[Emacs-diffs] master 46b8100 3/3: emacsclient: avoid background chatter

[Paul Eggert]

branch: master
commit 46b810081165fecae5086b71fafdb3eb19c30df5
Author: Paul Eggert <address@hidden>
Commit: Paul Eggert <address@hidden>

    emacsclient: avoid background chatter
    
    * lib-src/emacsclient.c (process_grouping): New function.
    (act_on_signals, main): Use it.
    (main): Omit "Waiting for Emacs..." and later "\n" messages
    if in background, since that messes up the screen.
---
 lib-src/emacsclient.c | 51 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index 653ab95..c596fb2 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -1095,6 +1095,26 @@ find_tty (const char **tty_type, const char **tty_name, 
bool noabort)
   return true;
 }
 
+/* Return the process group if in the foreground, the negative of the
+   process group if in the background, and zero if there is no
+   foreground process group for the controlling terminal.
+   Unfortunately, use of this function introduces an unavoidable race,
+   since whether the process is in the foreground or background can
+   change at any time.  */
+
+static pid_t
+process_grouping (void)
+{
+#ifdef SOCKETS_IN_FILE_SYSTEM
+  pid_t tcpgrp = tcgetpgrp (STDOUT_FILENO);
+  if (0 <= tcpgrp)
+    {
+      pid_t pgrp = getpgrp ();
+      return tcpgrp == pgrp ? pgrp : -pgrp;
+    }
+#endif
+  return 0;
+}
 
 #ifdef SOCKETS_IN_FILE_SYSTEM
 
@@ -1253,21 +1273,17 @@ act_on_signals (HSOCKET emacs_socket)
            {
              got_sigcont = 0;
              took_action = true;
-             pid_t tcpgrp = tcgetpgrp (STDOUT_FILENO);
-             if (0 <= tcpgrp)
+             pid_t grouping = process_grouping ();
+             if (grouping < 0)
                {
-                 pid_t pgrp = getpgrp ();
-                 if (tcpgrp == pgrp)
-                   {
-                     /* We are in the foreground.  */
-                     send_to_emacs (emacs_socket, "-resume \n");
-                   }
-                 else if (tty)
+                 if (tty)
                    {
-                     /* We are in the background; cancel the continue.  */
-                     kill (-pgrp, SIGTTIN);
+                     /* Cancel the continue.  */
+                     kill (grouping, SIGTTIN);
                    }
                }
+             else
+               send_to_emacs (emacs_socket, "-resume \n");
            }
 
          if (got_sigtstp)
@@ -1767,13 +1783,12 @@ main (int argc, char **argv)
       exit (EXIT_FAILURE);
     }
 
-#ifndef WINDOWSNT
+#ifdef SOCKETS_IN_FILE_SYSTEM
   if (tty)
     {
-      pid_t pgrp = getpgrp ();
-      pid_t tcpgrp = tcgetpgrp (STDOUT_FILENO);
-      if (0 <= tcpgrp && tcpgrp != pgrp)
-       kill (-pgrp, SIGTTIN);
+      pid_t grouping = process_grouping ();
+      if (grouping < 0)
+       kill (grouping, SIGTTIN);
     }
 #endif
 
@@ -1946,7 +1961,7 @@ main (int argc, char **argv)
   send_to_emacs (emacs_socket, "\n");
 
   /* Wait for an answer. */
-  if (!eval && !tty && !nowait && !quiet)
+  if (!eval && !tty && !nowait && !quiet && 0 <= process_grouping ())
     {
       printf ("Waiting for Emacs...");
       skiplf = false;
@@ -2052,7 +2067,7 @@ main (int argc, char **argv)
        }
     }
 
-  if (!skiplf)
+  if (!skiplf && 0 <= process_grouping ())
     printf ("\n");
 
   if (rl < 0)