gtk2/gtk/gtkmain.c

/* GTK - The GIMP Toolkit
 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

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

/**
 * SECTION:gtkmain
 * @Short_description: Library initialization, main event loop, and events
 * @Title: Main loop and Events
 * @See_also:See the GLib manual, especially #GMainLoop and signal-related
 *    functions such as g_signal_connect()
 *
 * Before using GTK+, you need to initialize it; initialization connects to the
 * window system display, and parses some standard command line arguments. The
 * gtk_init() macro initializes GTK+. gtk_init() exits the application if errors
 * occur; to avoid this, use gtk_init_check(). gtk_init_check() allows you to
 * recover from a failed GTK+ initialization - you might start up your
 * application in text mode instead.
 *
 * Like all GUI toolkits, GTK+ uses an event-driven programming model. When the
 * user is doing nothing, GTK+ sits in the “main loop” and
 * waits for input. If the user performs some action - say, a mouse click - then
 * the main loop “wakes up” and delivers an event to GTK+. GTK+ forwards the
 * event to one or more widgets.
 *
 * When widgets receive an event, they frequently emit one or more
 * “signals”. Signals notify your program that "something
 * interesting happened" by invoking functions you’ve connected to the signal
 * with g_signal_connect(). Functions connected to a signal are often termed
 * “callbacks”.
 *
 * When your callbacks are invoked, you would typically take some action - for
 * example, when an Open button is clicked you might display a
 * #GtkFileChooserDialog. After a callback finishes, GTK+ will return to the
 * main loop and await more user input.
 *
 * ## Typical main() function for a GTK+ application
 *
 * |[<!-- language="C" -->
 * int
 * main (int argc, char **argv)
 * {
 *   // Initialize i18n support with bindtextdomain(), etc.
 *
 *   ...
 *
 *   // Initialize the widget set
 *   gtk_init ();
 *
 *   // Create the main window
 *   mainwin = gtk_window_new (GTK_WINDOW_TOPLEVEL);
 *
 *   // Set up our GUI elements
 *
 *   ...
 *
 *   // Show the application window
 *   gtk_widget_show (mainwin);
 *
 *   // Enter the main event loop, and wait for user interaction
 *   gtk_main ();
 *
 *   // The user lost interest
 *   return 0;
 * }
 * ]|
 *
 * It’s OK to use the GLib main loop directly instead of gtk_main(), though it
 * involves slightly more typing. See #GMainLoop in the GLib documentation.
 */

#include "config.h"

#include "gdk/gdk.h"
#include "gdk/gdk-private.h"
#include "gsk/gskprivate.h"

#include <locale.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <sys/types.h>          /* For uid_t, gid_t */

#ifdef G_OS_WIN32
#define STRICT
#include <windows.h>
#undef STRICT
#endif

#include "gtkintl.h"

#include "gtkaccelmapprivate.h"
#include "gtkbox.h"
#include "gtkclipboardprivate.h"
#include "gtkdebug.h"
#include "gtkdebugupdatesprivate.h"
#include "gtkdndprivate.h"
#include "gtkmain.h"
#include "gtkmenu.h"
#include "gtkmodules.h"
#include "gtkmodulesprivate.h"
#include "gtkprivate.h"
#include "gtkrecentmanager.h"
#include "gtkselectionprivate.h"
#include "gtksettingsprivate.h"
#include "gtktooltipprivate.h"
#include "gtkversion.h"
#include "gtkwidgetprivate.h"
#include "gtkwindowprivate.h"
#include "gtkwindowgroup.h"

#include "a11y/gtkaccessibility.h"

static GtkWindowGroup *gtk_main_get_window_group (GtkWidget   *widget);

static guint gtk_main_loop_level = 0;
static gint pre_initialized = FALSE;
static gint gtk_initialized = FALSE;
static GList *current_events = NULL;

static GSList *main_loops = NULL;      /* stack of currently executing main loops */

typedef struct {
  GdkDisplay *display;
  guint flags;
} DisplayDebugFlags;

#define N_DEBUG_DISPLAYS 4

DisplayDebugFlags debug_flags[N_DEBUG_DISPLAYS];

#ifdef G_ENABLE_DEBUG
static const GDebugKey gtk_debug_keys[] = {
  { "misc", GTK_DEBUG_MISC },
  { "text", GTK_DEBUG_TEXT },
  { "tree", GTK_DEBUG_TREE },
  { "updates", GTK_DEBUG_UPDATES },
  { "keybindings", GTK_DEBUG_KEYBINDINGS },
  { "multihead", GTK_DEBUG_MULTIHEAD },
  { "modules", GTK_DEBUG_MODULES },
  { "geometry", GTK_DEBUG_GEOMETRY },
  { "icontheme", GTK_DEBUG_ICONTHEME },
  { "printing", GTK_DEBUG_PRINTING} ,
  { "builder", GTK_DEBUG_BUILDER },
  { "size-request", GTK_DEBUG_SIZE_REQUEST },
  { "no-css-cache", GTK_DEBUG_NO_CSS_CACHE },
  { "baselines", GTK_DEBUG_BASELINES },
  { "interactive", GTK_DEBUG_INTERACTIVE },
  { "touchscreen", GTK_DEBUG_TOUCHSCREEN },
  { "actions", GTK_DEBUG_ACTIONS },
  { "resize", GTK_DEBUG_RESIZE },
  { "layout", GTK_DEBUG_LAYOUT },
  { "snapshot", GTK_DEBUG_SNAPSHOT }
};
#endif /* G_ENABLE_DEBUG */

/**
 * gtk_get_major_version:
 *
 * Returns the major version number of the GTK+ library.
 * (e.g. in GTK+ version 3.1.5 this is 3.)
 *
 * This function is in the library, so it represents the GTK+ library
 * your code is running against. Contrast with the #GTK_MAJOR_VERSION
 * macro, which represents the major version of the GTK+ headers you
 * have included when compiling your code.
 *
 * Returns: the major version number of the GTK+ library
 *
 * Since: 3.0
 */
guint
gtk_get_major_version (void)
{
  return GTK_MAJOR_VERSION;
}

/**
 * gtk_get_minor_version:
 *
 * Returns the minor version number of the GTK+ library.
 * (e.g. in GTK+ version 3.1.5 this is 1.)
 *
 * This function is in the library, so it represents the GTK+ library
 * your code is are running against. Contrast with the
 * #GTK_MINOR_VERSION macro, which represents the minor version of the
 * GTK+ headers you have included when compiling your code.
 *
 * Returns: the minor version number of the GTK+ library
 *
 * Since: 3.0
 */
guint
gtk_get_minor_version (void)
{
  return GTK_MINOR_VERSION;
}

/**
 * gtk_get_micro_version:
 *
 * Returns the micro version number of the GTK+ library.
 * (e.g. in GTK+ version 3.1.5 this is 5.)
 *
 * This function is in the library, so it represents the GTK+ library
 * your code is are running against. Contrast with the
 * #GTK_MICRO_VERSION macro, which represents the micro version of the
 * GTK+ headers you have included when compiling your code.
 *
 * Returns: the micro version number of the GTK+ library
 *
 * Since: 3.0
 */
guint
gtk_get_micro_version (void)
{
  return GTK_MICRO_VERSION;
}

/**
 * gtk_get_binary_age:
 *
 * Returns the binary age as passed to `libtool`
 * when building the GTK+ library the process is running against.
 * If `libtool` means nothing to you, don't
 * worry about it.
 *
 * Returns: the binary age of the GTK+ library
 *
 * Since: 3.0
 */
guint
gtk_get_binary_age (void)
{
  return GTK_BINARY_AGE;
}

/**
 * gtk_get_interface_age:
 *
 * Returns the interface age as passed to `libtool`
 * when building the GTK+ library the process is running against.
 * If `libtool` means nothing to you, don't
 * worry about it.
 *
 * Returns: the interface age of the GTK+ library
 *
 * Since: 3.0
 */
guint
gtk_get_interface_age (void)
{
  return GTK_INTERFACE_AGE;
}

/**
 * gtk_check_version:
 * @required_major: the required major version
 * @required_minor: the required minor version
 * @required_micro: the required micro version
 *
 * Checks that the GTK+ library in use is compatible with the
 * given version. Generally you would pass in the constants
 * #GTK_MAJOR_VERSION, #GTK_MINOR_VERSION, #GTK_MICRO_VERSION
 * as the three arguments to this function; that produces
 * a check that the library in use is compatible with
 * the version of GTK+ the application or module was compiled
 * against.
 *
 * Compatibility is defined by two things: first the version
 * of the running library is newer than the version
 * @required_major.required_minor.@required_micro. Second
 * the running library must be binary compatible with the
 * version @required_major.required_minor.@required_micro
 * (same major version.)
 *
 * This function is primarily for GTK+ modules; the module
 * can call this function to check that it wasn’t loaded
 * into an incompatible version of GTK+. However, such a
 * check isn’t completely reliable, since the module may be
 * linked against an old version of GTK+ and calling the
 * old version of gtk_check_version(), but still get loaded
 * into an application using a newer version of GTK+.
 *
 * Returns: (nullable): %NULL if the GTK+ library is compatible with the
 *   given version, or a string describing the version mismatch.
 *   The returned string is owned by GTK+ and should not be modified
 *   or freed.
 */
const gchar*
gtk_check_version (guint required_major,
                   guint required_minor,
                   guint required_micro)
{
  gint gtk_effective_micro = 100 * GTK_MINOR_VERSION + GTK_MICRO_VERSION;
  gint required_effective_micro = 100 * required_minor + required_micro;

  if (required_major > GTK_MAJOR_VERSION)
    return "GTK+ version too old (major mismatch)";
  if (required_major < GTK_MAJOR_VERSION)
    return "GTK+ version too new (major mismatch)";
  if (required_effective_micro < gtk_effective_micro - GTK_BINARY_AGE)
    return "GTK+ version too new (micro mismatch)";
  if (required_effective_micro > gtk_effective_micro)
    return "GTK+ version too old (micro mismatch)";
  return NULL;
}

