A Vim take on Emacs' AceJump mode, itself based on Vim's PreciseJump and EasyMotion plugins

EasyJumpPreciseMotionAce.vim

" ACEJUMP
" Based on emacs' AceJump feature (http://www.emacswiki.org/emacs/AceJump).
" AceJump based on these Vim plugins:
"     EasyMotion (http://www.vim.org/scripts/script.php?script_id=3526)
"     PreciseJump (http://www.vim.org/scripts/script.php?script_id=3437)
" Type AJ mapping, followed by a lower or uppercase letter.
" All words on the screen starting with that letter will have
" their first letters replaced with a sequential character.
" Type this character to jump to that word.

highlight AceJumpGrey ctermfg=darkgrey guifg=lightgrey
highlight AceJumpRed ctermfg=darkred guibg=NONE guifg=black gui=NONE

function! AceJump ()
    " store some current values for restoring later
    let origPos = getpos('.')
    let origSearch = @/

    " prompt for and capture user's search character
    echo "AceJump to words starting with letter: "
    let letter = nr2char(getchar())
    " return if invalid key, mouse press, etc.
    if len(matchstr(letter, '\k')) != 1
        echo ""
        redraw
        return
    endif
    " redraws here and there to get past 'more' prompts
    redraw
    " row/col positions of words beginning with user's chosen letter
    let pos = []

    " monotone all text in visible part of window (dark grey by default)
    call matchadd('AceJumpGrey', '\%'.line('w0').'l\_.*\%'.line('w$').'l', 50)

    " loop over every line on the screen (just the visible lines)
    for row in range(line('w0'), line('w$'))
        " find all columns on this line where a word begins with our letter
        let col = 0
    let matchCol = match(' '.getline(row), '.\<'.letter, col)
    while matchCol != -1
        " store any matching row/col positions
        call add(pos, [row, matchCol])
        let col = matchCol + 1
        let matchCol = match(' '.getline(row), '.\<'.letter, col)
    endwhile
    endfor

    if len(pos) > 1
        " jump characters used to mark found words (user-editable)
        let chars = 'abcdefghijlkmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789,.;"[]<>{}|\\'

        if len(pos) > len(chars)
            " TODO add groupings here if more pos matches than jump characters
        endif

        " trim found positions list; cannot be longer than jump markers list
        let pos = pos[:len(chars)]

        " jumps list to pair jump characters with found word positions
        let jumps = {}
        " change each found word's first letter to a jump character
        for [r,c] in pos
            " stop marking words if there are no more jump characters
            if len(chars) == 0
                break
            endif
            " 'pop' the next jump character from the list
            let char = chars[0]
            let chars = chars[1:]
            " move cursor to the next found word
            call setpos('.', [0,r,c+1,0])
            " create jump character key to hold associated found word position
            let jumps[char] = [0,r,c+1,0]
            " replace first character in word with current jump character
            exe 'norm r'.char
            " change syntax on the jump character to make it highly visible
            call matchadd('AceJumpRed', '\%'.r.'l\%'.(c+1).'c', 50)
        endfor
        call setpos('.', origPos)

        " this redraw is critical to syntax highlighting
        redraw

        " prompt user again for the jump character to jump to
        echo 'AceJump to words starting with "'.letter.'" '
        let jumpChar = nr2char(getchar())

        " get rid of our syntax search highlighting
        call clearmatches()
        " clear out the status line
        echo ""
        redraw
        " restore previous search register value
        let @/ = origSearch

        " undo all the jump character letter replacement
        norm u

        " if the user input a proper jump character, jump to it
        if has_key(jumps, jumpChar)
            call setpos('.', jumps[jumpChar])
        else
            " if it didn't work out, restore original cursor position
            call setpos('.', origPos)
        endif
    elseif len(pos) == 1
        " if we only found one match, just jump to it without prompting
        " set position to the one match
        let [r,c] = pos[0]
        call setpos('.', [0,r,c+1,0])
    elseif len(pos) == 0
        " no matches; set position back to start
        call setpos('.', origPos)
    endif
    " turn off all search highlighting
    call clearmatches()
    " clean up the status line and return
    echo ""
    redraw
    return
endfunction

nnoremap <Leader>aj :call AceJump()<CR>