gdkwindow.c

/* GDK - The GIMP Drawing Kit
 * Copyright (C) 1995-2007 Peter Mattis, Spencer Kimball,
 * Josh MacDonald, Ryan Lortie
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Modified by the GTK+ Team and others 1997-2000.  See the AUTHORS
 * file for a list of people on the GTK+ Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
 */

#include "config.h"

#include <cairo-gobject.h>

#include "gdkwindow.h"

#include "gdkrectangle.h"
#include "gdkinternals.h"
#include "gdkintl.h"
#include "gdkscreenprivate.h"
#include "gdkdisplayprivate.h"
#include "gdkdeviceprivate.h"
#include "gdkvisualprivate.h"
#include "gdkmarshalers.h"
#include "gdkframeclockidle.h"
#include "gdkwindowimpl.h"
#include "gdkglcontextprivate.h"
#include "gdk-private.h"

#include <math.h>

#include <epoxy/gl.h>

/* for the use of round() */
#include "fallback-c89.c"

#ifdef GDK_WINDOWING_WAYLAND
#include "wayland/gdkwayland.h"
#endif

#undef DEBUG_WINDOW_PRINTING


/**
 * SECTION:windows
 * @Short_description: Onscreen display areas in the target window system
 * @Title: Windows
 *
 * A #GdkWindow is a (usually) rectangular region on the screen.
 * It’s a low-level object, used to implement high-level objects such as
 * #GtkWidget and #GtkWindow on the GTK+ level. A #GtkWindow is a toplevel
 * window, the thing a user might think of as a “window” with a titlebar
 * and so on; a #GtkWindow may contain many #GdkWindows. For example,
 * each #GtkButton has a #GdkWindow associated with it.
 *
 * # Composited Windows # {#COMPOSITED-WINDOWS}
 *
 * Normally, the windowing system takes care of rendering the contents
 * of a child window onto its parent window. This mechanism can be
 * intercepted by calling gdk_window_set_composited() on the child
 * window. For a “composited” window it is the
 * responsibility of the application to render the window contents at
 * the right spot.
 *
 * # Offscreen Windows # {#OFFSCREEN-WINDOWS}
 *
 * Offscreen windows are more general than composited windows, since
 * they allow not only to modify the rendering of the child window onto
 * its parent, but also to apply coordinate transformations.
 *
 * To integrate an offscreen window into a window hierarchy, one has
 * to call gdk_offscreen_window_set_embedder() and handle a number of
 * signals. The #GdkWindow::pick-embedded-child signal on the embedder
 * window is used to select an offscreen child at given coordinates,
 * and the #GdkWindow::to-embedder and #GdkWindow::from-embedder signals
 * on the offscreen window are used to translate coordinates between
 * the embedder and the offscreen window.
 *
 * For rendering an offscreen window onto its embedder, the contents
 * of the offscreen window are available as a surface, via
 * gdk_offscreen_window_get_surface().
 */


/* Historically a GdkWindow always matches a platform native window,
 * be it a toplevel window or a child window. In this setup the
 * GdkWindow (and other GdkDrawables) were platform independent classes,
 * and the actual platform specific implementation was in a delegate
 * object available as “impl” in the window object.
 *
 * With the addition of client side windows and offscreen windows this
 * changes a bit. The application-visible GdkWindow object behaves as
 * it did before, but not all such windows now have a corresponding native
 * window. Instead windows that are “client side” are emulated by the gdk
 * code such that clipping, drawing, moving, events etc work as expected.
 *
 * For GdkWindows that have a native window the “impl” object is the
 * same as before. However, for all client side windows the impl object
 * is shared with its parent (i.e. all client windows descendants of one
 * native window has the same impl.
 *
 * Additionally there is a new type of platform independent impl object,
 * GdkOffscreenWindow. All windows of type GDK_WINDOW_OFFSCREEN get an impl
 * of this type (while their children are generally GDK_WINDOW_CHILD virtual
 * windows). Such windows work by allocating a #cairo_surface_t as the backing
 * store for drawing operations, which is resized with the window.
 *
 * GdkWindows have a pointer to the “impl window” they are in, i.e.
 * the topmost GdkWindow which have the same “impl” value. This is stored
 * in impl_window, which is different from the window itself only for client
 * side windows.
 * All GdkWindows (native or not) track the position of the window in the parent
 * (x, y), the size of the window (width, height), the position of the window
 * with respect to the impl window (abs_x, abs_y). We also track the clip
 * region of the window wrt parent windows, in window-relative coordinates (clip_region).
 *
 * All toplevel windows are native windows, but also child windows can be
 * native (although not children of offscreens). We always listen to
 * a basic set of events (see get_native_event_mask) for these windows
 * so that we can emulate events for any client side children.
 *
 * For native windows we apply the calculated clip region as a window shape
 * so that eg. client side siblings that overlap the native child properly
 * draws over the native child window.
 */

