bug#40897: Negation of pixel-width :width expressions does not work

[Pip Cet <pipcet@gmail.com>]

On Mon, Apr 27, 2020 at 2:32 PM Eli Zaretskii <eliz@gnu.org> wrote:
> > From: Pip Cet <pipcet@gmail.com>
> > Date: Mon, 27 Apr 2020 08:47:50 +0000
> You say (3) is difficult to fix, but the patch below does succeed in
> preventing the stack overflow, so I don't think I understand why you
> thought this to be difficult.  What am I missing?

Circular lists can have a cycle of length greater than one. However, a
simple limitation of how deeply we recurse into the display spec would
work, and potentially be more robust. Would you agree with that?

Thank you for your other explanations. I've taken the opportunity to
have a look at the redisplay code. I'll confess it's a bit
overwhelming in its complexity, and my understanding so far is
tentative, but it seems to me like it "essentially" goes from buffer
text to the glyph matrix in one shot: there's no intermediate state
that represents what CSS would call the "resolved style" of the
document.

Trying to write this email, I'm realizing I need to think about this
more: I still think the current state of things, where we call Lisp as
part of redisplay but usually don't rely on it, is much better than to
exclude Lisp from the process entirely.