[PATCH] Call target_terminal_ours() before refreshing TUI's frame info

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

In some cases tui_show_frame_info() may get called while the inferior's
terminal settings are still in effect.  But when we call this function
we absolutely need to have our terminal settings in effect because the
function is responsible for redrawing TUI's windows following a change
in the selected frame or a change in the PC.  If our terminal settings
are not in effect, the screen does not get redrawn properly, causing
temporary display artifacts (which can be fixed via ^L).

This scenario happens most prominently when stepping through a program
in TUI while a watchpoint is in effect.

Here is an example backtrace for when tui_show_frame_info() gets called
while target_terminal_is_inferior() == 1:

  #1  0x00000000004988ee in tui_selected_frame_level_changed_hook (level=0)
  #2  0x0000000000617b99 in select_frame (fi=0x18c9820)
  #3  0x0000000000617c3f in get_selected_frame (message=message@entry=0x0)
  #4  0x00000000004ce534 in update_watchpoint (b=b@entry=0x2d9a760,
      reparse=reparse@entry=0)
  #5  0x00000000004d625e in insert_breakpoints ()
  #6  0x0000000000531cfe in keep_going (ecs=ecs@entry=0x7ffea7884ac0)
  #7  0x00000000005326d7 in process_event_stop_test (ecs=ecs@entry=0x7ffea7884ac0)
  #8  0x000000000053596e in handle_inferior_event_1 (ecs=0x7ffea7884ac0)

The fix is simple: call target_terminal_ours() before calling
tui_show_frame_info() in TUI's frame-changed hook, making sure to
restore the original terminal settings afterwards.

gdb/ChangeLog:

	* tui/tui-hooks.c (tui_selected_frame_level_changed_hook): Call
	target_terminal_ours() before calling tui_show_frame_info(), and
	restore the original terminal settings afterwards.
---
 gdb/tui/tui-hooks.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/gdb/tui/tui-hooks.c b/gdb/tui/tui-hooks.c
index e53f526..3331d67 100644
--- a/gdb/tui/tui-hooks.c
+++ b/gdb/tui/tui-hooks.c
@@ -127,11 +127,15 @@ tui_selected_frame_level_changed_hook (int level)
 {
   struct frame_info *fi;
   CORE_ADDR pc;
+  struct cleanup *old_chain;
 
   /* Negative level means that the selected frame was cleared.  */
   if (level < 0)
     return;
 
+  old_chain = make_cleanup_restore_target_terminal ();
+  target_terminal_ours ();
+
   fi = get_selected_frame (NULL);
   /* Ensure that symbols for this frame are read in.  Also, determine
      the source language of this frame, and switch to it if
@@ -160,6 +164,8 @@ tui_selected_frame_level_changed_hook (int level)
       tui_check_data_values (fi);
       tui_refreshing_registers = 0;
     }
+
+  do_cleanups (old_chain);
 }
 
 /* Called from print_frame_info to list the line we stopped in.  */
-- 
2.4.2.387.gf86f31a.dirty