/* This adds a local value to the GdkVisibilityState enum */
#define GDK_VISIBILITY_NOT_VIEWABLE 3

enum {
  PICK_EMBEDDED_CHILD, /* only called if children are embedded */
  TO_EMBEDDER,
  FROM_EMBEDDER,
  CREATE_SURFACE,
  LAST_SIGNAL
};

enum {
  PROP_0,
  PROP_CURSOR
};

/* Global info */

static void gdk_window_finalize   (GObject              *object);

static void gdk_window_set_property (GObject      *object,
                                     guint         prop_id,
                                     const GValue *value,
                                     GParamSpec   *pspec);
static void gdk_window_get_property (GObject      *object,
                                     guint         prop_id,
                                     GValue       *value,
                                     GParamSpec   *pspec);

static void gdk_window_clear_backing_region (GdkWindow *window);

static void recompute_visible_regions   (GdkWindow *private,
					 gboolean recalculate_children);
static void gdk_window_invalidate_in_parent (GdkWindow *private);
static void move_native_children        (GdkWindow *private);
static void update_cursor               (GdkDisplay *display,
                                         GdkDevice  *device);
static void impl_window_add_update_area (GdkWindow *impl_window,
					 cairo_region_t *region);
static void gdk_window_invalidate_region_full (GdkWindow       *window,
					       const cairo_region_t *region,
					       gboolean         invalidate_children);
static void gdk_window_invalidate_rect_full (GdkWindow          *window,
					     const GdkRectangle *rect,
					     gboolean            invalidate_children);
static cairo_surface_t *gdk_window_ref_impl_surface (GdkWindow *window);

static void gdk_window_set_frame_clock (GdkWindow      *window,
                                        GdkFrameClock  *clock);

static void draw_ugly_color (GdkWindow       *window,
                             const cairo_region_t *region,
                             int color);


static guint signals[LAST_SIGNAL] = { 0 };

static gpointer parent_class = NULL;

G_DEFINE_ABSTRACT_TYPE (GdkWindow, gdk_window, G_TYPE_OBJECT)

#ifdef DEBUG_WINDOW_PRINTING
char *
print_region (cairo_region_t *region)
{
  GString *s = g_string_new ("{");
  if (cairo_region_is_empty (region))
    {
      g_string_append (s, "empty");
    }
  else
    {
      int num = cairo_region_num_rectangles (region);
      cairo_rectangle_int_t r;

      if (num == 1)
	{
	  cairo_region_get_rectangle (region, 0, &r);
	  g_string_append_printf (s, "%dx%d @%d,%d", r.width, r.height, r.x, r.y);
	}
      else
	{
	  int i;
	  cairo_region_get_extents (region, &r);
	  g_string_append_printf (s, "extent: %dx%d @%d,%d, details: ", r.width, r.height, r.x, r.y);
	  for (i = 0; i < num; i++)
	    {
              cairo_region_get_rectangle (region, i, &r);
	      g_string_append_printf (s, "[%dx%d @%d,%d]", r.width, r.height, r.x, r.y);
	      if (i != num -1)
		g_string_append (s, ", ");
	    }
	}
    }
  g_string_append (s, "}");
  return g_string_free (s, FALSE);
}
#endif

static void
gdk_window_init (GdkWindow *window)
{
  /* 0-initialization is good for all other fields. */

  window->window_type = GDK_WINDOW_CHILD;

