Using H and L keys as context sensitive pagedown/pageup
From Vim Tips Wiki
created September 2, 2003 · complexity basic · author Usman Latif · version 5.7
The H and L keys move the cursor to the top or bottom of the window respectively. They can be a real time saver, instead of hitting j/k many times, a single H/L can move the cursor to the proper place. However, when you are already at the top of the window the H key does nothing and similarly at the bottom of the window the L key does nothing.
I started using the H/L keys a few days ago and quickly discovered that after getting to the top using H, I often want to scroll up. Hitting H again does nothing, so I wrote a function Hcontext which makes the H key context sensitive. I then mapped Hcontext to the H key. Now hitting the H key anywhere other than at the top of the window leads to the usual behavior but hitting H at the first line of the window causes the window to scroll one page back and positions the cursor at the top of the window. Similar behavior is implemented by the Lcontext function but in the other direction. Hitting L on the last line of the window now acts like the pagedown key.
Even if you have never used the H/L keys before you can now start using them as replacement pagedown/pageup keys. Just cut and paste the code at the end into your vimrc and put the following maps after that.
noremap H :call Hcontext()<CR> noremap L :call Lcontext()<CR>
The unmapped H and L keys take a numeric count as well. Unfortunately, I am not aware of a way to make that count available to the user functions I wrote. The typical vim behavior in case of user functions is to supply the count as a range to the user function. This works most of the time but sometimes the count gets rejected because of range checking.
function! Hcontext() if (winline() == 1 && line(".") != 1) exe "normal! \<pageup>H" else exe "normal! H" endif echo '' endfunc func! Lcontext() if (winline() == winheight(0) && line(".") != line("$")) exe "normal! \<pagedown>L" else exe "normal! L" endif echo '' endfunc
My suggestion for improvement is to take care of the scrolloff option. My modification of the function:
func! Hcontext() if (winline() == &so+1 && line(".") != 1) exe "normal! \<PageUp>H" else exe "normal! H" endif echo '' endfunc func! Lcontext() if (winline() == winheight(0)-&so && line(".") != line("$")) exe "normal! \<PageDown>L" else exe "normal! L" endif echo '' endfunc
I converted this tip to a plugin. See script#763.
I found some problems with the original implementation of the two functions. The functions don't work when the bottom or top line is longer than window width and is spread over multiple window lines. The cursor needs to be on the top or bottom-most window-line to work correctly.
I fixed the problem and the new code is below. However, there is one case where the functions don't work. This case occurs when a count is supplied that will take the cursor to a line that is not visible. The proper behavior is to do nothing, but the code below instead does a pagedown/pageup. In practice I don't expect this behavior to be a problem for anyone.
map <silent> H :<C-U>call HContext()<CR> map <silent> L :<C-U>call LContext()<CR> func! HContext() let moved = MoveCursor("H") if !moved && line('.') != 1 exe "normal! " . "\<pageup>H" endif endfunc func! LContext() let moved = MoveCursor("L") if !moved && line('.') != line('$') exe "normal! " . "\<pagedown>L" endif endfunc func! MoveCursor(key) let cnum = col('.') let lnum = line('.') let wline = winline() exe "normal! " . v:count . a:key let moved = cnum != col('.') || lnum != line('.') || wline != winline() return moved endfunc
This needs to be extended to support 2H, 3H and also line('w0') and line('w$') may be useful
Another solution I found on accident that I've been supremely happy with:
nnoremap J H nnoremap K L
Try it by pressing Shift+J, but when you let go of the shift, hold down j and it will scroll. (for completeness I mapped old functionality to the following)
nnoremap <C-J> J nnoremap <F1> K