Strange line wrapping behaviour on windows less than 80 columns wide

[christopher-dG]

When I write a long command or print some output that goes paste the edge of the window, the line wrapping behaviour is strange: it overflows until column 80, and then it wraps.

Example:

You can see the first output with a 70-character width has the wrapping issue, but it goes away when I widen the window to 82 characters.

• Emacs 27.2 (installed via homebrew, running in terminal, but confirmed on a GUI as well)
• vterm-20211226.817
• PROMPT='$ '

I've minimized my config to this (it happens without the screencast and keycast packages too):

(require 'package)
(setq package-archives
      '(("gnu" . "https://elpa.gnu.org/packages/")
        ("melpa" . "https://melpa.org/packages/")))
(unless (package-installed-p 'use-package)
  (package-refresh-contents)
  (package-install 'use-package))
(require 'use-package)
(setq use-package-always-ensure t)
(use-package gif-screencast
        :custom
        gif-screencast-args '("-x")
        gif-screencast-cropping-program "mogrify"
        gif-screencast-capture-format "ppm")
(use-package keycast)
(keycast-mode)
(use-package vterm)
(column-number-mode)

[jixiuf]

https://github.com/akermu/emacs-libvterm/blob/a940dd2ee8a82684860e320c0f6d5e15d31d916f/vterm.el#L202

[christopher-dG]

Lowering that fixed it, thank you!

Its actual behaviour is a bit puzzling to me though; it the minimum width was 80, then why was vterm allowed to run in windows of less width than that? It seems like something that should be documented a bit further.