Question

The problem is not solved although I accepted one answer.

Problem: Vim updates very slowly the screen in Screen in Mac, although lazyredraw and showcmd are off.

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The line numbers get on the foldColumn as below, for instance, when I have line numbers
alt text http://dl.getdropbox.com/u/175564/vimScreenFold.png

When I have nothing in my .vimrc, the problem can be seen by multiplied comment lines on top of one another:
alt text http://dl.getdropbox.com/u/175564/vimScatteredBug.png

I did not type the following comment more than once on the left-hand side

"set list...

Observations

1. seemed to occur only in comment lines and empty lines. However, I got the evidence (2) which shows that this is not the case.
2. scatters occurs mostly in the left-hand-side window. They occur also with a single window. However, it is harder to detect with it.
3. The bug occurs slightly differently when I have nothing in .vimrc. However, the “stagnation” occurs in both situations: with empty .vimrc and with non-empty .vimrc.

Identification of Bug

Dependent variables

1. dependent on comment signs automatically put by Vim. I noticed disappeared pixels when Vim put Python’s comment signs # automatically to my files, when it could not show the whole file.
2. dependent on at least OS/X Leopard.

Independent variables

1. file independent: occurs in all files edited by Vim
2. line independent: occurs in a Python code without comments and empty lines
3. .vimrc independent: occurs with empty .vimrc
4. .screenrc independent: occurs with empty .screenrc
5. shell independent: occurs with Bash and Zsh
6. Screen version independent: occurs with Leopard’s default screen and with Screen 4.0.3
7. independent of different comment characters: occurs when scrolling down, for instance, .zshrc, .vimrc and .screenrc

How can you disable Vim’s default settings?

Answer 1

I’m guessing that the issue might be with your termcap and terminfo settings. Try commenting those out from your screenrc, and restarting screen.

Also, what (non-virtual) terminal are you using?

Ah, it looks like you’re using OSX’s Terminal.app, which is exactly what I use (with screen/zsh/vim). /usr/bin/screen should work with /usr/bin/vim with an empty .screenrc and .vimrc by default.

% touch empty_screenrc
% cat empty_screerc
% /usr/bin/screen -c empty_screenrc
#...and within screen
% /usr/bin/vim -u NONE

If the problem still persists, the problem may be in your shell. But if this fixes the problem, I’d suggest posting your ~/.vimrc to aid in further diagnosis.