Re: How to determine the start of a visual block (C-V) when it starts in the void?

On Wednesday, January 30, 2013 9:49:52 AM UTC-6, Axel Bender wrote:
> Hi Ben,
>
> try this:
>
> xnoremap <silent> _C :<C-U>call SomeFunc()<CR> " My current mapping
> xnoremap <silent><expr>_D SomeFunc()<CR> " John's proposal
> xnoremap <silent> _E SomeFunc()<CR> " same w/o <expr>
>

This should be:
xnoremap <silent> _C :<C-U>call SomeFunc()<CR>
xnoremap <silent><expr>_D SomeFunc()

Your third mapping will never work, why do you expect it to? It is like pressing the keys S o m e F u n c ( ) and then <CR> in sequence, in visual mode. The S will replace the entire visual selection and enter the rest of the text in insert mode.

> fun! SomeFunc()
> let col = virtcol("'<") - 1
> let ecol = virtcol("'>")
>
> for l in range(line("'<"), line("'>"))
> call setline(l, strpart(getline(l), col, ecol - col))
> endfor
> endf
>

I modified this to echo the columns instead of doing whatever the for loop does.

> Select (ve=block) a visual block from "Fun" down to "ol ", the press _C, _D, and _E. Repeat the same (_C, _E) with an extended block (one line further down - in the void).

The first mapping clears visual mode and echos 1 on empty lines, as you reported, and as I and John expect, BECAUSE THE : ENDS VISUAL MODE. There is nothing you can do about this. There is nothing Vim SHOULD do about this. Visual mode is over. Done. Complete. You are no longer in visual block mode so the cursor can no longer be outside the real text.

The second mapping works as expected, getting the virtual column of the visual block selection, because IT NEVER LEAVES VISUAL MODE.

Note to call a function in a visual mode <expr> mapping, the function should return the text desired for the RHS of the mapping. In this case, adding:

return ""

to the end of the mapping lets it do no further action on the visual selection.

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