Re: set-frame-size should respect line-spacing!?

[Eli Zaretskii <eliz@gnu.org>]

> Cc: emacs-devel@gnu.org
> From: martin rudalics <rudalics@gmx.at>
> Date: Sat, 12 Oct 2019 10:25:13 +0200
> 
> I earlier explained why we cannot make 'set-frame-size' obey the line
> spacing of a specific buffer: A buffer might not be alone on a frame
> and even if it is, switching to a buffer previously displayed in that
> window might become inconvenient.
> 
> So we have a number of options which all will take considerable time
> to implement:

I think we should first decide whether we want to invest such an
effort to support a rare use case, which is also not without its
pitfalls (as you describe above).

A buffer can specify, in addition to line-spacing, other display
features that will affect the metrics of its lines.  The simplest
example is the face of the text to display, which can include the
font.  It could even do this extremely subtly, by displaying text that
belongs to a script whose font is higher or lower than the default
face's font.  In all of these cases, the original number of text lines
will be inaccurate for some buffers shown in the same window on the
same frame.

So I don't think I understand why we need to support these specialized
use cases.