/* GTK - The GIMP Toolkit
 * Copyright (C) 2017 Red Hat, Inc.
 * Copyright (C) 2018 Purism SPC
 *
 * 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 <string.h>
#include <wayland-client-protocol.h>

#include "gtk/gtkimcontextwayland.h"
#include "gtk/gtkintl.h"
#include "gtk/gtkimmoduleprivate.h"

#include "gdk/wayland/gdkwayland.h"
#include "text-input-unstable-v3-client-protocol.h"

typedef struct _GtkIMContextWaylandGlobal GtkIMContextWaylandGlobal;
typedef struct _GtkIMContextWayland GtkIMContextWayland;
typedef struct _GtkIMContextWaylandClass GtkIMContextWaylandClass;

struct _GtkIMContextWaylandGlobal
{
  struct wl_display *display;
  struct wl_registry *registry;
  uint32_t text_input_manager_wl_id;
  struct zwp_text_input_manager_v3 *text_input_manager;
  struct zwp_text_input_v3 *text_input;

  GtkIMContext *current;

  /* The input-method.enter event may happen before or after GTK focus-in,
   * so the context may not exist at the time. Same for leave and focus-out. */
  gboolean focused;

  guint serial;
};

struct _GtkIMContextWaylandClass
{
  GtkIMContextSimpleClass parent_class;
};

struct preedit {
  gchar *text;
  gint cursor_begin;
  gint cursor_end;
};

struct surrounding_delete {
  guint before_length;
  guint after_length;
};

struct _GtkIMContextWayland
{
  GtkIMContextSimple parent_instance;
  GtkWidget *widget;

  GtkGesture *gesture;
  gdouble press_x;
  gdouble press_y;

  struct {
    gchar *text;
    gint cursor_idx;
    gint anchor_idx;
  } surrounding;

  enum zwp_text_input_v3_change_cause surrounding_change;

  struct surrounding_delete pending_surrounding_delete;

  struct preedit current_preedit;
  struct preedit pending_preedit;

  gchar *pending_commit;

  cairo_rectangle_int_t cursor_rect;
  guint use_preedit : 1;
};

G_DEFINE_TYPE_WITH_CODE (GtkIMContextWayland, gtk_im_context_wayland, GTK_TYPE_IM_CONTEXT_SIMPLE,
			 gtk_im_module_ensure_extension_point ();
                         g_io_extension_point_implement (GTK_IM_MODULE_EXTENSION_POINT_NAME,
                                                         g_define_type_id,
                                                         "wayland",
                                                         10));

static GtkIMContextWaylandGlobal *global = NULL;

#define GTK_IM_CONTEXT_WAYLAND(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), gtk_im_context_wayland_get_type (), GtkIMContextWayland))


static void
enable (GtkIMContextWayland *context_wayland);

static void
disable (GtkIMContextWayland *context_wayland);

static void
notify_external_change (GtkIMContextWayland *context)
{
  gboolean result;

  if (!global->current)
    return;

  context->surrounding_change = ZWP_TEXT_INPUT_V3_CHANGE_CAUSE_OTHER;
  g_signal_emit_by_name (global->current, "retrieve-surrounding", &result);
}

static void
text_input_enter (void                     *data,
                  struct zwp_text_input_v3 *text_input,
                  struct wl_surface        *surface)
{
  global->focused = TRUE;

  if (global->current)
    enable (GTK_IM_CONTEXT_WAYLAND (global->current));
}

static void
text_input_leave (void                     *data,
                  struct zwp_text_input_v3 *text_input,
                  struct wl_surface        *surface)
{
  global->focused = FALSE;

  if (global->current)
    disable (GTK_IM_CONTEXT_WAYLAND (global->current));
}

static void
text_input_preedit (void                     *data,
                    struct zwp_text_input_v3 *text_input,
                    const char               *text,
                    gint                      cursor_begin,
                    gint                      cursor_end)
{
  GtkIMContextWayland *context;
  GtkIMContextWaylandGlobal *global = data;

