[PATCH v3] cli: Consume invalid escape sequences early

[Simon Glass]

On Tue, 10 Oct 2023 at 02:16, Yurii Monakov <monakov.y at gmail.com> wrote:
>
> Unexpected 'Esc' key presses are accumulated internally, even if it is
> already clear that the current escape sequence is invalid. This results
> in weird behaviour. For example, the next character after 'Esc' key
> simply disappears from input and 'Unknown command' is printed
> after 'Enter'.
>
> This commit fixes some issues with extra 'Esc' keys entered by user:
>
> 1. Sequence <Esc><Esc><Enter> right after autoboot stop gives:
> =>
> nknown command 'ry 'help'
> =>
> 2. Sequence <Esc><p><r><i><Enter> gives:
> => ri
> Unknown command 'ri' - try 'help'
> =>
> 3. Extra 'Esc' key presses break backspace functionality.
>
> Signed-off-by: Yurii Monakov <monakov.y at gmail.com>
> ---
> Changes for v2:
> - add tests and reword commit message
> Changes for v3:
> - fix indentation
>
>  common/cli_getch.c  |  2 ++
>  test/common/cread.c | 12 ++++++++++++
>  2 files changed, 14 insertions(+)

Reviewed-by: Simon Glass <sjg at chromium.org>

Unfortunately this shows a design flaw, one which is hard to fix in
general. But this does improve it.

The flaw is that we assume that character sequences have a time gap between
them, which allows figuring out when a sequence has finished.

But when starting up there may be buffered output with no gaps. I don't
think there is a general fix for this problem. One option is to have a
special mode at the start, where escape sequences are ignored. But the user
may press an arrow key on startup.

So I don't have anything much to suggest here. Let's see how this fix goes.
Perhaps it is enough.

Regards,
Simon