/*
 * gtkoverlay.c
 * This file is part of gtk
 *
 * Copyright (C) 2011 - Ignacio Casal Quinteiro, Mike Krüger
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include "gtkoverlay.h"
#include "gtkbuildable.h"
#include "gtkscrolledwindow.h"
#include "gtkmarshalers.h"

#include "gtkprivate.h"
#include "gtkintl.h"

/**
 * SECTION:gtkoverlay
 * @short_description: A container which overlays widgets on top of each other
 * @title: GtkOverlay
 *
 * GtkOverlay is a container which contains a single main child, on top
 * of which it can place “overlay” widgets. The
 * position of each overlay widget is determined by its #GtkWidget:halign
 * and #GtkWidget:valign properties. E.g. a widget with both alignments
 * set to %GTK_ALIGN_START will be placed at the top left corner of the
 * main widget, whereas an overlay with halign set to %GTK_ALIGN_CENTER
 * and valign set to %GTK_ALIGN_END will be placed a the bottom edge of
 * the main widget, horizontally centered. The position can be adjusted
 * by setting the margin properties of the child to non-zero values.
 *
 * More complicated placement of overlays is possible by connecting
 * to the #GtkOverlay::get-child-position signal.
 *
 * # GtkOverlay as GtkBuildable
 *
 * The GtkOverlay implementation of the GtkBuildable interface
 * supports placing a child as an overlay by specifying “overlay” as
 * the “type” attribute of a `<child>` element.
 */

struct _GtkOverlayPrivate
{
  GSList *children;
};

typedef struct _GtkOverlayChild GtkOverlayChild;

struct _GtkOverlayChild
{
  GtkWidget *widget;
  GdkWindow *window;
};

enum {
  GET_CHILD_POSITION,
  LAST_SIGNAL
};

static guint signals[LAST_SIGNAL] = { 0 };

static void gtk_overlay_buildable_init (GtkBuildableIface *iface);

G_DEFINE_TYPE_WITH_CODE (GtkOverlay, gtk_overlay, GTK_TYPE_BIN,
                         G_ADD_PRIVATE (GtkOverlay)
                         G_IMPLEMENT_INTERFACE (GTK_TYPE_BUILDABLE,
                                                gtk_overlay_buildable_init))

static void
gtk_overlay_compute_child_allocation (GtkOverlay      *overlay,
				      GtkOverlayChild *child,
				      GtkAllocation *window_allocation,
				      GtkAllocation *widget_allocation)
{
  gint left, right, top, bottom;
  GtkAllocation allocation, overlay_allocation;
  gboolean result;

  g_signal_emit (overlay, signals[GET_CHILD_POSITION],
                 0, child->widget, &allocation, &result);

  gtk_widget_get_allocation (GTK_WIDGET (overlay), &overlay_allocation);

  allocation.x += overlay_allocation.x;
  allocation.y += overlay_allocation.y;

  /* put the margins outside the window; also arrange things
   * so that the adjusted child allocation still ends up at 0, 0
   */
  left = gtk_widget_get_margin_start (child->widget);
  right = gtk_widget_get_margin_end (child->widget);
  top = gtk_widget_get_margin_top (child->widget);
  bottom = gtk_widget_get_margin_bottom (child->widget);

  if (widget_allocation)
    {
      widget_allocation->x = - left;
      widget_allocation->y = - top;
      widget_allocation->width = allocation.width;
      widget_allocation->height = allocation.height;
    }

  if (window_allocation)
    {
      window_allocation->x = allocation.x + left;
      window_allocation->y = allocation.y + top;
      window_allocation->width = allocation.width - (left + right);
      window_allocation->height = allocation.height - (top + bottom);
    }
}

static GdkWindow *
gtk_overlay_create_child_window (GtkOverlay *overlay,
                                 GtkOverlayChild *child)
{
  GtkWidget *widget = GTK_WIDGET (overlay);
  GtkAllocation allocation;
  GdkWindow *window;
  GdkWindowAttr attributes;
  gint attributes_mask;

  gtk_overlay_compute_child_allocation (overlay, child, &allocation, NULL);

  attributes.window_type = GDK_WINDOW_CHILD;
  attributes.wclass = GDK_INPUT_OUTPUT;
  attributes.width = allocation.width;
  attributes.height = allocation.height;
  attributes.x = allocation.x;
  attributes.y = allocation.y;
  attributes.visual = gtk_widget_get_visual (widget);
  attributes_mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL;
  attributes.event_mask = gtk_widget_get_events (widget) | GDK_EXPOSURE_MASK;

