Consistently use platform-specific function to detect window system.

* lisp.h (check_window_system): New prototype.  This function is
going to replace check_x, check_w32 and check_ns.
(have_menus_p): Mention msdos.c in comment.
* fontset.c (check_window_system_func): Remove.  Adjust all users.
* fontset.h (check_window_system_func): Remove prototype.
* nsterm.h (check_ns):
* xterm.h (check_x):
* w32term.h (check_w32): Likewise.
* menu.c (Fx_popup_menu): Use check_window_system.
* msdos.c (check_window_system): Define for MS-DOS.
* nsfns.m (check_window_system): Define for NS.  Adjust all users.
* w32fns.c (check_window_system): Likewise for MS-Windows.
* xfns.c (check_window_system): Likewise for X.
* font.c, frame.c, nsmenu.m, nsselect.m, nsterm.m, w32menu.c:
* xfaces.c, xmenu.c: Use check_window_system where appropriate.

1 files changed, 5 insertions, 8 deletions

diff --git a/src/xfns.c b/src/xfns.c
index b39b78004a..8b8d94d477 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -143,7 +143,7 @@ static struct x_display_info *x_display_info_for_name (Lisp_Object);
 /* Error if we are not connected to X.  */
 
 void
-check_x (void)
+check_window_system (void)
 {
   if (! x_in_use)
     error ("X windows are not in use or not initialized");
@@ -4525,7 +4525,7 @@ x_create_tip_frame (struct x_display_info *dpyinfo,
   Lisp_Object buffer;
   struct buffer *old_buffer;
 
-  check_x ();
+  check_window_system ();
 
   if (!dpyinfo->terminal->name)
     error ("Terminal is not live, can't create new frames on it");
@@ -5316,7 +5316,7 @@ Otherwise, if ONLY-DIR-P is non-nil, the user can only select directories.  */)
   ptrdiff_t count = SPECPDL_INDEX ();
   struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5, gcpro6;
 
-  check_x ();
+  check_window_system ();
 
   GCPRO6 (prompt, dir, default_filename, mustmatch, only_dir_p, file);
 
@@ -5486,7 +5486,7 @@ Otherwise, if ONLY-DIR-P is non-nil, the user can only select directories.  */)
   struct gcpro gcpro1, gcpro2, gcpro3, gcpro4, gcpro5, gcpro6;
   char *cdef_file;
 
-  check_x ();
+  check_window_system ();
 
   GCPRO6 (prompt, dir, default_filename, mustmatch, only_dir_p, file);
 
@@ -5548,7 +5548,7 @@ nil, it defaults to the selected frame. */)
   struct gcpro gcpro1, gcpro2;
   ptrdiff_t count = SPECPDL_INDEX ();
 
-  check_x ();
+  check_window_system ();
 
   if (popup_activated ())
     error ("Trying to use a menu from within a menu-entry");
@@ -5919,9 +5919,6 @@ When using Gtk+ tooltips, the tooltip face is not used.  */);
   defsubr (&Sx_focus_frame);
   defsubr (&Sx_backspace_delete_keys_p);
 
-  /* Setting callback functions for fontset handler.  */
-  check_window_system_func = check_x;
-
   defsubr (&Sx_show_tip);
   defsubr (&Sx_hide_tip);
   tip_timer = Qnil;