gnome-shell/src/st/st-widget.c

/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/*
 * st-widget.c: Base class for St actors
 *
 * Copyright 2007 OpenedHand
 * Copyright 2008, 2009 Intel Corporation.
 * Copyright 2009, 2010 Red Hat, Inc.
 * Copyright 2009 Abderrahim Kitouni
 * Copyright 2009, 2010 Florian Müllner
 * Copyright 2010 Adel Gadllah
 * Copyright 2012 Igalia, S.L.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU Lesser General Public License,
 * version 2.1, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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 program. If not, see <http://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdlib.h>
#include <string.h>
#include <math.h>

#include <clutter/clutter.h>

#include "st-widget.h"

#include "st-label.h"
#include "st-private.h"
#include "st-settings.h"
#include "st-texture-cache.h"
#include "st-theme-context.h"
#include "st-theme-node-transition.h"
#include "st-theme-node-private.h"

#include "st-widget-accessible.h"

#include <atk/atk-enum-types.h>

/* This is set in stone and also hard-coded in GDK. */
#define VIRTUAL_CORE_POINTER_ID 2

/*
 * Forward declaration for sake of StWidgetChild
 */
typedef struct _StWidgetPrivate        StWidgetPrivate;
struct _StWidgetPrivate
{
  StTheme      *theme;
  StThemeNode  *theme_node;
  gchar        *pseudo_class;
  gchar        *style_class;
  gchar        *inline_style;

  StThemeNodeTransition *transition_animation;

  guint is_style_dirty : 1;
  guint draw_bg_color : 1;
  guint draw_border_internal : 1;
  guint track_hover : 1;
  guint hover : 1;
  guint can_focus : 1;

  gulong texture_file_changed_id;

  AtkObject *accessible;
  AtkRole accessible_role;
  AtkStateSet *local_state_set;

  ClutterActor *label_actor;
  gchar        *accessible_name;

  StWidget *last_visible_child;
  StWidget *first_visible_child;

  StThemeNodePaintState paint_states[2];
  int current_paint_state : 2;
};

/**
 * SECTION:st-widget
 * @short_description: Base class for stylable actors
 *
 * #StWidget is a simple abstract class on top of #ClutterActor. It
 * provides basic themeing properties.
 *
 * Actors in the St library should subclass #StWidget if they plan
 * to obey to a certain #StStyle.
 */

enum
{
  PROP_0,

  PROP_THEME,
  PROP_PSEUDO_CLASS,
  PROP_STYLE_CLASS,
  PROP_STYLE,
  PROP_TRACK_HOVER,
  PROP_HOVER,
  PROP_CAN_FOCUS,
  PROP_LABEL_ACTOR,
  PROP_ACCESSIBLE_ROLE,
  PROP_ACCESSIBLE_NAME
};

enum
{
  STYLE_CHANGED,
  POPUP_MENU,
  RESOURCE_SCALE_CHANGED,

  LAST_SIGNAL
};

static guint signals[LAST_SIGNAL] = { 0, };

gfloat st_slow_down_factor = 1.0;

G_DEFINE_TYPE_WITH_PRIVATE (StWidget, st_widget, CLUTTER_TYPE_ACTOR);
#define ST_WIDGET_PRIVATE(w) ((StWidgetPrivate *)st_widget_get_instance_private (w))

static void st_widget_recompute_style (StWidget    *widget,
                                       StThemeNode *old_theme_node);
static gboolean st_widget_real_navigate_focus (StWidget         *widget,
                                               ClutterActor     *from,
                                               StDirectionType   direction);

static AtkObject * st_widget_get_accessible (ClutterActor *actor);

static void
st_widget_set_property (GObject      *gobject,
                        guint         prop_id,
                        const GValue *value,
                        GParamSpec   *pspec)
{
  StWidget *actor = ST_WIDGET (gobject);

  switch (prop_id)
    {
    case PROP_THEME:
      st_widget_set_theme (actor, g_value_get_object (value));
      break;

    case PROP_PSEUDO_CLASS:
      st_widget_set_style_pseudo_class (actor, g_value_get_string (value));
      break;

    case PROP_STYLE_CLASS:
      st_widget_set_style_class_name (actor, g_value_get_string (value));
      break;

    case PROP_STYLE:
      st_widget_set_style (actor, g_value_get_string (value));
      break;

    case PROP_TRACK_HOVER:
      st_widget_set_track_hover (actor, g_value_get_boolean (value));
      break;

    case PROP_HOVER:
      st_widget_set_hover (actor, g_value_get_boolean (value));
      break;

    case PROP_CAN_FOCUS:
      st_widget_set_can_focus (actor, g_value_get_boolean (value));
      break;

    case PROP_LABEL_ACTOR:
      st_widget_set_label_actor (actor, g_value_get_object (value));
      break;

    case PROP_ACCESSIBLE_ROLE:
      st_widget_set_accessible_role (actor, g_value_get_enum (value));
      break;

    case PROP_ACCESSIBLE_NAME:
      st_widget_set_accessible_name (actor, g_value_get_string (value));
      break;

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

static void
st_widget_get_property (GObject    *gobject,
                        guint       prop_id,
                        GValue     *value,
                        GParamSpec *pspec)
{
  StWidget *actor = ST_WIDGET (gobject);
  StWidgetPrivate *priv = st_widget_get_instance_private (ST_WIDGET (gobject));

  switch (prop_id)
    {
    case PROP_THEME:
      g_value_set_object (value, priv->theme);
      break;

    case PROP_PSEUDO_CLASS:
      g_value_set_string (value, priv->pseudo_class);
      break;

    case PROP_STYLE_CLASS:
      g_value_set_string (value, priv->style_class);
      break;

    case PROP_STYLE:
      g_value_set_string (value, priv->inline_style);
      break;

    case PROP_TRACK_HOVER:
      g_value_set_boolean (value, priv->track_hover);
      break;

    case PROP_HOVER:
      g_value_set_boolean (value, priv->hover);
      break;

    case PROP_CAN_FOCUS:
      g_value_set_boolean (value, priv->can_focus);
      break;

    case PROP_LABEL_ACTOR:
      g_value_set_object (value, priv->label_actor);
      break;

    case PROP_ACCESSIBLE_ROLE:
      g_value_set_enum (value, st_widget_get_accessible_role (actor));
      break;

    case PROP_ACCESSIBLE_NAME:
      g_value_set_string (value, priv->accessible_name);
      break;

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

static void
st_widget_remove_transition (StWidget *widget)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  if (priv->transition_animation)
    {
      g_object_run_dispose (G_OBJECT (priv->transition_animation));
      g_object_unref (priv->transition_animation);
      priv->transition_animation = NULL;
    }
}

static void
next_paint_state (StWidget *widget)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  priv->current_paint_state = (priv->current_paint_state + 1) % G_N_ELEMENTS (priv->paint_states);
}

static StThemeNodePaintState *
current_paint_state (StWidget *widget)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  return &priv->paint_states[priv->current_paint_state];
}

static void
st_widget_texture_cache_changed (StTextureCache *cache,
                                 GFile          *file,
                                 gpointer        user_data)
{
  StWidget *actor = ST_WIDGET (user_data);
  StWidgetPrivate *priv = st_widget_get_instance_private (actor);
  gboolean changed = FALSE;
  int i;

  for (i = 0; i < G_N_ELEMENTS (priv->paint_states); i++)
    {
      StThemeNodePaintState *paint_state = &priv->paint_states[i];
      changed |= st_theme_node_paint_state_invalidate_for_file (paint_state, file);
    }

  if (changed && clutter_actor_is_mapped (CLUTTER_ACTOR (actor)))
    clutter_actor_queue_redraw (CLUTTER_ACTOR (actor));
}

static void
st_widget_dispose (GObject *gobject)
{
  StWidget *actor = ST_WIDGET (gobject);
  StWidgetPrivate *priv = st_widget_get_instance_private (actor);

  g_clear_pointer (&priv->theme, g_object_unref);
  g_clear_pointer (&priv->theme_node, g_object_unref);

  st_widget_remove_transition (actor);

  g_clear_pointer (&priv->label_actor, g_object_unref);

  if (priv->texture_file_changed_id != 0)
    {
      g_signal_handler_disconnect (st_texture_cache_get_default (), priv->texture_file_changed_id);
      priv->texture_file_changed_id = 0;
    }

  g_clear_object (&priv->first_visible_child);
  g_clear_object (&priv->last_visible_child);

  G_OBJECT_CLASS (st_widget_parent_class)->dispose (gobject);
}

static void
st_widget_finalize (GObject *gobject)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (ST_WIDGET (gobject));
  guint i;

  g_free (priv->style_class);
  g_free (priv->pseudo_class);
  g_object_unref (priv->local_state_set);
  g_free (priv->accessible_name);
  g_free (priv->inline_style);

  for (i = 0; i < G_N_ELEMENTS (priv->paint_states); i++)
    st_theme_node_paint_state_free (&priv->paint_states[i]);

  G_OBJECT_CLASS (st_widget_parent_class)->finalize (gobject);
}


static void
st_widget_get_preferred_width (ClutterActor *self,
                               gfloat        for_height,
                               gfloat       *min_width_p,
                               gfloat       *natural_width_p)
{
  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));

  st_theme_node_adjust_for_width (theme_node, &for_height);

  CLUTTER_ACTOR_CLASS (st_widget_parent_class)->get_preferred_width (self, for_height, min_width_p, natural_width_p);

  st_theme_node_adjust_preferred_width (theme_node, min_width_p, natural_width_p);
}

static void
st_widget_get_preferred_height (ClutterActor *self,
                                gfloat        for_width,
                                gfloat       *min_height_p,
                                gfloat       *natural_height_p)
{
  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (self));

  st_theme_node_adjust_for_width (theme_node, &for_width);

  CLUTTER_ACTOR_CLASS (st_widget_parent_class)->get_preferred_height (self, for_width, min_height_p, natural_height_p);

  st_theme_node_adjust_preferred_height (theme_node, min_height_p, natural_height_p);
}

static void
st_widget_allocate (ClutterActor          *actor,
                    const ClutterActorBox *box,
                    ClutterAllocationFlags flags)
{
  StThemeNode *theme_node = st_widget_get_theme_node (ST_WIDGET (actor));
  ClutterActorBox content_box;

  /* Note that we can't just chain up to clutter_actor_real_allocate --
   * Clutter does some dirty tricks for backwards compatibility.
   * Clutter also passes the actor's allocation directly to the layout
   * manager, meaning that we can't modify it for children only.
   */

  clutter_actor_set_allocation (actor, box, flags);

  st_theme_node_get_content_box (theme_node, box, &content_box);

  /* If we've chained up to here, we want to allocate the children using the
   * currently installed layout manager */
  clutter_layout_manager_allocate (clutter_actor_get_layout_manager (actor),
                                   CLUTTER_CONTAINER (actor),
                                   &content_box,
                                   flags);
}