  if (!global->current)
    return;

  context = GTK_IM_CONTEXT_WAYLAND (global->current);
      
  g_free (context->pending_preedit.text);
  context->pending_preedit.text = g_strdup (text);
  context->pending_preedit.cursor_begin = cursor_begin;
  context->pending_preedit.cursor_end = cursor_end;
}

static void
text_input_preedit_apply (GtkIMContextWaylandGlobal *global)
{
  GtkIMContextWayland *context;
  gboolean state_change;
  struct preedit defaults = {0};

  if (!global->current)
    return;

  context = GTK_IM_CONTEXT_WAYLAND (global->current);

  state_change = ((context->pending_preedit.text == NULL)
                 != (context->current_preedit.text == NULL));

  if (state_change && !context->current_preedit.text)
    g_signal_emit_by_name (context, "preedit-start");

  g_free (context->current_preedit.text);
  context->current_preedit = context->pending_preedit;
  context->pending_preedit = defaults;

  g_signal_emit_by_name (context, "preedit-changed");

  if (state_change && !context->current_preedit.text)
    g_signal_emit_by_name (context, "preedit-end");
}

static void
text_input_commit (void                     *data,
                   struct zwp_text_input_v3 *text_input,
                   const char               *text)
{
  GtkIMContextWaylandGlobal *global = data;
  GtkIMContextWayland *context;

  if (!global->current)
      return;
  
  context = GTK_IM_CONTEXT_WAYLAND (global->current);

  g_free (context->pending_commit);
  context->pending_commit = g_strdup (text);
}

static void
text_input_commit_apply (GtkIMContextWaylandGlobal *global, gboolean valid)
{
  GtkIMContextWayland *context;
  context = GTK_IM_CONTEXT_WAYLAND (global->current);
  if (context->pending_commit && valid)
    g_signal_emit_by_name (global->current, "commit", context->pending_commit);
  g_free (context->pending_commit);
  context->pending_commit = NULL;
}

static void
text_input_delete_surrounding_text (void                     *data,
                                    struct zwp_text_input_v3 *text_input,
                                    uint32_t                  before_length,
                                    uint32_t                  after_length)
{
  GtkIMContextWaylandGlobal *global = data;
  GtkIMContextWayland *context;

  if (!global->current)
      return;
  
  context = GTK_IM_CONTEXT_WAYLAND (global->current);

  context->pending_surrounding_delete.before_length = before_length;
  context->pending_surrounding_delete.after_length = after_length;
}

static void
text_input_delete_surrounding_text_apply (GtkIMContextWaylandGlobal *global,
  gboolean valid)
{
  GtkIMContextWayland *context;
  gboolean retval;
  gint len;
  struct surrounding_delete defaults = {0};

  context = GTK_IM_CONTEXT_WAYLAND (global->current);

  len = context->pending_surrounding_delete.after_length
      + context->pending_surrounding_delete.before_length;
  if (len > 0 && valid)
    g_signal_emit_by_name (global->current, "delete-surrounding",
                           -context->pending_surrounding_delete.before_length,
                           len, &retval);
  context->pending_surrounding_delete = defaults;
}

static void
text_input_done (void                     *data,
                 struct zwp_text_input_v3 *text_input,
                 uint32_t                  serial)
{
  GtkIMContextWaylandGlobal *global = data;
  gboolean result;
  gboolean valid;
  
  if (!global->current)
    return;

  valid = serial == global->serial;
  text_input_delete_surrounding_text_apply(global, valid);
  text_input_commit_apply(global, valid);
  g_signal_emit_by_name (global->current, "retrieve-surrounding", &result);
  text_input_preedit_apply(global);
}

static const struct zwp_text_input_v3_listener text_input_listener = {
  text_input_enter,
  text_input_leave,
  text_input_preedit,
  text_input_commit,
  text_input_delete_surrounding_text,
  text_input_done,
};

