From 71b636cfbd7cadf4ffa2c384ecd546c555a94d9a Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Sat, 17 May 1997 07:00:23 +0000
Subject: [PATCH] Change NT:MSGWAITFORMULTIPLEOBJECTS to check for messages
 that were removed from the input queue and placed on one of the screen
 queues. This eliminates a serious bug in Edwin: running an asynchronous
 evaluation that did no output would cause Edwin to lock up until the
 evaluation completed.

---
 v7/src/microcode/ntscreen.c | 15 ++++++++++++++-
 v7/src/microcode/ntscreen.h |  3 ++-
 v7/src/microcode/prntio.c   | 23 +++++++++++++++--------
 3 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/v7/src/microcode/ntscreen.c b/v7/src/microcode/ntscreen.c
index 0e5a7ccfc..44915cb51 100644
--- a/v7/src/microcode/ntscreen.c
+++ b/v7/src/microcode/ntscreen.c
@@ -1,6 +1,6 @@
 /* -*-C-*-
 
-$Id: ntscreen.c,v 1.28 1997/04/03 04:41:04 cph Exp $
+$Id: ntscreen.c,v 1.29 1997/05/17 07:00:14 cph Exp $
 
 Copyright (c) 1993-97 Massachusetts Institute of Technology
 
@@ -3266,6 +3266,19 @@ Screen_PeekEvent (HANDLE hwnd, SCREEN_EVENT * event)
     *event = screen->queue_head->event;
   return  TRUE;
 }
+
+BOOL
+Screen_pending_events_p (void)
+{
+  SCREEN screen = registered_screens;
+  while (screen)
+    {
+      if ((screen -> n_events) != 0)
+	return (TRUE);
+      screen = (screen -> registry_link);
+    }
+  return (FALSE);
+}
 
 //---------------------------------------------------------------------------
 
diff --git a/v7/src/microcode/ntscreen.h b/v7/src/microcode/ntscreen.h
index 7f6759895..84640622c 100644
--- a/v7/src/microcode/ntscreen.h
+++ b/v7/src/microcode/ntscreen.h
@@ -1,6 +1,6 @@
 /* -*-C-*-
 
-$Id: ntscreen.h,v 1.14 1997/04/03 04:40:53 cph Exp $
+$Id: ntscreen.h,v 1.15 1997/05/17 06:59:56 cph Exp $
 
 Copyright (c) 1993-97 Massachusetts Institute of Technology
 
@@ -193,6 +193,7 @@ extern void screen_char_dimensions (HWND, int *, int *);
 // The following return false on no events
 extern BOOL  Screen_GetEvent (HANDLE, SCREEN_EVENT *);
 extern BOOL  Screen_PeekEvent (HANDLE, SCREEN_EVENT *);
+extern BOOL  Screen_pending_events_p (void);
 
 //---------------------------------------------------------------------------
 //  Messages
diff --git a/v7/src/microcode/prntio.c b/v7/src/microcode/prntio.c
index 3bdfa772d..759d34af1 100644
--- a/v7/src/microcode/prntio.c
+++ b/v7/src/microcode/prntio.c
@@ -1,6 +1,6 @@
 /* -*-C-*-
 
-$Id: prntio.c,v 1.5 1997/04/03 04:41:15 cph Exp $
+$Id: prntio.c,v 1.6 1997/05/17 07:00:23 cph Exp $
 
 Copyright (c) 1993-97 Massachusetts Institute of Technology
 
@@ -125,17 +125,24 @@ wait_for_multiple_objects (DWORD nhand, HANDLE * handles, DWORD timeout,
 {
   DWORD result;
   MSG m;
-  /* This is a kludge.  MsgWaitForMultipleObjects has a race
-     condition -- it ignores messages that are already queued.  So
-     check the queue as late as possible before the call, in order
-     to minimize the window in which we can get stuck waiting for
-     a message that has already arrived.  */
 #ifdef TRACE_SCREEN_MSGS
   fprintf (trace_file, "MsgWaitForMultipleObjects: timeout=0x%x\n", timeout);
   fflush (trace_file);
 #endif
-  if (msgp && (PeekMessage ((&m), 0, 0, 0, PM_NOREMOVE)))
-    return (((m.message) == WM_SCHEME_INTERRUPT) ? (nhand + 2) : (nhand + 1));
+  if (msgp)
+    {
+      if (Screen_pending_events_p ())
+	return (nhand + 1);
+      /* This is a kludge.  MsgWaitForMultipleObjects has a race
+	 condition -- it ignores messages that are already queued.  So
+	 check the queue as late as possible before the call, in order
+	 to minimize the window in which we can get stuck waiting for
+	 a message that has already arrived.  */
+      if (PeekMessage ((&m), 0, 0, 0, PM_NOREMOVE))
+	return (((m.message) == WM_SCHEME_INTERRUPT)
+		? (nhand + 2)
+		: (nhand + 1));
+    }
   result =
     (MsgWaitForMultipleObjects (nhand, handles, FALSE, timeout, QS_ALLINPUT));
 #ifdef TRACE_SCREEN_MSGS
-- 
2.25.1