Cygwin: pty: Fix screen distortion after less for native apps again.

- Commit c4b060e3fe seems to be not
  enough. Moreover, it does not work as expected at all in Win10
  1809. This patch essentially reverts that commit and add another
  fix. After all, the cause of the problem was a race issue in
  switch_to_pcon_out flag. That is, this flag is set when native
  app starts, however, it is delayed by wait_pcon_fwd(). Since the
  flag is not set yet when less starts, the data which should go
  into the output_handle accidentally goes into output_handle_cyg.
  This patch fixes the problem more essentially for the cause of
  the problem than previous one.

winsup/cygwin/fhandler.h

@@ -2354,7 +2354,6 @@ class fhandler_pty_slave: public fhandler_pty_common
   void setup_locale (void);
   void set_freeconsole_on_close (bool val);
   void trigger_redraw_screen (void);
-  void wait_pcon_fwd (void);
   void pull_pcon_input (void);
   void update_pcon_input_state (bool need_lock);
 };

winsup/cygwin/fhandler_tty.cc

@@ -1277,6 +1277,7 @@ fhandler_pty_slave::set_switch_to_pcon (int fd_set)
 {
   if (fd < 0)
     fd = fd_set;
+  acquire_output_mutex (INFINITE);
   if (fd == 0 && !get_ttyp ()->switch_to_pcon_in)
     {
       pull_pcon_input ();
@@ -1286,13 +1287,13 @@ fhandler_pty_slave::set_switch_to_pcon (int fd_set)
       get_ttyp ()->switch_to_pcon_in = true;
       if (isHybrid && !get_ttyp ()->switch_to_pcon_out)
 	{
-	  wait_pcon_fwd ();
+	  get_ttyp ()->wait_pcon_fwd ();
 	  get_ttyp ()->switch_to_pcon_out = true;
 	}
     }
   else if ((fd == 1 || fd == 2) && !get_ttyp ()->switch_to_pcon_out)
     {
-      wait_pcon_fwd ();
+      get_ttyp ()->wait_pcon_fwd ();
       if (get_ttyp ()->pcon_pid == 0 ||
 	  !pinfo (get_ttyp ()->pcon_pid))
 	get_ttyp ()->pcon_pid = myself->pid;
@@ -1300,6 +1301,7 @@ fhandler_pty_slave::set_switch_to_pcon (int fd_set)
       if (isHybrid)
 	get_ttyp ()->switch_to_pcon_in = true;
     }
+  release_output_mutex ();
 }
 
 void
@@ -1314,12 +1316,14 @@ fhandler_pty_slave::reset_switch_to_pcon (void)
     return;
   if (do_not_reset_switch_to_pcon)
     return;
+  acquire_output_mutex (INFINITE);
   if (get_ttyp ()->switch_to_pcon_out)
     /* Wait for pty_master_fwd_thread() */
-    wait_pcon_fwd ();
+    get_ttyp ()->wait_pcon_fwd ();
   get_ttyp ()->pcon_pid = 0;
   get_ttyp ()->switch_to_pcon_in = false;
   get_ttyp ()->switch_to_pcon_out = false;
+  release_output_mutex ();
   init_console_handler (true);
 }
 
@@ -1372,7 +1376,7 @@ fhandler_pty_slave::push_to_pcon_screenbuffer (const char *ptr, size_t len,
 	  p0 = (char *) memmem (p1, nlen - (p1-buf), "\033[?1049h", 8);
 	  if (p0)
 	    {
-	      p0 += 8;
+	      //p0 += 8;
 	      get_ttyp ()->screen_alternated = true;
 	      if (get_ttyp ()->switch_to_pcon_out)
 		do_not_reset_switch_to_pcon = true;
@@ -1384,7 +1388,7 @@ fhandler_pty_slave::push_to_pcon_screenbuffer (const char *ptr, size_t len,
 	  p1 = (char *) memmem (p0, nlen - (p0-buf), "\033[?1049l", 8);
 	  if (p1)
 	    {
-	      //p1 += 8;
+	      p1 += 8;
 	      get_ttyp ()->screen_alternated = false;
 	      do_not_reset_switch_to_pcon = false;
 	      memmove (p0, p1, buf+nlen - p1);
@@ -1504,8 +1508,9 @@ fhandler_pty_slave::write (const void *ptr, size_t len)
 
   reset_switch_to_pcon ();
 
-  bool output_to_pcon =
-    get_ttyp ()->switch_to_pcon_out && !get_ttyp ()->screen_alternated;
+  acquire_output_mutex (INFINITE);
+  bool output_to_pcon = get_ttyp ()->switch_to_pcon_out;
+  release_output_mutex ();
 
   UINT target_code_page = output_to_pcon ?
     GetConsoleOutputCP () : get_ttyp ()->term_code_page;
@@ -2420,8 +2425,6 @@ fhandler_pty_master::close ()
 	    }
 	  release_output_mutex ();
 	  master_fwd_thread->terminate_thread ();
-	  CloseHandle (get_ttyp ()->fwd_done);
-	  get_ttyp ()->fwd_done = NULL;
 	}
     }
 
