bug#65029: Italics bug when Emacs runs inside GNU Screen

[Eli Zaretskii]

> Date: Wed, 02 Aug 2023 23:37:54 +0000
> From:  James Ipswich via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> GNU Screen added italics support on its master branch a while ago
> [1]. If I run Emacs (29.1) inside GNU Screen (master), there are strange
> font issues.
> 
> All text that should be italicized, e.g. /text/ in org-mode or
> annotations provided by marginalia-mode, is underlined. Oddly, text that
> should not be italicized, e.g. the menu bar and the status bar, is in
> fact italicized. I am running xterm (383) with DejaVu fonts. Text
> displayed inside GNU Screen but outside Emacs is properly italicized.
> 
> If I replace xterm with urxvt or kitty, the issue persists. If I replace
> DejaVu with other fonts, the issue also persists. If I replace GNU
> Screen with Tmux, all italics are displayed correctly.
> 
> [1] https://savannah.gnu.org/bugs/?func=detailitem&item_id=36676

I guess Screen changes the terminfo entry of the terminal in some way?
Please step with GDB through init_tty and see what we get when we
query terminfo about the italics:

  tty->TS_enter_italic_mode = tgetstr ("ZH", address);

Please do this inside and outside of Screen, with the same terminal
emulator, and post the results.

Thanks.