetaCompositor *compositor = window->display->compositor;
  ClutterStage *stage = meta_compositor_get_stage (compositor);
  GList *l;

  /* If the window is obscured, then we're expecting to deal with sending
   * frame messages in a timeout, rather than in this paint cycle.
   */
  if (actor_x11->send_frame_messages_timer != 0)
    return;

  for (l = actor_x11->frames; l; l = l->next)
    {
      FrameData *frame = l->data;

      if (frame->frame_counter == -1)
        frame->frame_counter = clutter_stage_get_frame_counter (stage);
    }
}

static void
meta_window_actor_x11_frame_complete (MetaWindowActor  *actor,
                                      ClutterFrameInfo *frame_info,
                                      int64_t           presentation_time)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);
  GList *l;

  if (meta_window_actor_is_destroyed (actor))
    return;

  for (l = actor_x11->frames; l;)
    {
      GList *l_next = l->next;
      FrameData *frame = l->data;
      int64_t frame_counter = frame_info->frame_counter;

      if (frame->frame_counter != -1 && frame->frame_counter <= frame_counter)
        {
          MetaWindow *window =
            meta_window_actor_get_meta_window (actor);

          if (G_UNLIKELY (frame->frame_drawn_time == 0))
            g_warning ("%s: Frame has assigned frame counter but no frame drawn time",
                       window->desc);
          if (G_UNLIKELY (frame->frame_counter < frame_counter))
            g_warning ("%s: frame_complete callback never occurred for frame %" G_GINT64_FORMAT,
                       window->desc, frame->frame_counter);

          actor_x11->frames = g_list_delete_link (actor_x11->frames, l);
          send_frame_timings (actor_x11, frame, frame_info, presentation_time);
          frame_data_free (frame);
        }

      l = l_next;
    }
}

static void
surface_size_changed (MetaSurfaceActor *actor,
                      gpointer          user_data)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (user_data);

  meta_window_actor_x11_update_shape (actor_x11);
}

static void
meta_window_actor_x11_assign_surface_actor (MetaWindowActor  *actor,
                                            MetaSurfaceActor *surface_actor)
{
  MetaWindowActorClass *parent_class =
    META_WINDOW_ACTOR_CLASS (meta_window_actor_x11_parent_class);
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);
  MetaSurfaceActor *prev_surface_actor;

  prev_surface_actor = meta_window_actor_get_surface (actor);
  if (prev_surface_actor)
    {
      g_warn_if_fail (meta_is_wayland_compositor ());

      g_clear_signal_handler (&actor_x11->size_changed_id, prev_surface_actor);
      clutter_actor_remove_child (CLUTTER_ACTOR (actor),
                                  CLUTTER_ACTOR (prev_surface_actor));
    }

  parent_class->assign_surface_actor (actor, surface_actor);

  clutter_actor_add_child (CLUTTER_ACTOR (actor),
                           CLUTTER_ACTOR (surface_actor));

  meta_window_actor_x11_update_shape (actor_x11);

  actor_x11->size_changed_id =
    g_signal_connect (surface_actor, "size-changed",
                      G_CALLBACK (surface_size_changed),
                      actor_x11);
  actor_x11->repaint_scheduled_id =
    g_signal_connect (surface_actor, "repaint-scheduled",
                      G_CALLBACK (surface_repaint_scheduled),
                      actor_x11);
}

static void
meta_window_actor_x11_queue_frame_drawn (MetaWindowActor *actor,
                                         gboolean         skip_sync_delay)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);
  MetaWindow *window =
    meta_window_actor_get_meta_window (actor);
  FrameData *frame;

  if (meta_window_actor_is_destroyed (actor))
    return;

  frame = g_slice_new0 (FrameData);
  frame->frame_counter = -1;
  frame->sync_request_serial = window->sync_request_serial;

  actor_x11->frames = g_list_prepend (actor_x11->frames, frame);

  actor_x11->needs_frame_drawn = TRUE;

  if (skip_sync_delay)
    {
      ClutterActor *stage = clutter_actor_get_stage (CLUTTER_ACTOR (actor_x11));
      clutter_stage_skip_sync_delay (CLUTTER_STAGE (stage));
    }

  if (!actor_x11->repaint_scheduled)
    {
      MetaSurfaceActor *surface;
      gboolean is_obscured;

      surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));

      if (surface)
        is_obscured = meta_surface_actor_is_obscured (surface);
      else
        is_obscured = FALSE;