  window = gdk_window_new (gtk_widget_get_window (widget),
                           &attributes, attributes_mask);
  gtk_widget_register_window (widget, window);
  gtk_style_context_set_background (gtk_widget_get_style_context (widget), window);

  gtk_widget_set_parent_window (child->widget, window);
  
  return window;
}

static GtkAlign
effective_align (GtkAlign         align,
                 GtkTextDirection direction)
{
  switch (align)
    {
    case GTK_ALIGN_START:
      return direction == GTK_TEXT_DIR_RTL ? GTK_ALIGN_END : GTK_ALIGN_START;
    case GTK_ALIGN_END:
      return direction == GTK_TEXT_DIR_RTL ? GTK_ALIGN_START : GTK_ALIGN_END;
    default:
      return align;
    }
}

static void
gtk_overlay_get_main_widget_allocation (GtkOverlay *overlay,
                                        GtkAllocation *main_alloc_out)
{
  GtkWidget *main_widget;
  GtkAllocation main_alloc;

  main_widget = gtk_bin_get_child (GTK_BIN (overlay));

  /* special-case scrolled windows */
  if (GTK_IS_SCROLLED_WINDOW (main_widget))
    {
      GtkWidget *grandchild;
      gint x, y;
      gboolean res;

      grandchild = gtk_bin_get_child (GTK_BIN (main_widget));
      res = gtk_widget_translate_coordinates (grandchild, main_widget, 0, 0, &x, &y);

      if (res)
        {
          main_alloc.x = x;
          main_alloc.y = y;
        }
      else
        {
          main_alloc.x = 0;
          main_alloc.y = 0;
        }

      main_alloc.width = gtk_widget_get_allocated_width (grandchild);
      main_alloc.height = gtk_widget_get_allocated_height (grandchild);
    }
  else
    {
      main_alloc.x = 0;
      main_alloc.y = 0;
      main_alloc.width = gtk_widget_get_allocated_width (main_widget);
      main_alloc.height = gtk_widget_get_allocated_height (main_widget);
    }

  if (main_alloc_out)
    *main_alloc_out = main_alloc;
}

static void
gtk_overlay_child_update_style_classes (GtkOverlay *overlay,
                                        GtkWidget *child,
                                        GtkAllocation *child_allocation)
{
  GtkAllocation overlay_allocation, main_allocation;
  GtkAlign valign, halign;
  gboolean is_left, is_right, is_top, is_bottom;
  gboolean has_left, has_right, has_top, has_bottom;
  GtkStyleContext *context;

  context = gtk_widget_get_style_context (child);
  has_left = gtk_style_context_has_class (context, GTK_STYLE_CLASS_LEFT);
  has_right = gtk_style_context_has_class (context, GTK_STYLE_CLASS_RIGHT);
  has_top = gtk_style_context_has_class (context, GTK_STYLE_CLASS_TOP);
  has_bottom = gtk_style_context_has_class (context, GTK_STYLE_CLASS_BOTTOM);

  is_left = is_right = is_top = is_bottom = FALSE;

  gtk_overlay_get_main_widget_allocation (overlay, &main_allocation);
  gtk_widget_get_allocation (GTK_WIDGET (overlay), &overlay_allocation);

  main_allocation.x += overlay_allocation.x;
  main_allocation.y += overlay_allocation.y;

  halign = effective_align (gtk_widget_get_halign (child),
                            gtk_widget_get_direction (child));

  if (halign == GTK_ALIGN_START)
    is_left = (child_allocation->x == main_allocation.x);
  else if (halign == GTK_ALIGN_END)
    is_right = (child_allocation->x + child_allocation->width ==
                main_allocation.x + main_allocation.width);

  valign = gtk_widget_get_valign (child);

  if (valign == GTK_ALIGN_START)
    is_top = (child_allocation->y == main_allocation.y);
  else if (valign == GTK_ALIGN_END)
    is_bottom = (child_allocation->y + child_allocation->height ==
                 main_allocation.y + main_allocation.height);

  if (has_left && !is_left)
    gtk_style_context_remove_class (context, GTK_STYLE_CLASS_LEFT);
  else if (!has_left && is_left)
    gtk_style_context_add_class (context, GTK_STYLE_CLASS_LEFT);