  window->state = GDK_WINDOW_STATE_WITHDRAWN;
  window->fullscreen_mode = GDK_FULLSCREEN_ON_CURRENT_MONITOR;
  window->width = 1;
  window->height = 1;
  window->toplevel_window_type = -1;
  /* starts hidden */
  window->effective_visibility = GDK_VISIBILITY_NOT_VIEWABLE;
  window->visibility = GDK_VISIBILITY_FULLY_OBSCURED;
  /* Default to unobscured since some backends don't send visibility events */
  window->native_visibility = GDK_VISIBILITY_UNOBSCURED;

  window->device_cursor = g_hash_table_new_full (NULL, NULL,
                                                 NULL, g_object_unref);
}

/* Stop and return on the first non-NULL parent */
static gboolean
accumulate_get_window (GSignalInvocationHint *ihint,
		       GValue		       *return_accu,
		       const GValue	       *handler_return,
		       gpointer               data)
{
  g_value_copy (handler_return, return_accu);
  /* Continue while returning NULL */
  return g_value_get_object (handler_return) == NULL;
}

static gboolean
create_surface_accumulator (GSignalInvocationHint *ihint,
                            GValue                *return_accu,
                            const GValue          *handler_return,
                            gpointer               data)
{
  g_value_copy (handler_return, return_accu);

  /* Stop on the first non-NULL return value */
  return g_value_get_boxed (handler_return) == NULL;
}

static GQuark quark_pointer_window = 0;

static void
gdk_window_class_init (GdkWindowClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  parent_class = g_type_class_peek_parent (klass);

  object_class->finalize = gdk_window_finalize;
  object_class->set_property = gdk_window_set_property;
  object_class->get_property = gdk_window_get_property;

  klass->create_surface = _gdk_offscreen_window_create_surface;

  quark_pointer_window = g_quark_from_static_string ("gtk-pointer-window");


  /* Properties */

  /**
   * GdkWindow:cursor:
   *
   * The mouse pointer for a #GdkWindow. See gdk_window_set_cursor() and
   * gdk_window_get_cursor() for details.
   *
   * Since: 2.18
   */
  g_object_class_install_property (object_class,
                                   PROP_CURSOR,
                                   g_param_spec_object ("cursor",
                                                        P_("Cursor"),
                                                        P_("Cursor"),
                                                        GDK_TYPE_CURSOR,
                                                        G_PARAM_READWRITE));

  /**
   * GdkWindow::pick-embedded-child:
   * @window: the window on which the signal is emitted
   * @x: x coordinate in the window
   * @y: y coordinate in the window
   *
   * The ::pick-embedded-child signal is emitted to find an embedded
   * child at the given position.
   *
   * Returns: (nullable) (transfer none): the #GdkWindow of the
   *     embedded child at @x, @y, or %NULL
   *
   * Since: 2.18
   */
  signals[PICK_EMBEDDED_CHILD] =
    g_signal_new (g_intern_static_string ("pick-embedded-child"),
		  G_OBJECT_CLASS_TYPE (object_class),
		  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GdkWindowClass, pick_embedded_child),
		  accumulate_get_window, NULL,
		  _gdk_marshal_OBJECT__DOUBLE_DOUBLE,
		  GDK_TYPE_WINDOW,
		  2,
		  G_TYPE_DOUBLE,
		  G_TYPE_DOUBLE);

  /**
   * GdkWindow::to-embedder:
   * @window: the offscreen window on which the signal is emitted
   * @offscreen_x: x coordinate in the offscreen window
   * @offscreen_y: y coordinate in the offscreen window
   * @embedder_x: (out) (type double): return location for the x
   *     coordinate in the embedder window
   * @embedder_y: (out) (type double): return location for the y
   *     coordinate in the embedder window
   *
   * The ::to-embedder signal is emitted to translate coordinates
   * in an offscreen window to its embedder.
   *
   * See also #GdkWindow::from-embedder.
   *
   * Since: 2.18
   */
  signals[TO_EMBEDDER] =
    g_signal_new (g_intern_static_string ("to-embedder"),
		  G_OBJECT_CLASS_TYPE (object_class),
		  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GdkWindowClass, to_embedder),
		  NULL, NULL,
		  _gdk_marshal_VOID__DOUBLE_DOUBLE_POINTER_POINTER,
		  G_TYPE_NONE,
		  4,
		  G_TYPE_DOUBLE,
		  G_TYPE_DOUBLE,
		  G_TYPE_POINTER,
		  G_TYPE_POINTER);