/* This checks to see if the process is running suid or sgid
 * at the current time. If so, we don’t allow GTK+ to be initialized.
 * This is meant to be a mild check - we only error out if we
 * can prove the programmer is doing something wrong, not if
 * they could be doing something wrong. For this reason, we
 * don’t use issetugid() on BSD or prctl (PR_GET_DUMPABLE).
 */
static gboolean
check_setugid (void)
{
/* this isn't at all relevant on MS Windows and doesn't compile ... --hb */
#ifndef G_OS_WIN32
  uid_t ruid, euid, suid; /* Real, effective and saved user ID's */
  gid_t rgid, egid, sgid; /* Real, effective and saved group ID's */
  
#ifdef HAVE_GETRESUID
  if (getresuid (&ruid, &euid, &suid) != 0 ||
      getresgid (&rgid, &egid, &sgid) != 0)
#endif /* HAVE_GETRESUID */
    {
      suid = ruid = getuid ();
      sgid = rgid = getgid ();
      euid = geteuid ();
      egid = getegid ();
    }

  if (ruid != euid || ruid != suid ||
      rgid != egid || rgid != sgid)
    {
      g_warning ("This process is currently running setuid or setgid.\n"
                 "This is not a supported use of GTK+. You must create a helper\n"
                 "program instead. For further details, see:\n\n"
                 "    http://www.gtk.org/setuid.html\n\n"
                 "Refusing to initialize GTK+.");
      exit (1);
    }
#endif
  return TRUE;
}

static gboolean do_setlocale = TRUE;

/**
 * gtk_disable_setlocale:
 *
 * Prevents gtk_init(), gtk_init_check() and
 * gtk_parse_args() from automatically
 * calling `setlocale (LC_ALL, "")`. You would
 * want to use this function if you wanted to set the locale for
 * your program to something other than the user’s locale, or if
 * you wanted to set different values for different locale categories.
 *
 * Most programs should not need to call this function.
 **/
void
gtk_disable_setlocale (void)
{
  if (pre_initialized)
    g_warning ("gtk_disable_setlocale() must be called before gtk_init()");
    
  do_setlocale = FALSE;
}

#ifdef G_PLATFORM_WIN32
#undef gtk_init_check
#endif

static GString *gtk_modules_string = NULL;

#ifdef G_OS_WIN32

static char *iso639_to_check = NULL;
static char *iso3166_to_check = NULL;
static char *script_to_check = NULL;
static gboolean setlocale_called = FALSE;

static BOOL CALLBACK
enum_locale_proc (LPTSTR locale)
{
  LCID lcid;
  char iso639[10];
  char iso3166[10];
  char *endptr;


  lcid = strtoul (locale, &endptr, 16);
  if (*endptr == '\0' &&
      GetLocaleInfo (lcid, LOCALE_SISO639LANGNAME, iso639, sizeof (iso639)) &&
      GetLocaleInfo (lcid, LOCALE_SISO3166CTRYNAME, iso3166, sizeof (iso3166)))
    {
      if (strcmp (iso639, iso639_to_check) == 0 &&
          ((iso3166_to_check != NULL &&
            strcmp (iso3166, iso3166_to_check) == 0) ||
           (iso3166_to_check == NULL &&
            SUBLANGID (LANGIDFROMLCID (lcid)) == SUBLANG_DEFAULT)))
        {
          char language[100], country[100];
          char locale[300];

          if (script_to_check != NULL)
            {
              /* If lcid is the "other" script for this language,
               * return TRUE, i.e. continue looking.
               */
              if (strcmp (script_to_check, "Latn") == 0)
                {
                  switch (LANGIDFROMLCID (lcid))
                    {
                    case MAKELANGID (LANG_AZERI, SUBLANG_AZERI_CYRILLIC):
                      return TRUE;
                    case MAKELANGID (LANG_UZBEK, SUBLANG_UZBEK_CYRILLIC):
                      return TRUE;
                    case MAKELANGID (LANG_SERBIAN, SUBLANG_SERBIAN_CYRILLIC):
                      return TRUE;
                    case MAKELANGID (LANG_SERBIAN, 0x07):
                      /* Serbian in Bosnia and Herzegovina, Cyrillic */
                      return TRUE;
                    }
                }
              else if (strcmp (script_to_check, "Cyrl") == 0)
                {
                  switch (LANGIDFROMLCID (lcid))
                    {
                    case MAKELANGID (LANG_AZERI, SUBLANG_AZERI_LATIN):
                      return TRUE;
                    case MAKELANGID (LANG_UZBEK, SUBLANG_UZBEK_LATIN):
                      return TRUE;
                    case MAKELANGID (LANG_SERBIAN, SUBLANG_SERBIAN_LATIN):
                      return TRUE;
                    case MAKELANGID (LANG_SERBIAN, 0x06):
                      /* Serbian in Bosnia and Herzegovina, Latin */
                      return TRUE;
                    }
                }
            }

          SetThreadLocale (lcid);

          if (GetLocaleInfo (lcid, LOCALE_SENGLANGUAGE, language, sizeof (language)) &&
              GetLocaleInfo (lcid, LOCALE_SENGCOUNTRY, country, sizeof (country)))
            {
              strcpy (locale, language);
              strcat (locale, "_");
              strcat (locale, country);

              if (setlocale (LC_ALL, locale) != NULL)
                setlocale_called = TRUE;
            }

          return FALSE;
        }
    }

  return TRUE;
}
  
#endif

static void
setlocale_initialization (void)
{
  static gboolean initialized = FALSE;

  if (initialized)
    return;
  initialized = TRUE;

  if (do_setlocale)
    {
#ifdef G_OS_WIN32
      /* If some of the POSIXish environment variables are set, set
       * the Win32 thread locale correspondingly.
       */ 
      char *p = getenv ("LC_ALL");
      if (p == NULL)
        p = getenv ("LANG");

      if (p != NULL)
        {
          p = g_strdup (p);
          if (strcmp (p, "C") == 0)
            SetThreadLocale (LOCALE_SYSTEM_DEFAULT);
          else
            {
              /* Check if one of the supported locales match the
               * environment variable. If so, use that locale.
               */
              iso639_to_check = p;
              iso3166_to_check = strchr (iso639_to_check, '_');
              if (iso3166_to_check != NULL)
                {
                  *iso3166_to_check++ = '\0';

                  script_to_check = strchr (iso3166_to_check, '@');
                  if (script_to_check != NULL)
                    *script_to_check++ = '\0';

                  /* Handle special cases. */

                  /* The standard code for Serbia and Montenegro was
                   * "CS", but MSFT uses for some reason "SP". By now
                   * (October 2006), SP has split into two, "RS" and
                   * "ME", but don't bother trying to handle those
                   * yet. Do handle the even older "YU", though.
                   */
                  if (strcmp (iso3166_to_check, "CS") == 0 ||
                      strcmp (iso3166_to_check, "YU") == 0)
                    iso3166_to_check = "SP";
                }
              else
                {
                  script_to_check = strchr (iso639_to_check, '@');
                  if (script_to_check != NULL)
                    *script_to_check++ = '\0';
                  /* LANG_SERBIAN == LANG_CROATIAN, recognize just "sr" */
                  if (strcmp (iso639_to_check, "sr") == 0)
                    iso3166_to_check = "SP";
                }

              EnumSystemLocales (enum_locale_proc, LCID_SUPPORTED);
            }
          g_free (p);
        }
      if (!setlocale_called)
        setlocale (LC_ALL, "");
#else
      if (!setlocale (LC_ALL, ""))
        g_warning ("Locale not supported by C library.\n\tUsing the fallback 'C' locale.");
#endif
    }
}

static void
do_pre_parse_initialization (void)
{
  const gchar *env_string;
  double slowdown;

  if (pre_initialized)
    return;

  pre_initialized = TRUE;

  if (_gtk_module_has_mixed_deps (NULL))
    g_error ("GTK+ 2.x symbols detected. Using GTK+ 2.x and GTK+ 3 in the same process is not supported");

  gdk_pre_parse ();
  gdk_event_handler_set ((GdkEventFunc)gtk_main_do_event, NULL, NULL);

#ifdef G_ENABLE_DEBUG
  env_string = g_getenv ("GTK_DEBUG");
  if (env_string != NULL)
    {
      debug_flags[0].flags = g_parse_debug_string (env_string,
                                                   gtk_debug_keys,
                                                   G_N_ELEMENTS (gtk_debug_keys));
      env_string = NULL;
    }
#endif  /* G_ENABLE_DEBUG */

  env_string = g_getenv ("GTK3_MODULES");
  if (env_string)
    gtk_modules_string = g_string_new (env_string);

  env_string = g_getenv ("GTK_MODULES");
  if (env_string)
    {
      if (gtk_modules_string)
        g_string_append_c (gtk_modules_string, G_SEARCHPATH_SEPARATOR);
      else
        gtk_modules_string = g_string_new (NULL);

      g_string_append (gtk_modules_string, env_string);
    }

  env_string = g_getenv ("GTK_SLOWDOWN");
  if (env_string)
    {
      slowdown = g_ascii_strtod (env_string, NULL);
      _gtk_set_slowdown (slowdown);
    }
}

static void
gettext_initialization (void)
{
  setlocale_initialization ();

#ifdef ENABLE_NLS
  bindtextdomain (GETTEXT_PACKAGE, _gtk_get_localedir ());
  bindtextdomain (GETTEXT_PACKAGE "-properties", _gtk_get_localedir ());
#    ifdef HAVE_BIND_TEXTDOMAIN_CODESET
  bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
  bind_textdomain_codeset (GETTEXT_PACKAGE "-properties", "UTF-8");
#    endif
#endif
}

static void
default_display_notify_cb (GdkDisplayManager *dm)
{
  _gtk_accessibility_init ();
  debug_flags[0].display = gdk_display_get_default ();
}

static void
do_post_parse_initialization (void)
{
  GdkDisplayManager *display_manager;

  if (gtk_initialized)
    return;

  gettext_initialization ();