  if (has_right && !is_right)
    gtk_style_context_remove_class (context, GTK_STYLE_CLASS_RIGHT);
  else if (!has_right && is_right)
    gtk_style_context_add_class (context, GTK_STYLE_CLASS_RIGHT);

  if (has_top && !is_top)
    gtk_style_context_remove_class (context, GTK_STYLE_CLASS_TOP);
  else if (!has_top && is_top)
    gtk_style_context_add_class (context, GTK_STYLE_CLASS_TOP);

  if (has_bottom && !is_bottom)
    gtk_style_context_remove_class (context, GTK_STYLE_CLASS_BOTTOM);
  else if (!has_bottom && is_bottom)
    gtk_style_context_add_class (context, GTK_STYLE_CLASS_BOTTOM);
}

static void
gtk_overlay_child_allocate (GtkOverlay      *overlay,
                            GtkOverlayChild *child)
{
  GtkAllocation window_allocation, child_allocation;

  if (gtk_widget_get_mapped (GTK_WIDGET (overlay)))
    {
      if (gtk_widget_get_visible (child->widget))
        gdk_window_show (child->window);
      else if (gdk_window_is_visible (child->window))
        gdk_window_hide (child->window);
    }

  if (!gtk_widget_get_visible (child->widget))
    return;

  gtk_overlay_compute_child_allocation (overlay, child, &window_allocation, &child_allocation);

  if (child->window)
    gdk_window_move_resize (child->window,
                            window_allocation.x, window_allocation.y,
                            window_allocation.width, window_allocation.height);

  gtk_overlay_child_update_style_classes (overlay, child->widget, &window_allocation);
  gtk_widget_size_allocate (child->widget, &child_allocation);
}

static void
gtk_overlay_size_allocate (GtkWidget     *widget,
                           GtkAllocation *allocation)
{
  GtkOverlay *overlay = GTK_OVERLAY (widget);
  GtkOverlayPrivate *priv = overlay->priv;
  GSList *children;
  GtkWidget *main_widget;

  GTK_WIDGET_CLASS (gtk_overlay_parent_class)->size_allocate (widget, allocation);

  main_widget = gtk_bin_get_child (GTK_BIN (overlay));
  if (!main_widget || !gtk_widget_get_visible (main_widget))
    return;

  gtk_widget_size_allocate (main_widget, allocation);

  for (children = priv->children; children; children = children->next)
    gtk_overlay_child_allocate (overlay, children->data);
}

static gboolean
gtk_overlay_get_child_position (GtkOverlay    *overlay,
                                GtkWidget     *widget,
                                GtkAllocation *alloc)
{
  GtkAllocation main_alloc;
  GtkRequisition min, req;
  GtkAlign halign;
  GtkTextDirection direction;

  gtk_overlay_get_main_widget_allocation (overlay, &main_alloc);
  gtk_widget_get_preferred_size (widget, &min, &req);

  alloc->x = main_alloc.x;
  alloc->width = MAX (min.width, MIN (main_alloc.width, req.width));

  direction = gtk_widget_get_direction (widget);

  halign = gtk_widget_get_halign (widget);
  switch (effective_align (halign, direction))
    {
    case GTK_ALIGN_START:
      /* nothing to do */
      break;
    case GTK_ALIGN_FILL:
      alloc->width = MAX (alloc->width, main_alloc.width);
      break;
    case GTK_ALIGN_CENTER:
      alloc->x += main_alloc.width / 2 - req.width / 2;
      break;
    case GTK_ALIGN_END:
      alloc->x += main_alloc.width - req.width;
      break;
    case GTK_ALIGN_BASELINE:
    default:
      g_assert_not_reached ();
      break;
    }

  alloc->y = main_alloc.y;
  alloc->height = MAX  (min.height, MIN (main_alloc.height, req.height));

  switch (gtk_widget_get_valign (widget))
    {
    case GTK_ALIGN_START:
      /* nothing to do */
      break;
    case GTK_ALIGN_FILL:
      alloc->height = MAX (alloc->height, main_alloc.height);
      break;
    case GTK_ALIGN_CENTER:
      alloc->y += main_alloc.height / 2 - req.height / 2;
      break;
    case GTK_ALIGN_END:
      alloc->y += main_alloc.height - req.height;
      break;
    case GTK_ALIGN_BASELINE:
    default:
      g_assert_not_reached ();
      break;
    }

  return TRUE;
}

static void
gtk_overlay_realize (GtkWidget *widget)
{
  GtkOverlay *overlay = GTK_OVERLAY (widget);
  GtkOverlayPrivate *priv = overlay->priv;
  GtkOverlayChild *child;
  GSList *children;