static void
registry_handle_global (void               *data,
                        struct wl_registry *registry,
                        uint32_t            id,
                        const char         *interface,
                        uint32_t            version)
{
  GtkIMContextWaylandGlobal *global = data;
  GdkSeat *seat = gdk_display_get_default_seat (gdk_display_get_default ());

  if (strcmp (interface, "zwp_text_input_manager_v3") == 0)
    {
      global->text_input_manager_wl_id = id;
      global->text_input_manager =
        wl_registry_bind (global->registry, global->text_input_manager_wl_id,
                          &zwp_text_input_manager_v3_interface, 1);
      global->text_input =
        zwp_text_input_manager_v3_get_text_input (global->text_input_manager,
                                          gdk_wayland_seat_get_wl_seat (seat));
      global->serial = 0;
      zwp_text_input_v3_add_listener (global->text_input,
                                      &text_input_listener, global);
    }
}

static void
registry_handle_global_remove (void               *data,
                               struct wl_registry *registry,
                               uint32_t            id)
{
  GtkIMContextWaylandGlobal *global = data;

  if (id != global->text_input_manager_wl_id)
    return;

  g_clear_pointer(&global->text_input, zwp_text_input_v3_destroy);
  g_clear_pointer(&global->text_input_manager, zwp_text_input_manager_v3_destroy);
}

static const struct wl_registry_listener registry_listener = {
    registry_handle_global,
    registry_handle_global_remove
};

static void
gtk_im_context_wayland_global_init (GdkDisplay *display)
{
  if (global != NULL)
    return;

  global = g_new0 (GtkIMContextWaylandGlobal, 1);
  global->display = gdk_wayland_display_get_wl_display (display);
  global->registry = wl_display_get_registry (global->display);

  wl_registry_add_listener (global->registry, &registry_listener, global);
}

static void
notify_surrounding_text (GtkIMContextWayland *context)
{
  if (!global || !global->text_input)
    return;
  if (global->current != GTK_IM_CONTEXT (context))
    return;
  if (!context->surrounding.text)
    return;

  zwp_text_input_v3_set_surrounding_text (global->text_input,
                                          context->surrounding.text,
                                          context->surrounding.cursor_idx,
                                          context->surrounding.anchor_idx);
  zwp_text_input_v3_set_text_change_cause (global->text_input,
                                           context->surrounding_change);
}

static void
notify_cursor_location (GtkIMContextWayland *context)
{
  cairo_rectangle_int_t rect;

  if (!global || !global->text_input)
    return;
  if (global->current != GTK_IM_CONTEXT (context))
    return;
  if (!context->widget)
    return;

  rect = context->cursor_rect;
  gtk_widget_translate_coordinates (context->widget,
                                    gtk_widget_get_toplevel (context->widget),
                                    rect.x, rect.y,
                                    &rect.x, &rect.y);

  zwp_text_input_v3_set_cursor_rectangle (global->text_input,
                                          rect.x, rect.y,
                                          rect.width, rect.height);
}

static uint32_t
translate_hints (GtkInputHints   input_hints,
                 GtkInputPurpose purpose)
{
  uint32_t hints = 0;

  if (input_hints & GTK_INPUT_HINT_SPELLCHECK)
    hints |= ZWP_TEXT_INPUT_V3_CONTENT_HINT_SPELLCHECK;
  if (input_hints & GTK_INPUT_HINT_WORD_COMPLETION)
    hints |= ZWP_TEXT_INPUT_V3_CONTENT_HINT_COMPLETION;
  if (input_hints & GTK_INPUT_HINT_LOWERCASE)
    hints |= ZWP_TEXT_INPUT_V3_CONTENT_HINT_LOWERCASE;
  if (input_hints & GTK_INPUT_HINT_UPPERCASE_CHARS)
    hints |= ZWP_TEXT_INPUT_V3_CONTENT_HINT_UPPERCASE;
  if (input_hints & GTK_INPUT_HINT_UPPERCASE_WORDS)
    hints |= ZWP_TEXT_INPUT_V3_CONTENT_HINT_TITLECASE;
  if (input_hints & GTK_INPUT_HINT_UPPERCASE_SENTENCES)
    hints |= ZWP_TEXT_INPUT_V3_CONTENT_HINT_AUTO_CAPITALIZATION;