#ifdef SIGPIPE
  signal (SIGPIPE, SIG_IGN);
#endif

  if (debug_flags[0].flags & GTK_DEBUG_UPDATES)
    gtk_debug_updates_set_enabled (TRUE);

  gtk_widget_set_default_direction (gtk_get_locale_direction ());

  gsk_ensure_resources ();
  _gtk_ensure_resources ();

  _gtk_accel_map_init ();

  gtk_initialized = TRUE;

  if (gtk_modules_string)
    {
      _gtk_modules_init (NULL, NULL, gtk_modules_string->str);
      g_string_free (gtk_modules_string, TRUE);
    }
  else
    {
      _gtk_modules_init (NULL, NULL, NULL);
    }

  display_manager = gdk_display_manager_get ();
  if (gdk_display_manager_get_default_display (display_manager) != NULL)
    _gtk_accessibility_init ();

  g_signal_connect (display_manager, "notify::default-display",
                    G_CALLBACK (default_display_notify_cb),
                    NULL);
}

guint
gtk_get_display_debug_flags (GdkDisplay *display)
{
  gint i;

  for (i = 0; i < N_DEBUG_DISPLAYS; i++)
    {
      if (debug_flags[i].display == display)
        return debug_flags[i].flags;
    }

  return 0;
}

void
gtk_set_display_debug_flags (GdkDisplay *display,
                             guint       flags)
{
  gint i;

  for (i = 0; i < N_DEBUG_DISPLAYS; i++)
    {
      if (debug_flags[i].display == NULL)
        debug_flags[i].display = display;

      if (debug_flags[i].display == display)
        {
          debug_flags[i].flags = flags;
          return;
        }
    }
}

/**
 * gtk_get_debug_flags:
 *
 * Returns the GTK+ debug flags.
 *
 * This function is intended for GTK+ modules that want
 * to adjust their debug output based on GTK+ debug flags.
 *
 * Returns: the GTK+ debug flags.
 */
guint
gtk_get_debug_flags (void)
{
  return gtk_get_display_debug_flags (gdk_display_get_default ());
}

/**
 * gtk_set_debug_flags:
 *
 * Sets the GTK+ debug flags.
 */
void
gtk_set_debug_flags (guint flags)
{
  gtk_set_display_debug_flags (gdk_display_get_default (), flags);
}

gboolean
gtk_simulate_touchscreen (void)
{
  static gint test_touchscreen;

  if (test_touchscreen == 0)
    test_touchscreen = g_getenv ("GTK_TEST_TOUCHSCREEN") != NULL ? 1 : -1;

  return test_touchscreen > 0 || (gtk_get_debug_flags () & GTK_DEBUG_TOUCHSCREEN) != 0;
 }

#ifdef G_PLATFORM_WIN32
#undef gtk_init_check
#endif

/**
 * gtk_init_check:
 *
 * This function does the same work as gtk_init() with only a single
 * change: It does not terminate the program if the windowing system
 * can’t be initialized. Instead it returns %FALSE on failure.
 *
 * This way the application can fall back to some other means of
 * communication with the user - for example a curses or command line
 * interface.
 *
 * Returns: %TRUE if the windowing system has been successfully
 *     initialized, %FALSE otherwise
 */
gboolean
gtk_init_check (void)
{
  gboolean ret;

  if (gtk_initialized)
    return TRUE;

  gettext_initialization ();

  if (!check_setugid ())
    return FALSE;

  do_pre_parse_initialization ();
  do_post_parse_initialization ();

  ret = gdk_display_open_default () != NULL;

  if (gtk_get_debug_flags () & GTK_DEBUG_INTERACTIVE)
    gtk_window_set_interactive_debugging (TRUE);

  return ret;
}

#ifdef G_PLATFORM_WIN32
#undef gtk_init
#endif

/**
 * gtk_init:
 *
 * Call this function before using any other GTK+ functions in your GUI
 * applications.  It will initialize everything needed to operate the
 * toolkit and parses some standard command line options.
 *
 * If you are using #GtkApplication, you don't have to call gtk_init()
 * or gtk_init_check(); the #GtkApplication::startup handler
 * does it for you.
 *
 * This function will terminate your program if it was unable to
 * initialize the windowing system for some reason. If you want
 * your program to fall back to a textual interface you want to
 * call gtk_init_check() instead.
 *
 * Since 2.18, GTK+ calls `signal (SIGPIPE, SIG_IGN)`
 * during initialization, to ignore SIGPIPE signals, since these are
 * almost never wanted in graphical applications. If you do need to
 * handle SIGPIPE for some reason, reset the handler after gtk_init(),
 * but notice that other libraries (e.g. libdbus or gvfs) might do
 * similar things.
 */
void
gtk_init (void)
{
  if (!gtk_init_check ())
    {
      const char *display_name_arg = gdk_get_display_arg_name ();
      if (display_name_arg == NULL)
        display_name_arg = getenv ("DISPLAY");
      g_warning ("cannot open display: %s", display_name_arg ? display_name_arg : "");
      exit (1);
    }
}

#ifdef G_OS_WIN32

/* This is relevant when building with gcc for Windows (MinGW),
 * where we want to be struct packing compatible with MSVC,
 * i.e. use the -mms-bitfields switch.
 * For Cygwin there should be no need to be compatible with MSVC,
 * so no need to use G_PLATFORM_WIN32.
 */

static void
check_sizeof_GtkWindow (size_t sizeof_GtkWindow)
{
  if (sizeof_GtkWindow != sizeof (GtkWindow))
    g_error ("Incompatible build!\n"
             "The code using GTK+ thinks GtkWindow is of different\n"
             "size than it actually is in this build of GTK+.\n"
             "On Windows, this probably means that you have compiled\n"
             "your code with gcc without the -mms-bitfields switch,\n"
             "or that you are using an unsupported compiler.");
}

/* In GTK+ 2.0 the GtkWindow struct actually is the same size in
 * gcc-compiled code on Win32 whether compiled with -fnative-struct or
 * not. Unfortunately this wan’t noticed until after GTK+ 2.0.1. So,
 * from GTK+ 2.0.2 on, check some other struct, too, where the use of
 * -fnative-struct still matters. GtkBox is one such.
 */
static void
check_sizeof_GtkBox (size_t sizeof_GtkBox)
{
  if (sizeof_GtkBox != sizeof (GtkBox))
    g_error ("Incompatible build!\n"
             "The code using GTK+ thinks GtkBox is of different\n"
             "size than it actually is in this build of GTK+.\n"
             "On Windows, this probably means that you have compiled\n"
             "your code with gcc without the -mms-bitfields switch,\n"
             "or that you are using an unsupported compiler.");
}

/* These two functions might get more checks added later, thus pass
 * in the number of extra args.
 */
void
gtk_init_abi_check (int num_checks, size_t sizeof_GtkWindow, size_t sizeof_GtkBox)
{
  check_sizeof_GtkWindow (sizeof_GtkWindow);
  if (num_checks >= 2)
    check_sizeof_GtkBox (sizeof_GtkBox);
  gtk_init ();
}

gboolean
gtk_init_check_abi_check (int num_checks, size_t sizeof_GtkWindow, size_t sizeof_GtkBox)
{
  check_sizeof_GtkWindow (sizeof_GtkWindow);
  if (num_checks >= 2)
    check_sizeof_GtkBox (sizeof_GtkBox);
  return gtk_init_check ();
}

#endif

/**
 * gtk_get_locale_direction:
 *
 * Get the direction of the current locale. This is the expected
 * reading direction for text and UI.
 *
 * This function depends on the current locale being set with
 * setlocale() and will default to setting the %GTK_TEXT_DIR_LTR
 * direction otherwise. %GTK_TEXT_DIR_NONE will never be returned.
 *
 * GTK+ sets the default text direction according to the locale
 * during gtk_init(), and you should normally use
 * gtk_widget_get_direction() or gtk_widget_get_default_direction()
 * to obtain the current direcion.
 *
 * This function is only needed rare cases when the locale is
 * changed after GTK+ has already been initialized. In this case,
 * you can use it to update the default text direction as follows:
 *
 * |[<!-- language="C" -->
 * setlocale (LC_ALL, new_locale);
 * direction = gtk_get_locale_direction ();
 * gtk_widget_set_default_direction (direction);
 * ]|
 *
 * Returns: the #GtkTextDirection of the current locale
 *
 * Since: 3.12
 */
GtkTextDirection
gtk_get_locale_direction (void)
{
  /* Translate to default:RTL if you want your widgets
   * to be RTL, otherwise translate to default:LTR.
   * Do *not* translate it to "predefinito:LTR", if it
   * it isn't default:LTR or default:RTL it will not work
   */
  gchar            *e   = _("default:LTR");
  GtkTextDirection  dir = GTK_TEXT_DIR_LTR;

  if (g_strcmp0 (e, "default:RTL") == 0)
    dir = GTK_TEXT_DIR_RTL;
  else if (g_strcmp0 (e, "default:LTR") != 0)
    g_warning ("Whoever translated default:LTR did so wrongly. Defaulting to LTR.");

  return dir;
}

/**
 * gtk_get_default_language:
 *
 * Returns the #PangoLanguage for the default language currently in
 * effect. (Note that this can change over the life of an
 * application.) The default language is derived from the current
 * locale. It determines, for example, whether GTK+ uses the
 * right-to-left or left-to-right text direction.
 *
 * This function is equivalent to pango_language_get_default().
 * See that function for details.
 *
 * Returns: (transfer none): the default language as a #PangoLanguage,
 *     must not be freed
 */
PangoLanguage *
gtk_get_default_language (void)
{
  return pango_language_get_default ();
}

