1 files changed, 57 insertions, 25 deletions

diff --git a/src/process.c b/src/process.c
index 09d262f0c6f..6db62dc6f35 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2174,19 +2174,14 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
             set_waiting_for_input (&timeout);
         }
 
-      {
-        int old_timers_run = timers_run;
-        if (XINT (read_kbd) && detect_input_pending_run_timers (do_display))
-          {
-            nfds = 0;
-            FD_ZERO (&Available);
-          }
-        else if (timers_run != old_timers_run)
-          ;
-        else
-          nfds = select (MAXDESC, &Available, (SELECT_TYPE *)0, (SELECT_TYPE *)0,
-                         &timeout);
-      }
+      if (XINT (read_kbd) && detect_input_pending ())
+        {
+          nfds = 0;
+          FD_ZERO (&Available);
+        }
+      else
+        nfds = select (MAXDESC, &Available, (SELECT_TYPE *)0, (SELECT_TYPE *)0,
+                       &timeout);
 
       xerrno = errno;
 
@@ -3830,6 +3825,8 @@ extern int timers_run;
      1 to return when input is available, or
      -1 means caller will actually read the input, so don't throw to
        the quit handler.
+     a cons cell, meaning wait until its car is non-nil
+       (and gobble terminal input into the buffer if any arrives), or
      We know that read_kbd will never be a Lisp_Process, since
      `subprocesses' isn't defined.
 
@@ -3847,6 +3844,14 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
   EMACS_TIME end_time, timeout;
   SELECT_TYPE waitchannels;
   int xerrno;
+  Lisp_Object *wait_for_cell = 0;
+
+  /* If waiting for non-nil in a cell, record where.  */
+  if (CONSP (read_kbd))
+    {
+      wait_for_cell = &XCONS (read_kbd)->car;
+      XSETFASTINT (read_kbd, 0);
+    }
 
   /* What does time_limit really mean?  */
   if (time_limit || microsecs)
@@ -3874,17 +3879,16 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
       int nfds;
       int timeout_reduced_for_timers = 0;
 
-      if (XINT (read_kbd))
-        FD_SET (0, &waitchannels);
-      else
-        FD_ZERO (&waitchannels);
-
       /* If calling from keyboard input, do not quit
          since we want to return C-g as an input character.
          Otherwise, do pending quit if requested.  */
       if (XINT (read_kbd) >= 0)
         QUIT;
 
+      /* Exit now if the cell we're waiting for became non-nil.  */
+      if (wait_for_cell && ! NILP (*wait_for_cell))
+        break;
+
       /* Compute time from now till when time limit is up */
       /* Exit if already run out */
       if (time_limit > 0 || microsecs)
@@ -3899,13 +3903,22 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
          run timer events directly.
          (Callers that will immediately read keyboard events
          call timer_delay on their own.)  */
-      if (XINT (read_kbd) >= 0)
+      if (1)
         {
           EMACS_TIME timer_delay;
-          int old_timers_run = timers_run;
+          int old_timers_run;
+
+        retry:
+          old_timers_run = timers_run;
           timer_delay = timer_check (1);
           if (timers_run != old_timers_run && do_display)
-            redisplay_preserve_echo_area ();
+            {
+              redisplay_preserve_echo_area ();
+              /* We must retry, since a timer may have requeued itself
+                 and that could alter the time delay.  */
+              goto retry;
+            }
+
           if (! EMACS_TIME_NEG_P (timer_delay) && time_limit != -1)
             {
               EMACS_TIME difference;
@@ -3923,15 +3936,30 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
       if (XINT (read_kbd) < 0)
         set_waiting_for_input (&timeout);
 
+      /* Wait till there is something to do.  */
+
+      if (! XINT (read_kbd) && wait_for_cell == 0)
+        FD_ZERO (&waitchannels);
+      else
+        FD_SET (0, &waitchannels);
+
       /* If a frame has been newly mapped and needs updating,
          reprocess its display stuff.  */
       if (frame_garbaged && do_display)
-        redisplay_preserve_echo_area ();
+        {
+          clear_waiting_for_input ();
+          redisplay_preserve_echo_area ();
+          if (XINT (read_kbd) < 0)
+            set_waiting_for_input (&timeout);
+        }
 
       {
         int old_timers_run = timers_run;
-        if (XINT (read_kbd) && detect_input_pending_run_timers (do_display))
-          nfds = 0;
+        if (XINT (read_kbd) && detect_input_pending ())
+          {
+            nfds = 0;
+            FD_ZERO (&waitchannels);
+          }
         else if (timers_run != old_timers_run)
           ;
         else
@@ -3972,13 +4000,17 @@ wait_reading_process_input (time_limit, microsecs, read_kbd, do_display)
 
       /* Check for keyboard input */
 
-      if (XINT (read_kbd) != 0
+      if ((XINT (read_kbd) != 0 || wait_for_cell)
           && detect_input_pending_run_timers (do_display))
         {
           swallow_events (do_display);
           if (detect_input_pending_run_timers (do_display))
             break;
         }
+
+      /* Exit now if the cell we're waiting for became non-nil.  */
+      if (wait_for_cell && ! NILP (*wait_for_cell))
+        break;
     }
 
   start_polling ();