/**
 * st_widget_paint_background:
 * @widget: The #StWidget
 *
 * Paint the background of the widget. This is meant to be called by
 * subclasses of StWidget that need to paint the background without
 * painting children.
 */
void
st_widget_paint_background (StWidget *widget)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);
  CoglFramebuffer *framebuffer;
  StThemeNode *theme_node;
  ClutterActorBox allocation;
  float resource_scale;
  guint8 opacity;

  if (!st_widget_get_resource_scale (widget, &resource_scale))
    return;

  framebuffer = cogl_get_draw_framebuffer ();
  theme_node = st_widget_get_theme_node (widget);

  clutter_actor_get_allocation_box (CLUTTER_ACTOR (widget), &allocation);

  opacity = clutter_actor_get_paint_opacity (CLUTTER_ACTOR (widget));

  if (priv->transition_animation)
    st_theme_node_transition_paint (priv->transition_animation,
                                    framebuffer,
                                    &allocation,
                                    opacity,
                                    resource_scale);
  else
    st_theme_node_paint (theme_node,
                         current_paint_state (widget),
                         framebuffer,
                         &allocation,
                         opacity,
                         resource_scale);
}

static void
st_widget_paint (ClutterActor *actor)
{
  st_widget_paint_background (ST_WIDGET (actor));

  /* Chain up so we paint children. */
  CLUTTER_ACTOR_CLASS (st_widget_parent_class)->paint (actor);
}

static void
st_widget_parent_set (ClutterActor *widget,
                      ClutterActor *old_parent)
{
  StWidget *self = ST_WIDGET (widget);
  ClutterActorClass *parent_class;
  ClutterActor *new_parent;

  parent_class = CLUTTER_ACTOR_CLASS (st_widget_parent_class);
  if (parent_class->parent_set)
    parent_class->parent_set (widget, old_parent);

  new_parent = clutter_actor_get_parent (widget);

  /* don't send the style changed signal if we no longer have a parent actor */
  if (new_parent)
    st_widget_style_changed (self);
}

static void
st_widget_map (ClutterActor *actor)
{
  StWidget *self = ST_WIDGET (actor);

  CLUTTER_ACTOR_CLASS (st_widget_parent_class)->map (actor);

  st_widget_ensure_style (self);
}

static void
st_widget_unmap (ClutterActor *actor)
{
  StWidget *self = ST_WIDGET (actor);
  StWidgetPrivate *priv = st_widget_get_instance_private (self);

  CLUTTER_ACTOR_CLASS (st_widget_parent_class)->unmap (actor);

  if (priv->track_hover && priv->hover)
    st_widget_set_hover (self, FALSE);
}

static void
notify_children_of_style_change (ClutterActor *self)
{
  ClutterActorIter iter;
  ClutterActor *actor;

  clutter_actor_iter_init (&iter, self);
  while (clutter_actor_iter_next (&iter, &actor))
    {
      if (ST_IS_WIDGET (actor))
        st_widget_style_changed (ST_WIDGET (actor));
      else
        notify_children_of_style_change (actor);
    }
}

static void
st_widget_real_style_changed (StWidget *self)
{
  clutter_actor_queue_redraw ((ClutterActor *) self);
  notify_children_of_style_change ((ClutterActor *) self);
}

void
st_widget_style_changed (StWidget *widget)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);
  StThemeNode *old_theme_node = NULL;

  priv->is_style_dirty = TRUE;
  if (priv->theme_node)
    {
      old_theme_node = priv->theme_node;
      priv->theme_node = NULL;
    }

  /* update the style only if we are mapped */
  if (clutter_actor_is_mapped (CLUTTER_ACTOR (widget)))
    st_widget_recompute_style (widget, old_theme_node);

  if (old_theme_node)
    g_object_unref (old_theme_node);
}

static void
on_theme_context_changed (StThemeContext *context,
                          ClutterStage   *stage)
{
  notify_children_of_style_change (CLUTTER_ACTOR (stage));
}

static StThemeNode *
get_root_theme_node (ClutterStage *stage)
{
  StThemeContext *context = st_theme_context_get_for_stage (stage);

  if (!g_object_get_data (G_OBJECT (context), "st-theme-initialized"))
    {
      g_object_set_data (G_OBJECT (context), "st-theme-initialized", GUINT_TO_POINTER (1));
      g_signal_connect (G_OBJECT (context), "changed",
                        G_CALLBACK (on_theme_context_changed), stage);
    }

  return st_theme_context_get_root_node (context);
}

/**
 * st_widget_get_theme_node:
 * @widget: a #StWidget
 *
 * Gets the theme node holding style information for the widget.
 * The theme node is used to access standard and custom CSS
 * properties of the widget.
 *
 * Note: it is a fatal error to call this on a widget that is
 *  not been added to a stage.
 *
 * Return value: (transfer none): the theme node for the widget.
 *   This is owned by the widget. When attributes of the widget
 *   or the environment that affect the styling change (for example
 *   the style_class property of the widget), it will be recreated,
 *   and the ::style-changed signal will be emitted on the widget.
 */
StThemeNode *
st_widget_get_theme_node (StWidget *widget)
{
  StWidgetPrivate *priv;

  g_return_val_if_fail (ST_IS_WIDGET (widget), NULL);

  priv = st_widget_get_instance_private (widget);

  if (priv->theme_node == NULL)
    {
      StThemeContext *context;
      StThemeNode *tmp_node;
      StThemeNode *parent_node = NULL;
      ClutterStage *stage = NULL;
      ClutterActor *parent;
      char *pseudo_class, *direction_pseudo_class;

      parent = clutter_actor_get_parent (CLUTTER_ACTOR (widget));
      while (parent != NULL)
        {
          if (parent_node == NULL && ST_IS_WIDGET (parent))
            parent_node = st_widget_get_theme_node (ST_WIDGET (parent));
          else if (CLUTTER_IS_STAGE (parent))
            stage = CLUTTER_STAGE (parent);

          parent = clutter_actor_get_parent (parent);
        }

      if (stage == NULL)
        {
          g_critical ("st_widget_get_theme_node called on the widget %s which is not in the stage.",
                      st_describe_actor (CLUTTER_ACTOR (widget)));
          return g_object_new (ST_TYPE_THEME_NODE, NULL);
        }

      if (parent_node == NULL)
        parent_node = get_root_theme_node (CLUTTER_STAGE (stage));

      /* Always append a "magic" pseudo class indicating the text
       * direction, to allow to adapt the CSS when necessary without
       * requiring separate style sheets.
       */
      if (clutter_actor_get_text_direction (CLUTTER_ACTOR (widget)) == CLUTTER_TEXT_DIRECTION_RTL)
        direction_pseudo_class = (char *)"rtl";
      else
        direction_pseudo_class = (char *)"ltr";

      if (priv->pseudo_class)
        pseudo_class = g_strconcat(priv->pseudo_class, " ",
                                   direction_pseudo_class, NULL);
      else
        pseudo_class = direction_pseudo_class;

      context = st_theme_context_get_for_stage (stage);
      tmp_node = st_theme_node_new (context, parent_node, priv->theme,
                                    G_OBJECT_TYPE (widget),
                                    clutter_actor_get_name (CLUTTER_ACTOR (widget)),
                                    priv->style_class,
                                    pseudo_class,
                                    priv->inline_style);

      if (pseudo_class != direction_pseudo_class)
        g_free (pseudo_class);

      priv->theme_node = g_object_ref (st_theme_context_intern_node (context,
                                                                     tmp_node));
      g_object_unref (tmp_node);
    }

  return priv->theme_node;
}

/**
 * st_widget_peek_theme_node:
 * @widget: a #StWidget
 *
 * Returns the theme node for the widget if it has already been
 * computed, %NULL if the widget hasn't been added to a  stage or the theme
 * node hasn't been computed. If %NULL is returned, then ::style-changed
 * will be reliably emitted before the widget is allocated or painted.
 *
 * Return value: (transfer none): the theme node for the widget.
 *   This is owned by the widget. When attributes of the widget
 *   or the environment that affect the styling change (for example
 *   the style_class property of the widget), it will be recreated,
 *   and the ::style-changed signal will be emitted on the widget.
 */
StThemeNode *
st_widget_peek_theme_node (StWidget *widget)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), NULL);

  return ST_WIDGET_PRIVATE (widget)->theme_node;
}

static gboolean
st_widget_enter (ClutterActor         *actor,
                 ClutterCrossingEvent *event)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (ST_WIDGET (actor));

  if (priv->track_hover)
    {
      if (clutter_actor_contains (actor, event->source))
        st_widget_set_hover (ST_WIDGET (actor), TRUE);
      else
        {
          /* The widget has a grab and is being told about an
           * enter-event outside its hierarchy. Hopefully we already
           * got a leave-event, but if not, handle it now.
           */
          st_widget_set_hover (ST_WIDGET (actor), FALSE);
        }
    }

  if (CLUTTER_ACTOR_CLASS (st_widget_parent_class)->enter_event)
    return CLUTTER_ACTOR_CLASS (st_widget_parent_class)->enter_event (actor, event);
  else
    return FALSE;
}

static gboolean
st_widget_leave (ClutterActor         *actor,
                 ClutterCrossingEvent *event)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (ST_WIDGET (actor));

  if (priv->track_hover)
    {
      if (!event->related || !clutter_actor_contains (actor, event->related))
        st_widget_set_hover (ST_WIDGET (actor), FALSE);
    }

  if (CLUTTER_ACTOR_CLASS (st_widget_parent_class)->leave_event)
    return CLUTTER_ACTOR_CLASS (st_widget_parent_class)->leave_event (actor, event);
  else
    return FALSE;
}

static void
st_widget_key_focus_in (ClutterActor *actor)
{
  StWidget *widget = ST_WIDGET (actor);

  st_widget_add_style_pseudo_class (widget, "focus");
}

static void
st_widget_key_focus_out (ClutterActor *actor)
{
  StWidget *widget = ST_WIDGET (actor);

  st_widget_remove_style_pseudo_class (widget, "focus");
}

static gboolean
st_widget_key_press_event (ClutterActor    *actor,
                           ClutterKeyEvent *event)
{
  if (event->keyval == CLUTTER_KEY_Menu ||
      (event->keyval == CLUTTER_KEY_F10 &&
       (event->modifier_state & CLUTTER_SHIFT_MASK)))
    {
      st_widget_popup_menu (ST_WIDGET (actor));
      return TRUE;
    }

  return FALSE;
}

static gboolean
st_widget_get_paint_volume (ClutterActor *self,
                            ClutterPaintVolume *volume)
{
  ClutterActorBox paint_box, alloc_box;
  StThemeNode *theme_node;
  StWidgetPrivate *priv;
  ClutterVertex origin;