  if (purpose == GTK_INPUT_PURPOSE_PIN ||
      purpose == GTK_INPUT_PURPOSE_PASSWORD)
    {
      hints |= (ZWP_TEXT_INPUT_V3_CONTENT_HINT_HIDDEN_TEXT |
                ZWP_TEXT_INPUT_V3_CONTENT_HINT_SENSITIVE_DATA);
    }

  return hints;
}

static uint32_t
translate_purpose (GtkInputPurpose purpose)
{
  switch (purpose)
    {
    case GTK_INPUT_PURPOSE_FREE_FORM:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_NORMAL;
    case GTK_INPUT_PURPOSE_ALPHA:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_ALPHA;
    case GTK_INPUT_PURPOSE_DIGITS:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_DIGITS;
    case GTK_INPUT_PURPOSE_NUMBER:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_NUMBER;
    case GTK_INPUT_PURPOSE_PHONE:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_PHONE;
    case GTK_INPUT_PURPOSE_URL:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_URL;
    case GTK_INPUT_PURPOSE_EMAIL:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_EMAIL;
    case GTK_INPUT_PURPOSE_NAME:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_NAME;
    case GTK_INPUT_PURPOSE_PASSWORD:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_PASSWORD;
    case GTK_INPUT_PURPOSE_PIN:
      return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_PIN;
    default:
      g_assert_not_reached ();
    }

  return ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_NORMAL;
}

static void
notify_content_type (GtkIMContextWayland *context)
{
  GtkInputHints hints;
  GtkInputPurpose purpose;

  if (global->current != GTK_IM_CONTEXT (context))
    return;

  g_object_get (context,
                "input-hints", &hints,
                "input-purpose", &purpose,
                NULL);

  zwp_text_input_v3_set_content_type (global->text_input,
                                      translate_hints (hints, purpose),
                                      translate_purpose (purpose));
}

static void
commit_state (GtkIMContextWayland *context)
{
  if (global->current != GTK_IM_CONTEXT (context))
    return;
  global->serial++;
  zwp_text_input_v3_commit (global->text_input);
  context->surrounding_change = ZWP_TEXT_INPUT_V3_CHANGE_CAUSE_INPUT_METHOD;
}

static void
gtk_im_context_wayland_finalize (GObject *object)
{
  GtkIMContextWayland *context = GTK_IM_CONTEXT_WAYLAND (object);

  g_clear_object (&context->widget);
  g_clear_object (&context->gesture);

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

static void
pressed_cb (GtkGestureMultiPress *gesture,
            gint                  n_press,
            gdouble               x,
            gdouble               y,
            GtkIMContextWayland  *context)
{
  if (n_press == 1)
    {
      context->press_x = x;
      context->press_y = y;
    }
}

static void
released_cb (GtkGestureMultiPress *gesture,
             gint                  n_press,
             gdouble               x,
             gdouble               y,
             GtkIMContextWayland  *context)
{
  GtkInputHints hints;
  gboolean result;

  g_object_get (context, "input-hints", &hints, NULL);

  if (global->focused &&
      n_press == 1 &&
      (hints & GTK_INPUT_HINT_INHIBIT_OSK) == 0 &&
      !gtk_drag_check_threshold (context->widget,
                                 context->press_x,
                                 context->press_y,
                                 x, y))
    {
      zwp_text_input_v3_enable (global->text_input);
      g_signal_emit_by_name (global->current, "retrieve-surrounding", &result);
      commit_state (context);
    }
}

static void
gtk_im_context_wayland_set_client_widget (GtkIMContext *context,
                                          GtkWidget    *widget)
{
  GtkIMContextWayland *context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  if (widget == context_wayland->widget)
    return;

