Subject: stipples as fill-column indicator

From: Johann Höchtl <[email-masked]>
Date: Sun, 13 Apr 2025 09:09:34 +0200

I follow
https://emacs.stackexchange.com/questions/81278/how-to-have-a-solid-fill-column-indicator-when-line-spacing-is-greater-than-zero
to set stipples as fill-column-indicator

The result is

I get this result on Windows using Emacs HEAD as well as on Linux using
Emacs 30.1 pgtk-build (Arch repo)

While the screenshot has display-line-numbers-mode enabled, it is not
necessary to expose the IMHO bug.

To reproduce:

emacs -q --load fc.el fc.el

fc.el attached.

To my understanding according to
https://www.gnu.org/software/emacs/manual/html_node/elisp/Face-Attributes.html
:

> Alternatively, the value can specify the bitmap directly, with a list of
the form (width height data). Here, width and height specify the size in
pixels, and data is a string containing the raw bits of the bitmap, row by
row.

so :stipple '(7 1 " ") has a bit mask of  "0010 0000" and to my
understanding should result in a single black horizontal line. Alas it
produces two, which I consider a bug.

This, however, is not consistent. On Linux, when I add more lines to the
file so that display-line-numbers-mode would result in a shift of the
'viewport', sometimes only one line is displayed, as expected. On Windows
the behaviour remains consistent is so far as always two lines are display