/**
 * gtk_main:
 *
 * Runs the main loop until gtk_main_quit() is called.
 *
 * You can nest calls to gtk_main(). In that case gtk_main_quit()
 * will make the innermost invocation of the main loop return.
 */
void
gtk_main (void)
{
  GMainLoop *loop;

  gtk_main_loop_level++;

  loop = g_main_loop_new (NULL, TRUE);
  main_loops = g_slist_prepend (main_loops, loop);

  if (g_main_loop_is_running (main_loops->data))
    {
      gdk_threads_leave ();
      g_main_loop_run (loop);
      gdk_threads_enter ();
      gdk_flush ();
    }

  main_loops = g_slist_remove (main_loops, loop);

  g_main_loop_unref (loop);

  gtk_main_loop_level--;

  if (gtk_main_loop_level == 0)
    {
      /* Keep this section in sync with gtk_application_shutdown() */

      /* Try storing all clipboard data we have */
      _gtk_clipboard_store_all ();

      /* Synchronize the recent manager singleton */
      _gtk_recent_manager_sync ();
    }
}

/**
 * gtk_main_level:
 *
 * Asks for the current nesting level of the main loop.
 *
 * Returns: the nesting level of the current invocation
 *     of the main loop
 */
guint
gtk_main_level (void)
{
  return gtk_main_loop_level;
}

/**
 * gtk_main_quit:
 *
 * Makes the innermost invocation of the main loop return
 * when it regains control.
 */
void
gtk_main_quit (void)
{
  g_return_if_fail (main_loops != NULL);

  g_main_loop_quit (main_loops->data);
}

/**
 * gtk_events_pending:
 *
 * Checks if any events are pending.
 *
 * This can be used to update the UI and invoke timeouts etc.
 * while doing some time intensive computation.
 *
 * ## Updating the UI during a long computation
 *
 * |[<!-- language="C" -->
 *  // computation going on...
 *
 *  while (gtk_events_pending ())
 *    gtk_main_iteration ();
 *
 *  // ...computation continued
 * ]|
 *
 * Returns: %TRUE if any events are pending, %FALSE otherwise
 */
gboolean
gtk_events_pending (void)
{
  gboolean result;

  gdk_threads_leave ();
  result = g_main_context_pending (NULL);
  gdk_threads_enter ();

  return result;
}

/**
 * gtk_main_iteration:
 *
 * Runs a single iteration of the mainloop.
 *
 * If no events are waiting to be processed GTK+ will block
 * until the next event is noticed. If you don’t want to block
 * look at gtk_main_iteration_do() or check if any events are
 * pending with gtk_events_pending() first.
 *
 * Returns: %TRUE if gtk_main_quit() has been called for the
 *     innermost mainloop
 */
gboolean
gtk_main_iteration (void)
{
  gdk_threads_leave ();
  g_main_context_iteration (NULL, TRUE);
  gdk_threads_enter ();

  if (main_loops)
    return !g_main_loop_is_running (main_loops->data);
  else
    return TRUE;
}

/**
 * gtk_main_iteration_do:
 * @blocking: %TRUE if you want GTK+ to block if no events are pending
 *
 * Runs a single iteration of the mainloop.
 * If no events are available either return or block depending on
 * the value of @blocking.
 *
 * Returns: %TRUE if gtk_main_quit() has been called for the
 *     innermost mainloop
 */
gboolean
gtk_main_iteration_do (gboolean blocking)
{
  gdk_threads_leave ();
  g_main_context_iteration (NULL, blocking);
  gdk_threads_enter ();

  if (main_loops)
    return !g_main_loop_is_running (main_loops->data);
  else
    return TRUE;
}

static void
rewrite_events_translate (GdkWindow *old_window,
                          GdkWindow *new_window,
                          gdouble   *x,
                          gdouble   *y)
{
  gint old_origin_x, old_origin_y;
  gint new_origin_x, new_origin_y;

  gdk_window_get_origin (old_window, &old_origin_x, &old_origin_y);
  gdk_window_get_origin (new_window, &new_origin_x, &new_origin_y);

  *x += old_origin_x - new_origin_x;
  *y += old_origin_y - new_origin_y;
}

static GdkEvent *
rewrite_event_for_window (GdkEvent  *event,
                          GdkWindow *new_window)
{
  event = gdk_event_copy (event);

  switch (event->type)
    {
    case GDK_SCROLL:
      rewrite_events_translate (event->any.window,
                                new_window,
                                &event->scroll.x, &event->scroll.y);
      break;
    case GDK_BUTTON_PRESS:
    case GDK_2BUTTON_PRESS:
    case GDK_3BUTTON_PRESS:
    case GDK_BUTTON_RELEASE:
      rewrite_events_translate (event->any.window,
                                new_window,
                                &event->button.x, &event->button.y);
      break;
    case GDK_MOTION_NOTIFY:
      rewrite_events_translate (event->any.window,
                                new_window,
                                &event->motion.x, &event->motion.y);
      break;
    case GDK_TOUCH_BEGIN:
    case GDK_TOUCH_UPDATE:
    case GDK_TOUCH_END:
    case GDK_TOUCH_CANCEL:
      rewrite_events_translate (event->any.window,
                                new_window,
                                &event->touch.x, &event->touch.y);
      break;
    case GDK_TOUCHPAD_SWIPE:
      rewrite_events_translate (event->any.window,
                                new_window,
                                &event->touchpad_swipe.x,
                                &event->touchpad_swipe.y);
      break;
    case GDK_TOUCHPAD_PINCH:
      rewrite_events_translate (event->any.window,
                                new_window,
                                &event->touchpad_pinch.x,
                                &event->touchpad_pinch.y);
      break;
    case GDK_KEY_PRESS:
    case GDK_KEY_RELEASE:
    case GDK_PROXIMITY_IN:
    case GDK_PROXIMITY_OUT:
      break;

    default:
      return event;
    }

  g_object_unref (event->any.window);
  event->any.window = g_object_ref (new_window);

  return event;
}

/* If there is a pointer or keyboard grab in effect with owner_events = TRUE,
 * then what X11 does is deliver the event normally if it was going to this
 * client, otherwise, delivers it in terms of the grab window. This function
 * rewrites events to the effect that events going to the same window group
 * are delivered normally, otherwise, the event is delivered in terms of the
 * grab window.
 */
static GdkEvent *
rewrite_event_for_grabs (GdkEvent *event)
{
  GdkWindow *grab_window;
  GtkWidget *event_widget, *grab_widget;
  gpointer grab_widget_ptr;
  gboolean owner_events;
  GdkDisplay *display;
  GdkDevice *device;

  switch (event->type)
    {
    case GDK_SCROLL:
    case GDK_BUTTON_PRESS:
    case GDK_2BUTTON_PRESS:
    case GDK_3BUTTON_PRESS:
    case GDK_BUTTON_RELEASE:
    case GDK_MOTION_NOTIFY:
    case GDK_PROXIMITY_IN:
    case GDK_PROXIMITY_OUT:
    case GDK_KEY_PRESS:
    case GDK_KEY_RELEASE:
    case GDK_TOUCH_BEGIN:
    case GDK_TOUCH_UPDATE:
    case GDK_TOUCH_END:
    case GDK_TOUCH_CANCEL:
    case GDK_TOUCHPAD_SWIPE:
    case GDK_TOUCHPAD_PINCH:
      display = gdk_window_get_display (event->any.window);
      device = gdk_event_get_device (event);

      if (!gdk_device_grab_info (display, device, &grab_window, &owner_events) ||
          !owner_events)
        return NULL;
      break;
    default:
      return NULL;
    }

  event_widget = gtk_get_event_widget (event);
  gdk_window_get_user_data (grab_window, &grab_widget_ptr);
  grab_widget = grab_widget_ptr;

  if (grab_widget &&
      gtk_main_get_window_group (grab_widget) != gtk_main_get_window_group (event_widget))
    return rewrite_event_for_window (event, grab_window);
  else
    return NULL;
}

static GtkWidget *
widget_get_popover_ancestor (GtkWidget *widget,
                             GtkWindow *window)
{
  GtkWidget *parent = gtk_widget_get_parent (widget);

  while (parent && parent != GTK_WIDGET (window))
    {
      widget = parent;
      parent = gtk_widget_get_parent (widget);
    }

  if (!parent || parent != GTK_WIDGET (window))
    return NULL;

  if (_gtk_window_is_popover_widget (GTK_WINDOW (window), widget))
    return widget;

  return NULL;
}

static gboolean
check_event_in_child_popover (GtkWidget *event_widget,
                              GtkWidget *grab_widget)
{
  GtkWidget *window, *popover = NULL, *popover_parent = NULL;

  if (grab_widget == event_widget)
    return FALSE;

  window = gtk_widget_get_ancestor (event_widget, GTK_TYPE_WINDOW);

  if (!window)
    return FALSE;

  popover = widget_get_popover_ancestor (event_widget, GTK_WINDOW (window));

  if (!popover)
    return FALSE;

  popover_parent = _gtk_window_get_popover_parent (GTK_WINDOW (window), popover);

  if (!popover_parent)
    return FALSE;

  return (popover_parent == grab_widget || gtk_widget_is_ancestor (popover_parent, grab_widget));
}

static GdkNotifyType
get_virtual_notify_type (GdkNotifyType notify_type)
{
  switch (notify_type)
    {
    case GDK_NOTIFY_ANCESTOR:
    case GDK_NOTIFY_INFERIOR:
      return GDK_NOTIFY_VIRTUAL;
    case GDK_NOTIFY_NONLINEAR:
      return GDK_NOTIFY_NONLINEAR_VIRTUAL;
    default:
      g_assert_not_reached ();
      return GDK_NOTIFY_UNKNOWN;
    }
}

static void
synth_crossing (GtkWidget       *widget,
                GtkWidget       *toplevel,
                gboolean         enter,
                GtkWidget       *other_widget,
                GdkEvent        *source,
                GdkNotifyType    notify_type,
                GdkCrossingMode  crossing_mode)
{
  GdkEvent *event;
  gdouble x, y;

