Add variable to control AutoTrigger

[jdujava]

Now it is possible to disable AutoTrigger in the current buffer by setting the buffer variable b:UltiSnipsAutoTrigger = 0.

Now it is possible to disable AutoTrigger via global variable g:UltiSnipsAutoTrigger, and to dynamically toggle AutoTrigger on/off with Ultisnips#ToggleAutoTrigger().

This is just a first crude shot at implementing this "toggling feature" (documentation and so on TODO).
What do you think, is this alright, or is there perhaps some better way in your opinion?

[SirVer]

I worry a bit about performance. Calling out to vim.eval is slow and this code will run on every cursor movement. This should probably be checked in vimscript before calling into python. Overall, I am fine with the feature.

[ces42]

I worry a bit about performance. Calling out to vim.eval is slow and this code will run on every cursor movement. This should probably be checked in vimscript before calling into python. Overall, I am fine with the feature.

Yes this can be done much better by removing/re-creating the UltiSnips_AutoTrigger autogroup from plugin/UltiSnips.vim using vimscript. There's no need to write python code for this.

[jdujava]

To not complicate things, I added only a global toggling mechanism.

@ces42 To be honest, I wasn't sure wheter UltiSnips_Manager._track_change() was needed also for other purposes than AutoTrigger, so I tried it this way. But I am certainly open to other (possibly better) solutions!

[ces42]

Adding this to autoload/UltiSnips.vim provides control over autotrigger:

function! UltiSnips#EnableAutotrigger() abort
    augroup UltiSnips_AutoTrigger
        au!
        au InsertCharPre * call UltiSnips#TrackChange()
        au TextChangedI * call UltiSnips#TrackChange()
        if exists('##TextChangedP')
            au TextChangedP * call UltiSnips#TrackChange()
        endif
    augroup END
endfunction

function! UltiSnips#DisableAutotrigger() abort
    augroup UltiSnips_AutoTrigger
        au!
    augroup END
endfunction

function! UltiSnips#ToggleAutotrigger() abort
    " if exists('#UltiSnips_AutoTrigger')
    if exists('#UltiSnips_AutoTrigger#TextChangedI')
        call UltiSnips#DisableAutotrigger()
    else
        call UltiSnips#EnableAutotrigger()
    endif
endfunction

EDIT: apparently the augroup doesn't get deleted when you do au!, only it's autocommands. So you need to replace exists('#UltiSnips_AutoTrigger') with exists('#UltiSnips_AutoTrigger#TextChangedI').

[SirVer]

Great, but a test is still missing. Will you work on that @jdujava ?

[jdujava]

@SirVer Added tests and documentation, does it look OK?

[jdujava]

@SirVer is it good to merge, or is there perhaps anything else to do?

[SirVer]

@jdujava Yes, it looks great, an exemplary contribution to an open source project. Thank you very much! Sorry that I took so long to get around to it.