  if (context_wayland->widget)
    {
      gtk_widget_remove_controller (context_wayland->widget, GTK_EVENT_CONTROLLER (context_wayland->gesture));
      context_wayland->gesture = NULL;
    }

  g_set_object (&context_wayland->widget, widget);

  if (widget)
    {
      GtkGesture *gesture;

      gesture = gtk_gesture_multi_press_new ();
      gtk_event_controller_set_propagation_phase (GTK_EVENT_CONTROLLER (gesture),
                                                  GTK_PHASE_CAPTURE);
      g_signal_connect (gesture, "pressed",
                        G_CALLBACK (pressed_cb), context);
      g_signal_connect (gesture, "released",
                        G_CALLBACK (released_cb), context);
      gtk_widget_add_controller (widget, GTK_EVENT_CONTROLLER (gesture));
      context_wayland->gesture = gesture;
    }
}

static void
gtk_im_context_wayland_get_preedit_string (GtkIMContext   *context,
                                           gchar         **str,
                                           PangoAttrList **attrs,
                                           gint           *cursor_pos)
{
  GtkIMContextWayland *context_wayland = GTK_IM_CONTEXT_WAYLAND (context);
  const char *preedit_str;

  if (attrs)
    *attrs = NULL;

  GTK_IM_CONTEXT_CLASS (gtk_im_context_wayland_parent_class)->get_preedit_string (context,
                                                                                  str, attrs,
                                                                                  cursor_pos);

  /* If the parent implementation returns a len>0 string, go with it */
  if (str && *str)
    {
      if (**str)
        return;

      g_free (*str);
    }

  preedit_str =
    context_wayland->current_preedit.text ? context_wayland->current_preedit.text : "";

  if (str)
    *str = g_strdup (preedit_str);
  if (cursor_pos)
    *cursor_pos = context_wayland->current_preedit.cursor_begin;

  if (attrs)
    {
      if (!*attrs)
        *attrs = pango_attr_list_new ();
      pango_attr_list_insert (*attrs,
                              pango_attr_underline_new (PANGO_UNDERLINE_SINGLE));
      if (context_wayland->current_preedit.cursor_begin
          != context_wayland->current_preedit.cursor_end)
        {
          /* FIXME: Oh noes, how to highlight while taking into account user preferences? */
          PangoAttribute *cursor = pango_attr_weight_new (PANGO_WEIGHT_BOLD);
          cursor->start_index = context_wayland->current_preedit.cursor_begin;
          cursor->end_index = context_wayland->current_preedit.cursor_end;
          pango_attr_list_insert (*attrs, cursor);
        }
    }
}

static gboolean
gtk_im_context_wayland_filter_keypress (GtkIMContext *context,
                                        GdkEventKey  *key)
{
  /* This is done by the compositor */
  return GTK_IM_CONTEXT_CLASS (gtk_im_context_wayland_parent_class)->filter_keypress (context, key);
}

static void
enable (GtkIMContextWayland *context_wayland)
{
  gboolean result;
  zwp_text_input_v3_enable (global->text_input);
  g_signal_emit_by_name (global->current, "retrieve-surrounding", &result);
  notify_content_type (context_wayland);
  notify_cursor_location (context_wayland);
  commit_state (context_wayland);
}

static void
disable (GtkIMContextWayland *context_wayland)
{
  zwp_text_input_v3_disable (global->text_input);
  commit_state (context_wayland);

  /* after disable, incoming state changes won't take effect anyway */
  if (context_wayland->current_preedit.text)
    {
      text_input_preedit (global, global->text_input, NULL, 0, 0);
      text_input_preedit_apply (global);
    }
}

static void
gtk_im_context_wayland_focus_in (GtkIMContext *context)
{
  GtkIMContextWayland *context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  if (global->current == context)
    return;
  if (!global->text_input)
    return;

  global->current = context;

  if (global->focused)
    enable (context_wayland);
}

static void
gtk_im_context_wayland_focus_out (GtkIMContext *context)
{
  GtkIMContextWayland *context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  if (global->current != context)
    return;

  if (global->focused)
    disable (context_wayland);

  global->current = NULL;
}

static void
gtk_im_context_wayland_reset (GtkIMContext *context)
{
  notify_external_change (GTK_IM_CONTEXT_WAYLAND (context));