  event = gdk_event_new (enter ? GDK_ENTER_NOTIFY : GDK_LEAVE_NOTIFY);
  gdk_event_set_user_data (event, G_OBJECT (widget));
  gdk_event_set_device (event, gdk_event_get_device (source));
  gdk_event_set_source_device (event, gdk_event_get_source_device (source));

  event->any.window = g_object_ref (gtk_widget_get_window (toplevel));
  if (other_widget)
    event->crossing.subwindow = g_object_ref (gtk_widget_get_window (other_widget));

  if (enter)
    gtk_widget_set_state_flags (widget, GTK_STATE_FLAG_PRELIGHT, FALSE);
  else
    gtk_widget_unset_state_flags (widget, GTK_STATE_FLAG_PRELIGHT);

  gdk_event_get_coords (source, &x, &y);
  event->crossing.x = x;
  event->crossing.y = y;
  event->crossing.mode = crossing_mode;
  event->crossing.detail = notify_type;

  gtk_widget_event (widget, event);
  gdk_event_free (event);
}

static GtkWidget *
update_pointer_focus_state (GtkWindow *toplevel,
                            GdkEvent  *event,
                            GtkWidget *new_target)
{
  GtkWidget *old_target = NULL;
  GdkEventSequence *sequence;
  GdkDevice *device;
  gdouble x, y;

  device = gdk_event_get_device (event);
  sequence = gdk_event_get_event_sequence (event);
  old_target = gtk_window_lookup_pointer_focus_widget (toplevel, device, sequence);
  if (old_target == new_target)
    return old_target;

  gdk_event_get_coords (event, &x, &y);
  gtk_window_update_pointer_focus (toplevel, device, sequence,
                                   new_target, x, y);

  return old_target;
}

static void
gtk_synthesize_crossing_events (GtkWindow       *toplevel,
                                GtkWidget       *old_target,
                                GtkWidget       *new_target,
                                GdkEvent        *event,
                                GdkCrossingMode  mode)
{
  GtkWidget *ancestor = NULL, *widget;
  GdkNotifyType enter_type, leave_type, notify_type;

  if (old_target && new_target)
    ancestor = gtk_widget_common_ancestor (old_target, new_target);

  if (ancestor == old_target)
    {
      leave_type = GDK_NOTIFY_INFERIOR;
      enter_type = GDK_NOTIFY_ANCESTOR;
    }
  else if (ancestor == new_target)
    {
      leave_type = GDK_NOTIFY_ANCESTOR;
      enter_type = GDK_NOTIFY_INFERIOR;
    }
  else
    enter_type = leave_type = GDK_NOTIFY_NONLINEAR;

  if (old_target)
    {
      widget = old_target;

      while (widget != ancestor)
        {
          notify_type = (widget == old_target) ?
            leave_type : get_virtual_notify_type (leave_type);

          synth_crossing (widget, GTK_WIDGET (toplevel), FALSE,
                          new_target, event, notify_type, mode);
          widget = gtk_widget_get_parent (widget);
        }
    }

  if (new_target)
    {
      GSList *widgets = NULL;

      widget = new_target;

      while (widget != ancestor)
        {
          widgets = g_slist_prepend (widgets, widget);
          widget = gtk_widget_get_parent (widget);
        }

      while (widgets)
        {
          widget = widgets->data;
          widgets = g_slist_delete_link (widgets, widgets);
          notify_type = (widget == new_target) ?
            enter_type : get_virtual_notify_type (enter_type);

          synth_crossing (widget, GTK_WIDGET (toplevel), TRUE,
                          old_target, event, notify_type, mode);
        }
    }
}

static gboolean
is_pointing_event (GdkEvent *event)
{
  switch (event->type)
    {
    case GDK_MOTION_NOTIFY:
    case GDK_ENTER_NOTIFY:
    case GDK_LEAVE_NOTIFY:
    case GDK_BUTTON_PRESS:
    case GDK_BUTTON_RELEASE:
    case GDK_SCROLL:
    case GDK_TOUCH_BEGIN:
    case GDK_TOUCH_UPDATE:
    case GDK_TOUCH_END:
    case GDK_TOUCH_CANCEL:
    case GDK_TOUCHPAD_PINCH:
    case GDK_TOUCHPAD_SWIPE:
      return TRUE;
      break;
    default:
      return FALSE;
    }
}

static GtkWidget *
handle_pointing_event (GdkEvent *event)
{
  GtkWidget *target = NULL, *old_target = NULL, *widget;
  GtkWindow *toplevel;
  GdkEventSequence *sequence;
  GdkDevice *device;
  gdouble x, y;

  widget = gtk_get_event_widget (event);
  device = gdk_event_get_device (event);
  if (!device || !gdk_event_get_coords (event, &x, &y))
    return widget;

  toplevel = GTK_WINDOW (gtk_widget_get_toplevel (widget));
  if (!GTK_IS_WINDOW (toplevel))
    return widget;

  sequence = gdk_event_get_event_sequence (event);

  switch (event->type)
    {
    case GDK_LEAVE_NOTIFY:
      if (event->crossing.mode == GDK_CROSSING_GRAB ||
          event->crossing.mode == GDK_CROSSING_UNGRAB)
        break;
    case GDK_TOUCH_END:
    case GDK_TOUCH_CANCEL:
      old_target = update_pointer_focus_state (toplevel, event, NULL);
      break;
    case GDK_ENTER_NOTIFY:
      if (event->crossing.mode == GDK_CROSSING_GRAB ||
          event->crossing.mode == GDK_CROSSING_UNGRAB)
        break;
    case GDK_TOUCH_BEGIN:
    case GDK_TOUCH_UPDATE:
    case GDK_MOTION_NOTIFY:
      target = _gtk_toplevel_pick (toplevel, x, y, NULL, NULL);
      old_target = update_pointer_focus_state (toplevel, event, target);

      if (event->type == GDK_MOTION_NOTIFY || event->type == GDK_ENTER_NOTIFY)
        {
          if (!gtk_window_lookup_pointer_focus_implicit_grab (toplevel, device,
                                                              sequence))
            {
              gtk_synthesize_crossing_events (toplevel, old_target, target,
                                              event, GDK_CROSSING_NORMAL);
            }

          gtk_window_maybe_update_cursor (toplevel, NULL, device);
        }

      if (event->type == GDK_TOUCH_BEGIN)
        gtk_window_set_pointer_focus_grab (toplevel, device, sequence, target);

      /* Let it take the effective pointer focus anyway, as it may change due
       * to implicit grabs.
       */
      target = NULL;
      break;
    case GDK_BUTTON_PRESS:
    case GDK_BUTTON_RELEASE:
      target = gtk_window_lookup_effective_pointer_focus_widget (toplevel,
                                                                 device,
                                                                 sequence);
      gtk_window_set_pointer_focus_grab (toplevel, device, sequence,
                                         event->type == GDK_BUTTON_PRESS ?
                                         target : NULL);

      if (event->type == GDK_BUTTON_RELEASE)
        {
          old_target = target;
          target = _gtk_toplevel_pick (toplevel, x, y, NULL, NULL);
          gtk_synthesize_crossing_events (toplevel, old_target, target, event,
                                          GDK_CROSSING_UNGRAB);
          gtk_window_maybe_update_cursor (toplevel, NULL, device);
        }
      break;
    case GDK_SCROLL:
    case GDK_TOUCHPAD_PINCH:
    case GDK_TOUCHPAD_SWIPE:
      break;
    default:
      g_assert_not_reached ();
    }

  if (!target)
    target = gtk_window_lookup_effective_pointer_focus_widget (toplevel,
                                                               device,
                                                               sequence);
  return target ? target : old_target;
}

/**
 * gtk_main_do_event:
 * @event: An event to process (normally passed by GDK)
 *
 * Processes a single GDK event.
 *
 * This is public only to allow filtering of events between GDK and GTK+.
 * You will not usually need to call this function directly.
 *
 * While you should not call this function directly, you might want to
 * know how exactly events are handled. So here is what this function
 * does with the event:
 *
 * 1. Compress enter/leave notify events. If the event passed build an
 *    enter/leave pair together with the next event (peeked from GDK), both
 *    events are thrown away. This is to avoid a backlog of (de-)highlighting
 *    widgets crossed by the pointer.
 * 
 * 2. Find the widget which got the event. If the widget can’t be determined
 *    the event is thrown away unless it belongs to a INCR transaction.
 *
 * 3. Then the event is pushed onto a stack so you can query the currently
 *    handled event with gtk_get_current_event().
 * 
 * 4. The event is sent to a widget. If a grab is active all events for widgets
 *    that are not in the contained in the grab widget are sent to the latter
 *    with a few exceptions:
 *    - Deletion and destruction events are still sent to the event widget for
 *      obvious reasons.
 *    - Events which directly relate to the visual representation of the event
 *      widget.
 *    - Leave events are delivered to the event widget if there was an enter
 *      event delivered to it before without the paired leave event.
 *    - Drag events are not redirected because it is unclear what the semantics
 *      of that would be.
 * 
 * 5. After finishing the delivery the event is popped from the event stack.
 */
void
gtk_main_do_event (GdkEvent *event)
{
  GtkWidget *event_widget;
  GtkWidget *grab_widget = NULL;
  GtkWidget *topmost_widget = NULL;
  GtkWindowGroup *window_group;
  GdkEvent *rewritten_event = NULL;
  GdkDevice *device;
  GList *tmp_list;

  if (event->type == GDK_SETTING)
    {
      _gtk_settings_handle_event (&event->setting);
      return;
    }

  if (event->type == GDK_OWNER_CHANGE)
    {
      _gtk_clipboard_handle_event (&event->owner_change);
      return;
    }

