ultimate-vim/sources_non_forked/vim-go/autoload/go/ui.vim

let s:buf_nr = -1

"OpenWindow opens a new scratch window and put's the content into the window
function! go#ui#OpenWindow(title, content, filetype)
    " Ensure there's only one return window in this session/tabpage
    call go#util#Windo("unlet! w:vim_go_return_window")
    " Mark the window we're leaving as such
    let w:vim_go_return_window = 1

    " reuse existing buffer window if it exists otherwise create a new one
    if !bufexists(s:buf_nr)
        execute 'botright new'
        file `="[" . a:title . "]"`
        let s:buf_nr = bufnr('%')
    elseif bufwinnr(s:buf_nr) == -1
        execute 'botright new'
        execute s:buf_nr . 'buffer'
    elseif bufwinnr(s:buf_nr) != bufwinnr('%')
        execute bufwinnr(s:buf_nr) . 'wincmd w'
    endif

    " Resize window to content length
    exe 'resize' . len(a:content)

    execute "setlocal filetype=".a:filetype

    " some sane default values for a readonly buffer
    setlocal bufhidden=delete
    setlocal buftype=nofile
    setlocal noswapfile
    setlocal nobuflisted
    setlocal winfixheight
    setlocal cursorline " make it easy to distinguish
    setlocal nonumber
    setlocal norelativenumber
    setlocal showbreak=""

    " we need this to purge the buffer content
    setlocal modifiable

    "delete everything first from the buffer
    %delete _

    " add the content
    call append(0, a:content)

    " delete last line that comes from the append call
    $delete _

    " set it back to non modifiable
    setlocal nomodifiable

    " Remove the '... [New File]' message line from the command line
    echon
endfunction

function! go#ui#GetReturnWindow()
    for l:wn in range(1, winnr("$"))
        if !empty(getwinvar(l:wn, "vim_go_return_window"))
            return l:wn
        endif
    endfor
endfunction

" CloseWindow closes the current window
function! go#ui#CloseWindow()
    " Close any window associated with the ui buffer, if it's there
    if bufexists(s:buf_nr)
        let ui_window_number = bufwinnr(s:buf_nr)
        if ui_window_number != -1
            execute ui_window_number . 'close'
        endif
    endif

    "return to original window, if it's there
    let l:rw = go#ui#GetReturnWindow()
    if !empty(l:rw)
        execute l:rw . 'wincmd w'
        unlet! w:vim_go_return_window
    endif
endfunction

" OpenDefinition parses the current line and jumps to it by openening a new
" tab
function! go#ui#OpenDefinition(filter)
    let curline = getline('.')

    " don't touch our first line or any blank line
    if curline =~ a:filter || curline =~ "^$"
        " supress information about calling this function
        echo ""
        return
    endif

    " format: 'interface file:lnum:coln'
    let mx = '^\(^\S*\)\s*\(.\{-}\):\(\d\+\):\(\d\+\)'

    " parse it now into the list
    let tokens = matchlist(curline, mx)

    " convert to: 'file:lnum:coln'
    let expr = tokens[2] . ":" . tokens[3] . ":" .  tokens[4]

    " jump to it in a new tab, we use explicit lgetexpr so we can later change
    " the behaviour via settings (like opening in vsplit instead of tab)
    lgetexpr expr
    tab split
    ll 1

    " center the word
    norm! zz
endfunction