  /* Setting the paint volume does not make sense when we don't have any allocation */
  if (!clutter_actor_has_allocation (self))
    return FALSE;

  priv = st_widget_get_instance_private (ST_WIDGET (self));

  theme_node = st_widget_get_theme_node (ST_WIDGET (self));
  clutter_actor_get_allocation_box (self, &alloc_box);

  if (priv->transition_animation)
    st_theme_node_transition_get_paint_box (priv->transition_animation,
                                            &alloc_box, &paint_box);
  else
    st_theme_node_get_paint_box (theme_node, &alloc_box, &paint_box);

  origin.x = paint_box.x1 - alloc_box.x1;
  origin.y = paint_box.y1 - alloc_box.y1;
  origin.z = 0.0f;

  clutter_paint_volume_set_origin (volume, &origin);
  clutter_paint_volume_set_width (volume, paint_box.x2 - paint_box.x1);
  clutter_paint_volume_set_height (volume, paint_box.y2 - paint_box.y1);

  if (!clutter_actor_get_clip_to_allocation (self))
    {
      ClutterActor *child;
      /* Based on ClutterGroup/ClutterBox; include the children's
       * paint volumes, since they may paint outside our allocation.
       */
      for (child = clutter_actor_get_first_child (self);
           child != NULL;
           child = clutter_actor_get_next_sibling (child))
        {
          const ClutterPaintVolume *child_volume;

          if (!clutter_actor_is_visible (child))
            continue;

          child_volume = clutter_actor_get_transformed_paint_volume (child, self);
          if (!child_volume)
            return FALSE;

          clutter_paint_volume_union (volume, child_volume);
        }
    }

  return TRUE;
}

static GList *
st_widget_real_get_focus_chain (StWidget *widget)
{
  GList *children, *l, *visible = NULL;

  children = clutter_actor_get_children (CLUTTER_ACTOR (widget));

  for (l = children; l; l = l->next)
    {
      if (clutter_actor_is_visible (CLUTTER_ACTOR (l->data)))
        visible = g_list_prepend (visible, l->data);
    }

  g_list_free (children);

  return g_list_reverse (visible);
}

static void
st_widget_class_init (StWidgetClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  ClutterActorClass *actor_class = CLUTTER_ACTOR_CLASS (klass);
  GParamSpec *pspec;

  gobject_class->set_property = st_widget_set_property;
  gobject_class->get_property = st_widget_get_property;
  gobject_class->dispose = st_widget_dispose;
  gobject_class->finalize = st_widget_finalize;

  actor_class->get_preferred_width = st_widget_get_preferred_width;
  actor_class->get_preferred_height = st_widget_get_preferred_height;
  actor_class->allocate = st_widget_allocate;
  actor_class->paint = st_widget_paint;
  actor_class->get_paint_volume = st_widget_get_paint_volume;
  actor_class->parent_set = st_widget_parent_set;
  actor_class->map = st_widget_map;
  actor_class->unmap = st_widget_unmap;

  actor_class->enter_event = st_widget_enter;
  actor_class->leave_event = st_widget_leave;
  actor_class->key_focus_in = st_widget_key_focus_in;
  actor_class->key_focus_out = st_widget_key_focus_out;
  actor_class->key_press_event = st_widget_key_press_event;

  actor_class->get_accessible = st_widget_get_accessible;

  klass->style_changed = st_widget_real_style_changed;
  klass->navigate_focus = st_widget_real_navigate_focus;
  klass->get_accessible_type = st_widget_accessible_get_type;
  klass->get_focus_chain = st_widget_real_get_focus_chain;

  /**
   * StWidget:pseudo-class:
   *
   * The pseudo-class of the actor. Typical values include "hover", "active",
   * "focus".
   */
  g_object_class_install_property (gobject_class,
                                   PROP_PSEUDO_CLASS,
                                   g_param_spec_string ("pseudo-class",
                                                        "Pseudo Class",
                                                        "Pseudo class for styling",
                                                        "",
                                                        ST_PARAM_READWRITE));
  /**
   * StWidget:style-class:
   *
   * The style-class of the actor for use in styling.
   */
  g_object_class_install_property (gobject_class,
                                   PROP_STYLE_CLASS,
                                   g_param_spec_string ("style-class",
                                                        "Style Class",
                                                        "Style class for styling",
                                                        "",
                                                        ST_PARAM_READWRITE));

  /**
   * StWidget:style:
   *
   * Inline style information for the actor as a ';'-separated list of
   * CSS properties.
   */
  g_object_class_install_property (gobject_class,
                                   PROP_STYLE,
                                   g_param_spec_string ("style",
                                                        "Style",
                                                        "Inline style string",
                                                        "",
                                                        ST_PARAM_READWRITE));

  /**
   * StWidget:theme:
   *
   * A theme set on this actor overriding the global theming for this actor
   * and its descendants
   */
  g_object_class_install_property (gobject_class,
                                   PROP_THEME,
                                   g_param_spec_object ("theme",
                                                        "Theme",
                                                        "Theme override",
                                                        ST_TYPE_THEME,
                                                        ST_PARAM_READWRITE));

  /**
   * StWidget:track-hover:
   *
   * Determines whether the widget tracks pointer hover state. If
   * %TRUE (and the widget is visible and reactive), the
   * #StWidget:hover property and "hover" style pseudo class will be
   * adjusted automatically as the pointer moves in and out of the
   * widget.
   */
  pspec = g_param_spec_boolean ("track-hover",
                                "Track hover",
                                "Determines whether the widget tracks hover state",
                                FALSE,
                                ST_PARAM_READWRITE);
  g_object_class_install_property (gobject_class,
                                   PROP_TRACK_HOVER,
                                   pspec);

  /**
   * StWidget:hover:
   *
   * Whether or not the pointer is currently hovering over the widget. This is
   * only tracked automatically if #StWidget:track-hover is %TRUE, but you can
   * adjust it manually in any case.
   */
  pspec = g_param_spec_boolean ("hover",
                                "Hover",
                                "Whether the pointer is hovering over the widget",
                                FALSE,
                                ST_PARAM_READWRITE);
  g_object_class_install_property (gobject_class,
                                   PROP_HOVER,
                                   pspec);

  /**
   * StWidget:can-focus:
   *
   * Whether or not the widget can be focused via keyboard navigation.
   */
  pspec = g_param_spec_boolean ("can-focus",
                                "Can focus",
                                "Whether the widget can be focused via keyboard navigation",
                                FALSE,
                                ST_PARAM_READWRITE);
  g_object_class_install_property (gobject_class,
                                   PROP_CAN_FOCUS,
                                   pspec);

  /**
   * ClutterActor:label-actor:
   *
   * An actor that labels this widget.
   */
  g_object_class_install_property (gobject_class,
                                   PROP_LABEL_ACTOR,
                                   g_param_spec_object ("label-actor",
                                                        "Label",
                                                        "Label that identifies this widget",
                                                        CLUTTER_TYPE_ACTOR,
                                                        ST_PARAM_READWRITE));
  /**
   * StWidget:accessible-role:
   *
   * The accessible role of this object
   */
  g_object_class_install_property (gobject_class,
                                   PROP_ACCESSIBLE_ROLE,
                                   g_param_spec_enum ("accessible-role",
                                                      "Accessible Role",
                                                      "The accessible role of this object",
                                                      ATK_TYPE_ROLE,
                                                      ATK_ROLE_INVALID,
                                                      G_PARAM_READWRITE));


  /**
   * StWidget:accessible-name:
   *
   * Object instance's name for assistive technology access.
   */
  g_object_class_install_property (gobject_class,
                                   PROP_ACCESSIBLE_NAME,
                                   g_param_spec_string ("accessible-name",
                                                        "Accessible name",
                                                        "Object instance's name for assistive technology access.",
                                                        NULL,
                                                        ST_PARAM_READWRITE));

  /**
   * StWidget::style-changed:
   * @widget: the #StWidget
   *
   * Emitted when the style information that the widget derives from the
   * theme changes
   */
  signals[STYLE_CHANGED] =
    g_signal_new ("style-changed",
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (StWidgetClass, style_changed),
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * StWidget::popup-menu:
   * @widget: the #StWidget
   *
   * Emitted when the user has requested a context menu (eg, via a
   * keybinding)
   */
  signals[POPUP_MENU] =
    g_signal_new ("popup-menu",
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (StWidgetClass, popup_menu),
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);

  /**
   * StWidget::resource-scale-changed:
   * @widget: the #StWidget
   *
   * Emitted when the paint scale that the widget will be painted as
   * changed.
   */
  signals[RESOURCE_SCALE_CHANGED] =
    g_signal_new ("resource-scale-changed",
                  G_TYPE_FROM_CLASS (klass),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (StWidgetClass, resource_scale_changed),
                  NULL, NULL, NULL,
                  G_TYPE_NONE, 0);
}

/**
 * st_widget_set_theme:
 * @actor: a #StWidget
 * @theme: a new style class string
 *
 * Overrides the theme that would be inherited from the actor's parent
 * or the stage with an entirely new theme (set of stylesheets).
 */
void
st_widget_set_theme (StWidget  *actor,
                     StTheme   *theme)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));

  priv = st_widget_get_instance_private (actor);

  if (theme != priv->theme)
    {
      if (priv->theme)
        g_object_unref (priv->theme);
      priv->theme = g_object_ref (theme);

      st_widget_style_changed (actor);

      g_object_notify (G_OBJECT (actor), "theme");
    }
}

/**
 * st_widget_get_theme:
 * @actor: a #StWidget
 *
 * Gets the overriding theme set on the actor. See st_widget_set_theme()
 *
 * Return value: (transfer none): the overriding theme, or %NULL
 */
StTheme *
st_widget_get_theme (StWidget *actor)
{
  g_return_val_if_fail (ST_IS_WIDGET (actor), NULL);

  return ST_WIDGET_PRIVATE (actor)->theme;
}

static const gchar *
find_class_name (const gchar *class_list,
                 const gchar *class_name)
{
  gint len = strlen (class_name);
  const gchar *match;

  if (!class_list)
    return NULL;

  for (match = strstr (class_list, class_name); match; match = strstr (match + 1, class_name))
    {
      if ((match == class_list || g_ascii_isspace (match[-1])) &&
          (match[len] == '\0' || g_ascii_isspace (match[len])))
        return match;
    }

  return NULL;
}

static gboolean
set_class_list (gchar       **class_list,
                const gchar  *new_class_list)
{
  if (g_strcmp0 (*class_list, new_class_list) != 0)
    {
      g_free (*class_list);
      *class_list = g_strdup (new_class_list);
      return TRUE;
    }
  else
    return FALSE;
}

static gboolean
add_class_name (gchar       **class_list,
                const gchar  *class_name)
{
  gchar *new_class_list;

  if (*class_list)
    {
      if (find_class_name (*class_list, class_name))
        return FALSE;

      new_class_list = g_strdup_printf ("%s %s", *class_list, class_name);
      g_free (*class_list);
      *class_list = new_class_list;
    }
  else
    *class_list = g_strdup (class_name);

  return TRUE;
}

static gboolean
remove_class_name (gchar       **class_list,
                   const gchar  *class_name)
{
  const gchar *match, *end;
  gchar *new_class_list;

  if (!*class_list)
    return FALSE;

  if (strcmp (*class_list, class_name) == 0)
    {
      g_free (*class_list);
      *class_list = NULL;
      return TRUE;
    }

  match = find_class_name (*class_list, class_name);
  if (!match)
    return FALSE;
  end = match + strlen (class_name);