      /* A frame was marked by the client without actually doing any
       * damage or any unobscured, or while we had the window frozen
       * (e.g. during an interactive resize.) We need to make sure that the
       * pre_paint/post_paint functions get called, enabling us to
       * send a _NET_WM_FRAME_DRAWN. We do a 1-pixel redraw to get
       * consistent timing with non-empty frames. If the window
       * is completely obscured we fire off the send_frame_messages timeout.
       */
      if (is_obscured)
        {
          queue_send_frame_messages_timeout (actor_x11);
        }
      else if (surface)
        {
          const cairo_rectangle_int_t clip = { 0, 0, 1, 1 };
          clutter_actor_queue_redraw_with_clip (CLUTTER_ACTOR (surface), &clip);
          actor_x11->repaint_scheduled = TRUE;
        }
    }
}

static gboolean
has_shadow (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));

  if (actor_x11->shadow_mode == META_SHADOW_MODE_FORCED_OFF)
    return FALSE;
  if (actor_x11->shadow_mode == META_SHADOW_MODE_FORCED_ON)
    return TRUE;

  /* Leaving out shadows for maximized and fullscreen windows is an effeciency
   * win and also prevents the unsightly effect of the shadow of maximized
   * window appearing on an adjacent window */
  if ((meta_window_get_maximized (window) == META_MAXIMIZE_BOTH) ||
      meta_window_is_fullscreen (window))
    return FALSE;

  /*
   * If we have two snap-tiled windows, we don't want the shadow to obstruct
   * the other window.
   */
  if (meta_window_get_tile_match (window))
    return FALSE;

  /*
   * Always put a shadow around windows with a frame - This should override
   * the restriction about not putting a shadow around ARGB windows.
   */
  if (meta_window_get_frame (window))
    return TRUE;

  /*
   * Do not add shadows to non-opaque (ARGB32) windows, as we can't easily
   * generate shadows for them.
   */
  if (!meta_window_actor_is_opaque (META_WINDOW_ACTOR (actor_x11)))
    return FALSE;

  /*
   * If a window specifies that it has custom frame extents, that likely
   * means that it is drawing a shadow itself. Don't draw our own.
   */
  if (window->has_custom_frame_extents)
    return FALSE;

  /*
   * Generate shadows for all other windows.
   */
  return TRUE;
}

gboolean
meta_window_actor_x11_should_unredirect (MetaWindowActorX11 *actor_x11)
{
  MetaSurfaceActor *surface;
  MetaSurfaceActorX11 *surface_x11;

  if (meta_window_actor_is_destroyed (META_WINDOW_ACTOR (actor_x11)))
    return FALSE;

  surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  if (!surface)
    return FALSE;

  if (!META_IS_SURFACE_ACTOR_X11 (surface))
    return FALSE;

  surface_x11 = META_SURFACE_ACTOR_X11 (surface);
  return meta_surface_actor_x11_should_unredirect (surface_x11);
}

void
meta_window_actor_x11_set_unredirected (MetaWindowActorX11 *actor_x11,
                                        gboolean            unredirected)
{
  MetaSurfaceActor *surface;
  MetaSurfaceActorX11 *surface_x11;

  surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  g_assert (surface);

  g_return_if_fail (META_IS_SURFACE_ACTOR_X11 (surface));

  surface_x11 = META_SURFACE_ACTOR_X11 (surface);
  meta_surface_actor_x11_set_unredirected (surface_x11, unredirected);
}

static const char *
get_shadow_class (MetaWindowActorX11 *actor_x11)
{
  if (actor_x11->shadow_class)
    {
      return actor_x11->shadow_class;
    }
  else
    {
      MetaWindow *window =
        meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
      MetaWindowType window_type;

      window_type = meta_window_get_window_type (window);
      switch (window_type)
        {
        case META_WINDOW_DROPDOWN_MENU:
        case META_WINDOW_COMBO:
          return "dropdown-menu";
        case META_WINDOW_POPUP_MENU:
          return "popup-menu";
        default:
          {
            MetaFrameType frame_type;

            frame_type = meta_window_get_frame_type (window);
            return meta_frame_type_to_string (frame_type);
          }
        }
    }
}

static void
get_shadow_params (MetaWindowActorX11 *actor_x11,
                   gboolean            appears_focused,
                   MetaShadowParams   *params)
{
  const char *shadow_class = get_shadow_class (actor_x11);

  meta_shadow_factory_get_params (actor_x11->shadow_factory,
                                  shadow_class, appears_focused,
                                  params);
}

