Page up/down and keep cursor position

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created 2002 · complexity basic · author Simon "neoneye" Strandgaard · version 6.0

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Borland behaviour = the cursor keeps the same xy position during pageup/down.

I'm new to Vim scripting, im sure it can be done smarter?

I read VimTip105 and it gave me a clue of how BorlandPageUp/Down could be done.

" i could'nt find any get_number_of_visible_lines function, so i made my own.
function GetNumberOfVisibleLines()
  let cur_line = line(".")
  let cur_col = virtcol(".")
  normal H
  let top_line = line(".")
  normal L
  let bot_line = line(".")
  execute "normal " . cur_line . "G"
  execute "normal " . cur_col . "|"
  return bot_line - top_line
endfunc

" noremap <PageUp> 39<C-U>:set scroll=0<CR>
function! MyPageUp()
  let visible_lines = GetNumberOfVisibleLines()
  execute "normal " . visible_lines . "\<C-U>:set scroll=0\r"
endfunction

" noremap <PageDown> 39<C-D>:set scroll=0<CR>
function! MyPageDown()
  let visible_lines = GetNumberOfVisibleLines()
  execute "normal " . visible_lines . "\<C-D>:set scroll=0\r"
endfunction

" BorlandPascal pageup/down behaviour!
" todo: when hitting top/bottom of file, then restore Y to lastY
noremap <PageUp> :call MyPageUp()<CR>
noremap <PageDown> :call MyPageDown()<CR>

Comments

For maintaining the same x coordinate, :help 'startofline'.

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And CTRL-U (up), CTRL-D (down) may also be useful for what you want (half page scrolls)

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A solution that I use (easier, I would say, but has a small side-effect) is this:

map <PageDown> :set scroll=0<CR>:set scroll^=2<CR>:set scroll-=1<CR><C-D>:set scroll=0<CR>
map <PageUp> :set scroll=0<CR>:set scroll^=2<CR>:set scroll-=1<CR><C-U>:set scroll=0<CR>

I found Vim's normal PgUp/PgDn behaviour weird - I think it's different from every other editor I've used and I was unable to get used to it. The above two lines are godsent!

Ditto on the above two lines. They work exactly as I want! (SRS)

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See Combining move and scroll. You might find it useful to incorporate the improvements into this tip.

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A solution that works in insert and visual modes too:

nnoremap <silent> <PageUp> <C-U><C-U>
vnoremap <silent> <PageUp> <C-U><C-U>
inoremap <silent> <PageUp> <C-\><C-O><C-U><C-\><C-O><C-U>

nnoremap <silent> <PageDown> <C-D><C-D>
vnoremap <silent> <PageDown> <C-D><C-D>
inoremap <silent> <PageDown> <C-\><C-O><C-D><C-\><C-O><C-D>

It assumes that "scroll" has its default value. Also there is an intermediate redraw, but that could be perceived as a feature, really.

I've spent a whole day trying to simulate sometheing like the <C-\><C-O> command for Visual mode (hoping for the universal solution -- a way to call any normal mode command from any mode), yet it looks like impossible if the command in question is supposed to be a custom movement command, modifying selection.

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Another method that does not move cursor from screen position when scrolling, even with long lines that wrap:

 function! s:GetNumScroll(num)
   let num_rows = winheight(0)
   let num_scroll = a:num
   if (a:num == -1)
     let num_scroll = (num_rows + 1) / 2
   elseif (a:num == -2)
     let num_scroll = num_rows
   endif
   if (num_scroll < 1)
     let num_scroll = 1
   endif
   return num_scroll
 endfunction
 
 function! s:RtrnToOrig(before_scr_line)
   normal H
   let delta = a:before_scr_line - winline()
   while (delta != 0)
     if (delta < 0)
       let delta = winline() - a:before_scr_line
       let iter = 1
       while (iter <= delta)
         execute "normal" "gk"
         let iter +=1
       endwhile
     elseif (delta > 0)
       let iter = 1
       while (iter <= delta)
         execute "normal" "gj"
         let iter +=1
       endwhile
     endif
     let delta = a:before_scr_line - winline()
   endwhile
 endfunction
 
 function! s:scrollUP(num)
   let num_scroll = <SID>GetNumScroll(a:num)
   let num_rows = winheight(0)
   " -------------
   let before_scr_line = winline()
   normal L
   let after_scr_line = winline()
   let extra = num_rows - after_scr_line
   let extra += num_scroll
   " move by 1 to prevent over scrolling
   let iter = 1
   while (iter <= extra)
     execute "normal" "gj"
     let iter +=1
   endwhile
   " -------------
   call <SID>RtrnToOrig(before_scr_line)
 endfunction
 
 function! s:scrollDN(num)
   let num_scroll = <SID>GetNumScroll(a:num)
   " -------------
   let before_scr_line = winline()
   normal H
   let after_scr_line = line(".")
   execute "normal" "gk"
   let after_scr2_line = line(".")
   if ( (after_scr_line == after_scr2_line) && (after_scr_line > 1) )
     execute "normal" "gk"
   endif
   let extra = (num_scroll - 1)
   let extra += (winline() - 1)
   " move by 1 to prevent over scrolling
   let iter = 1
   while (iter <= extra)
     execute "normal" "gk"
     let iter +=1
   endwhile
   " -------------
   call <SID>RtrnToOrig(before_scr_line)
 endfunction
 
  nmap <silent> <C-J>     :call <SID>scrollUP(1)<CR>
  nmap <silent> <C-K>     :call <SID>scrollDN(1)<CR>
  nmap <silent> <C-F>     :call <SID>scrollUP(-1)<CR>
  nmap <silent> <C-B>     :call <SID>scrollDN(-1)<CR>
  nmap <silent> <PageDown>:call <SID>scrollUP(-2)<CR>
  nmap <silent> <PageUp>  :call <SID>scrollDN(-2)<CR>