  /* Adjust either match or end to include a space as well.
   * (One or the other must be possible at this point.)
   */
  if (match != *class_list)
    match--;
  else
    end++;

  new_class_list = g_strdup_printf ("%.*s%s", (int)(match - *class_list),
                                    *class_list, end);
  g_free (*class_list);
  *class_list = new_class_list;

  return TRUE;
}

/**
 * st_widget_set_style_class_name:
 * @actor: a #StWidget
 * @style_class_list: (nullable): a new style class list string
 *
 * Set the style class name list. @style_class_list can either be
 * %NULL, for no classes, or a space-separated list of style class
 * names. See also st_widget_add_style_class_name() and
 * st_widget_remove_style_class_name().
 */
void
st_widget_set_style_class_name (StWidget    *actor,
                                const gchar *style_class_list)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));

  priv = st_widget_get_instance_private (actor);

  if (set_class_list (&priv->style_class, style_class_list))
    {
      st_widget_style_changed (actor);
      g_object_notify (G_OBJECT (actor), "style-class");
    }
}

/**
 * st_widget_add_style_class_name:
 * @actor: a #StWidget
 * @style_class: a style class name string
 *
 * Adds @style_class to @actor's style class name list, if it is not
 * already present.
 */
void
st_widget_add_style_class_name (StWidget    *actor,
                                const gchar *style_class)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));
  g_return_if_fail (style_class != NULL);

  priv = st_widget_get_instance_private (actor);

  if (add_class_name (&priv->style_class, style_class))
    {
      st_widget_style_changed (actor);
      g_object_notify (G_OBJECT (actor), "style-class");
    }
}

/**
 * st_widget_remove_style_class_name:
 * @actor: a #StWidget
 * @style_class: a style class name string
 *
 * Removes @style_class from @actor's style class name, if it is
 * present.
 */
void
st_widget_remove_style_class_name (StWidget    *actor,
                                   const gchar *style_class)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));
  g_return_if_fail (style_class != NULL);

  priv = st_widget_get_instance_private (actor);

  if (remove_class_name (&priv->style_class, style_class))
    {
      st_widget_style_changed (actor);
      g_object_notify (G_OBJECT (actor), "style-class");
    }
}

/**
 * st_widget_get_style_class_name:
 * @actor: a #StWidget
 *
 * Get the current style class name
 *
 * Returns: the class name string. The string is owned by the #StWidget and
 * should not be modified or freed.
 */
const gchar*
st_widget_get_style_class_name (StWidget *actor)
{
  g_return_val_if_fail (ST_IS_WIDGET (actor), NULL);

  return ST_WIDGET_PRIVATE (actor)->style_class;
}

/**
 * st_widget_has_style_class_name:
 * @actor: a #StWidget
 * @style_class: a style class string
 *
 * Tests if @actor's style class list includes @style_class.
 *
 * Returns: whether or not @actor's style class list includes
 * @style_class.
 */
gboolean
st_widget_has_style_class_name (StWidget    *actor,
                                const gchar *style_class)
{
  StWidgetPrivate *priv;

  g_return_val_if_fail (ST_IS_WIDGET (actor), FALSE);

  priv = st_widget_get_instance_private (actor);

  return find_class_name (priv->style_class, style_class) != NULL;
}

/**
 * st_widget_get_style_pseudo_class:
 * @actor: a #StWidget
 *
 * Get the current style pseudo class list.
 *
 * Note that an actor can have multiple pseudo classes; if you just
 * want to test for the presence of a specific pseudo class, use
 * st_widget_has_style_pseudo_class().
 *
 * Returns: the pseudo class list string. The string is owned by the
 * #StWidget and should not be modified or freed.
 */
const gchar*
st_widget_get_style_pseudo_class (StWidget *actor)
{
  g_return_val_if_fail (ST_IS_WIDGET (actor), NULL);

  return ST_WIDGET_PRIVATE (actor)->pseudo_class;
}

/**
 * st_widget_has_style_pseudo_class:
 * @actor: a #StWidget
 * @pseudo_class: a pseudo class string
 *
 * Tests if @actor's pseudo class list includes @pseudo_class.
 *
 * Returns: whether or not @actor's pseudo class list includes
 * @pseudo_class.
 */
gboolean
st_widget_has_style_pseudo_class (StWidget    *actor,
                                  const gchar *pseudo_class)
{
  StWidgetPrivate *priv;

  g_return_val_if_fail (ST_IS_WIDGET (actor), FALSE);

  priv = st_widget_get_instance_private (actor);

  return find_class_name (priv->pseudo_class, pseudo_class) != NULL;
}

/**
 * st_widget_set_style_pseudo_class:
 * @actor: a #StWidget
 * @pseudo_class_list: (nullable): a new pseudo class list string
 *
 * Set the style pseudo class list. @pseudo_class_list can either be
 * %NULL, for no classes, or a space-separated list of pseudo class
 * names. See also st_widget_add_style_pseudo_class() and
 * st_widget_remove_style_pseudo_class().
 */
void
st_widget_set_style_pseudo_class (StWidget    *actor,
                                  const gchar *pseudo_class_list)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));

  priv = st_widget_get_instance_private (actor);

  if (set_class_list (&priv->pseudo_class, pseudo_class_list))
    {
      st_widget_style_changed (actor);
      g_object_notify (G_OBJECT (actor), "pseudo-class");
    }
}

/**
 * st_widget_add_style_pseudo_class:
 * @actor: a #StWidget
 * @pseudo_class: a pseudo class string
 *
 * Adds @pseudo_class to @actor's pseudo class list, if it is not
 * already present.
 */
void
st_widget_add_style_pseudo_class (StWidget    *actor,
                                  const gchar *pseudo_class)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));
  g_return_if_fail (pseudo_class != NULL);

  priv = st_widget_get_instance_private (actor);

  if (add_class_name (&priv->pseudo_class, pseudo_class))
    {
      st_widget_style_changed (actor);
      g_object_notify (G_OBJECT (actor), "pseudo-class");
    }
}

/**
 * st_widget_remove_style_pseudo_class:
 * @actor: a #StWidget
 * @pseudo_class: a pseudo class string
 *
 * Removes @pseudo_class from @actor's pseudo class, if it is present.
 */
void
st_widget_remove_style_pseudo_class (StWidget    *actor,
                                     const gchar *pseudo_class)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));
  g_return_if_fail (pseudo_class != NULL);

  priv = st_widget_get_instance_private (actor);

  if (remove_class_name (&priv->pseudo_class, pseudo_class))
    {
      st_widget_style_changed (actor);
      g_object_notify (G_OBJECT (actor), "pseudo-class");
    }
}

/**
 * st_widget_set_style:
 * @actor: a #StWidget
 * @style: (nullable): a inline style string, or %NULL
 *
 * Set the inline style string for this widget. The inline style string is an
 * optional ';'-separated list of CSS properties that override the style as
 * determined from the stylesheets of the current theme.
 */
void
st_widget_set_style (StWidget  *actor,
                     const gchar *style)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (actor));

  priv = st_widget_get_instance_private (actor);

  if (g_strcmp0 (style, priv->inline_style))
    {
      g_free (priv->inline_style);
      priv->inline_style = g_strdup (style);

      st_widget_style_changed (actor);

      g_object_notify (G_OBJECT (actor), "style");
    }
}

/**
 * st_widget_get_style:
 * @actor: a #StWidget
 *
 * Get the current inline style string. See st_widget_set_style().
 *
 * Returns: The inline style string, or %NULL. The string is owned by the
 * #StWidget and should not be modified or freed.
 */
const gchar*
st_widget_get_style (StWidget *actor)
{
  g_return_val_if_fail (ST_IS_WIDGET (actor), NULL);

  return ST_WIDGET_PRIVATE (actor)->inline_style;
}

/**
 * st_widget_get_resource_scale:
 * @widget: A #StWidget
 * @resource_scale: (out): return location for the resource scale
 *
 * Retrieves the resource scale for this #StWidget, if available.
 *
 * The resource scale refers to the scale the actor should use for its resources.
 */
gboolean
st_widget_get_resource_scale (StWidget *widget,
                              float    *resource_scale)
{
  return clutter_actor_get_resource_scale (CLUTTER_ACTOR (widget),
                                           resource_scale);
}

static void
st_widget_set_first_visible_child (StWidget     *widget,
                                   ClutterActor *actor)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  if (priv->first_visible_child == NULL && actor == NULL)
    return;

  if (priv->first_visible_child != NULL &&
      CLUTTER_ACTOR (priv->first_visible_child) == actor)
    return;

  if (priv->first_visible_child != NULL)
    {
      st_widget_remove_style_pseudo_class (priv->first_visible_child, "first-child");
      g_clear_object (&priv->first_visible_child);
    }

  if (actor == NULL)
    return;

  if (ST_IS_WIDGET (actor))
    {
      st_widget_add_style_pseudo_class (ST_WIDGET (actor), "first-child");
      priv->first_visible_child = g_object_ref (ST_WIDGET (actor));
    }
}

static void
st_widget_set_last_visible_child (StWidget     *widget,
                                  ClutterActor *actor)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  if (priv->last_visible_child == NULL && actor == NULL)
    return;

  if (priv->last_visible_child != NULL &&
      CLUTTER_ACTOR (priv->last_visible_child) == actor)
    return;

  if (priv->last_visible_child != NULL)
    {
      st_widget_remove_style_pseudo_class (priv->last_visible_child, "last-child");
      g_clear_object (&priv->last_visible_child);
    }

  if (actor == NULL)
    return;

  if (ST_IS_WIDGET (actor))
    {
      st_widget_add_style_pseudo_class (ST_WIDGET (actor), "last-child");
      priv->last_visible_child = g_object_ref (ST_WIDGET (actor));
    }
}

static void
st_widget_name_notify (StWidget   *widget,
                       GParamSpec *pspec,
                       gpointer    data)
{
  st_widget_style_changed (widget);
}

static void
st_widget_resource_scale_notify (StWidget   *widget,
                                 GParamSpec *pspec,
                                 gpointer    data)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);
  int i;

  for (i = 0; i < G_N_ELEMENTS (priv->paint_states); i++)
    st_theme_node_paint_state_invalidate (&priv->paint_states[i]);

  g_signal_emit (widget, signals[RESOURCE_SCALE_CHANGED], 0);

  if (clutter_actor_is_mapped (CLUTTER_ACTOR (widget)))
    clutter_actor_queue_redraw (CLUTTER_ACTOR (widget));
}

static void
st_widget_reactive_notify (StWidget   *widget,
                           GParamSpec *pspec,
                           gpointer    data)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  if (clutter_actor_get_reactive (CLUTTER_ACTOR (widget)))
    st_widget_remove_style_pseudo_class (widget, "insensitive");
  else
    st_widget_add_style_pseudo_class (widget, "insensitive");

