/* LIBGIMP - The GIMP Library
 * Copyright (C) 1995 Spencer Kimball and Peter Mattis
 *
 * gimphelpui.c
 * Copyright (C) 2000-2003 Michael Natterer <mitch@gimp.org>
 *
 * 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
 * Library 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, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include "config.h"

#include <gtk/gtk.h>
#include <gdk/gdkkeysyms.h>

#include "gimpwidgetstypes.h"

#include "gimpdialog.h"
#include "gimphelpui.h"
#include "gimpwidgets-private.h"


typedef enum
{
  GIMP_WIDGET_HELP_TYPE_HELP = 0xff
} GimpWidgetHelpType;


/*  local function prototypes  */

static const gchar * gimp_help_get_help_data       (GtkWidget      *widget,
                                                    GtkWidget     **help_widget,
                                                    gpointer       *ret_data);
static gboolean   gimp_help_callback               (GtkWidget      *widget,
                                                    GimpWidgetHelpType help_type,
                                                    GimpHelpFunc    help_func);

static gboolean   gimp_context_help_idle_start     (gpointer        widget);
static gboolean   gimp_context_help_button_press   (GtkWidget      *widget,
                                                    GdkEventButton *bevent,
                                                    gpointer        data);
static gboolean   gimp_context_help_idle_show_help (gpointer        data);


/*  local variables  */

static GtkTooltips *tool_tips = NULL;


/*  public functions  */

/**
 * _gimp_help_init:
 *
 * This function initializes GIMP's help system.
 *
 * Currently it only creates a #GtkTooltips object with gtk_tooltips_new()
 * which will be used by gimp_help_set_help_data().
 *
 * Nota that this function is called automatically by gimp_widgets_init().
 **/
void
_gimp_help_init (void)
{
  if (tool_tips)
    {
      g_warning ("_gimp_help_init() must only be called once!");
      return;
    }

  tool_tips = gtk_tooltips_new ();

  /* take ownership of the tooltips */
  g_object_ref (tool_tips);
  gtk_object_sink (GTK_OBJECT (tool_tips));
}

/**
 * gimp_help_enable_tooltips:
 *
 * This function calls gtk_tooltips_enable().
 **/
void
gimp_help_enable_tooltips (void)
{
  gtk_tooltips_enable (tool_tips);
}

/**
 * gimp_help_disable_tooltips:
 *
 * This function calls gtk_tooltips_disable().
 **/
void
gimp_help_disable_tooltips (void)
{
  gtk_tooltips_disable (tool_tips);
}

/**
 * gimp_standard_help_func:
 * @help_id:   A unique help identifier.
 * @help_data: The @help_data passed to gimp_help_connect().
 *
 * This is the standard GIMP help function which does nothing but calling
 * gimp_help(). It is the right function to use in almost all cases.
 **/
void
gimp_standard_help_func (const gchar *help_id,
                         gpointer     help_data)
{
  if (! _gimp_standard_help_func)
    {
      g_warning ("%s: you must call gimp_widgets_init() before using "
                 "the help system", G_STRFUNC);
      return;
    }

  (* _gimp_standard_help_func) (help_id, help_data);
}

/**
 * gimp_help_connect:
 * @widget: The widget you want to connect the help accelerator for. Will
 *          be a #GtkWindow in most cases.
 * @help_func: The function which will be called if the user presses "F1".
 * @help_id:   The @help_id which will be passed to @help_func.
 * @help_data: The @help_data pointer which will be passed to @help_func.
 *
 * Note that this function is automatically called by all libgimp dialog
 * constructors. You only have to call it for windows/dialogs you created
 * "manually".
 **/
void
gimp_help_connect (GtkWidget    *widget,
                   GimpHelpFunc  help_func,
                   const gchar  *help_id,
                   gpointer      help_data)
{
  static gboolean initialized = FALSE;

  g_return_if_fail (GTK_IS_WIDGET (widget));
  g_return_if_fail (help_func != NULL);

