bug#26133: 25.1; XBM images broken - worked in 24.3

[Alan Third]

On Fri, Jul 26, 2019 at 01:47:00PM +0200, Lars Ingebrigtsen wrote:
> "Devon Sean McCullough" <Emacs-Hacker2016@jovi.net> writes:
> 
> > ; Please find attached screen shots of this Emacs 24.3 vs. Emacs 25.1 bug:
> > (progn (insert-image (create-image "/* Example at
> > https://en.Wikipedia.org/wiki/X_BitMap */
> > #define test_width 16
> > #define test_height 7
> > static char test_bits[] = { 0x13, 0x00, 0x15, 0x00, 0x93, 0xcd, 0x55,
> > 0xa5, 0x93, 0xc5, 0x00, 0x80,0x00, 0x60 };"
> >                                (quote xbm) t))
> >        (insert emacs-version))
> > ; MacOS 10.11.6 Emacs 24.3 displays a proper [Blarg] glyph.
> > ; MacOS 10.11.6 Emacs 25.1 displays a scrambled [alBgra] glyph with the
> > "a" split in two, i.e., [Blarg] glyph with each octet LSB-MSB reversed.
> >
> > It seems in XBM image bool-vector data
> >
> >     (A) octets are sometimes little-endian and sometimes big-endian
> >     (B) rows are sometimes padded to octet boundaries and sometimes not
> >
> > It would be helpful to standardize -- or at least document -- such
> > per-version per-platform differences
> > as XBM is the only programmatically accessible graphical element natively
> > supported in vanilla Emacs!
> 
> I'm unable to reproduce this bug with Emacs 27 on GNU/Linux -- are you
> still seeing this problem?  The image code has gotten a lot of work in
> the years after you reported this problem...

I can reproduce it on the NS port. I can reverse the way it draws the
pixels, but that then reverses the fringe bitmaps too, so I’m not sure
what the difference is here.

-- 
Alan Third