static void
get_shape_bounds (MetaWindowActorX11    *actor_x11,
                  cairo_rectangle_int_t *bounds)
{
  cairo_region_get_extents (actor_x11->shape_region, bounds);
}

static void
get_shadow_bounds (MetaWindowActorX11    *actor_x11,
                   gboolean               appears_focused,
                   cairo_rectangle_int_t *bounds)
{
  MetaShadow *shadow;
  cairo_rectangle_int_t shape_bounds;
  MetaShadowParams params;

  shadow = appears_focused ? actor_x11->focused_shadow
                           : actor_x11->unfocused_shadow;

  get_shape_bounds (actor_x11, &shape_bounds);
  get_shadow_params (actor_x11, appears_focused, &params);

  meta_shadow_get_bounds (shadow,
                          params.x_offset + shape_bounds.x,
                          params.y_offset + shape_bounds.y,
                          shape_bounds.width,
                          shape_bounds.height,
                          bounds);
}

/* If we have an ARGB32 window that we decorate with a frame, it's
 * probably something like a translucent terminal - something where
 * the alpha channel represents transparency rather than a shape.  We
 * don't want to show the shadow through the translucent areas since
 * the shadow is wrong for translucent windows (it should be
 * translucent itself and colored), and not only that, will /look/
 * horribly wrong - a misplaced big black blob. As a hack, what we
 * want to do is just draw the shadow as normal outside the frame, and
 * inside the frame draw no shadow.  This is also not even close to
 * the right result, but looks OK. We also apply this approach to
 * windows set to be partially translucent with _NET_WM_WINDOW_OPACITY.
 */
static gboolean
clip_shadow_under_window (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));

  if (window->frame)
    return TRUE;

  return meta_window_actor_is_opaque (META_WINDOW_ACTOR (actor_x11));
}

/**
 * set_clip_region_beneath:
 * @actor_x11: a #MetaWindowActorX11
 * @clip_region: the region of the screen that isn't completely
 *  obscured beneath the main window texture.
 *
 * Provides a hint as to what areas need to be drawn *beneath*
 * the main window texture.  This is the relevant clip region
 * when drawing the shadow, properly accounting for areas of the
 * shadow hid by the window itself. This will be set before painting
 * then unset afterwards.
 */
static void
set_clip_region_beneath (MetaWindowActorX11 *actor_x11,
                         cairo_region_t     *beneath_region)
{
  MetaWindow *window;
  gboolean appears_focused;

  window = meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  appears_focused = meta_window_appears_focused (window);
  if (appears_focused ? actor_x11->focused_shadow : actor_x11->unfocused_shadow)
    {
      g_clear_pointer (&actor_x11->shadow_clip, cairo_region_destroy);

      if (beneath_region)
        {
          actor_x11->shadow_clip = cairo_region_copy (beneath_region);

          if (clip_shadow_under_window (actor_x11))
            {
              cairo_region_t *frame_bounds;

              frame_bounds = meta_window_get_frame_bounds (window);
              if (frame_bounds)
                cairo_region_subtract (actor_x11->shadow_clip, frame_bounds);
            }
        }
      else
        {
          actor_x11->shadow_clip = NULL;
        }
    }
}

static void
check_needs_shadow (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  MetaShadow *old_shadow = NULL;
  MetaShadow **shadow_location;
  gboolean recompute_shadow;
  gboolean should_have_shadow;
  gboolean appears_focused;

  /* Calling has_shadow() here at every pre-paint is cheap
   * and avoids the need to explicitly handle window type changes, which
   * we would do if tried to keep track of when we might be adding or removing
   * a shadow more explicitly. We only keep track of changes to the *shape* of
   * the shadow with actor_x11->recompute_shadow.
   */

  should_have_shadow = has_shadow (actor_x11);
  appears_focused = meta_window_appears_focused (window);

  if (appears_focused)
    {
      recompute_shadow = actor_x11->recompute_focused_shadow;
      actor_x11->recompute_focused_shadow = FALSE;
      shadow_location = &actor_x11->focused_shadow;
    }
  else
    {
      recompute_shadow = actor_x11->recompute_unfocused_shadow;
      actor_x11->recompute_unfocused_shadow = FALSE;
      shadow_location = &actor_x11->unfocused_shadow;
    }

  if (!should_have_shadow || recompute_shadow)
    {
      if (*shadow_location != NULL)
        {
          old_shadow = *shadow_location;
          *shadow_location = NULL;
        }
    }

  if (!*shadow_location && should_have_shadow)
    {
      MetaShadowFactory *factory = actor_x11->shadow_factory;
      const char *shadow_class = get_shadow_class (actor_x11);
      cairo_rectangle_int_t shape_bounds;

