Some emojis break urwid-based TUI with tmux

[maximbaz]

Hello,

I was trying out https://github.com/isamert/scli when I noticed that UI often gets corrupted when emojis are involved, and it turns out z4h is somewhat to blame 🙂

I believe I managed to get consistent repro steps down to a small script below, so you won't need to install too many dependencies. To reproduce, you only need urwid installed, and then save this script (say in /tmp/repro.py) which has the important bits from scli:

import urwid


class StatusLine(urwid.WidgetWrap):
    def __init__(self, unread_count=0):
        self._text = urwid.Text("Left: ")
        self._unreads_widget = urwid.Text("Right: 0")
        self._status_cols = urwid.Columns(
            [self._text, ("pack", self._unreads_widget)], dividechars=1
        )
        placeholder = urwid.WidgetPlaceholder(self._status_cols)
        super().__init__(placeholder)

    def set_text(self, new_text):
        self._text.set_text(self._text.text + new_text)


def keypress(key):
    status_line.set_text("🟩")


fill = urwid.Filler(urwid.Text("Hello World"))
status_line = StatusLine()
w = urwid.Frame(fill, footer=status_line)

loop = urwid.MainLoop(w, unhandled_input=keypress)
loop.run()

Now:

• kitty --config NONE
• z4h up-to-date
• .zshrc containing just one line z4h init || return
• Run python /tmp/repro.py - you will see status bar with Left: and Right: 0 in the bottom row.
• Press Space, an emoji is drawn on the left side in the bottom row.

Expected: nothing changes on the screen, except the appearance of the emoji symbol.
Actual: The entire screen, all rows, get moved up by one row.

Finally:

• If you keep pressing Space, things will get progressively worse.
• Add zstyle ':z4h:' start-tmux no to your .zshrc - the bug will no longer reproduce.

[romkatv]

Thanks for filing the bug and providing a lot of information. I appreciate it.

This bug unfortunately falls under the category of bugs that I won't be looking into: #35 (comment)