Subject: bug#56808: 29.0.50; Elusive display problem on macOS

From: Alexander Adolf <[email-masked]>
Date: Fri, 29 Jul 2022 15:17:54 +0200

Hello Eli,

I'm on a Mac, too, and can confirm Gerd's observations.

Eli Zaretskii <[email-masked]> writes:

> [...]
> Are there any :align-to display properties involved in this?
> ("C-x =" could help you find out.)

I've done "C-u C-x =" across different locations in the indentation
until my fingers started aching, but no traces of :align-to display
properties, or anything else that seemed suspicious to me. It always
showed the expected font choice and size, i.e. all glyphs were reported
to be of the same size.

> Can you run this under a debugger and show the display elements in the
> offending glyph_row?  The easiest way of doing that with GDB is like
> this:
> [...]

Under lldb, most things show up as opaque Lisp_Object, i.e. can't drill
any deeper into those. I hence fail to figure out which buffer I'm
looking at when the breakpoint in set_cursor_from_row triggers. Lldb
does seem to find type information about the glyph_row though. Anything
in the row I should be looking out for?

FWIW, here are a few examples of gdb vs. lldb commands:
https://developer.apple.com/library/archive/documentation/IDEs/Conceptual/gdb_to_lldb_transition_guide/document/lldb-command-examples.html#//apple_ref/doc/uid/TP40012917-CH3-SW1

Hoping to have helped,

  --alexander