      if (!actor_x11->shadow_shape)
        {
          actor_x11->shadow_shape =
            meta_window_shape_new (actor_x11->shape_region);
        }

      get_shape_bounds (actor_x11, &shape_bounds);
      *shadow_location =
        meta_shadow_factory_get_shadow (factory,
                                        actor_x11->shadow_shape,
                                        shape_bounds.width, shape_bounds.height,
                                        shadow_class, appears_focused);
    }

  if (old_shadow)
    meta_shadow_unref (old_shadow);
}

void
meta_window_actor_x11_process_damage (MetaWindowActorX11 *actor_x11,
                                      XDamageNotifyEvent *event)
{
  MetaSurfaceActor *surface;

  surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  if (surface)
    meta_surface_actor_process_damage (surface,
                                       event->area.x,
                                       event->area.y,
                                       event->area.width,
                                       event->area.height);

  meta_window_actor_notify_damaged (META_WINDOW_ACTOR (actor_x11));
}

static cairo_region_t *
scan_visible_region (guchar         *mask_data,
                     int             stride,
                     cairo_region_t *scan_area)
{
  int i, n_rects = cairo_region_num_rectangles (scan_area);
  MetaRegionBuilder builder;

  meta_region_builder_init (&builder);

  for (i = 0; i < n_rects; i++)
    {
      int x, y;
      cairo_rectangle_int_t rect;

      cairo_region_get_rectangle (scan_area, i, &rect);

      for (y = rect.y; y < (rect.y + rect.height); y++)
        {
          for (x = rect.x; x < (rect.x + rect.width); x++)
            {
              int x2 = x;
              while (mask_data[y * stride + x2] == 255 && x2 < (rect.x + rect.width))
                x2++;

              if (x2 > x)
                {
                  meta_region_builder_add_rectangle (&builder, x, y, x2 - x, 1);
                  x = x2;
                }
            }
        }
    }

  return meta_region_builder_finish (&builder);
}

static void
build_and_scan_frame_mask (MetaWindowActorX11    *actor_x11,
                           cairo_rectangle_int_t *client_area,
                           cairo_region_t        *shape_region)
{
  ClutterBackend *backend = clutter_get_default_backend ();
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  CoglContext *ctx = clutter_backend_get_cogl_context (backend);
  MetaSurfaceActor *surface =
    meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  uint8_t *mask_data;
  unsigned int tex_width, tex_height;
  MetaShapedTexture *stex;
  CoglTexture *paint_tex;
  CoglTexture2D *mask_texture;
  int stride;
  cairo_t *cr;
  cairo_surface_t *image;
  GError *error = NULL;

  stex = meta_surface_actor_get_texture (surface);
  g_return_if_fail (stex);

  meta_shaped_texture_set_mask_texture (stex, NULL);

  paint_tex = meta_shaped_texture_get_texture (stex);
  if (paint_tex == NULL)
    return;

  tex_width = cogl_texture_get_width (paint_tex);
  tex_height = cogl_texture_get_height (paint_tex);

  stride = cairo_format_stride_for_width (CAIRO_FORMAT_A8, tex_width);

  /* Create data for an empty image */
  mask_data = g_malloc0 (stride * tex_height);

  image = cairo_image_surface_create_for_data (mask_data,
                                               CAIRO_FORMAT_A8,
                                               tex_width,
                                               tex_height,
                                               stride);
  cr = cairo_create (image);

  gdk_cairo_region (cr, shape_region);
  cairo_fill (cr);

  if (window->frame)
    {
      cairo_region_t *frame_paint_region, *scanned_region;
      cairo_rectangle_int_t rect = { 0, 0, tex_width, tex_height };

      /* Make sure we don't paint the frame over the client window. */
      frame_paint_region = cairo_region_create_rectangle (&rect);
      cairo_region_subtract_rectangle (frame_paint_region, client_area);

      gdk_cairo_region (cr, frame_paint_region);
      cairo_clip (cr);

      meta_frame_get_mask (window->frame, cr);

      cairo_surface_flush (image);
      scanned_region = scan_visible_region (mask_data, stride, frame_paint_region);
      cairo_region_union (shape_region, scanned_region);
      cairo_region_destroy (scanned_region);
      cairo_region_destroy (frame_paint_region);
    }

  cairo_destroy (cr);
  cairo_surface_destroy (image);

  mask_texture = cogl_texture_2d_new_from_data (ctx, tex_width, tex_height,
                                                COGL_PIXEL_FORMAT_A_8,
                                                stride, mask_data, &error);