  /**
   * GdkWindow::from-embedder:
   * @window: the offscreen window on which the signal is emitted
   * @embedder_x: x coordinate in the embedder window
   * @embedder_y: y coordinate in the embedder window
   * @offscreen_x: (out) (type double): return location for the x
   *     coordinate in the offscreen window
   * @offscreen_y: (out) (type double): return location for the y
   *     coordinate in the offscreen window
   *
   * The ::from-embedder signal is emitted to translate coordinates
   * in the embedder of an offscreen window to the offscreen window.
   *
   * See also #GdkWindow::to-embedder.
   *
   * Since: 2.18
   */
  signals[FROM_EMBEDDER] =
    g_signal_new (g_intern_static_string ("from-embedder"),
		  G_OBJECT_CLASS_TYPE (object_class),
		  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GdkWindowClass, from_embedder),
		  NULL, NULL,
		  _gdk_marshal_VOID__DOUBLE_DOUBLE_POINTER_POINTER,
		  G_TYPE_NONE,
		  4,
		  G_TYPE_DOUBLE,
		  G_TYPE_DOUBLE,
		  G_TYPE_POINTER,
		  G_TYPE_POINTER);

  /**
   * GdkWindow::create-surface:
   * @window: the offscreen window on which the signal is emitted
   * @width: the width of the offscreen surface to create
   * @height: the height of the offscreen surface to create
   *
   * The ::create-surface signal is emitted when an offscreen window
   * needs its surface (re)created, which happens either when the
   * window is first drawn to, or when the window is being
   * resized. The first signal handler that returns a non-%NULL
   * surface will stop any further signal emission, and its surface
   * will be used.
   *
   * Note that it is not possible to access the window's previous
   * surface from within any callback of this signal. Calling
   * gdk_offscreen_window_get_surface() will lead to a crash.
   *
   * Returns: the newly created #cairo_surface_t for the offscreen window
   *
   * Since: 3.0
   */
  signals[CREATE_SURFACE] =
    g_signal_new (g_intern_static_string ("create-surface"),
                  G_OBJECT_CLASS_TYPE (object_class),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GdkWindowClass, create_surface),
                  create_surface_accumulator, NULL,
                  _gdk_marshal_BOXED__INT_INT,
                  CAIRO_GOBJECT_TYPE_SURFACE,
                  2,
                  G_TYPE_INT,
                  G_TYPE_INT);
}

static void
device_removed_cb (GdkDeviceManager *device_manager,
                   GdkDevice        *device,
                   GdkWindow        *window)
{
  window->devices_inside = g_list_remove (window->devices_inside, device);
  g_hash_table_remove (window->device_cursor, device);

  if (window->device_events)
    g_hash_table_remove (window->device_events, device);
}

static void
gdk_window_finalize (GObject *object)
{
  GdkWindow *window = GDK_WINDOW (object);
  GdkDeviceManager *device_manager;

  device_manager = gdk_display_get_device_manager (gdk_window_get_display (window));
  g_signal_handlers_disconnect_by_func (device_manager, device_removed_cb, window);

  if (!GDK_WINDOW_DESTROYED (window))
    {
      if (GDK_WINDOW_TYPE (window) != GDK_WINDOW_FOREIGN)
	{
	  g_warning ("losing last reference to undestroyed window\n");
	  _gdk_window_destroy (window, FALSE);
	}
      else
	/* We use TRUE here, to keep us from actually calling
	 * XDestroyWindow() on the window
	 */
	_gdk_window_destroy (window, TRUE);
    }

  if (window->impl)
    {
      g_object_unref (window->impl);
      window->impl = NULL;
    }

  if (window->impl_window != window)
    {
      g_object_unref (window->impl_window);
      window->impl_window = NULL;
    }

  if (window->shape)
    cairo_region_destroy (window->shape);

  if (window->input_shape)
    cairo_region_destroy (window->input_shape);

  if (window->cursor)
    g_object_unref (window->cursor);

  if (window->device_cursor)
    g_hash_table_destroy (window->device_cursor);

  if (window->device_events)
    g_hash_table_destroy (window->device_events);

  if (window->source_event_masks)
    g_hash_table_destroy (window->source_event_masks);

  if (window->devices_inside)
    g_list_free (window->devices_inside);

