X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/adf2fc4a01efe77d73cd52bc9173914ed56ff531..6a4b1b17293ed0e4c7f7f3a33e058f63ccd290eb:/src/xgselect.c

diff --git a/src/xgselect.c b/src/xgselect.c
index 7a754bd75c..bf889a90e9 100644
--- a/src/xgselect.c
+++ b/src/xgselect.c
@@ -1,6 +1,6 @@
 /* Function for handling the GLib event loop.
 
-Copyright (C) 2009-2013 Free Software Foundation, Inc.
+Copyright (C) 2009-2014 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
 
@@ -25,8 +25,21 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <glib.h>
 #include <errno.h>
+#include <stdbool.h>
 #include <timespec.h>
 #include "frame.h"
+#include "blockinput.h"
+
+/* `xg_select' is a `pselect' replacement.  Why do we need a separate function?
+   1. Timeouts.  Glib and Gtk rely on timer events.  If we did pselect
+      with a greater timeout then the one scheduled by Glib, we would
+      not allow Glib to process its timer events.  We want Glib to
+      work smoothly, so we need to reduce our timeout to match Glib.
+   2. Descriptors.  Glib may listen to more file descriptors than we do.
+      So we add Glib descriptors to our pselect pool, but we don't change
+      the value returned by the function.  The return value  matches only
+      the descriptors passed as arguments, making it compatible with
+      plain pselect.  */
 
 int
 xg_select (int fds_lim, fd_set *rfds, fd_set *wfds, fd_set *efds,
@@ -40,17 +53,12 @@ xg_select (int fds_lim, fd_set *rfds, fd_set *wfds, fd_set *efds,
   int have_wfds = wfds != NULL;
   GPollFD gfds_buf[128];
   GPollFD *gfds = gfds_buf;
-  int gfds_size = sizeof gfds_buf / sizeof *gfds_buf;
+  int gfds_size = ARRAYELTS (gfds_buf);
   int n_gfds, retval = 0, our_fds = 0, max_fds = fds_lim - 1;
   int i, nfds, tmo_in_millisec;
+  bool need_to_dispatch;
   USE_SAFE_ALLOCA;
 
-  /* Do not try to optimize with an initial check with g_main_context_pending
-     and a call to pselect if it returns false.  If Gdk has a timeout for 0.01
-     second, and Emacs has a timeout for 1 second, g_main_context_pending will
-     return false, but the timeout will be 1 second, thus missing the gdk
-     timeout with a lot.  */
-
   context = g_main_context_default ();
 
   if (rfds) all_rfds = *rfds;
@@ -124,23 +132,31 @@ xg_select (int fds_lim, fd_set *rfds, fd_set *wfds, fd_set *efds,
         }
     }
 
-  if (our_fds > 0 || (nfds == 0 && tmop == &tmo))
-    {
-
-      /* If Gtk+ is in use eventually gtk_main_iteration will be called,
-         unless retval is zero.  */
+  /* If Gtk+ is in use eventually gtk_main_iteration will be called,
+     unless retval is zero.  */
 #ifdef USE_GTK
-      if (retval == 0)
+  need_to_dispatch = retval == 0;
+#else
+  need_to_dispatch = true;
 #endif
-        while (g_main_context_pending (context))
-          g_main_context_dispatch (context);
+  if (need_to_dispatch)
+    {
+      int pselect_errno = errno;
+      /* Prevent g_main_dispatch recursion, that would occur without
+         block_input wrapper, because event handlers call
+         unblock_input.  Event loop recursion was causing Bug#15801.  */
+      block_input ();
+      while (g_main_context_pending (context))
+        g_main_context_dispatch (context);
+      unblock_input ();
+      errno = pselect_errno;
+    }
 
-      /* To not have to recalculate timeout, return like this.  */
-      if (retval == 0)
-        {
-          retval = -1;
-          errno = EINTR;
-        }
+  /* To not have to recalculate timeout, return like this.  */
+  if ((our_fds > 0 || (nfds == 0 && tmop == &tmo)) && (retval == 0))
+    {
+      retval = -1;
+      errno = EINTR;
     }
 
   return retval;