  /* Find the widget which got the event. We store the widget
   * in the user_data field of GdkWindow's. Ignore the event
   * if we don't have a widget for it, except for GDK_PROPERTY_NOTIFY
   * events which are handled specially. Though this happens rarely,
   * bogus events can occur for e.g. destroyed GdkWindows.
   */
  event_widget = gtk_get_event_widget (event);
  if (!event_widget)
    {
      /* To handle selection INCR transactions, we select
       * PropertyNotify events on the requestor window and create
       * a corresponding (fake) GdkWindow so that events get here.
       * There won't be a widget though, so we have to handle
       * them specially
       */
      if (event->type == GDK_PROPERTY_NOTIFY)
        _gtk_selection_incr_event (event->any.window,
                                   &event->property);

      return;
    }

  /* If pointer or keyboard grabs are in effect, munge the events
   * so that each window group looks like a separate app.
   */
  rewritten_event = rewrite_event_for_grabs (event);
  if (rewritten_event)
    {
      event = rewritten_event;
      event_widget = gtk_get_event_widget (event);
    }

  /* Push the event onto a stack of current events for
   * gtk_current_event_get().
   */
  current_events = g_list_prepend (current_events, event);

  if (is_pointing_event (event))
    event_widget = handle_pointing_event (event);

  if (!event_widget)
    goto cleanup;

  window_group = gtk_main_get_window_group (event_widget);
  device = gdk_event_get_device (event);

  /* check whether there is a (device) grab in effect... */
  if (device)
    grab_widget = gtk_window_group_get_current_device_grab (window_group, device);

  if (!grab_widget)
    grab_widget = gtk_window_group_get_current_grab (window_group);

  if (GTK_IS_WINDOW (event_widget) ||
      (grab_widget && grab_widget != event_widget &&
       !gtk_widget_is_ancestor (event_widget, grab_widget)))
    {
      /* Ignore event if we got a grab on another toplevel */
      if (!grab_widget ||
          gtk_widget_get_toplevel (event_widget) == gtk_widget_get_toplevel (grab_widget))
        {
          if (_gtk_window_check_handle_wm_event (event))
            goto cleanup;
        }
    }

  /* Find out the topmost widget where captured event propagation
   * should start, which is the widget holding the GTK+ grab
   * if any, otherwise it's left NULL and events are emitted
   * from the toplevel (or topmost parentless parent).
   */
  if (grab_widget)
    topmost_widget = grab_widget;

  /* If the grab widget is an ancestor of the event widget
   * then we send the event to the original event widget.
   * This is the key to implementing modality.
   */
  if (!grab_widget ||
      ((gtk_widget_is_sensitive (event_widget) || event->type == GDK_SCROLL) &&
       gtk_widget_is_ancestor (event_widget, grab_widget)))
    grab_widget = event_widget;

  /* popovers are not really a "child" of their "parent" in the widget/window
   * hierarchy sense, we however want to interact with popovers spawn by widgets
   * within grab_widget. If this is the case, we let the event go through
   * unaffected by the grab.
   */
  if (check_event_in_child_popover (event_widget, grab_widget))
    grab_widget = event_widget;

  gdk_event_set_user_data (event, G_OBJECT (event_widget));

  /* If the widget receiving events is actually blocked by another
   * device GTK+ grab
   */
  if (device &&
      _gtk_window_group_widget_is_blocked_for_device (window_group, grab_widget, device))
    goto cleanup;

  /* Not all events get sent to the grabbing widget.
   * The delete, destroy, expose, focus change and resize
   * events still get sent to the event widget because
   * 1) these events have no meaning for the grabbing widget
   * and 2) redirecting these events to the grabbing widget
   * could cause the display to be messed up.
   *
   * Drag events are also not redirected, since it isn't
   * clear what the semantics of that would be.
   */
  switch (event->type)
    {
    case GDK_NOTHING:
      break;

    case GDK_DELETE:
      g_object_ref (event_widget);
      if ((!gtk_window_group_get_current_grab (window_group) || gtk_widget_get_toplevel (gtk_window_group_get_current_grab (window_group)) == event_widget) &&
          !gtk_widget_event (event_widget, event))
        gtk_widget_destroy (event_widget);
      g_object_unref (event_widget);
      break;

    case GDK_DESTROY:
      /* Unexpected GDK_DESTROY from the outside, ignore for
       * child windows, handle like a GDK_DELETE for toplevels
       */
      if (!gtk_widget_get_parent (event_widget))
        {
          g_object_ref (event_widget);
          if (!gtk_widget_event (event_widget, event) &&
              gtk_widget_get_realized (event_widget))
            gtk_widget_destroy (event_widget);
          g_object_unref (event_widget);
        }
      break;

    case GDK_EXPOSE:
      if (event->any.window)
        gtk_widget_render (event_widget, event->any.window, event->expose.region);
      break;

    case GDK_PROPERTY_NOTIFY:
    case GDK_FOCUS_CHANGE:
    case GDK_CONFIGURE:
    case GDK_MAP:
    case GDK_UNMAP:
    case GDK_SELECTION_CLEAR:
    case GDK_SELECTION_REQUEST:
    case GDK_SELECTION_NOTIFY:
    case GDK_CLIENT_EVENT:
    case GDK_VISIBILITY_NOTIFY:
    case GDK_WINDOW_STATE:
    case GDK_GRAB_BROKEN:
    case GDK_DAMAGE:
      if (!_gtk_widget_captured_event (event_widget, event))
        gtk_widget_event (event_widget, event);
      break;

    case GDK_KEY_PRESS:
    case GDK_KEY_RELEASE:
      /* make focus visible in a window that receives a key event */
      {
        GtkWidget *window;

        window = gtk_widget_get_toplevel (grab_widget);
        if (GTK_IS_WINDOW (window))
          gtk_window_set_focus_visible (GTK_WINDOW (window), TRUE);
      }

      /* Catch alt press to enable auto-mnemonics;
       * menus are handled elsewhere
       * FIXME: this does not work with mnemonic modifiers other than Alt
       */
      if ((event->key.keyval == GDK_KEY_Alt_L || event->key.keyval == GDK_KEY_Alt_R) &&
          ((event->key.state & (gtk_accelerator_get_default_mod_mask ()) & ~(GDK_RELEASE_MASK|GDK_MOD1_MASK)) == 0) &&
          !GTK_IS_MENU_SHELL (grab_widget))
        {
          gboolean mnemonics_visible;
          GtkWidget *window;

          mnemonics_visible = (event->type == GDK_KEY_PRESS);

          window = gtk_widget_get_toplevel (grab_widget);
          if (GTK_IS_WINDOW (window))
            {
              if (mnemonics_visible)
                _gtk_window_schedule_mnemonics_visible (GTK_WINDOW (window));
              else
                gtk_window_set_mnemonics_visible (GTK_WINDOW (window), FALSE);
            }
        }
      /* else fall through */
    case GDK_SCROLL:
    case GDK_BUTTON_PRESS:
    case GDK_2BUTTON_PRESS:
    case GDK_3BUTTON_PRESS:
    case GDK_TOUCH_BEGIN:
    case GDK_MOTION_NOTIFY:
    case GDK_BUTTON_RELEASE:
    case GDK_PROXIMITY_IN:
    case GDK_PROXIMITY_OUT:
    case GDK_TOUCH_UPDATE:
    case GDK_TOUCH_END:
    case GDK_TOUCH_CANCEL:
    case GDK_TOUCHPAD_SWIPE:
    case GDK_TOUCHPAD_PINCH:
    case GDK_PAD_BUTTON_PRESS:
    case GDK_PAD_BUTTON_RELEASE:
    case GDK_PAD_RING:
    case GDK_PAD_STRIP:
    case GDK_PAD_GROUP_MODE:
      if (!_gtk_propagate_captured_event (grab_widget, event, topmost_widget))
        gtk_propagate_event (grab_widget, event);
      break;

    case GDK_ENTER_NOTIFY:
    case GDK_LEAVE_NOTIFY:
      /* Crossing event propagation happens during picking */
      break;

    case GDK_DRAG_STATUS:
    case GDK_DROP_FINISHED:
      _gtk_drag_source_handle_event (event_widget, event);
      break;
    case GDK_DRAG_ENTER:
    case GDK_DRAG_LEAVE:
    case GDK_DRAG_MOTION:
    case GDK_DROP_START:
      _gtk_drag_dest_handle_event (event_widget, event);
      break;
    default:
      g_assert_not_reached ();
      break;
    }

  if (event->type == GDK_ENTER_NOTIFY
      || event->type == GDK_LEAVE_NOTIFY
      || event->type == GDK_BUTTON_PRESS
      || event->type == GDK_2BUTTON_PRESS
      || event->type == GDK_3BUTTON_PRESS
      || event->type == GDK_KEY_PRESS
      || event->type == GDK_DRAG_ENTER
      || event->type == GDK_GRAB_BROKEN
      || event->type == GDK_MOTION_NOTIFY
      || event->type == GDK_TOUCH_UPDATE
      || event->type == GDK_SCROLL)
    {
      _gtk_tooltip_handle_event (event);
    }

 cleanup:
  tmp_list = current_events;
  current_events = g_list_remove_link (current_events, tmp_list);
  g_list_free_1 (tmp_list);

  if (rewritten_event)
    gdk_event_free (rewritten_event);
}

/**
 * gtk_true:
 *
 * All this function does it to return %TRUE.
 *
 * This can be useful for example if you want to inhibit the deletion
 * of a window. Of course you should not do this as the user expects
 * a reaction from clicking the close icon of the window...
 *
 * ## A persistent window
 *
 * |[<!-- language="C" -->
 * #include <gtk/gtk.h>
 *
 * int
 * main (int argc, char **argv)
 * {
 *   GtkWidget *win, *but;
 *   const char *text = "Close yourself. I mean it!";
 *
 *   gtk_init (&argc, &argv);
 *
 *   win = gtk_window_new (GTK_WINDOW_TOPLEVEL);
 *   g_signal_connect (win,
 *                     "delete-event",
 *                     G_CALLBACK (gtk_true),
 *                     NULL);
 *   g_signal_connect (win, "destroy",
 *                     G_CALLBACK (gtk_main_quit),
 *                     NULL);
 *
 *   but = gtk_button_new_with_label (text);
 *   g_signal_connect_swapped (but, "clicked",
 *                             G_CALLBACK (gtk_object_destroy),
 *                             win);
 *   gtk_container_add (GTK_CONTAINER (win), but);
 *
 *   gtk_widget_show (win);
 *
 *   gtk_main ();
 *
 *   return 0;
 * }
 * ]|
 *
 * Returns: %TRUE
 */
gboolean
gtk_true (void)
{
  return TRUE;
}

