[PATCH 3/5] tui: simplify and fix up handling of start_line in tui_redisplay_readline

[Patrick Palka <patrick@parcs.ath.cx>]

This patch makes three small changes:

The code guarded by the c == '\n' condition is dead code because
whatever value start_line and curch get set to will be overwritten after
the while-loop finishes anyway.  So this patch removes this dead code.

Besides that, the remaining two writes to start_line are combined into
one write.

Finally, if start_line ever falls below 0, which can happen if the
command line is so long that it wraps along the height of the entire
command window, just reset it to 0 so that we avoid passing an invalid y
parameter to wmove() later, and emit a beep to "warn" the user that the
command line is too long.

gdb/ChangeLog:

	* tui/tui-io.c (tui_redisplay_readline): Simplify the updating
	of start_line.  If start_line is negative, re-set it to 0 and
	emit a beep.
---
 gdb/tui/tui-io.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
index ba42c18..5b9ca20 100644
--- a/gdb/tui/tui-io.c
+++ b/gdb/tui/tui-io.c
@@ -270,26 +270,33 @@ tui_redisplay_readline (void)
 	{
           waddch (w, c);
 	}
-      if (c == '\n')
-        {
-          getyx (w, TUI_CMD_WIN->detail.command_info.start_line,
-                 TUI_CMD_WIN->detail.command_info.curch);
-        }
       getyx (w, line, col);
       if (col < prev_col)
         height++;
       prev_col = col;
     }
+
   wclrtobot (w);
-  getyx (w, TUI_CMD_WIN->detail.command_info.start_line,
-         TUI_CMD_WIN->detail.command_info.curch);
+
+  TUI_CMD_WIN->detail.command_info.start_line
+    = getcury (w) - (height - 1);
+  TUI_CMD_WIN->detail.command_info.curch
+    = getcurx (w);
+
+  /* This can happen if the command line is so long that it wraps along the
+     height of the entire window.  */
+  if (TUI_CMD_WIN->detail.command_info.start_line < 0)
+    {
+      beep ();
+      TUI_CMD_WIN->detail.command_info.start_line = 0;
+    }
+
   if (c_line >= 0)
     {
       wmove (w, c_line, c_pos);
       TUI_CMD_WIN->detail.command_info.cur_line = c_line;
       TUI_CMD_WIN->detail.command_info.curch = c_pos;
     }
-  TUI_CMD_WIN->detail.command_info.start_line -= height - 1;
 
   wrefresh (w);
   fflush(stdout);
-- 
2.5.0.rc0.5.g91e10c5.dirty