  if (priv->track_hover)
    st_widget_sync_hover(widget);
}

static ClutterActor *
find_nearest_visible_backwards (ClutterActor *actor)
{
  ClutterActor *prev = actor;

  while (prev != NULL && !clutter_actor_is_visible (prev))
    prev = clutter_actor_get_previous_sibling (prev);
  return prev;
}

static ClutterActor *
find_nearest_visible_forward (ClutterActor *actor)
{
  ClutterActor *next = actor;

  while (next != NULL && !clutter_actor_is_visible (next))
    next = clutter_actor_get_next_sibling (next);
  return next;
}

static void
st_widget_visible_notify (StWidget   *widget,
                          GParamSpec *pspec,
                          gpointer    data)
{
  ClutterActor *actor = CLUTTER_ACTOR (widget);
  ClutterActor *parent = clutter_actor_get_parent (actor);

  if (parent == NULL || !ST_IS_WIDGET (parent))
    return;

  if (clutter_actor_is_visible (actor))
    {
      ClutterActor *before, *after;

      before = clutter_actor_get_previous_sibling (actor);
      if (find_nearest_visible_backwards (before) == NULL)
        st_widget_set_first_visible_child (ST_WIDGET (parent), actor);

      after = clutter_actor_get_next_sibling (actor);
      if (find_nearest_visible_forward (after) == NULL)
        st_widget_set_last_visible_child (ST_WIDGET (parent), actor);
    }
  else
    {
      if (st_widget_has_style_pseudo_class (widget, "first-child"))
        {
          ClutterActor *new_first;

          new_first = find_nearest_visible_forward (CLUTTER_ACTOR (widget));
          st_widget_set_first_visible_child (ST_WIDGET (parent), new_first);
        }

      if (st_widget_has_style_pseudo_class (widget, "last-child"))
        {
          ClutterActor *new_last;

          new_last = find_nearest_visible_backwards (CLUTTER_ACTOR (widget));
          st_widget_set_last_visible_child (ST_WIDGET (parent), new_last);
        }
    }
}

static void
st_widget_first_child_notify (StWidget   *widget,
                              GParamSpec *pspec,
                              gpointer    data)
{
  ClutterActor *first_child;

  first_child = clutter_actor_get_first_child (CLUTTER_ACTOR (widget));
  st_widget_set_first_visible_child (widget, find_nearest_visible_forward (first_child));
}

static void
st_widget_last_child_notify (StWidget   *widget,
                             GParamSpec *pspec,
                             gpointer    data)
{
  ClutterActor *last_child;

  last_child = clutter_actor_get_last_child (CLUTTER_ACTOR (widget));
  st_widget_set_last_visible_child (widget, find_nearest_visible_backwards (last_child));
}

static void
st_widget_init (StWidget *actor)
{
  StWidgetPrivate *priv;
  guint i;

  priv = st_widget_get_instance_private (actor);
  priv->transition_animation = NULL;
  priv->local_state_set = atk_state_set_new ();

  /* connect style changed */
  g_signal_connect (actor, "notify::name", G_CALLBACK (st_widget_name_notify), NULL);
  g_signal_connect (actor, "notify::resource-scale", G_CALLBACK (st_widget_resource_scale_notify), NULL);
  g_signal_connect (actor, "notify::reactive", G_CALLBACK (st_widget_reactive_notify), NULL);

  g_signal_connect (actor, "notify::visible", G_CALLBACK (st_widget_visible_notify), NULL);
  g_signal_connect (actor, "notify::first-child", G_CALLBACK (st_widget_first_child_notify), NULL);
  g_signal_connect (actor, "notify::last-child", G_CALLBACK (st_widget_last_child_notify), NULL);
  priv->texture_file_changed_id = g_signal_connect (st_texture_cache_get_default (), "texture-file-changed",
                                                    G_CALLBACK (st_widget_texture_cache_changed), actor);

  for (i = 0; i < G_N_ELEMENTS (priv->paint_states); i++)
    st_theme_node_paint_state_init (&priv->paint_states[i]);
}

static void
on_transition_completed (StThemeNodeTransition *transition,
                         StWidget              *widget)
{
  next_paint_state (widget);

  st_theme_node_paint_state_copy (current_paint_state (widget),
                                  st_theme_node_transition_get_new_paint_state (transition));

  st_widget_remove_transition (widget);
}

static void
st_widget_recompute_style (StWidget    *widget,
                           StThemeNode *old_theme_node)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);
  StThemeNode *new_theme_node = st_widget_get_theme_node (widget);
  int transition_duration;
  StSettings *settings;
  gboolean paint_equal;
  gboolean animations_enabled;

  if (new_theme_node == old_theme_node)
    {
      priv->is_style_dirty = FALSE;
      return;
    }

  _st_theme_node_apply_margins (new_theme_node, CLUTTER_ACTOR (widget));

  if (!old_theme_node ||
      !st_theme_node_geometry_equal (old_theme_node, new_theme_node))
    clutter_actor_queue_relayout ((ClutterActor *) widget);

  transition_duration = st_theme_node_get_transition_duration (new_theme_node);

  paint_equal = st_theme_node_paint_equal (old_theme_node, new_theme_node);

  settings = st_settings_get ();
  g_object_get (settings, "enable-animations", &animations_enabled, NULL);

  if (animations_enabled && transition_duration > 0)
    {
      if (priv->transition_animation != NULL)
        {
          st_theme_node_transition_update (priv->transition_animation,
                                           new_theme_node);
        }
      else if (old_theme_node && !paint_equal)
        {
          /* Since our transitions are only of the painting done by StThemeNode, we
           * only want to start a transition when what is painted changes; if
           * other visual aspects like the foreground color of a label change,
           * we can't animate that anyways.
           */

          priv->transition_animation =
            st_theme_node_transition_new (old_theme_node,
                                          new_theme_node,
                                          current_paint_state (widget),
                                          transition_duration);

          g_signal_connect (priv->transition_animation, "completed",
                            G_CALLBACK (on_transition_completed), widget);
          g_signal_connect_swapped (priv->transition_animation,
                                    "new-frame",
                                    G_CALLBACK (clutter_actor_queue_redraw),
                                    widget);
        }
    }
  else if (priv->transition_animation)
    {
      st_widget_remove_transition (widget);
    }

  if (!paint_equal)
    {
      next_paint_state (widget);

      if (!st_theme_node_paint_equal (new_theme_node, current_paint_state (widget)->node))
        st_theme_node_paint_state_invalidate (current_paint_state (widget));
    }

  g_signal_emit (widget, signals[STYLE_CHANGED], 0);
  priv->is_style_dirty = FALSE;
}

/**
 * st_widget_ensure_style:
 * @widget: A #StWidget
 *
 * Ensures that @widget has read its style information.
 *
 */
void
st_widget_ensure_style (StWidget *widget)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (priv->is_style_dirty)
    st_widget_recompute_style (widget, NULL);
}

/**
 * st_widget_set_track_hover:
 * @widget: A #StWidget
 * @track_hover: %TRUE if the widget should track the pointer hover state
 *
 * Enables hover tracking on the #StWidget.
 *
 * If hover tracking is enabled, and the widget is visible and
 * reactive, then @widget's #StWidget:hover property will be updated
 * automatically to reflect whether the pointer is in @widget (or one
 * of its children), and @widget's #StWidget:pseudo-class will have
 * the "hover" class added and removed from it accordingly.
 *
 * Note that currently it is not possible to correctly track the hover
 * state when another actor has a pointer grab. You can use
 * st_widget_sync_hover() to update the property manually in this
 * case.
 */
void
st_widget_set_track_hover (StWidget *widget,
                           gboolean  track_hover)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (priv->track_hover != track_hover)
    {
      priv->track_hover = track_hover;
      g_object_notify (G_OBJECT (widget), "track-hover");

      if (priv->track_hover)
        st_widget_sync_hover (widget);
      else
        st_widget_set_hover (widget, FALSE);
    }
}

/**
 * st_widget_get_track_hover:
 * @widget: A #StWidget
 *
 * Returns the current value of the track-hover property. See
 * st_widget_set_track_hover() for more information.
 *
 * Returns: current value of track-hover on @widget
 */
gboolean
st_widget_get_track_hover (StWidget *widget)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), FALSE);

  return ST_WIDGET_PRIVATE (widget)->track_hover;
}

/**
 * st_widget_set_hover:
 * @widget: A #StWidget
 * @hover: whether the pointer is hovering over the widget
 *
 * Sets @widget's hover property and adds or removes "hover" from its
 * pseudo class accordingly.
 *
 * If you have set #StWidget:track-hover, you should not need to call
 * this directly. You can call st_widget_sync_hover() if the hover
 * state might be out of sync due to another actor's pointer grab.
 */
void
st_widget_set_hover (StWidget *widget,
                     gboolean  hover)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (priv->hover != hover)
    {
      priv->hover = hover;
      if (priv->hover)
        st_widget_add_style_pseudo_class (widget, "hover");
      else
        st_widget_remove_style_pseudo_class (widget, "hover");
      g_object_notify (G_OBJECT (widget), "hover");
    }
}

/**
 * st_widget_sync_hover:
 * @widget: A #StWidget
 *
 * Sets @widget's hover state according to the current pointer
 * position. This can be used to ensure that it is correct after
 * (or during) a pointer grab.
 */
void
st_widget_sync_hover (StWidget *widget)
{
  ClutterDeviceManager *device_manager;
  ClutterInputDevice *pointer;
  ClutterActor *pointer_actor;

  device_manager = clutter_device_manager_get_default ();
  pointer = clutter_device_manager_get_device (device_manager, VIRTUAL_CORE_POINTER_ID);
  pointer_actor = clutter_input_device_get_pointer_actor (pointer);
  if (pointer_actor && clutter_actor_get_reactive (CLUTTER_ACTOR (widget)))
    st_widget_set_hover (widget, clutter_actor_contains (CLUTTER_ACTOR (widget), pointer_actor));
  else
    st_widget_set_hover (widget, FALSE);
}

/**
 * st_widget_get_hover:
 * @widget: A #StWidget
 *
 * If #StWidget:track-hover is set, this returns whether the pointer
 * is currently over the widget.
 *
 * Returns: current value of hover on @widget
 */
gboolean
st_widget_get_hover (StWidget *widget)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), FALSE);

  return ST_WIDGET_PRIVATE (widget)->hover;
}

/**
 * st_widget_set_can_focus:
 * @widget: A #StWidget
 * @can_focus: %TRUE if the widget can receive keyboard focus
 *   via keyboard navigation
 *
 * Marks @widget as being able to receive keyboard focus via
 * keyboard navigation.
 */
void
st_widget_set_can_focus (StWidget *widget,
                         gboolean  can_focus)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (priv->can_focus != can_focus)
    {
      priv->can_focus = can_focus;
      g_object_notify (G_OBJECT (widget), "can-focus");
    }
}