  if (error)
    {
      g_warning ("Failed to allocate mask texture: %s", error->message);
      g_error_free (error);
    }

  if (mask_texture)
    {
      meta_shaped_texture_set_mask_texture (stex, COGL_TEXTURE (mask_texture));
      cogl_object_unref (mask_texture);
    }
  else
    {
      meta_shaped_texture_set_mask_texture (stex, NULL);
    }

  g_free (mask_data);
}

static void
invalidate_shadow (MetaWindowActorX11 *actor_x11)
{
  actor_x11->recompute_focused_shadow = TRUE;
  actor_x11->recompute_unfocused_shadow = TRUE;

  if (meta_window_actor_is_frozen (META_WINDOW_ACTOR (actor_x11)))
    return;

  clutter_actor_queue_redraw (CLUTTER_ACTOR (actor_x11));
}

static void
update_shape_region (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  cairo_region_t *region = NULL;
  cairo_rectangle_int_t client_area;

  meta_window_get_client_area_rect (window, &client_area);

  if (window->frame && window->shape_region)
    {
      region = cairo_region_copy (window->shape_region);
      cairo_region_translate (region, client_area.x, client_area.y);
    }
  else if (window->shape_region != NULL)
    {
      region = cairo_region_reference (window->shape_region);
    }
  else
    {
      /* If we don't have a shape on the server, that means that
       * we have an implicit shape of one rectangle covering the
       * entire window. */
      region = cairo_region_create_rectangle (&client_area);
    }

  if (window->shape_region || window->frame)
    build_and_scan_frame_mask (actor_x11, &client_area, region);

  g_clear_pointer (&actor_x11->shape_region, cairo_region_destroy);
  actor_x11->shape_region = region;

  g_clear_pointer (&actor_x11->shadow_shape, meta_window_shape_unref);

  invalidate_shadow (actor_x11);
}

static void
update_input_region (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  MetaSurfaceActor *surface =
    meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  cairo_region_t *region;

  if (window->shape_region && window->input_region)
    {
      region = cairo_region_copy (window->shape_region);
      cairo_region_intersect (region, window->input_region);
    }
  else if (window->shape_region)
    {
      region = cairo_region_reference (window->shape_region);
    }
  else if (window->input_region)
    {
      region = cairo_region_reference (window->input_region);
    }
  else
    {
      region = NULL;
    }

  meta_surface_actor_set_input_region (surface, region);
  cairo_region_destroy (region);
}

static gboolean
is_actor_maybe_transparent (MetaWindowActorX11 *actor_x11)
{
  MetaSurfaceActor *surface;
  MetaShapedTexture *stex;

  surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  if (!surface)
    return TRUE;

  if (META_IS_SURFACE_ACTOR_X11 (surface) &&
      meta_surface_actor_x11_is_unredirected (META_SURFACE_ACTOR_X11 (surface)))
    return FALSE;

  stex = meta_surface_actor_get_texture (surface);
  if (!meta_shaped_texture_has_alpha (stex))
    return FALSE;

  return TRUE;
}

static void
update_opaque_region (MetaWindowActorX11 *actor_x11)
{
  MetaWindow *window =
    meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  gboolean is_maybe_transparent;
  cairo_region_t *opaque_region;
  MetaSurfaceActor *surface;

  is_maybe_transparent = is_actor_maybe_transparent (actor_x11);
  if (is_maybe_transparent && window->opaque_region)
    {
      cairo_rectangle_int_t client_area;

      meta_window_get_client_area_rect (window, &client_area);

      /* The opaque region is defined to be a part of the
       * window which ARGB32 will always paint with opaque
       * pixels. For these regions, we want to avoid painting
       * windows and shadows beneath them.
       *
       * If the client gives bad coordinates where it does not
       * fully paint, the behavior is defined by the specification
       * to be undefined, and considered a client bug. In mutter's
       * case, graphical glitches will occur.
       */
      opaque_region = cairo_region_copy (window->opaque_region);
      cairo_region_translate (opaque_region, client_area.x, client_area.y);
      cairo_region_intersect (opaque_region, actor_x11->shape_region);
    }
  else if (is_maybe_transparent)
    {
      opaque_region = NULL;
    }
  else
    {
      opaque_region = cairo_region_reference (actor_x11->shape_region);
    }

  surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  meta_surface_actor_set_opaque_region (surface, opaque_region);
  cairo_region_destroy (opaque_region);
}

