bug#36337: 26.1; XBM images are sometimes not displayed correctly

[Pip Cet]

On Sun, Jun 23, 2019 at 4:41 PM Eli Zaretskii <eliz@gnu.org> wrote:
> > From: Pip Cet <pipcet@gmail.com>
> > Date: Sun, 23 Jun 2019 16:26:16 +0000
> > Cc: triska@metalevel.at, 36337@debbugs.gnu.org
> >
> > My suggestion would be to expand `substring' to work on bool vectors,
> > then building a vector of bool vectors and using the existing code for
> > that case. Less code in image.c, plus a new utility function that
> > might be generally useful.
>
> Or maybe we should have a variant of make-bool-vector that accepts 2
> dimension s instead of just one?

I don't really see how that would be generally useful, to be honest.
In fact, I just played around with removing bool vector support
entirely.

> > (However, do we want to encourage people to use bool vectors?)
> Why not?

We seem to lack even very basic functions for interacting with bool
vectors, and hardly anyone appears to be using them. Even the :stipple
face property doesn't. Emacs starts up fine with bool vector support
removed. We can use vectors of nil/t (in most cases) or unibyte
strings or bignums (which have arbitrary size limits now, but
bigbignums would be just a few lines of code, I think).

And people _think_ bool vectors have a natural presentation as bytes,
but they don't, because some people start with the most significant
bit.

So I just don't see where bool vectors fit in.

> Evidently, it's convenient in this particular use case.

Is the convenience worth a thousand lines of code (much of it C) and
documentation?

0001-Don-t-assume-the-width-of-xbm-images-is-divisible-by.patch
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