@@ -2903,17 +2906,6 @@ fhandler_pty_slave::set_freeconsole_on_close (bool val)
   freeconsole_on_close = val;
 }
 
-void
-fhandler_pty_slave::wait_pcon_fwd (void)
-{
-  acquire_output_mutex (INFINITE);
-  get_ttyp ()->pcon_last_time = GetTickCount ();
-  ResetEvent (get_ttyp ()->fwd_done);
-  release_output_mutex ();
-  while (get_ttyp ()->fwd_done
-	 && cygwait (get_ttyp ()->fwd_done, 1) == WAIT_TIMEOUT);
-}
-
 void
 fhandler_pty_slave::trigger_redraw_screen (void)
 {
@@ -2967,12 +2959,14 @@ fhandler_pty_slave::fixup_after_attach (bool native_maybe, int fd_set)
 	    {
 	      DWORD mode = ENABLE_PROCESSED_OUTPUT | ENABLE_WRAP_AT_EOL_OUTPUT;
 	      SetConsoleMode (get_output_handle (), mode);
+	      acquire_output_mutex (INFINITE);
 	      if (!get_ttyp ()->switch_to_pcon_out)
-		wait_pcon_fwd ();
+		get_ttyp ()->wait_pcon_fwd ();
 	      if (get_ttyp ()->pcon_pid == 0 ||
 		  !pinfo (get_ttyp ()->pcon_pid))
 		get_ttyp ()->pcon_pid = myself->pid;
 	      get_ttyp ()->switch_to_pcon_out = true;
+	      release_output_mutex ();
 
 	      if (get_ttyp ()->need_redraw_screen)
 		trigger_redraw_screen ();
@@ -3258,19 +3252,9 @@ fhandler_pty_master::pty_master_fwd_thread ()
     {
       if (get_pseudo_console ())
 	{
-	  /* The forwarding in pseudo console sometimes stops for
-	     16-32 msec even if it already has data to transfer.
-	     If the time without transfer exceeds 32 msec, the
-	     forwarding is supposed to be finished. */
-	  const int sleep_in_pcon = 16;
-	  const int time_to_wait = sleep_in_pcon * 2 + 1/* margine */;
 	  get_ttyp ()->pcon_last_time = GetTickCount ();
 	  while (::bytes_available (rlen, from_slave) && rlen == 0)
 	    {
-	      acquire_output_mutex (INFINITE);
-	      if (GetTickCount () - get_ttyp ()->pcon_last_time > time_to_wait)
-		SetEvent (get_ttyp ()->fwd_done);
-	      release_output_mutex ();
 	      /* Forcibly transfer input if it is requested by slave.
 		 This happens when input data should be transfered
 		 from the input pipe for cygwin apps to the input pipe
@@ -3342,7 +3326,6 @@ fhandler_pty_master::pty_master_fwd_thread ()
 	  /* OPOST processing was already done in pseudo console,
 	     so just write it to to_master_cyg. */
 	  DWORD written;
-	  acquire_output_mutex (INFINITE);
 	  while (rlen>0)
 	    {
 	      if (!WriteFile (to_master_cyg, ptr, wlen, &written, NULL))
@@ -3353,7 +3336,6 @@ fhandler_pty_master::pty_master_fwd_thread ()
 	      ptr += written;
 	      wlen = (rlen -= written);
 	    }
-	  release_output_mutex ();
 	  mb_str_free (buf);
 	  continue;
 	}
@@ -3695,7 +3677,6 @@ fhandler_pty_master::setup ()
       errstr = "pty master forwarding thread";
       goto err;
     }
-  get_ttyp ()->fwd_done = CreateEvent (&sec_none, true, false, NULL);
 
   t.winsize.ws_col = 80;
   t.winsize.ws_row = 25;

winsup/cygwin/tty.cc

@@ -244,7 +244,6 @@ tty::init ()
   pcon_pid = 0;
   term_code_page = 0;
   need_redraw_screen = true;
-  fwd_done = NULL;
   pcon_last_time = 0;
   pcon_in_empty = true;
   req_transfer_input_to_pcon = false;
@@ -307,6 +306,12 @@ tty::set_switch_to_pcon_out (bool v)
 void
 tty::wait_pcon_fwd (void)
 {
+  /* The forwarding in pseudo console sometimes stops for
+     16-32 msec even if it already has data to transfer.
+     If the time without transfer exceeds 32 msec, the
+     forwarding is supposed to be finished. pcon_last_time
+     is reset to GetTickCount() in pty master forwarding
+     thread when the last data is transfered. */
   const int sleep_in_pcon = 16;
   const int time_to_wait = sleep_in_pcon * 2 + 1/* margine */;
   pcon_last_time = GetTickCount ();

winsup/cygwin/tty.h

@@ -105,7 +105,6 @@ private:
   pid_t pcon_pid;
   UINT term_code_page;
   bool need_redraw_screen;
-  HANDLE fwd_done;
   DWORD pcon_last_time;
   bool pcon_in_empty;
   bool req_transfer_input_to_pcon;