static void
check_needs_reshape (MetaWindowActorX11 *actor_x11)
{
  if (!actor_x11->needs_reshape)
    return;

  update_shape_region (actor_x11);
  update_input_region (actor_x11);
  update_opaque_region (actor_x11);

  actor_x11->needs_reshape = FALSE;
}

void
meta_window_actor_x11_update_shape (MetaWindowActorX11 *actor_x11)
{
  MetaSurfaceActor *surface =
    meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));

  actor_x11->needs_reshape = TRUE;

  if (meta_window_actor_is_frozen (META_WINDOW_ACTOR (actor_x11)))
    return;

  clutter_actor_queue_redraw (CLUTTER_ACTOR (surface));
}

static void
handle_updates (MetaWindowActorX11 *actor_x11)
{
  MetaSurfaceActor *surface =
    meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));

  if (meta_window_actor_is_frozen (META_WINDOW_ACTOR (actor_x11)))
    {
      /* The window is frozen due to a pending animation: we'll wait until
       * the animation finishes to reshape and repair the window */
      return;
    }

  if (META_IS_SURFACE_ACTOR_X11 (surface) &&
      meta_surface_actor_x11_is_unredirected (META_SURFACE_ACTOR_X11 (surface)))
    return;

  meta_surface_actor_pre_paint (surface);

  if (!meta_surface_actor_is_visible (surface))
    return;

  check_needs_reshape (actor_x11);
  check_needs_shadow (actor_x11);
}

static void
meta_window_actor_x11_pre_paint (MetaWindowActor *actor)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);

  handle_updates (actor_x11);

  assign_frame_counter_to_frames (actor_x11);
}

static void
meta_window_actor_x11_paint (ClutterActor        *actor,
                             ClutterPaintContext *paint_context)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);
  MetaWindow *window;
  gboolean appears_focused;
  MetaShadow *shadow;

 /* This window got damage when obscured; we set up a timer
  * to send frame completion events, but since we're drawing
  * the window now (for some other reason) cancel the timer
  * and send the completion events normally */
  if (actor_x11->send_frame_messages_timer != 0)
    {
      remove_frame_messages_timer (actor_x11);
      assign_frame_counter_to_frames (actor_x11);
    }

  window = meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  appears_focused = meta_window_appears_focused (window);
  shadow = appears_focused ? actor_x11->focused_shadow
                           : actor_x11->unfocused_shadow;

  if (shadow)
    {
      MetaShadowParams params;
      cairo_rectangle_int_t shape_bounds;
      cairo_region_t *clip = actor_x11->shadow_clip;
      CoglFramebuffer *framebuffer;

      get_shape_bounds (actor_x11, &shape_bounds);
      get_shadow_params (actor_x11, appears_focused, &params);

      /* The frame bounds are already subtracted from actor_x11->shadow_clip
       * if that exists.
       */
      if (!clip && clip_shadow_under_window (actor_x11))
        {
          cairo_region_t *frame_bounds;
          cairo_rectangle_int_t bounds;

          get_shadow_bounds (actor_x11, appears_focused, &bounds);
          clip = cairo_region_create_rectangle (&bounds);

          frame_bounds = meta_window_get_frame_bounds (window);
          if (frame_bounds)
            cairo_region_subtract (clip, frame_bounds);
        }

      framebuffer = clutter_paint_context_get_framebuffer (paint_context);
      meta_shadow_paint (shadow,
                         framebuffer,
                         params.x_offset + shape_bounds.x,
                         params.y_offset + shape_bounds.y,
                         shape_bounds.width,
                         shape_bounds.height,
                         (clutter_actor_get_paint_opacity (actor) *
                          params.opacity * window->opacity) / (255 * 255),
                         clip,
                         clip_shadow_under_window (actor_x11));

      if (clip && clip != actor_x11->shadow_clip)
        cairo_region_destroy (clip);
    }

  CLUTTER_ACTOR_CLASS (meta_window_actor_x11_parent_class)->paint (actor,
                                                                   paint_context);
}

static void
meta_window_actor_x11_post_paint (MetaWindowActor *actor)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);

  actor_x11->repaint_scheduled = FALSE;

  if (meta_window_actor_is_destroyed (actor))
    return;