  GTK_IM_CONTEXT_CLASS (gtk_im_context_wayland_parent_class)->reset (context);
}

static void
gtk_im_context_wayland_set_cursor_location (GtkIMContext *context,
                                            GdkRectangle *rect)
{
  GtkIMContextWayland *context_wayland;

  context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  context_wayland->cursor_rect = *rect;
  notify_cursor_location (context_wayland);
  commit_state (context_wayland);
}

static void
gtk_im_context_wayland_set_use_preedit (GtkIMContext *context,
                                        gboolean      use_preedit)
{
  GtkIMContextWayland *context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  context_wayland->use_preedit = !!use_preedit;
}

static void
gtk_im_context_wayland_set_surrounding (GtkIMContext *context,
                                        const gchar  *text,
                                        gint          len,
                                        gint          cursor_index)
{
  GtkIMContextWayland *context_wayland;

  context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  g_free (context_wayland->surrounding.text);
  context_wayland->surrounding.text = g_strdup (text);
  context_wayland->surrounding.cursor_idx = cursor_index;
  /* Anchor is not exposed via the set_surrounding interface, emulating. */
  context_wayland->surrounding.anchor_idx = cursor_index;

  notify_surrounding_text (context_wayland);
  /* State changes coming from reset don't have any other opportunity to get
   * committed. */
  if (context_wayland->surrounding_change !=
      ZWP_TEXT_INPUT_V3_CHANGE_CAUSE_INPUT_METHOD)
    commit_state (context_wayland);
}

static gboolean
gtk_im_context_wayland_get_surrounding (GtkIMContext  *context,
                                        gchar        **text,
                                        gint          *cursor_index)
{
  GtkIMContextWayland *context_wayland;

  context_wayland = GTK_IM_CONTEXT_WAYLAND (context);

  if (!context_wayland->surrounding.text)
    return FALSE;

  *text = context_wayland->surrounding.text;
  *cursor_index = context_wayland->surrounding.cursor_idx;
  return TRUE;
}

static void
gtk_im_context_wayland_class_init (GtkIMContextWaylandClass *klass)
{
  GObjectClass *object_class = G_OBJECT_CLASS (klass);
  GtkIMContextClass *im_context_class = GTK_IM_CONTEXT_CLASS (klass);

  object_class->finalize = gtk_im_context_wayland_finalize;

  im_context_class->set_client_widget = gtk_im_context_wayland_set_client_widget;
  im_context_class->get_preedit_string = gtk_im_context_wayland_get_preedit_string;
  im_context_class->filter_keypress = gtk_im_context_wayland_filter_keypress;
  im_context_class->focus_in = gtk_im_context_wayland_focus_in;
  im_context_class->focus_out = gtk_im_context_wayland_focus_out;
  im_context_class->reset = gtk_im_context_wayland_reset;
  im_context_class->set_cursor_location = gtk_im_context_wayland_set_cursor_location;
  im_context_class->set_use_preedit = gtk_im_context_wayland_set_use_preedit;
  im_context_class->set_surrounding = gtk_im_context_wayland_set_surrounding;
  im_context_class->get_surrounding = gtk_im_context_wayland_get_surrounding;
}

static void
on_content_type_changed (GtkIMContextWayland *context)
{
  notify_content_type (context);
  commit_state (context);
}

static void
gtk_im_context_wayland_init (GtkIMContextWayland *context)
{
  gtk_im_context_wayland_global_init (gdk_display_get_default ());

  context->use_preedit = TRUE;
  g_signal_connect_swapped (context, "notify::input-purpose",
                            G_CALLBACK (on_content_type_changed), context);
  g_signal_connect_swapped (context, "notify::input-hints",
                            G_CALLBACK (on_content_type_changed), context);
}