  /*  set up the help signals
   */
  if (! initialized)
    {
      GtkBindingSet *binding_set;

      binding_set =
        gtk_binding_set_by_class (g_type_class_peek (GTK_TYPE_WIDGET));

      gtk_binding_entry_add_signal (binding_set, GDK_F1, 0,
                                    "show_help", 1,
                                    GTK_TYPE_WIDGET_HELP_TYPE,
                                    GIMP_WIDGET_HELP_TYPE_HELP);
      gtk_binding_entry_add_signal (binding_set, GDK_KP_F1, 0,
                                    "show_help", 1,
                                    GTK_TYPE_WIDGET_HELP_TYPE,
                                    GIMP_WIDGET_HELP_TYPE_HELP);

      initialized = TRUE;
    }

  gimp_help_set_help_data (widget, NULL, help_id);

  g_object_set_data (G_OBJECT (widget), "gimp-help-data", help_data);

  g_signal_connect (widget, "show_help",
                    G_CALLBACK (gimp_help_callback),
                    help_func);

  gtk_widget_add_events (widget, GDK_BUTTON_PRESS_MASK);
}

/**
 * gimp_help_set_help_data:
 * @widget:  The #GtkWidget you want to set a @tooltip and/or @help_id for.
 * @tooltip: The text for this widget's tooltip (or %NULL).
 * @help_id: The @help_id for the #GtkTipsQuery tooltips inspector.
 *
 * The reason why we don't use gtk_tooltips_set_tip() is that it's
 * impossible to set a @private_tip (aka @help_id) without a visible
 * @tooltip.
 *
 * This function can be called with #NULL for @tooltip. Use this feature
 * if you want to set a help link for a widget which shouldn't have
 * a visible tooltip.
 **/
void
gimp_help_set_help_data (GtkWidget   *widget,
                         const gchar *tooltip,
                         const gchar *help_id)
{
  g_return_if_fail (GTK_IS_WIDGET (widget));

  if (tooltip)
    gtk_tooltips_set_tip (tool_tips, widget, tooltip, help_id);
  else
    g_object_set_qdata (G_OBJECT (widget), GIMP_HELP_ID, (gpointer) help_id);
}

/**
 * gimp_context_help:
 * @widget: Any #GtkWidget on the screen.
 *
 * This function invokes the context help inspector.
 *
 * The mouse cursor will turn turn into a question mark and the user can
 * click on any widget of the application which started the inspector.
 *
 * If the widget the user clicked on has a @help_id string attached
 * (see gimp_help_set_help_data()), the corresponding help page will
 * be displayed. Otherwise the help system will ascend the widget hierarchy
 * until it finds an attached @help_id string (which should be the
 * case at least for every window/dialog).
 **/
void
gimp_context_help (GtkWidget *widget)
{
  g_return_if_fail (GTK_IS_WIDGET (widget));

  gimp_help_callback (widget, GTK_WIDGET_HELP_WHATS_THIS, NULL);
}

/**
 * gimp_help_id_quark:
 *
 * This function returns the #GQuark which should be used as key when
 * attaching help IDs to widgets and objects.
 *
 * Return value: The #GQuark.
 *
 * Since: GIMP 2.2
 **/
GQuark
gimp_help_id_quark (void)
{
  static GQuark quark = 0;

  if (! quark)
    quark = g_quark_from_static_string ("gimp-help-id");

  return quark;
}


/*  private functions  */

static const gchar *
gimp_help_get_help_data (GtkWidget  *widget,
                         GtkWidget **help_widget,
                         gpointer   *ret_data)
{
  GtkTooltipsData *tooltips_data;
  gchar           *help_id   = NULL;
  gpointer         help_data = NULL;

  for (; widget; widget = widget->parent)
    {
      tooltips_data = gtk_tooltips_data_get (widget);

      if (tooltips_data && tooltips_data->tip_private)
        help_id = tooltips_data->tip_private;
      else
        help_id = g_object_get_qdata (G_OBJECT (widget), GIMP_HELP_ID);

      help_data = g_object_get_data (G_OBJECT (widget), "gimp-help-data");