  /* If the window had damage, but wasn't actually redrawn because
   * it is obscured, we should wait until timer expiration before
   * sending _NET_WM_FRAME_* messages.
   */
  if (actor_x11->send_frame_messages_timer == 0 &&
      actor_x11->needs_frame_drawn)
    {
      GList *l;

      for (l = actor_x11->frames; l; l = l->next)
        {
          FrameData *frame = l->data;

          if (frame->frame_drawn_time == 0)
            do_send_frame_drawn (actor_x11, frame);
        }

      actor_x11->needs_frame_drawn = FALSE;
    }
}

static gboolean
meta_window_actor_x11_get_paint_volume (ClutterActor       *actor,
                                        ClutterPaintVolume *volume)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);
  MetaWindow *window;
  gboolean appears_focused;
  MetaSurfaceActor *surface;

  /* The paint volume is computed before paint functions are called
   * so our bounds might not be updated yet. Force an update. */
  handle_updates (actor_x11);

  window = meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
  appears_focused = meta_window_appears_focused (window);
  if (appears_focused ? actor_x11->focused_shadow : actor_x11->unfocused_shadow)
    {
      cairo_rectangle_int_t shadow_bounds;
      ClutterActorBox shadow_box;

      /* We could compute an full clip region as we do for the window
       * texture, but the shadow is relatively cheap to draw, and
       * a little more complex to clip, so we just catch the case where
       * the shadow is completely obscured and doesn't need to be drawn
       * at all.
       */

      get_shadow_bounds (actor_x11, appears_focused, &shadow_bounds);
      shadow_box.x1 = shadow_bounds.x;
      shadow_box.x2 = shadow_bounds.x + shadow_bounds.width;
      shadow_box.y1 = shadow_bounds.y;
      shadow_box.y2 = shadow_bounds.y + shadow_bounds.height;

      clutter_paint_volume_union_box (volume, &shadow_box);
    }

  surface = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  if (surface)
    {
      ClutterActor *surface_actor = CLUTTER_ACTOR (surface);
      const ClutterPaintVolume *child_volume;

      child_volume = clutter_actor_get_transformed_paint_volume (surface_actor,
                                                                 actor);
      if (!child_volume)
        return FALSE;

      clutter_paint_volume_union (volume, child_volume);
    }

  return TRUE;
}

static void
meta_window_actor_x11_queue_destroy (MetaWindowActor *actor)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);

  if (actor_x11->send_frame_messages_timer != 0)
    remove_frame_messages_timer (actor_x11);
}

static void
meta_window_actor_x11_set_property (GObject      *object,
                                    guint         prop_id,
                                    const GValue *value,
                                    GParamSpec   *pspec)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (object);

  switch (prop_id)
    {
    case PROP_SHADOW_MODE:
      {
        MetaShadowMode newv = g_value_get_enum (value);

        if (newv == actor_x11->shadow_mode)
          return;

        actor_x11->shadow_mode = newv;

        invalidate_shadow (actor_x11);
      }
      break;
    case PROP_SHADOW_CLASS:
      {
        const char *newv = g_value_get_string (value);

        if (g_strcmp0 (newv, actor_x11->shadow_class) == 0)
          return;

        g_free (actor_x11->shadow_class);
        actor_x11->shadow_class = g_strdup (newv);

        invalidate_shadow (actor_x11);
      }
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
    }
}

static void
meta_window_actor_x11_get_property (GObject      *object,
                                    guint         prop_id,
                                    GValue       *value,
                                    GParamSpec   *pspec)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (object);

  switch (prop_id)
    {
    case PROP_SHADOW_MODE:
      g_value_set_enum (value, actor_x11->shadow_mode);
      break;
    case PROP_SHADOW_CLASS:
      g_value_set_string (value, actor_x11->shadow_class);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
    }
}

static void
meta_window_actor_x11_constructed (GObject *object)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (object);
  MetaWindowActor *actor = META_WINDOW_ACTOR (actor_x11);
  MetaWindow *window = meta_window_actor_get_meta_window (actor);

  /*
   * Start off with an empty shape region to maintain the invariant that it's
   * always set.
   */
  actor_x11->shape_region = cairo_region_create ();

  G_OBJECT_CLASS (meta_window_actor_x11_parent_class)->constructed (object);

