Re: [PATCH 3/3] Replace TUI's select_frame hook (PR tui/13378)

[Pedro Alves <palves at redhat dot com>]

On 06/27/2015 03:50 AM, Patrick Palka wrote:
> Actually, we should not call tui_show_frame_info(NULL) when there are no
> stack frames, because doing so empties the source window after invoking
> "continue&". That was a last-minute change with no justification anyway.
> 
> Here is a revised patch with a much smaller diffstat.

On 06/27/2015 03:35 AM, Patrick Palka wrote:

> Effectively, with this patch, frame/PC changes that do not immediately
> precede an inferior-stop event or a prompt display event no longer cause
> TUI's frame and register information to be updated.

It seems to me that this doesn't update the info when the
program stops after continue& ...

> @@ -107,6 +108,9 @@ tui_on_sync_execution_done (void)
>  {
>    if (!interp_quiet_p (tui_interp))
>      display_gdb_prompt (NULL);
> +
> +  if (tui_active)
> +    tui_refresh_frame_and_register_information ();
>  }
>

... when sync/foreground execution is done, we show the
prompt (display_gdb_prompt above), so the before_prompt observer
is already taking care of refreshing.

But when background/async execution is done, we don't call
sync_execution_done observers, so this hook isn't called.
So I'm not seeing what this bit in tui_on_sync_execution_done
is for.

I think that for for stops (either after background or foreground
execution), the TUI refreshes itself from within the
deprecated_print_frame_info_listing_hook, called from:

#0  tui_show_frame_info (fi=0xf20b50) at /home/pedro/gdb/mygit/build/../src/gdb/tui/tui-stack.c:337
#1  0x00000000005266c5 in tui_print_frame_info_listing_hook (s=0x1978100, line=92, stopline=93, noerror=0) at /home/pedro/gdb/mygit/build/../src/gdb/tui/tui-hooks.c:177
#2  0x000000000063a6f7 in print_frame_info (frame=0xf20b50, print_level=0, print_what=SRC_AND_LOC, print_args=1, set_current_sal=1)
    at /home/pedro/gdb/mygit/build/../src/gdb/stack.c:895
#3  0x0000000000638e2f in print_stack_frame (frame=0xf20b50, print_level=0, print_what=SRC_AND_LOC, set_current_sal=1)
    at /home/pedro/gdb/mygit/build/../src/gdb/stack.c:162
#4  0x0000000000632c14 in print_stop_event (ws=0x7fffffffd120) at /home/pedro/gdb/mygit/build/../src/gdb/infrun.c:6536
#5  0x0000000000632fa5 in normal_stop () at /home/pedro/gdb/mygit/build/../src/gdb/infrun.c:6701

I think this hooking in deprecated_print_frame_info_listing_hook
is also a too-low-level place, and is likely contributing
to flicker in other situations.  I think we should move
to doing whatever we do in it to a normal_stop observer instead.
(tbc, doesn't have to be this patch.)

> And as a result of this change and of the previous change to
> tui_show_frame_info, the TUI is much more disciplined about updating the
> screen, and so the flicker as described in the PR is totally gone.

I think we should sort out patch 3 before patch 2.  AFAICS, the
important one is this one, right?

Thanks,
Pedro Alves