bug#57434: 28.1.91; Terminal Emacs Mac OS flickering.

[Dmitrii Kuragin]

I agree with Gerd on the discoveries.

Here's some code how tmux works with that [1], we can probably avoid it by providing a frame-local flag which enables the functionality, so that multiple emacs clients might be connected from potentially different terminals.

We can improve the default value of the flag based on terminal capabilities later once we have confidence in the way it works and probably extend it to support different specifications of syncing.

[1]: https://github.com/tmux/tmux/blob/9c34aad21c0837123a51a5a4233a016805d3e526/tty-features.c#L474

On Thu, Sep 8, 2022 at 2:35 AM Gerd Möllmann <gerd.moellmann@gmail.com> wrote:

Eli Zaretskii <eliz@gnu.org> writes:

> I guess by P1 you mean these two sequences:
>
>   BSU: ESC P = 1 s ESC \
>   ESU: ESC P = 2 s ESC \
>
> whereas by P2 you mean these:
>
>   DECRQM: ESC [ ? 2026 $ p
>   DECRPM: ESC [ ? 2026 ; n $ y  (with n = 0..4, and 0 or 4 means "no support")
>   BSU:    ESC [ ? 2026 h
>   ESU:    ESC [ ? 2026 l

Yes, that looks like them.

>
>> > Do you happen to know where is the definitive documentation of Sync?
>>
>> Sorry, I don't know a definitive documentation.
>
> And any documentation at all?

Not even that.  I tried to find something today, but nothing useful
turned up.

>
> Anyway, given the problems usually related to querying terminals about
> potentially unsupported features, and the general mess in this field,
> I think our best bet is to have a function that could switch the
> frame-update hooks between these 3 states:
>
>   . unused
>   . used with P1 BSU/ESU sequences
>   . used with P2 BSU/ESU sequences
>
> WDYT?

Yes, something like that, I guess.

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