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

static void
gdk_window_set_property (GObject      *object,
                         guint         prop_id,
                         const GValue *value,
                         GParamSpec   *pspec)
{
  GdkWindow *window = (GdkWindow *)object;

  switch (prop_id)
    {
    case PROP_CURSOR:
      gdk_window_set_cursor (window, g_value_get_object (value));
      break;

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

static void
gdk_window_get_property (GObject    *object,
                         guint       prop_id,
                         GValue     *value,
                         GParamSpec *pspec)
{
  GdkWindow *window = (GdkWindow *) object;

  switch (prop_id)
    {
    case PROP_CURSOR:
      g_value_set_object (value, gdk_window_get_cursor (window));
      break;

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

static gboolean
gdk_window_is_offscreen (GdkWindow *window)
{
  return window->window_type == GDK_WINDOW_OFFSCREEN;
}

static GdkWindow *
gdk_window_get_impl_window (GdkWindow *window)
{
  return window->impl_window;
}

GdkWindow *
_gdk_window_get_impl_window (GdkWindow *window)
{
  return gdk_window_get_impl_window (window);
}

static gboolean
gdk_window_has_impl (GdkWindow *window)
{
  return window->impl_window == window;
}

static gboolean
gdk_window_is_toplevel (GdkWindow *window)
{
  return
    window->parent == NULL ||
    window->parent->window_type == GDK_WINDOW_ROOT;
}

gboolean
_gdk_window_has_impl (GdkWindow *window)
{
  return gdk_window_has_impl (window);
}

static gboolean
gdk_window_has_no_impl (GdkWindow *window)
{
  return window->impl_window != window;
}

static void
remove_sibling_overlapped_area (GdkWindow *window,
				cairo_region_t *region)
{
  GdkWindow *parent;
  GdkWindow *sibling;
  cairo_region_t *child_region;
  GdkRectangle r;
  GList *l;
  cairo_region_t *shape;

  parent = window->parent;

  if (gdk_window_is_toplevel (window))
    return;

  /* Convert from from window coords to parent coords */
  cairo_region_translate (region, window->x, window->y);

  for (l = parent->children; l; l = l->next)
    {
      sibling = l->data;

      if (sibling == window)
	break;

      if (!GDK_WINDOW_IS_MAPPED (sibling) || sibling->input_only || sibling->composited)
	continue;

      /* Ignore offscreen children, as they don't draw in their parent and
       * don't take part in the clipping */
      if (gdk_window_is_offscreen (sibling))
	continue;

      r.x = sibling->x;
      r.y = sibling->y;
      r.width = sibling->width;
      r.height = sibling->height;

      child_region = cairo_region_create_rectangle (&r);

      if (sibling->shape)
	{
	  /* Adjust shape region to parent window coords */
	  cairo_region_translate (sibling->shape, sibling->x, sibling->y);
	  cairo_region_intersect (child_region, sibling->shape);
	  cairo_region_translate (sibling->shape, -sibling->x, -sibling->y);
	}
      else if (window->window_type == GDK_WINDOW_FOREIGN)
	{
	  shape = GDK_WINDOW_IMPL_GET_CLASS (sibling)->get_shape (sibling);
	  if (shape)
	    {
	      cairo_region_intersect (child_region, shape);
	      cairo_region_destroy (shape);
	    }
	}

      cairo_region_subtract (region, child_region);
      cairo_region_destroy (child_region);
    }

  remove_sibling_overlapped_area (parent, region);