  GTK_WIDGET_CLASS (gtk_overlay_parent_class)->realize (widget);

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

      if (child->window == NULL)
	child->window = gtk_overlay_create_child_window (overlay, child);
    }
}

static void
gtk_overlay_unrealize (GtkWidget *widget)
{
  GtkOverlay *overlay = GTK_OVERLAY (widget);
  GtkOverlayPrivate *priv = overlay->priv;
  GtkOverlayChild *child;
  GSList *children;

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

      gtk_widget_set_parent_window (child->widget, NULL);
      gtk_widget_unregister_window (widget, child->window);
      gdk_window_destroy (child->window);
      child->window = NULL;
    }

  GTK_WIDGET_CLASS (gtk_overlay_parent_class)->unrealize (widget);
}

static void
gtk_overlay_map (GtkWidget *widget)
{
  GtkOverlay *overlay = GTK_OVERLAY (widget);
  GtkOverlayPrivate *priv = overlay->priv;
  GtkOverlayChild *child;
  GSList *children;

  GTK_WIDGET_CLASS (gtk_overlay_parent_class)->map (widget);

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

      if (child->window != NULL &&
          gtk_widget_get_visible (child->widget) &&
          gtk_widget_get_child_visible (child->widget))
        gdk_window_show (child->window);
    }
}

static void
gtk_overlay_unmap (GtkWidget *widget)
{
  GtkOverlay *overlay = GTK_OVERLAY (widget);
  GtkOverlayPrivate *priv = overlay->priv;
  GtkOverlayChild *child;
  GSList *children;

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

      if (child->window != NULL &&
          gdk_window_is_visible (child->window))
        gdk_window_hide (child->window);
    }

  GTK_WIDGET_CLASS (gtk_overlay_parent_class)->unmap (widget);
}

static gboolean
gtk_overlay_draw (GtkWidget *widget,
                  cairo_t   *cr)
{
  GtkOverlay *overlay = GTK_OVERLAY (widget);
  GtkOverlayPrivate *priv = overlay->priv;
  GtkOverlayChild *child;
  GSList *children;

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

      if (gtk_cairo_should_draw_window (cr, child->window))
        {
          cairo_save (cr);
          gtk_cairo_transform_to_window (cr, widget, child->window);
          gtk_render_background (gtk_widget_get_style_context (widget),
                                 cr,
                                 0, 0,
                                 gdk_window_get_width (child->window),
                                 gdk_window_get_height (child->window));
          cairo_restore (cr);
        }
    }

  GTK_WIDGET_CLASS (gtk_overlay_parent_class)->draw (widget, cr);

  return FALSE;
}

static void
gtk_overlay_remove (GtkContainer *container,
                    GtkWidget    *widget)
{
  GtkOverlayPrivate *priv = GTK_OVERLAY (container)->priv;
  GtkOverlayChild *child;
  GSList *children;

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

      if (child->widget == widget)
        {
          if (child->window != NULL)
            {
              gtk_widget_unregister_window (GTK_WIDGET (container), child->window);
              gdk_window_destroy (child->window);
            }

          gtk_widget_unparent (widget);

          priv->children = g_slist_delete_link (priv->children, children);
          g_slice_free (GtkOverlayChild, child);

          return;
        }
    }

  GTK_CONTAINER_CLASS (gtk_overlay_parent_class)->remove (container, widget);
}

static void
gtk_overlay_forall (GtkContainer *overlay,
                    gboolean      include_internals,
                    GtkCallback   callback,
                    gpointer      callback_data)
{
  GtkOverlayPrivate *priv = GTK_OVERLAY (overlay)->priv;
  GtkOverlayChild *child;
  GSList *children;
  GtkWidget *main_widget;

  main_widget = gtk_bin_get_child (GTK_BIN (overlay));
  if (main_widget)
    (* callback) (main_widget, callback_data);

  children = priv->children;
  while (children)
    {
      child = children->data;
      children = children->next;