/**
 * st_widget_get_can_focus:
 * @widget: A #StWidget
 *
 * Returns the current value of the can-focus property. See
 * st_widget_set_can_focus() for more information.
 *
 * Returns: current value of can-focus on @widget
 */
gboolean
st_widget_get_can_focus (StWidget *widget)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), FALSE);

  return ST_WIDGET_PRIVATE (widget)->can_focus;
}

/**
 * st_widget_popup_menu:
 * @self: A #StWidget
 *
 * Asks the widget to pop-up a context menu.
 */
void
st_widget_popup_menu (StWidget *self)
{
  g_signal_emit (self, signals[POPUP_MENU], 0);
}

/* filter @children to contain only only actors that overlap @rbox
 * when moving in @direction. (Assuming no transformations.)
 */
static GList *
filter_by_position (GList            *children,
                    ClutterActorBox  *rbox,
                    StDirectionType   direction)
{
  ClutterActorBox cbox;
  ClutterVertex abs_vertices[4];
  GList *l, *ret;
  ClutterActor *child;

  for (l = children, ret = NULL; l; l = l->next)
    {
      child = l->data;
      clutter_actor_get_abs_allocation_vertices (child, abs_vertices);
      clutter_actor_box_from_vertices (&cbox, abs_vertices);

      /* Filter out children if they are in the wrong direction from
       * @rbox, or if they don't overlap it. To account for floating-
       * point imprecision, an actor is "down" (etc.) from an another
       * actor even if it overlaps it by up to 0.1 pixels.
       */
      switch (direction)
        {
        case ST_DIR_UP:
          if (cbox.y2 > rbox->y1 + 0.1)
            continue;
          break;

        case ST_DIR_DOWN:
          if (cbox.y1 < rbox->y2 - 0.1)
            continue;
          break;

        case ST_DIR_LEFT:
          if (cbox.x2 > rbox->x1 + 0.1)
            continue;
          break;

        case ST_DIR_RIGHT:
          if (cbox.x1 < rbox->x2 - 0.1)
            continue;
          break;

        case ST_DIR_TAB_BACKWARD:
        case ST_DIR_TAB_FORWARD:
        default:
          g_return_val_if_reached (NULL);
        }

      ret = g_list_prepend (ret, child);
    }

  g_list_free (children);
  return ret;
}


static void
get_midpoint (ClutterActorBox *box,
              int             *x,
              int             *y)
{
  *x = (box->x1 + box->x2) / 2;
  *y = (box->y1 + box->y2) / 2;
}

static double
get_distance (ClutterActor    *actor,
              ClutterActorBox *bbox)
{
  int ax, ay, bx, by, dx, dy;
  ClutterActorBox abox;
  ClutterVertex abs_vertices[4];

  clutter_actor_get_abs_allocation_vertices (actor, abs_vertices);
  clutter_actor_box_from_vertices (&abox, abs_vertices);

  get_midpoint (&abox, &ax, &ay);
  get_midpoint (bbox, &bx, &by);
  dx = ax - bx;
  dy = ay - by;

  /* Not the exact distance, but good enough to sort by. */
  return dx*dx + dy*dy;
}

static int
sort_by_distance (gconstpointer  a,
                  gconstpointer  b,
                  gpointer       user_data)
{
  ClutterActor *actor_a = (ClutterActor *)a;
  ClutterActor *actor_b = (ClutterActor *)b;
  ClutterActorBox *box = user_data;

  return get_distance (actor_a, box) - get_distance (actor_b, box);
}

static gboolean
st_widget_real_navigate_focus (StWidget         *widget,
                               ClutterActor     *from,
                               StDirectionType   direction)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);
  ClutterActor *widget_actor, *focus_child;
  GList *children, *l;

  widget_actor = CLUTTER_ACTOR (widget);
  if (from == widget_actor)
    return FALSE;

  /* Figure out if @from is a descendant of @widget, and if so,
   * set @focus_child to the immediate child of @widget that
   * contains (or *is*) @from.
   */
  focus_child = from;
  while (focus_child && clutter_actor_get_parent (focus_child) != widget_actor)
    focus_child = clutter_actor_get_parent (focus_child);

  if (priv->can_focus)
    {
      if (!focus_child)
        {
          if (clutter_actor_is_mapped (widget_actor))
            {
              /* Accept focus from outside */
              clutter_actor_grab_key_focus (widget_actor);
              return TRUE;
            }
          else
            {
              /* Refuse to set focus on hidden actors */
              return FALSE;
            }
        }
      else
        {
          /* Yield focus from within: since @widget itself is
           * focusable we don't allow the focus to be navigated
           * within @widget.
           */
          return FALSE;
        }
    }

  /* See if we can navigate within @focus_child */
  if (focus_child && ST_IS_WIDGET (focus_child))
    {
      if (st_widget_navigate_focus (ST_WIDGET (focus_child), from, direction, FALSE))
        return TRUE;
    }

  children = st_widget_get_focus_chain (widget);
  if (direction == ST_DIR_TAB_FORWARD ||
      direction == ST_DIR_TAB_BACKWARD)
    {
      /* At this point we know that we want to navigate focus to one of
       * @widget's immediate children; the next one after @focus_child, or the
       * first one if @focus_child is %NULL. (With "next" and "first" being
       * determined by @direction.)
       */
      if (direction == ST_DIR_TAB_BACKWARD)
        children = g_list_reverse (children);

      if (focus_child)
        {
          /* Remove focus_child and any earlier children */
          while (children && children->data != focus_child)
            children = g_list_delete_link (children, children);
          if (children)
            children = g_list_delete_link (children, children);
        }
    }
  else /* direction is an arrow key, not tab */
    {
      ClutterActorBox sort_box;
      ClutterVertex abs_vertices[4];

      /* Compute the allocation box of the previous focused actor. If there
       * was no previous focus, use the coordinates of the appropriate edge of
       * @widget.
       *
       * Note that all of this code assumes the actors are not
       * transformed (or at most, they are all scaled by the same
       * amount). If @widget or any of its children is rotated, or
       * any child is inconsistently scaled, then the focus chain will
       * probably be unpredictable.
       */
      if (from)
        {
          clutter_actor_get_abs_allocation_vertices (from, abs_vertices);
          clutter_actor_box_from_vertices (&sort_box, abs_vertices);
        }
      else
        {
          clutter_actor_get_abs_allocation_vertices (widget_actor, abs_vertices);
          clutter_actor_box_from_vertices (&sort_box, abs_vertices);
          switch (direction)
            {
            case ST_DIR_UP:
              sort_box.y1 = sort_box.y2;
              break;
            case ST_DIR_DOWN:
              sort_box.y2 = sort_box.y1;
              break;
            case ST_DIR_LEFT:
              sort_box.x1 = sort_box.x2;
              break;
            case ST_DIR_RIGHT:
              sort_box.x2 = sort_box.x1;
              break;
            case ST_DIR_TAB_FORWARD:
            case ST_DIR_TAB_BACKWARD:
            default:
              g_warn_if_reached ();
            }
        }

      if (from)
        children = filter_by_position (children, &sort_box, direction);
      if (children)
        children = g_list_sort_with_data (children, sort_by_distance, &sort_box);
    }

  /* Now try each child in turn */
  for (l = children; l; l = l->next)
    {
      if (ST_IS_WIDGET (l->data))
        {
          if (st_widget_navigate_focus (l->data, from, direction, FALSE))
            {
              g_list_free (children);
              return TRUE;
            }
        }
    }

  g_list_free (children);
  return FALSE;
}


/**
 * st_widget_navigate_focus:
 * @widget: the "top level" container
 * @from: (nullable): the actor that the focus is coming from
 * @direction: the direction focus is moving in
 * @wrap_around: whether focus should wrap around
 *
 * Tries to update the keyboard focus within @widget in response to a
 * keyboard event.
 *
 * If @from is a descendant of @widget, this attempts to move the
 * keyboard focus to the next descendant of @widget (in the order
 * implied by @direction) that has the #StWidget:can-focus property
 * set. If @from is %NULL, this attempts to focus either @widget
 * itself, or its first descendant in the order implied by
 * @direction. If @from is outside of @widget, it behaves as if it was
 * a descendant if @direction is one of the directional arrows and as
 * if it was %NULL otherwise.
 *
 * If a container type is marked #StWidget:can-focus, the expected
 * behavior is that it will only take up a single slot on the focus
 * chain as a whole, rather than allowing navigation between its child
 * actors (or having a distinction between itself being focused and
 * one of its children being focused).
 *
 * Some widget classes might have slightly different behavior from the
 * above, where that would make more sense.
 *
 * If @wrap_around is %TRUE and @from is a child of @widget, but the
 * widget has no further children that can accept the focus in the
 * given direction, then st_widget_navigate_focus() will try a second
 * time, using a %NULL @from, which should cause it to reset the focus
 * to the first available widget in the given direction.
 *
 * Return value: %TRUE if clutter_actor_grab_key_focus() has been
 * called on an actor. %FALSE if not.
 */
gboolean
st_widget_navigate_focus (StWidget         *widget,
                          ClutterActor     *from,
                          StDirectionType   direction,
                          gboolean          wrap_around)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), FALSE);

  if (ST_WIDGET_GET_CLASS (widget)->navigate_focus (widget, from, direction))
    return TRUE;
  if (wrap_around && from && clutter_actor_contains (CLUTTER_ACTOR (widget), from))
    return ST_WIDGET_GET_CLASS (widget)->navigate_focus (widget, NULL, direction);
  return FALSE;
}

static gboolean
append_actor_text (GString      *desc,
                   ClutterActor *actor)
{
  if (CLUTTER_IS_TEXT (actor))
    {
      g_string_append_printf (desc, " (\"%s\")",
                              clutter_text_get_text (CLUTTER_TEXT (actor)));
      return TRUE;
    }
  else if (ST_IS_LABEL (actor))
    {
      g_string_append_printf (desc, " (\"%s\")",
                              st_label_get_text (ST_LABEL (actor)));
      return TRUE;
    }
  else
    return FALSE;
}

/**
 * st_describe_actor:
 * @actor: a #ClutterActor
 *
 * Creates a string describing @actor, for use in debugging. This
 * includes the class name and actor name (if any), plus if @actor
 * is an #StWidget, its style class and pseudo class names.
 *
 * Return value: the debug name.
 */
char *
st_describe_actor (ClutterActor *actor)
{
  GString *desc;
  const char *name;
  int i;

  if (!actor)
    return g_strdup ("[null]");

  desc = g_string_new (NULL);
  g_string_append_printf (desc, "[%p %s", actor,
                          G_OBJECT_TYPE_NAME (actor));

  if (ST_IS_WIDGET (actor))
    {
      const char *style_class = st_widget_get_style_class_name (ST_WIDGET (actor));
      const char *pseudo_class = st_widget_get_style_pseudo_class (ST_WIDGET (actor));
      char **classes;

      if (style_class)
        {
          classes = g_strsplit (style_class, ",", -1);
          for (i = 0; classes[i]; i++)
            {
              g_strchug (classes[i]);
              g_string_append_printf (desc, ".%s", classes[i]);
            }
          g_strfreev (classes);
        }

      if (pseudo_class)
        {
          classes = g_strsplit (pseudo_class, ",", -1);
          for (i = 0; classes[i]; i++)
            {
              g_strchug (classes[i]);
              g_string_append_printf (desc, ":%s", classes[i]);
            }
          g_strfreev (classes);
        }
    }

  name = clutter_actor_get_name (actor);
  if (name)
    g_string_append_printf (desc, " \"%s\"", name);

  if (!append_actor_text (desc, actor))
    {
      GList *children, *l;