  /* Convert back to window coords */
  cairo_region_translate (region, -window->x, -window->y);
}

static void
remove_child_area (GdkWindow *window,
		   gboolean for_input,
		   cairo_region_t *region)
{
  GdkWindow *child;
  cairo_region_t *child_region;
  GdkRectangle r;
  GList *l;
  cairo_region_t *shape;

  for (l = window->children; l; l = l->next)
    {
      child = l->data;

      /* If region is empty already, no need to do
	 anything potentially costly */
      if (cairo_region_is_empty (region))
	break;

      if (!GDK_WINDOW_IS_MAPPED (child) || child->input_only || child->composited)
	continue;

      /* Ignore offscreen children, as they don't draw in their parent and
       * don't take part in the clipping */
      if (gdk_window_is_offscreen (child))
	continue;

      r.x = child->x;
      r.y = child->y;
      r.width = child->width;
      r.height = child->height;

      /* Bail early if child totally outside region */
      if (cairo_region_contains_rectangle (region, &r) == CAIRO_REGION_OVERLAP_OUT)
	continue;

      child_region = cairo_region_create_rectangle (&r);

      if (child->shape)
	{
	  /* Adjust shape region to parent window coords */
	  cairo_region_translate (child->shape, child->x, child->y);
	  cairo_region_intersect (child_region, child->shape);
	  cairo_region_translate (child->shape, -child->x, -child->y);
	}
      else if (window->window_type == GDK_WINDOW_FOREIGN)
	{
	  shape = GDK_WINDOW_IMPL_GET_CLASS (child)->get_shape (child);
	  if (shape)
	    {
	      cairo_region_intersect (child_region, shape);
	      cairo_region_destroy (shape);
	    }
	}

      if (for_input)
	{
	  if (child->input_shape)
	    cairo_region_intersect (child_region, child->input_shape);
	  else if (window->window_type == GDK_WINDOW_FOREIGN)
	    {
	      shape = GDK_WINDOW_IMPL_GET_CLASS (child)->get_input_shape (child);
	      if (shape)
		{
		  cairo_region_intersect (child_region, shape);
		  cairo_region_destroy (shape);
		}
	    }
	}

      cairo_region_subtract (region, child_region);
      cairo_region_destroy (child_region);
    }
}

static GdkVisibilityState
effective_visibility (GdkWindow *window)
{
  GdkVisibilityState native;

  if (!gdk_window_is_viewable (window))
    return GDK_VISIBILITY_NOT_VIEWABLE;

  native = window->impl_window->native_visibility;

  if (native == GDK_VISIBILITY_FULLY_OBSCURED ||
      window->visibility == GDK_VISIBILITY_FULLY_OBSCURED)
    return GDK_VISIBILITY_FULLY_OBSCURED;
  else if (native == GDK_VISIBILITY_UNOBSCURED)
    return window->visibility;
  else /* native PARTIAL, private partial or unobscured  */
    return GDK_VISIBILITY_PARTIAL;
}

static void
gdk_window_update_visibility (GdkWindow *window)
{
  GdkVisibilityState new_visibility;
  GdkEvent *event;

  new_visibility = effective_visibility (window);

  if (new_visibility != window->effective_visibility)
    {
      window->effective_visibility = new_visibility;

      if (new_visibility != GDK_VISIBILITY_NOT_VIEWABLE &&
	  window->event_mask & GDK_VISIBILITY_NOTIFY_MASK)
	{
	  event = _gdk_make_event (window, GDK_VISIBILITY_NOTIFY,
				   NULL, FALSE);
	  event->visibility.state = new_visibility;
	}
    }
}

static void
gdk_window_update_visibility_recursively (GdkWindow *window,
					  GdkWindow *only_for_impl)
{
  GdkWindow *child;
  GList *l;

  gdk_window_update_visibility (window);
  for (l = window->children; l != NULL; l = l->next)
    {
      child = l->data;
      if ((only_for_impl == NULL) ||
	  (only_for_impl == child->impl_window))
	gdk_window_update_visibility_recursively (child, only_for_impl);
    }
}

static gboolean
should_apply_clip_as_shape (GdkWindow *window)
{
  return
    gdk_window_has_impl (window) &&
    /* Not for offscreens */
    !gdk_window_is_offscreen (window) &&
    /* or for non-shaped toplevels */
    (!gdk_window_is_toplevel (window) ||
     window->shape != NULL || window->applied_shape) &&
    /* or for foreign windows */
    window->window_type != GDK_WINDOW_FOREIGN &&
    /* or for the root window */
    window->window_type != GDK_WINDOW_ROOT;
}

static void
apply_shape (GdkWindow *window,
	     cairo_region_t *region)
{
  GdkWindowImplClass *impl_class;