/**
 * gtk_false:
 *
 * Analogical to gtk_true(), this function does nothing
 * but always returns %FALSE.
 *
 * Returns: %FALSE
 */
gboolean
gtk_false (void)
{
  return FALSE;
}

static GtkWindowGroup *
gtk_main_get_window_group (GtkWidget *widget)
{
  GtkWidget *toplevel = NULL;

  if (widget)
    toplevel = gtk_widget_get_toplevel (widget);

  if (GTK_IS_WINDOW (toplevel))
    return gtk_window_get_group (GTK_WINDOW (toplevel));
  else
    return gtk_window_get_group (NULL);
}

typedef struct
{
  GtkWidget *old_grab_widget;
  GtkWidget *new_grab_widget;
  gboolean   was_grabbed;
  gboolean   is_grabbed;
  gboolean   from_grab;
  GList     *notified_windows;
  GdkDevice *device;
} GrabNotifyInfo;

static void
synth_crossing_for_grab_notify (GtkWidget       *from,
                                GtkWidget       *to,
                                GrabNotifyInfo  *info,
                                GList           *devices,
                                GdkCrossingMode  mode)
{
  while (devices)
    {
      GdkDevice *device = devices->data;
      GdkWindow *from_window, *to_window;

      /* Do not propagate events more than once to
       * the same windows if non-multidevice aware.
       */
      if (!from)
        from_window = NULL;
      else
        {
          from_window = _gtk_widget_get_device_window (from, device);

          if (from_window &&
              !gdk_window_get_support_multidevice (from_window) &&
              g_list_find (info->notified_windows, from_window))
            from_window = NULL;
        }

      if (!to)
        to_window = NULL;
      else
        {
          to_window = _gtk_widget_get_device_window (to, device);

          if (to_window &&
              !gdk_window_get_support_multidevice (to_window) &&
              g_list_find (info->notified_windows, to_window))
            to_window = NULL;
        }

      if (from_window || to_window)
        {
          _gtk_widget_synthesize_crossing ((from_window) ? from : NULL,
                                           (to_window) ? to : NULL,
                                           device, mode);

          if (from_window)
            info->notified_windows = g_list_prepend (info->notified_windows, from_window);

          if (to_window)
            info->notified_windows = g_list_prepend (info->notified_windows, to_window);
        }

      devices = devices->next;
    }
}

static void
gtk_grab_notify_foreach (GtkWidget *child,
                         gpointer   data)
{
  GrabNotifyInfo *info = data;
  gboolean was_grabbed, is_grabbed, was_shadowed, is_shadowed;
  GList *devices;

  was_grabbed = info->was_grabbed;
  is_grabbed = info->is_grabbed;

  info->was_grabbed = info->was_grabbed || (child == info->old_grab_widget);
  info->is_grabbed = info->is_grabbed || (child == info->new_grab_widget);

  was_shadowed = info->old_grab_widget && !info->was_grabbed;
  is_shadowed = info->new_grab_widget && !info->is_grabbed;

  g_object_ref (child);

  if (was_shadowed || is_shadowed)
    {
      GtkWidget *p;

      for (p = _gtk_widget_get_first_child (child);
           p != NULL;
           p = _gtk_widget_get_next_sibling (p))
        {
          gtk_grab_notify_foreach (p, info);
        }
    }

  if (info->device &&
      _gtk_widget_get_device_window (child, info->device))
    {
      /* Device specified and is on widget */
      devices = g_list_prepend (NULL, info->device);
    }
  else
    devices = _gtk_widget_list_devices (child);

  if (is_shadowed)
    {
      _gtk_widget_set_shadowed (child, TRUE);
      if (!was_shadowed && devices &&
          gtk_widget_is_sensitive (child))
        synth_crossing_for_grab_notify (child, info->new_grab_widget,
                                        info, devices,
                                        GDK_CROSSING_GTK_GRAB);
    }
  else
    {
      _gtk_widget_set_shadowed (child, FALSE);
      if (was_shadowed && devices &&
          gtk_widget_is_sensitive (child))
        synth_crossing_for_grab_notify (info->old_grab_widget, child,
                                        info, devices,
                                        info->from_grab ? GDK_CROSSING_GTK_GRAB :
                                        GDK_CROSSING_GTK_UNGRAB);
    }

  if (was_shadowed != is_shadowed)
    _gtk_widget_grab_notify (child, was_shadowed);

  g_object_unref (child);
  g_list_free (devices);

  info->was_grabbed = was_grabbed;
  info->is_grabbed = is_grabbed;
}

static void
gtk_grab_notify (GtkWindowGroup *group,
                 GdkDevice      *device,
                 GtkWidget      *old_grab_widget,
                 GtkWidget      *new_grab_widget,
                 gboolean        from_grab)
{
  GList *toplevels;
  GrabNotifyInfo info = { 0 };

  if (old_grab_widget == new_grab_widget)
    return;

  info.old_grab_widget = old_grab_widget;
  info.new_grab_widget = new_grab_widget;
  info.from_grab = from_grab;
  info.device = device;

  g_object_ref (group);

  toplevels = gtk_window_list_toplevels ();
  g_list_foreach (toplevels, (GFunc)g_object_ref, NULL);

  while (toplevels)
    {
      GtkWindow *toplevel = toplevels->data;
      toplevels = g_list_delete_link (toplevels, toplevels);

      info.was_grabbed = FALSE;
      info.is_grabbed = FALSE;

      if (group == gtk_window_get_group (toplevel))
        gtk_grab_notify_foreach (GTK_WIDGET (toplevel), &info);
      g_object_unref (toplevel);
    }

  g_list_free (info.notified_windows);
  g_object_unref (group);
}

/**
 * gtk_grab_add: (method)
 * @widget: The widget that grabs keyboard and pointer events
 *
 * Makes @widget the current grabbed widget.
 *
 * This means that interaction with other widgets in the same
 * application is blocked and mouse as well as keyboard events
 * are delivered to this widget.
 *
 * If @widget is not sensitive, it is not set as the current
 * grabbed widget and this function does nothing.
 */
void
gtk_grab_add (GtkWidget *widget)
{
  GtkWindowGroup *group;
  GtkWidget *old_grab_widget;

  g_return_if_fail (widget != NULL);

  if (!gtk_widget_has_grab (widget) && gtk_widget_is_sensitive (widget))
    {
      _gtk_widget_set_has_grab (widget, TRUE);

      group = gtk_main_get_window_group (widget);

      old_grab_widget = gtk_window_group_get_current_grab (group);

      g_object_ref (widget);
      _gtk_window_group_add_grab (group, widget);

      gtk_grab_notify (group, NULL, old_grab_widget, widget, TRUE);
    }
}

/**
 * gtk_grab_get_current:
 *
 * Queries the current grab of the default window group.
 *
 * Returns: (transfer none) (nullable): The widget which currently
 *     has the grab or %NULL if no grab is active
 */
GtkWidget*
gtk_grab_get_current (void)
{
  GtkWindowGroup *group;

  group = gtk_main_get_window_group (NULL);

  return gtk_window_group_get_current_grab (group);
}

/**
 * gtk_grab_remove: (method)
 * @widget: The widget which gives up the grab
 *
 * Removes the grab from the given widget.
 *
 * You have to pair calls to gtk_grab_add() and gtk_grab_remove().
 *
 * If @widget does not have the grab, this function does nothing.
 */
void
gtk_grab_remove (GtkWidget *widget)
{
  GtkWindowGroup *group;
  GtkWidget *new_grab_widget;

  g_return_if_fail (widget != NULL);

  if (gtk_widget_has_grab (widget))
    {
      _gtk_widget_set_has_grab (widget, FALSE);

      group = gtk_main_get_window_group (widget);
      _gtk_window_group_remove_grab (group, widget);
      new_grab_widget = gtk_window_group_get_current_grab (group);

      gtk_grab_notify (group, NULL, widget, new_grab_widget, FALSE);

      g_object_unref (widget);
    }
}

/**
 * gtk_device_grab_add:
 * @widget: a #GtkWidget
 * @device: a #GdkDevice to grab on.
 * @block_others: %TRUE to prevent other devices to interact with @widget.
 *
 * Adds a GTK+ grab on @device, so all the events on @device and its
 * associated pointer or keyboard (if any) are delivered to @widget.
 * If the @block_others parameter is %TRUE, any other devices will be
 * unable to interact with @widget during the grab.
 *
 * Since: 3.0
 */
void
gtk_device_grab_add (GtkWidget *widget,
                     GdkDevice *device,
                     gboolean   block_others)
{
  GtkWindowGroup *group;
  GtkWidget *old_grab_widget;

  g_return_if_fail (GTK_IS_WIDGET (widget));
  g_return_if_fail (GDK_IS_DEVICE (device));

  group = gtk_main_get_window_group (widget);
  old_grab_widget = gtk_window_group_get_current_device_grab (group, device);

  if (old_grab_widget != widget)
    _gtk_window_group_add_device_grab (group, widget, device, block_others);

  gtk_grab_notify (group, device, old_grab_widget, widget, TRUE);
}

/**
 * gtk_device_grab_remove:
 * @widget: a #GtkWidget
 * @device: a #GdkDevice
 *
 * Removes a device grab from the given widget.
 *
 * You have to pair calls to gtk_device_grab_add() and
 * gtk_device_grab_remove().
 *
 * Since: 3.0
 */
void
gtk_device_grab_remove (GtkWidget *widget,
                        GdkDevice *device)
{
  GtkWindowGroup *group;
  GtkWidget *new_grab_widget;

  g_return_if_fail (GTK_IS_WIDGET (widget));
  g_return_if_fail (GDK_IS_DEVICE (device));

  group = gtk_main_get_window_group (widget);
  _gtk_window_group_remove_device_grab (group, widget, device);
  new_grab_widget = gtk_window_group_get_current_device_grab (group, device);

  gtk_grab_notify (group, device, widget, new_grab_widget, FALSE);
}

/**
 * gtk_get_current_event:
 *
 * Obtains a copy of the event currently being processed by GTK+.
 *
 * For example, if you are handling a #GtkButton::clicked signal,
 * the current event will be the #GdkEventButton that triggered
 * the ::clicked signal.
 *
 * Returns: (transfer full) (nullable): a copy of the current event, or
 *     %NULL if there is no current event. The returned event must be
 *     freed with gdk_event_free().
 */
GdkEvent*
gtk_get_current_event (void)
{
  if (current_events)
    return gdk_event_copy (current_events->data);
  else
    return NULL;
}