      (* callback) (child->widget, callback_data);
    }
}

static void
gtk_overlay_class_init (GtkOverlayClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);
  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
  GtkContainerClass *container_class = GTK_CONTAINER_CLASS (klass);

  widget_class->size_allocate = gtk_overlay_size_allocate;
  widget_class->realize = gtk_overlay_realize;
  widget_class->unrealize = gtk_overlay_unrealize;
  widget_class->map = gtk_overlay_map;
  widget_class->unmap = gtk_overlay_unmap;
  widget_class->draw = gtk_overlay_draw;

  container_class->remove = gtk_overlay_remove;
  container_class->forall = gtk_overlay_forall;

  klass->get_child_position = gtk_overlay_get_child_position;

  /**
   * GtkOverlay::get-child-position:
   * @overlay: the #GtkOverlay
   * @widget: the child widget to position
   * @allocation: (out caller-allocates): return location for the allocation
   *
   * The ::get-child-position signal is emitted to determine
   * the position and size of any overlay child widgets. A
   * handler for this signal should fill @allocation with
   * the desired position and size for @widget, relative to
   * the 'main' child of @overlay.
   *
   * The default handler for this signal uses the @widget's
   * halign and valign properties to determine the position
   * and gives the widget its natural size (except that an
   * alignment of %GTK_ALIGN_FILL will cause the overlay to
   * be full-width/height). If the main child is a
   * #GtkScrolledWindow, the overlays are placed relative
   * to its contents.
   *
   * Return: %TRUE if the @allocation has been filled
   */
  signals[GET_CHILD_POSITION] =
    g_signal_new (I_("get-child-position"),
                  G_TYPE_FROM_CLASS (object_class),
                  G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GtkOverlayClass, get_child_position),
                  _gtk_boolean_handled_accumulator, NULL,
                  _gtk_marshal_BOOLEAN__OBJECT_BOXED,
                  G_TYPE_BOOLEAN, 2,
                  GTK_TYPE_WIDGET,
                  GDK_TYPE_RECTANGLE | G_SIGNAL_TYPE_STATIC_SCOPE);
}

static void
gtk_overlay_init (GtkOverlay *overlay)
{
  overlay->priv = gtk_overlay_get_instance_private (overlay);

  gtk_widget_set_has_window (GTK_WIDGET (overlay), FALSE);
}

static void
gtk_overlay_buildable_add_child (GtkBuildable *buildable,
                                 GtkBuilder   *builder,
                                 GObject      *child,
                                 const gchar  *type)
{
  if (type && strcmp (type, "overlay") == 0)
    gtk_overlay_add_overlay (GTK_OVERLAY (buildable), GTK_WIDGET (child));
  else if (!type)
    gtk_container_add (GTK_CONTAINER (buildable), GTK_WIDGET (child));
  else
    GTK_BUILDER_WARN_INVALID_CHILD_TYPE (buildable, type);
}

static void
gtk_overlay_buildable_init (GtkBuildableIface *iface)
{
  iface->add_child = gtk_overlay_buildable_add_child;
}

/**
 * gtk_overlay_new:
 *
 * Creates a new #GtkOverlay.
 *
 * Returns: a new #GtkOverlay object.
 *
 * Since: 3.2
 */
GtkWidget *
gtk_overlay_new (void)
{
  return g_object_new (GTK_TYPE_OVERLAY, NULL);
}

/**
 * gtk_overlay_add_overlay:
 * @overlay: a #GtkOverlay
 * @widget: a #GtkWidget to be added to the container
 *
 * Adds @widget to @overlay.
 *
 * The widget will be stacked on top of the main widget
 * added with gtk_container_add().
 *
 * The position at which @widget is placed is determined
 * from its #GtkWidget:halign and #GtkWidget:valign properties.
 *
 * Since: 3.2
 */
void
gtk_overlay_add_overlay (GtkOverlay *overlay,
                         GtkWidget  *widget)
{
  GtkOverlayPrivate *priv = overlay->priv;
  GtkOverlayChild *child;

  g_return_if_fail (GTK_IS_OVERLAY (overlay));
  g_return_if_fail (GTK_IS_WIDGET (widget));

  child = g_slice_new0 (GtkOverlayChild);
  child->widget = widget;

  priv->children = g_slist_append (priv->children, child);

  if (gtk_widget_get_realized (GTK_WIDGET (overlay)))
    {
      child->window = gtk_overlay_create_child_window (overlay, child);
      gtk_widget_set_parent (widget, GTK_WIDGET (overlay));
    }
  else
    gtk_widget_set_parent (widget, GTK_WIDGET (overlay));

}