  /* We trash whether we applied a shape so that
     we can avoid unsetting it many times, which
     could happen in e.g. apply_clip_as_shape as
     windows get resized */
  impl_class = GDK_WINDOW_IMPL_GET_CLASS (window->impl);
  if (region)
    impl_class->shape_combine_region (window,
				      region, 0, 0);
  else if (window->applied_shape)
    impl_class->shape_combine_region (window,
				      NULL, 0, 0);

  window->applied_shape = region != NULL;
}

static gboolean
region_rect_equal (const cairo_region_t *region,
                   const GdkRectangle *rect)
{
    GdkRectangle extents;

    if (cairo_region_num_rectangles (region) != 1)
        return FALSE;

    cairo_region_get_extents (region, &extents);

    return extents.x == rect->x &&
        extents.y == rect->y &&
        extents.width == rect->width &&
        extents.height == rect->height;
}

static void
apply_clip_as_shape (GdkWindow *window)
{
  GdkRectangle r;
  cairo_region_t *region;

  r.x = r.y = 0;
  r.width = window->width;
  r.height = window->height;

  region = cairo_region_copy (window->clip_region);
  remove_sibling_overlapped_area (window, region);

  /* We only apply the clip region if would differ
     from the actual clip region implied by the size
     of the window. This is to avoid unneccessarily
     adding meaningless shapes to all native subwindows */
  if (!region_rect_equal (region, &r))
    apply_shape (window, region);
  else
    apply_shape (window, NULL);

  cairo_region_destroy (region);
}

static void
recompute_visible_regions_internal (GdkWindow *private,
				    gboolean   recalculate_clip,
				    gboolean   recalculate_children)
{
  GdkRectangle r;
  GList *l;
  GdkWindow *child;
  cairo_region_t *new_clip;
  gboolean clip_region_changed;
  gboolean abs_pos_changed;
  int old_abs_x, old_abs_y;

  old_abs_x = private->abs_x;
  old_abs_y = private->abs_y;

  /* Update absolute position */
  if (gdk_window_has_impl (private))
    {
      /* Native window starts here */
      private->abs_x = 0;
      private->abs_y = 0;
    }
  else
    {
      private->abs_x = private->parent->abs_x + private->x;
      private->abs_y = private->parent->abs_y + private->y;
    }

  abs_pos_changed =
    private->abs_x != old_abs_x ||
    private->abs_y != old_abs_y;

  /* Update clip region based on:
   * parent clip
   * window size/position
   */
  clip_region_changed = FALSE;
  if (recalculate_clip)
    {
      if (private->viewable)
	{
	  /* Calculate visible region (sans children) in parent window coords */
	  r.x = private->x;
	  r.y = private->y;
	  r.width = private->width;
	  r.height = private->height;
	  new_clip = cairo_region_create_rectangle (&r);

	  if (!gdk_window_is_toplevel (private))
	    cairo_region_intersect (new_clip, private->parent->clip_region);

	  /* Convert from parent coords to window coords */
	  cairo_region_translate (new_clip, -private->x, -private->y);

	  if (should_apply_clip_as_shape (private) && private->shape)
	    cairo_region_intersect (new_clip, private->shape);
	}
      else
	  new_clip = cairo_region_create ();

      if (private->clip_region == NULL ||
	  !cairo_region_equal (private->clip_region, new_clip))
	clip_region_changed = TRUE;

      if (private->clip_region)
	cairo_region_destroy (private->clip_region);
      private->clip_region = new_clip;
    }

  if (clip_region_changed)
    {
      GdkVisibilityState visibility;
      gboolean fully_visible;

      if (cairo_region_is_empty (private->clip_region))