Fix pieces of code being too expensive over slow network connections

* lisp/menu-bar.el (menu-bar-edit-menu): Test buffer-read-only
before gui-backend-selection-exists-p.  This places the less
expensive condition before the more expensive one.
* src/xfns.c (compute_tip_xy): Use cached monitor attributes
whenever available.
(Fx_show_tip): Remove code that really did nothing.
(Fx_backspace_delete_keys_p): Do not download the entire keymap
from the server upon creating a frame.
* src/xmenu.c (create_and_show_popup_menu): Use
x_translate_coordinates_to_root.
(x_menu_show): Use x_translate_coordinates_to_root.
* src/xselect.c (Fx_selection_exists_p): If a temporary
selection owner can be found, use it.
* src/xterm.c (x_translate_coordinates_to_root)
(x_handle_selection_monitor_event, x_find_selection_owner): New
functions.  These functions try to avoid downloading data from
the X server in places that are called very often (i.e. during
tool bar updates.)
(handle_one_xevent): Handle selection notify events.  Also catch
some mistakes found.  Fetch all kinds of key names as well.
(x_create_special_window): New function.
(x_term_init, x_delete_display): Ask for all key names.  Also,
passively monitor selections that are given to
`x-selection-exists-p' during redisplay, so we do not have to
ask the server about them upon each redisplay.
(syms_of_xterm): New variable `x-fast-selection-list'.
* src/xterm.h (struct x_monitored_selection): New structure.
(X_INVALID_WINDOW): New define.
(struct x_display_info): New fields for selection monitoring.
Also, record the fixes extension base.

1 files changed, 22 insertions, 3 deletions

diff --git a/src/xselect.c b/src/xselect.c
index 66782d41723..498c28af536 100644
--- a/src/xselect.c
+++ b/src/xselect.c
@@ -2376,12 +2376,19 @@ On Nextstep, TERMINAL is unused.  */)
 {
   Window owner;
   Atom atom;
+#ifdef HAVE_XFIXES
+  Window temp_owner;
+#endif
   struct frame *f = frame_for_x_selection (terminal);
   struct x_display_info *dpyinfo;
 
   CHECK_SYMBOL (selection);
-  if (NILP (selection)) selection = QPRIMARY;
-  if (EQ (selection, Qt)) selection = QSECONDARY;
+
+  if (NILP (selection))
+    selection = QPRIMARY;
+
+  if (EQ (selection, Qt))
+    selection = QSECONDARY;
 
   if (!f)
     return Qnil;
@@ -2392,10 +2399,22 @@ On Nextstep, TERMINAL is unused.  */)
     return Qt;
 
   atom = symbol_to_x_atom (dpyinfo, selection);
-  if (atom == 0) return Qnil;
+
+  if (!atom)
+    return Qnil;
+
+#ifdef HAVE_XFIXES
+  /* See if this information can be obtained without a roundtrip.  */
+  temp_owner = x_find_selection_owner (dpyinfo, atom);
+
+  if (temp_owner != X_INVALID_WINDOW)
+    return (temp_owner != None ? Qt : Qnil);
+#endif
+
   block_input ();
   owner = XGetSelectionOwner (dpyinfo->display, atom);
   unblock_input ();
+
   return (owner ? Qt : Qnil);
 }