Prompt redrawing issues with wrapped prompt on SIGWINCH

[Daniel Hahler <genml+zsh-workers@thequod.de>]

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I am seeing weird redrawing issues when resizing the terminal window with the prompt at the bottom, and the prompt needs to be rewrapped.

TEST CASE:

1. zsh -f
2. setopt promptsubst
3. PS1="\${(pl:\$((\$COLUMNS))::=:)} %# "

Now fill the terminal window, e.g. with "ls", so that the prompt gets displayed at the bottom.

When resizing the terminal window now, Zsh does not redraw itself properly: the prompt will moves upwards, overwriting output from "ls".

This also happens with a static PS1, when the window gets too narrow:

PS1="===================================== %# "


There is no clear pattern in what goes wrong. With my prompt it will also duplicate the first part of it, and it seems to make a difference if the first line is "full" before the linebreak.

1. Start:
⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[🐍 ?]
❯❯

2. Make it smaller:
⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[🐍 ?]
❯❯ 

3. Larger again (original size):
⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[🐍 ?]
❯❯

4. Smaller again:
⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[~]⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯[🐍 ?]
❯❯


My terminal is rxvt-unicode, but this also happens with gnome-terminal.

I am using the awesome window manager, using a tiled layout and use mod-j/k to resize the window.

Using TRAPWINCH shows a single WINCH signal per resize.

In case this isn't reproducible for you I'd like to get some pointers how to debug this.
It's probably related to zsh's SIGWINCH handling?


Thanks,
Daniel.
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