Sunday, August 21, 2016

Re: Changing the defaults with Vim 8

On 08/20/2016 01:22 PM, Bram Moolenaar wrote:
> Hirohito Higashi wrote:
>> `set ttimeoutlen=0` will solve the above.
>>
>> I have invested in above setting more than a year, but the
>> trouble does not happen even once.
>
> Zero only works when you are directly using a terminal. When
> using a remote shell it might not work properly. But one
> second is indeed too much.
>
> I have it set to 200, this still has some lag. I think 100
> would work for just about everyone.

I ran for a long time without trouble using 50 milliseconds.
But even this eventually proved too long once I began using
Alt-letter mappings in console Vim. The key sequence for Alt-j
is <Esc>j. I would frequently press <Esc> to exit insert mode
followed quickly by the j key, and Vim would misinterpret the
sequence as Alt-j (which would then invoke my insert-mode
mapping for Alt-j). I found experimentally that I could set
ttimeoutlen to 5 to avoid most instances of this kind of
incorrect key interpretation. This value has never proved to be
too small in my use. I've never noticed a case of Vim timing
out in the middle of a valid multi-key sequence and splitting it
incorrectly into multiple keypresses, even when using Vim across
an SSH connection; however, these connections were typically
done over a local Ethernet, so on a slower network it's possible
that such splitting could occur (such that Alt-j might be split
erroneously into <Esc> followed by j). I consider this an
unlikely case, since the multi-key sequence will probably be
written to the network as a unit and carried in a single network
packet, regardless of the speed of the network; still, until we
start using uniquely decodable key sequences so we don't have to
rely on timeouts, there will always be some risk of incorrect
key interpretation.

I think 100ms is better than 200ms as a default. I wouldn't
suggest a default as low as 5ms due to the possible risk of
misinterpreting multi-byte key sequences, even though I've never
personally noticed such a failure. Users like myself who
require shorter values can always override the default. I'll
also note that I've seen 100ms used elsewhere, such as in Tim
Pope's "Sensible Defaults" plugin:
https://github.com/tpope/vim-sensible/blob/master/plugin/sensible.vim#L28

Michael Henry

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