      /* Do a limited search of @actor's children looking for a label */
      children = clutter_actor_get_children (actor);
      for (l = children, i = 0; l && i < 20; l = l->next, i++)
        {
          if (append_actor_text (desc, l->data))
            break;
          children = g_list_concat (children, clutter_actor_get_children (l->data));
        }
      g_list_free (children);
    }

  g_string_append_c (desc, ']');

  return g_string_free (desc, FALSE);
}

/**
 * st_set_slow_down_factor:
 * @factor: new slow-down factor
 *
 * Set a global factor applied to all animation durations
 */
void
st_set_slow_down_factor (gfloat factor)
{
  st_slow_down_factor = factor;
}

/**
 * st_get_slow_down_factor:
 *
 * Returns: the global factor applied to all animation durations
 */
gfloat
st_get_slow_down_factor (void)
{
  return st_slow_down_factor;
}


/**
 * st_widget_get_label_actor:
 * @widget: a #StWidget
 *
 * Gets the label that identifies @widget if it is defined
 *
 * Return value: (transfer none): the label that identifies the widget
 */
ClutterActor *
st_widget_get_label_actor (StWidget *widget)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), NULL);

  return ST_WIDGET_PRIVATE (widget)->label_actor;
}

/**
 * st_widget_set_label_actor:
 * @widget: a #StWidget
 * @label: a #ClutterActor
 *
 * Sets @label as the #ClutterActor that identifies (labels)
 * @widget. @label can be %NULL to indicate that @widget is not
 * labelled any more
 */

void
st_widget_set_label_actor (StWidget     *widget,
                           ClutterActor *label)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (priv->label_actor != label)
    {
      if (priv->label_actor)
        g_object_unref (priv->label_actor);

      if (label != NULL)
        priv->label_actor = g_object_ref (label);
      else
        priv->label_actor = NULL;

      g_object_notify (G_OBJECT (widget), "label-actor");
    }
}

/**
 * st_widget_set_accessible_name:
 * @widget: widget to set the accessible name for
 * @name: (nullable): a character string to be set as the accessible name
 *
 * This method sets @name as the accessible name for @widget.
 *
 * Usually you will have no need to set the accessible name for an
 * object, as usually there is a label for most of the interface
 * elements. So in general it is better to just use
 * @st_widget_set_label_actor. This method is only required when you
 * need to set an accessible name and there is no available label
 * object.
 *
 */
void
st_widget_set_accessible_name (StWidget    *widget,
                               const gchar *name)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (priv->accessible_name != NULL)
    g_free (priv->accessible_name);

  priv->accessible_name = g_strdup (name);
  g_object_notify (G_OBJECT (widget), "accessible-name");
}

/**
 * st_widget_get_accessible_name:
 * @widget: widget to get the accessible name for
 *
 * Gets the accessible name for this widget. See
 * st_widget_set_accessible_name() for more information.
 *
 * Return value: a character string representing the accessible name
 * of the widget.
 */
const gchar *
st_widget_get_accessible_name (StWidget    *widget)
{
  g_return_val_if_fail (ST_IS_WIDGET (widget), NULL);

  return ST_WIDGET_PRIVATE (widget)->accessible_name;
}

/**
 * st_widget_set_accessible_role:
 * @widget: widget to set the accessible role for
 * @role: The role to use
 *
 * This method sets @role as the accessible role for @widget. This
 * role describes what kind of user interface element @widget is and
 * is provided so that assistive technologies know how to present
 * @widget to the user.
 *
 * Usually you will have no need to set the accessible role for an
 * object, as this information is extracted from the context of the
 * object (ie: a #StButton has by default a push button role). This
 * method is only required when you need to redefine the role
 * currently associated with the widget, for instance if it is being
 * used in an unusual way (ie: a #StButton used as a togglebutton), or
 * if a generic object is used directly (ie: a container as a menu
 * item).
 *
 * If @role is #ATK_ROLE_INVALID, the role will not be changed
 * and the accessible's default role will be used instead.
 */
void
st_widget_set_accessible_role (StWidget *widget,
                               AtkRole   role)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);
  priv->accessible_role = role;

  g_object_notify (G_OBJECT (widget), "accessible-role");
}


/**
 * st_widget_get_accessible_role:
 * @widget: widget to get the accessible role for
 *
 * Gets the #AtkRole for this widget. See
 * st_widget_set_accessible_role() for more information.
 *
 * Return value: accessible #AtkRole for this widget
 */
AtkRole
st_widget_get_accessible_role (StWidget *widget)
{
  StWidgetPrivate *priv;
  AtkRole role = ATK_ROLE_INVALID;

  g_return_val_if_fail (ST_IS_WIDGET (widget), ATK_ROLE_INVALID);

  priv = st_widget_get_instance_private (widget);

  if (priv->accessible_role != ATK_ROLE_INVALID)
    role = priv->accessible_role;
  else if (priv->accessible != NULL)
    role = atk_object_get_role (priv->accessible);

  return role;
}

static void
notify_accessible_state_change (StWidget     *widget,
                                AtkStateType  state,
                                gboolean      value)
{
  StWidgetPrivate *priv = st_widget_get_instance_private (widget);

  if (priv->accessible != NULL)
    atk_object_notify_state_change (priv->accessible, state, value);
}

/**
 * st_widget_add_accessible_state:
 * @widget: A #StWidget
 * @state: #AtkStateType state to add
 *
 * This method adds @state as one of the accessible states for
 * @widget. The list of states of a widget describes the current state
 * of user interface element @widget and is provided so that assistive
 * technologies know how to present @widget to the user.
 *
 * Usually you will have no need to add accessible states for an
 * object, as the accessible object can extract most of the states
 * from the object itself (ie: a #StButton knows when it is pressed).
 * This method is only required when one cannot extract the
 * information automatically from the object itself (i.e.: a generic
 * container used as a toggle menu item will not automatically include
 * the toggled state).
 *
 */
void
st_widget_add_accessible_state (StWidget    *widget,
                                AtkStateType state)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (atk_state_set_add_state (priv->local_state_set, state))
    notify_accessible_state_change (widget, state, TRUE);
}

/**
 * st_widget_remove_accessible_state:
 * @widget: A #StWidget
 * @state: #AtkState state to remove
 *
 * This method removes @state as on of the accessible states for
 * @widget. See st_widget_add_accessible_state() for more information.
 *
 */
void
st_widget_remove_accessible_state (StWidget    *widget,
                                   AtkStateType state)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));

  priv = st_widget_get_instance_private (widget);

  if (atk_state_set_remove_state (priv->local_state_set, state))
    notify_accessible_state_change (widget, state, FALSE);
}

/******************************************************************************/
/*************************** ACCESSIBILITY SUPPORT ****************************/
/******************************************************************************/

/* GObject */

static void st_widget_accessible_dispose    (GObject *gobject);

/* AtkObject */
static AtkStateSet *st_widget_accessible_ref_state_set (AtkObject *obj);
static void         st_widget_accessible_initialize    (AtkObject *obj,
                                                        gpointer   data);
static AtkRole      st_widget_accessible_get_role      (AtkObject *obj);

/* Private methods */
static void on_pseudo_class_notify (GObject    *gobject,
                                    GParamSpec *pspec,
                                    gpointer    data);
static void on_can_focus_notify    (GObject    *gobject,
                                    GParamSpec *pspec,
                                    gpointer    data);
static void on_label_notify        (GObject    *gobject,
                                    GParamSpec *pspec,
                                    gpointer    data);
static void check_pseudo_class     (StWidgetAccessible *self,
                                    StWidget *widget);
static void check_labels           (StWidgetAccessible *self,
                                    StWidget *widget);

struct _StWidgetAccessiblePrivate
{
  /* Cached values (used to avoid extra notifications) */
  gboolean selected;
  gboolean checked;

  /* The current_label. Right now there are the proper atk
   * relationships between this object and the label
   */
  AtkObject *current_label;
};

G_DEFINE_TYPE_WITH_PRIVATE (StWidgetAccessible, st_widget_accessible, CALLY_TYPE_ACTOR)

static AtkObject *
st_widget_get_accessible (ClutterActor *actor)
{
  StWidget *widget = NULL;
  StWidgetPrivate *priv;

  g_return_val_if_fail (ST_IS_WIDGET (actor), NULL);

  widget = ST_WIDGET (actor);
  priv = st_widget_get_instance_private (widget);

  if (priv->accessible == NULL)
    {
      priv->accessible =
        g_object_new (ST_WIDGET_GET_CLASS (widget)->get_accessible_type (),
                      NULL);

      atk_object_initialize (priv->accessible, actor);

      /* AtkGObjectAccessible, which StWidgetAccessible derives from, clears
       * the back reference to the object in a weak notify for the object;
       * weak-ref notification, which occurs during g_object_real_dispose(),
       * is then the optimal time to clear the forward reference. We
       * can't clear the reference in dispose() before chaining up, since
       * clutter_actor_dispose() causes notifications to be sent out, which
       * will result in a new accessible object being created.
       */
      g_object_add_weak_pointer (G_OBJECT (actor),
                                 (gpointer *)&priv->accessible);
    }

  return priv->accessible;
}

/**
 * st_widget_set_accessible:
 * @widget: A #StWidget
 * @accessible: an accessible (#AtkObject)
 *
 * This method allows to set a customly created accessible object to
 * this widget. For example if you define a new subclass of
 * #StWidgetAccessible at the javascript code.
 *
 * NULL is a valid value for @accessible. That contemplates the
 * hypothetical case of not needing anymore a custom accessible object
 * for the widget. Next call of st_widget_get_accessible() would
 * create and return a default accessible.
 *
 * It assumes that the call to atk_object_initialize that bound the
 * gobject with the custom accessible object was already called, so
 * not a responsibility of this method.
 *
 */
void
st_widget_set_accessible (StWidget    *widget,
                          AtkObject   *accessible)
{
  StWidgetPrivate *priv;

  g_return_if_fail (ST_IS_WIDGET (widget));
  g_return_if_fail (accessible == NULL || ATK_IS_GOBJECT_ACCESSIBLE (accessible));

  priv = st_widget_get_instance_private (widget);

  if (priv->accessible != accessible)
    {
      if (priv->accessible)
        {
          g_object_remove_weak_pointer (G_OBJECT (widget),
                                        (gpointer *)&priv->accessible);
          g_object_unref (priv->accessible);
          priv->accessible = NULL;
        }

      if (accessible)
        {
          priv->accessible =  g_object_ref (accessible);
          /* See note in st_widget_get_accessible() */
          g_object_add_weak_pointer (G_OBJECT (widget),
                                     (gpointer *)&priv->accessible);
        }
      else
        priv->accessible = NULL;
    }
}