/**
 * gtk_get_current_event_time:
 *
 * If there is a current event and it has a timestamp,
 * return that timestamp, otherwise return %GDK_CURRENT_TIME.
 *
 * Returns: the timestamp from the current event,
 *     or %GDK_CURRENT_TIME.
 */
guint32
gtk_get_current_event_time (void)
{
  if (current_events)
    return gdk_event_get_time (current_events->data);
  else
    return GDK_CURRENT_TIME;
}

/**
 * gtk_get_current_event_state:
 * @state: (out): a location to store the state of the current event
 *
 * If there is a current event and it has a state field, place
 * that state field in @state and return %TRUE, otherwise return
 * %FALSE.
 *
 * Returns: %TRUE if there was a current event and it
 *     had a state field
 */
gboolean
gtk_get_current_event_state (GdkModifierType *state)
{
  g_return_val_if_fail (state != NULL, FALSE);

  if (current_events)
    return gdk_event_get_state (current_events->data, state);
  else
    {
      *state = 0;
      return FALSE;
    }
}

/**
 * gtk_get_current_event_device:
 *
 * If there is a current event and it has a device, return that
 * device, otherwise return %NULL.
 *
 * Returns: (transfer none) (nullable): a #GdkDevice, or %NULL
 */
GdkDevice *
gtk_get_current_event_device (void)
{
  if (current_events)
    return gdk_event_get_device (current_events->data);
  else
    return NULL;
}

/**
 * gtk_get_event_widget:
 * @event: a #GdkEvent
 *
 * If @event is %NULL or the event was not associated with any widget,
 * returns %NULL, otherwise returns the widget that received the event
 * originally.
 *
 * Returns: (transfer none) (nullable): the widget that originally
 *     received @event, or %NULL
 */
GtkWidget*
gtk_get_event_widget (const GdkEvent *event)
{
  GtkWidget *widget;
  gpointer widget_ptr;

  widget = NULL;
  if (event && event->any.window &&
      (event->type == GDK_DESTROY || !gdk_window_is_destroyed (event->any.window)))
    {
      gdk_window_get_user_data (event->any.window, &widget_ptr);
      widget = widget_ptr;
    }

  return widget;
}

/**
 * gtk_get_event_target:
 * @event: a #GdkEvent
 *
 * If @event is %NULL or the event was not associated with any widget,
 * returns %NULL, otherwise returns the widget that is the deepmost
 * receiver of the event.
 *
 * Returns: (transfer none) (nullable): the target widget, or %NULL
 *
 * Since: 3.92
 */
GtkWidget *
gtk_get_event_target (const GdkEvent *event)
{
  return GTK_WIDGET (gdk_event_get_user_data (event));
}

/**
 * gtk_get_event_target_with_type:
 * @event: a #GdkEvent
 *
 * If @event is %NULL or the event was not associated with any widget,
 * returns %NULL, otherwise returns first widget found from the event
 * target to the toplevel that matches @type.
 *
 * Returns: (transfer none) (nullable): the widget in the target stack
 * with the given type, or %NULL
 *
 * Since: 3.92
 */
GtkWidget *
gtk_get_event_target_with_type (GdkEvent *event,
                                GType     type)
{
  GtkWidget *target;

  target = gtk_get_event_target (event);
  while (target && !g_type_is_a (G_OBJECT_TYPE (target), type))
    target = gtk_widget_get_parent (target);

  return target;
}

static gboolean
propagate_event_up (GtkWidget *widget,
                    GdkEvent  *event,
                    GtkWidget *topmost)
{
  gboolean handled_event = FALSE;

  /* Propagate event up the widget tree so that
   * parents can see the button and motion
   * events of the children.
   */
  while (TRUE)
    {
      GtkWidget *tmp;

      g_object_ref (widget);

      /* Scroll events are special cased here because it
       * feels wrong when scrolling a GtkViewport, say,
       * to have children of the viewport eat the scroll
       * event
       */
      if (!gtk_widget_is_sensitive (widget))
        handled_event = event->type != GDK_SCROLL;
      else
        handled_event = gtk_widget_event (widget, event);

      tmp = gtk_widget_get_parent (widget);
      g_object_unref (widget);

      if (widget == topmost)
        break;

      widget = tmp;

      if (handled_event || !widget)
        break;
    }

  return handled_event;
}

static gboolean
propagate_event_down (GtkWidget *widget,
                      GdkEvent  *event,
                      GtkWidget *topmost)
{
  gint handled_event = FALSE;
  GList *widgets = NULL;
  GList *l;

  widgets = g_list_prepend (widgets, g_object_ref (widget));
  while (widget && widget != topmost)
    {
      widget = gtk_widget_get_parent (widget);
      if (!widget)
        break;

      widgets = g_list_prepend (widgets, g_object_ref (widget));

      if (widget == topmost)
        break;
    }

  for (l = widgets; l && !handled_event; l = l->next)
    {
      widget = (GtkWidget *)l->data;

      if (!gtk_widget_is_sensitive (widget))
        {
          /* stop propagating on SCROLL, but don't handle the event, so it
           * can propagate up again and reach its handling widget
           */
          if (event->type == GDK_SCROLL)
            break;
          else
            handled_event = TRUE;
        }
      else
        handled_event = _gtk_widget_captured_event (widget, event);
    }
  g_list_free_full (widgets, (GDestroyNotify)g_object_unref);

  return handled_event;
}

static gboolean
propagate_event (GtkWidget *widget,
                 GdkEvent  *event,
                 gboolean   captured,
                 GtkWidget *topmost)
{
  gboolean handled_event = FALSE;
  gboolean (* propagate_func) (GtkWidget *widget, const GdkEvent *event);

  propagate_func = captured ? _gtk_widget_captured_event : gtk_widget_event;

  if (event->type == GDK_KEY_PRESS || event->type == GDK_KEY_RELEASE)
    {
      /* Only send key events within Window widgets to the Window
       * The Window widget will in turn pass the
       * key event on to the currently focused widget
       * for that window.
       */
      GtkWidget *window;

      window = gtk_widget_get_toplevel (widget);
      if (GTK_IS_WINDOW (window))
        {
          g_object_ref (widget);
          /* If there is a grab within the window, give the grab widget
           * a first crack at the key event
           */
          if (widget != window && gtk_widget_has_grab (widget))
            handled_event = propagate_func (widget, event);

          if (!handled_event &&
              gtk_widget_is_sensitive (window))
            handled_event = propagate_func (window, event);

          g_object_unref (widget);
          return handled_event;
        }
    }

  /* Other events get propagated up/down the widget tree */
  return captured ?
    propagate_event_down (widget, event, topmost) :
    propagate_event_up (widget, event, topmost);
}

/**
 * gtk_propagate_event:
 * @widget: a #GtkWidget
 * @event: an event
 *
 * Sends an event to a widget, propagating the event to parent widgets
 * if the event remains unhandled.
 *
 * Events received by GTK+ from GDK normally begin in gtk_main_do_event().
 * Depending on the type of event, existence of modal dialogs, grabs, etc.,
 * the event may be propagated; if so, this function is used.
 *
 * gtk_propagate_event() calls gtk_widget_event() on each widget it
 * decides to send the event to. So gtk_widget_event() is the lowest-level
 * function; it simply emits the #GtkWidget::event and possibly an
 * event-specific signal on a widget. gtk_propagate_event() is a bit
 * higher-level, and gtk_main_do_event() is the highest level.
 *
 * All that said, you most likely don’t want to use any of these
 * functions; synthesizing events is rarely needed. There are almost
 * certainly better ways to achieve your goals. For example, use
 * gtk_widget_queue_draw() instead
 * of making up expose events.
 */
void
gtk_propagate_event (GtkWidget *widget,
                     GdkEvent  *event)
{
  g_return_if_fail (GTK_IS_WIDGET (widget));
  g_return_if_fail (event != NULL);

  propagate_event (widget, event, FALSE, NULL);
}

gboolean
_gtk_propagate_captured_event (GtkWidget *widget,
                               GdkEvent  *event,
                               GtkWidget *topmost)
{
  return propagate_event (widget, event, TRUE, topmost);
}

GtkWidget *
_gtk_toplevel_pick (GtkWindow *toplevel,
                    gdouble    x,
                    gdouble    y,
                    gdouble   *x_out,
                    gdouble   *y_out)
{
  GtkWidget *target = NULL, *widget = GTK_WIDGET (toplevel);

  while (widget)
    {
      target = widget;
      widget = GTK_WIDGET_GET_CLASS (target)->pick (widget, x, y, &x, &y);
    }

  if (x_out)
    *x_out = x;
  if (y_out)
    *y_out = y;

  return target;
}