  /* If a window doesn't start off with updates frozen, we should
   * we should send a _NET_WM_FRAME_DRAWN immediately after the first drawn.
   */
  if (window->extended_sync_request_counter &&
      !meta_window_updates_are_frozen (window))
    meta_window_actor_queue_frame_drawn (actor, FALSE);
}

static void
meta_window_actor_x11_cull_out (MetaCullable   *cullable,
                                cairo_region_t *unobscured_region,
                                cairo_region_t *clip_region)
{
  cullable_parent_iface->cull_out (cullable, unobscured_region, clip_region);

  set_clip_region_beneath (META_WINDOW_ACTOR_X11 (cullable), clip_region);
}

static void
meta_window_actor_x11_reset_culling (MetaCullable *cullable)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (cullable);

  g_clear_pointer (&actor_x11->shadow_clip, cairo_region_destroy);

  cullable_parent_iface->reset_culling (cullable);
}

static void
cullable_iface_init (MetaCullableInterface *iface)
{
  cullable_parent_iface = g_type_interface_peek_parent (iface);

  iface->cull_out = meta_window_actor_x11_cull_out;
  iface->reset_culling = meta_window_actor_x11_reset_culling;
}

static void
meta_window_actor_x11_dispose (GObject *object)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (object);
  MetaSurfaceActor *surface_actor;

  g_clear_signal_handler (&actor_x11->shadow_factory_changed_handler_id,
                          actor_x11->shadow_factory);

  if (actor_x11->send_frame_messages_timer != 0)
    remove_frame_messages_timer (actor_x11);

  surface_actor = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
  if (surface_actor)
    {
      g_clear_signal_handler (&actor_x11->repaint_scheduled_id, surface_actor);
      g_clear_signal_handler (&actor_x11->size_changed_id, surface_actor);
    }

  g_clear_pointer (&actor_x11->shape_region, cairo_region_destroy);
  g_clear_pointer (&actor_x11->shadow_clip, cairo_region_destroy);

  g_clear_pointer (&actor_x11->shadow_class, g_free);
  g_clear_pointer (&actor_x11->focused_shadow, meta_shadow_unref);
  g_clear_pointer (&actor_x11->unfocused_shadow, meta_shadow_unref);
  g_clear_pointer (&actor_x11->shadow_shape, meta_window_shape_unref);

  G_OBJECT_CLASS (meta_window_actor_x11_parent_class)->dispose (object);
}

static void
meta_window_actor_x11_finalize (GObject *object)
{
  MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (object);

  g_list_free_full (actor_x11->frames, (GDestroyNotify) frame_data_free);

  G_OBJECT_CLASS (meta_window_actor_x11_parent_class)->finalize (object);
}

static void
meta_window_actor_x11_class_init (MetaWindowActorX11Class *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);
  ClutterActorClass *actor_class = CLUTTER_ACTOR_CLASS (klass);
  MetaWindowActorClass *window_actor_class = META_WINDOW_ACTOR_CLASS (klass);
  GParamSpec *pspec;

  window_actor_class->frame_complete = meta_window_actor_x11_frame_complete;
  window_actor_class->assign_surface_actor = meta_window_actor_x11_assign_surface_actor;
  window_actor_class->queue_frame_drawn = meta_window_actor_x11_queue_frame_drawn;
  window_actor_class->pre_paint = meta_window_actor_x11_pre_paint;
  window_actor_class->post_paint = meta_window_actor_x11_post_paint;
  window_actor_class->queue_destroy = meta_window_actor_x11_queue_destroy;

  actor_class->paint = meta_window_actor_x11_paint;
  actor_class->get_paint_volume = meta_window_actor_x11_get_paint_volume;

  object_class->constructed = meta_window_actor_x11_constructed;
  object_class->set_property = meta_window_actor_x11_set_property;
  object_class->get_property = meta_window_actor_x11_get_property;
  object_class->dispose = meta_window_actor_x11_dispose;
  object_class->finalize = meta_window_actor_x11_finalize;

  pspec = g_param_spec_enum ("shadow-mode",
                             "Shadow mode",
                             "Decides when to paint shadows",
                             META_TYPE_SHADOW_MODE,
                             META_SHADOW_MODE_AUTO,
                             G_PARAM_READWRITE);

  g_object_class_install_property (object_class,
                                   PROP_SHADOW_MODE,
                                   pspec);

  pspec = g_param_spec_string ("shadow-class",
                               "Name of the shadow class for this window.",
                               "NULL means to use the default shadow class for this window type",
                               NULL,
                               G_PARAM_READWRITE);

  g_object_class_install_property (object_class,
                                   PROP_SHADOW_CLASS,
                                   pspec);
}

static void
meta_window_actor_x11_init (MetaWindowActorX11 *self)
{
  /* We do this now since we might be going right back into the frozen state. */
  g_signal_connect (self, "thawed", G_CALLBACK (handle_updates), NULL);

  self->shadow_factory = meta_shadow_factory_get_default ();
  self->shadow_factory_changed_handler_id =
    g_signal_connect (self->shadow_factory,
                      "changed",
                      G_CALLBACK (invalidate_shadow),
                      self);
}