static const gchar *
st_widget_accessible_get_name (AtkObject *obj)
{
  const gchar* name = NULL;

  g_return_val_if_fail (ST_IS_WIDGET_ACCESSIBLE (obj), NULL);

  name = ATK_OBJECT_CLASS (st_widget_accessible_parent_class)->get_name (obj);
  if (name == NULL)
    {
      StWidget *widget = NULL;

      widget = ST_WIDGET (atk_gobject_accessible_get_object (ATK_GOBJECT_ACCESSIBLE (obj)));

      if (widget == NULL)
        name = NULL;
      else
        name = st_widget_get_accessible_name (widget);
    }

  return name;
}

static void
st_widget_accessible_class_init (StWidgetAccessibleClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  AtkObjectClass *atk_class = ATK_OBJECT_CLASS (klass);

  gobject_class->dispose = st_widget_accessible_dispose;

  atk_class->ref_state_set = st_widget_accessible_ref_state_set;
  atk_class->initialize = st_widget_accessible_initialize;
  atk_class->get_role = st_widget_accessible_get_role;
  atk_class->get_name = st_widget_accessible_get_name;
}

static void
st_widget_accessible_init (StWidgetAccessible *self)
{
  StWidgetAccessiblePrivate *priv = st_widget_accessible_get_instance_private (self);

  self->priv = priv;
}

static void
st_widget_accessible_dispose (GObject *gobject)
{
  StWidgetAccessible *self = ST_WIDGET_ACCESSIBLE (gobject);

  if (self->priv->current_label)
    {
      g_object_unref (self->priv->current_label);
      self->priv->current_label = NULL;
    }

  G_OBJECT_CLASS (st_widget_accessible_parent_class)->dispose (gobject);
}

static void
on_accessible_name_notify (GObject    *gobject,
                           GParamSpec *pspec,
                           AtkObject  *accessible)
{
  g_object_notify (G_OBJECT (accessible), "accessible-name");
}

static void
st_widget_accessible_initialize (AtkObject *obj,
                                 gpointer   data)
{
  ATK_OBJECT_CLASS (st_widget_accessible_parent_class)->initialize (obj, data);

  g_signal_connect (data, "notify::pseudo-class",
                    G_CALLBACK (on_pseudo_class_notify),
                    obj);

  g_signal_connect (data, "notify::can-focus",
                    G_CALLBACK (on_can_focus_notify),
                    obj);

  g_signal_connect (data, "notify::label-actor",
                    G_CALLBACK (on_label_notify),
                    obj);

  g_signal_connect (data, "notify::accessible-name",
                    G_CALLBACK (on_accessible_name_notify),
                    obj);

  /* Check the cached selected state and notify the first selection.
   * Ie: it is required to ensure a first notification when Alt+Tab
   * popup appears
   */
  check_pseudo_class (ST_WIDGET_ACCESSIBLE (obj), ST_WIDGET (data));
  check_labels (ST_WIDGET_ACCESSIBLE (obj), ST_WIDGET (data));
}

static AtkStateSet *
st_widget_accessible_ref_state_set (AtkObject *obj)
{
  AtkStateSet *result = NULL;
  AtkStateSet *aux_set = NULL;
  ClutterActor *actor = NULL;
  StWidget *widget = NULL;
  StWidgetPrivate *widget_priv;
  StWidgetAccessible *self = NULL;

  result = ATK_OBJECT_CLASS (st_widget_accessible_parent_class)->ref_state_set (obj);

  actor = CLUTTER_ACTOR (atk_gobject_accessible_get_object (ATK_GOBJECT_ACCESSIBLE (obj)));

  if (actor == NULL) /* State is defunct */
    return result;

  widget = ST_WIDGET (actor);
  self = ST_WIDGET_ACCESSIBLE (obj);
  widget_priv = st_widget_get_instance_private (widget);

  /* priv->selected should be properly updated on the
   * ATK_STATE_SELECTED notification callbacks
   */
  if (self->priv->selected)
    atk_state_set_add_state (result, ATK_STATE_SELECTED);

  if (self->priv->checked)
    atk_state_set_add_state (result, ATK_STATE_CHECKED);

  /* On clutter there isn't any tip to know if a actor is focusable or
   * not, anyone can receive the key_focus. For this reason
   * cally_actor sets any actor as FOCUSABLE. This is not the case on
   * St, where we have can_focus. But this means that we need to
   * remove the state FOCUSABLE if it is not focusable
   */
  if (st_widget_get_can_focus (widget))
    atk_state_set_add_state (result, ATK_STATE_FOCUSABLE);
  else
    atk_state_set_remove_state (result, ATK_STATE_FOCUSABLE);

  /* We add the states added externally if required */
  if (!atk_state_set_is_empty (widget_priv->local_state_set))
    {
      aux_set = atk_state_set_or_sets (result, widget_priv->local_state_set);

      g_object_unref (result); /* previous result will not be used */
      result = aux_set;
    }

  return result;
}

static AtkRole
st_widget_accessible_get_role (AtkObject *obj)
{
  StWidget *widget = NULL;
  StWidgetPrivate *priv;

  g_return_val_if_fail (ST_IS_WIDGET_ACCESSIBLE (obj), ATK_ROLE_INVALID);

  widget = ST_WIDGET (atk_gobject_accessible_get_object (ATK_GOBJECT_ACCESSIBLE (obj)));

  if (widget == NULL)
    return ATK_ROLE_INVALID;

  priv = st_widget_get_instance_private (widget);
  if (priv->accessible_role != ATK_ROLE_INVALID)
    return priv->accessible_role;

  return ATK_OBJECT_CLASS (st_widget_accessible_parent_class)->get_role (obj);
}

static void
on_pseudo_class_notify (GObject    *gobject,
                        GParamSpec *pspec,
                        gpointer    data)
{
  check_pseudo_class (ST_WIDGET_ACCESSIBLE (data),
                      ST_WIDGET (gobject));
}

/*
 * In some cases the only way to check some states are checking the
 * pseudo-class. Like if the object is selected (see bug 637830) or if
 * the object is toggled. This method also notifies a state change if
 * the value is different to the one cached.
 *
 * We also assume that if the object uses that pseudo-class, it makes
 * sense to notify that state change. It would be possible to refine
 * that behaviour checking the role (ie: notify CHECKED changes only
 * for CHECK_BUTTON roles).
 *
 * In a ideal world we would have a more standard way to get the
 * state, like the widget-context (as in the case of
 * gtktreeview-cells), or something like the property "can-focus". But
 * for the moment this is enough, and we can update that in the future
 * if required.
 */
static void
check_pseudo_class (StWidgetAccessible *self,
                    StWidget *widget)
{
  gboolean found = FALSE;

  found = st_widget_has_style_pseudo_class (widget,
                                            "selected");

  if (found != self->priv->selected)
    {
      self->priv->selected = found;
      atk_object_notify_state_change (ATK_OBJECT (self),
                                      ATK_STATE_SELECTED,
                                      found);
    }

  found = st_widget_has_style_pseudo_class (widget,
                                            "checked");
  if (found != self->priv->checked)
    {
      self->priv->checked = found;
      atk_object_notify_state_change (ATK_OBJECT (self),
                                      ATK_STATE_CHECKED,
                                      found);
    }
}

static void
on_can_focus_notify (GObject    *gobject,
                     GParamSpec *pspec,
                     gpointer    data)
{
  gboolean can_focus = st_widget_get_can_focus (ST_WIDGET (gobject));

  atk_object_notify_state_change (ATK_OBJECT (data),
                                  ATK_STATE_FOCUSABLE, can_focus);
}

static void
on_label_notify (GObject    *gobject,
                 GParamSpec *pspec,
                 gpointer    data)
{
  check_labels (ST_WIDGET_ACCESSIBLE (data), ST_WIDGET (gobject));
}

static void
check_labels (StWidgetAccessible *widget_accessible,
              StWidget           *widget)
{
  ClutterActor *label = NULL;
  AtkObject *label_accessible = NULL;

  /* We only call this method at startup, and when the label changes,
   * so it is fine to remove the previous relationships if we have the
   * current_label by default
   */
  if (widget_accessible->priv->current_label != NULL)
    {
      AtkObject *previous_label = widget_accessible->priv->current_label;

      atk_object_remove_relationship (ATK_OBJECT (widget_accessible),
                                      ATK_RELATION_LABELLED_BY,
                                      previous_label);

      atk_object_remove_relationship (previous_label,
                                      ATK_RELATION_LABEL_FOR,
                                      ATK_OBJECT (widget_accessible));

      g_object_unref (previous_label);
    }

  label = st_widget_get_label_actor (widget);
  if (label == NULL)
    {
      widget_accessible->priv->current_label = NULL;
    }
  else
    {
      label_accessible = clutter_actor_get_accessible (label);
      widget_accessible->priv->current_label = g_object_ref (label_accessible);

      atk_object_add_relationship (ATK_OBJECT (widget_accessible),
                                   ATK_RELATION_LABELLED_BY,
                                   label_accessible);

      atk_object_add_relationship (label_accessible,
                                   ATK_RELATION_LABEL_FOR,
                                   ATK_OBJECT (widget_accessible));
    }
}

/**
 * st_widget_get_focus_chain:
 * @widget: An #StWidget
 *
 * Gets a list of the focusable children of @widget, in "Tab"
 * order. By default, this returns all visible
 * (as in clutter_actor_is_visible()) children of @widget.
 *
 * Returns: (element-type Clutter.Actor) (transfer container):
 *   @widget's focusable children
 */
GList *
st_widget_get_focus_chain (StWidget *widget)
{
  return ST_WIDGET_GET_CLASS (widget)->get_focus_chain (widget);
}

/**
 * st_get_align_factors:
 * @x_align: an #StAlign
 * @y_align: an #StAlign
 * @x_align_out: (out) (optional): @x_align as a #gdouble
 * @y_align_out: (out) (optional): @y_align as a #gdouble
 *
 * Converts @x_align and @y_align to #gdouble values.
 */
void
st_get_align_factors (StAlign   x_align,
                      StAlign   y_align,
                      gdouble  *x_align_out,
                      gdouble  *y_align_out)
{
  if (x_align_out)
    {
      switch (x_align)
        {
        case ST_ALIGN_START:
          *x_align_out = 0.0;
          break;

        case ST_ALIGN_MIDDLE:
          *x_align_out = 0.5;
          break;

        case ST_ALIGN_END:
          *x_align_out = 1.0;
          break;

        default:
          g_warn_if_reached ();
          break;
        }
    }

  if (y_align_out)
    {
      switch (y_align)
        {
        case ST_ALIGN_START:
          *y_align_out = 0.0;
          break;

        case ST_ALIGN_MIDDLE:
          *y_align_out = 0.5;
          break;

        case ST_ALIGN_END:
          *y_align_out = 1.0;
          break;

        default:
          g_warn_if_reached ();
          break;
        }
    }
}