      if (help_id)
        {
          if (help_widget)
            *help_widget = widget;

          if (ret_data)
            *ret_data = help_data;

          return (const gchar *) help_id;
        }
    }

  if (help_widget)
    *help_widget = NULL;

  if (ret_data)
    *ret_data = NULL;

  return NULL;
}

static gboolean
gimp_help_callback (GtkWidget          *widget,
                    GimpWidgetHelpType  help_type,
                    GimpHelpFunc        help_func)
{
  switch (help_type)
    {
    case GIMP_WIDGET_HELP_TYPE_HELP:
      if (help_func)
        {
          GtkTooltipsData *tooltips_data;
          gchar           *help_id   = NULL;
          gpointer         help_data = NULL;

          tooltips_data = gtk_tooltips_data_get (widget);

          if (tooltips_data && tooltips_data->tip_private)
            help_id = tooltips_data->tip_private;
          else
            help_id = g_object_get_qdata (G_OBJECT (widget), GIMP_HELP_ID);

          help_data = g_object_get_data (G_OBJECT (widget), "gimp-help-data");

          (* help_func) (help_id, help_data);
        }
      return TRUE;

    case GTK_WIDGET_HELP_WHATS_THIS:
      g_idle_add (gimp_context_help_idle_start, widget);
      return TRUE;

    default:
      break;
    }

  return FALSE;
}

/*  Do all the actual context help calls in idle functions and check for
 *  some widget holding a grab before starting the query because strange
 *  things happen if (1) the help browser pops up while the query has
 *  grabbed the pointer or (2) the query grabs the pointer while some
 *  other part of the gimp has grabbed it (e.g. a tool, eek)
 */

static gboolean
gimp_context_help_idle_start (gpointer widget)
{
  if (! gtk_grab_get_current ())
    {
      GtkWidget     *invisible;
      GdkCursor     *cursor;
      GdkGrabStatus  status;

      invisible = gtk_invisible_new_for_screen (gtk_widget_get_screen (widget));
      gtk_widget_show (invisible);

      cursor = gdk_cursor_new_for_display (gtk_widget_get_display (invisible),
                                           GDK_QUESTION_ARROW);

      status = gdk_pointer_grab (invisible->window, TRUE,
                                 GDK_BUTTON_PRESS_MASK   |
                                 GDK_BUTTON_RELEASE_MASK |
                                 GDK_ENTER_NOTIFY_MASK   |
                                 GDK_LEAVE_NOTIFY_MASK,
                                 NULL, cursor,
                                 GDK_CURRENT_TIME);

      gdk_cursor_unref (cursor);

      if (status != GDK_GRAB_SUCCESS)
        {
          gtk_widget_destroy (invisible);
          return FALSE;
        }

      gtk_grab_add (invisible);

      g_signal_connect (invisible, "button_press_event",
                        G_CALLBACK (gimp_context_help_button_press),
                        NULL);
    }

  return FALSE;
}

static gboolean
gimp_context_help_button_press (GtkWidget      *widget,
                                GdkEventButton *bevent,
                                gpointer        data)
{
  GtkWidget *event_widget;

  event_widget = gtk_get_event_widget ((GdkEvent *) bevent);

  if (event_widget && bevent->button == 1 && bevent->type == GDK_BUTTON_PRESS)
    {
      gtk_grab_remove (widget);
      gdk_display_pointer_ungrab (gtk_widget_get_display (widget),
                                  bevent->time);
      gtk_widget_destroy (widget);

      if (event_widget != widget)
        g_idle_add (gimp_context_help_idle_show_help, event_widget);
    }

  return TRUE;
}

static gboolean
gimp_context_help_idle_show_help (gpointer data)
{
  GtkWidget   *help_widget;
  const gchar *help_id   = NULL;
  gpointer     help_data = NULL;

  help_id = gimp_help_get_help_data (GTK_WIDGET (data), &help_widget,
                                     &help_data);

  if (help_id)
    gimp_standard_help_func (help_id, help_data);

  return FALSE;
}