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Date:      Thu, 18 Dec 2008 09:58:34 -0500
From:      Coleman Kane <cokane@FreeBSD.org>
To:        Jeremy Messenger <mezz7@cox.net>
Cc:        freebsd-ports@freebsd.org
Subject:   Re: APNG patch for graphics/png port
Message-ID:  <1229612314.3893.14.camel@localhost>
In-Reply-To: <op.ul8oa7m49aq2h7@localhost>
References:  <1229278954.1718.10.camel@localhost> <op.ul6s9fow9aq2h7@localhost> <1229380736.6657.3.camel@localhost> <op.ul8oa7m49aq2h7@localhost>

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On Mon, 2008-12-15 at 23:02 -0600, Jeremy Messenger wrote:
> On Mon, 15 Dec 2008 16:38:56 -0600, Coleman Kane <cokane@freebsd.org>
> wrote:
>=20
> > On Sun, 2008-12-14 at 22:54 -0600, Jeremy Messenger wrote:
> >> On Sun, 14 Dec 2008 12:22:34 -0600, Coleman Kane <cokane@freebsd.org>
> >> wrote:
> >>
> >> > Hello,
> >> >
> >> > I recently played with building Thunderbird 3.0b1 from source (it =20
> >> works
> >> > pretty well, btw). I was playing with some of the options to enable
> >> > using the system versions of a number of libraries, rather than =20
> >> relying
> >> > upon statically linking them into the project.
> >>
> >> We should keep compile static link, because PNG folks disapprove =20
> >> Mozilla's
> >> APNG patch. It's what we did with Firefox 3.
> >>
> >> Cheers,
> >> Mezz
> >>
> >
> > Any idea why the mozilla folk jumped on further developing APNG, rather
> > than just using (much more mature) MNG for the same purpose?
>=20
> I have no idea. The google has found useful links and I think two URLs
> might help you. I didn't read there as I have no interest with and don't
> care about APNG vs MNG.
>=20
> http://mozilla.wikia.com/wiki/APNG_vs_MNG
> http://en.wikipedia.org/wiki/APNG#History
>=20
> Cheers,
> Mezz
>=20

Short version:

whatwg.org and Mozilla people seemed to think that an "Animated PNG"
specification would work best (quickest adoption) if they piggy-backed
it on top of the already supported PNG file format. Due to the political
implications of such things, the hill was much steeper to climb to get
everyone to agree to use MNG than it was to get them to use APNG, even
though the latter is basically a reimplementation of the former
(actually MNG is a superset of APNG functionality). One key component
was that a non-APNG viewer will still view the first image in an APNG,
while an MNG file would come up with a "broken image" placeholder.
Another key component was that IE would be more likely to adopt it (we
remember how long it took them to adopt PNG, right?) if it was based on
PNG rather than MNG.

The PNG maintainers, coming at it from a pure maintainability standpoint
stood their ground and said that they didn't want to absorb the burden
of maintaining an "Animated" feature within libpng, they would rather
that be handled by the separate libmng.

So now we basically have an unofficial fork of libpng that I'd call
"mozilla-libpng", which implements the desired features from WHATWG, but
makes a very liberal interpretation of the PNG specification.

Oh yeah, and it also is based upon a Specification started by an SoC'er,
and a patchset which is no longer maintained by him, and instead is
maintained by mozilla.org at their discretion (read: whenever they
update their png dependency). Again it is unofficial, and Mozilla.org's
specification is unfinished as of now.

And, from the bug report linked in one of the articles above, it doesn't
seem like the two camps are getting along very well. PNG maintainers
won't accept APNG, and WHATWG and Mozilla.org won't replace it with MNG.

Especially now that APNG is pretty much out of the bag, my opinion is
that the libpng people should either adopt APNG into their tree, or
yield control over PNG to Mozilla.org. It's not about being the "right"
thing to do, it is about avoiding a highly user-confusing feature-based
fork of a file format.

Okay. So that was actually still kinda long.

--=20
Coleman Kane

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