[Okular-devel] [PATCH] Fix rendering of DVI documents

[Benoit Jacob]

2009/10/2 Albert Astals Cid <aacid at kde.org>:
> A Divendres, 2 d'octubre de 2009, Benoit Jacob va escriure:
>> 2009/10/2 Albert Astals Cid <aacid at kde.org>:
>> > A Divendres, 2 d'octubre de 2009, Elvis Stansvik va escriure:
>> >> 2009/10/2 Albert Astals Cid <aacid at kde.org>:
>> >> > A Divendres, 2 d'octubre de 2009, Benoit Jacob va escriure:
>> >> >> Hi List,
>> >> >>
>> >> >> I noticed that the rendering of DVI documents was broken exactly in
>> >> >> the same way as what I observed with PDF documents, namely, it used
>> >> >> auto-hinting which looks especially bad with TeX fonts.
>> >> >>
>> >> >> Attached is a 1-line patch that changes it. I need your permission to
>> >> >>  commit.
>> >> >>
>> >> >> Screenshots:
>> >> >> * original :
>> >> >>  http://picasaweb.google.ca/lh/photo/fry54ANy23UesNpFhbWanA?feat=dire
>> >> >>ctl ink * fixed :
>> >> >>  http://picasaweb.google.ca/lh/photo/OjQIZ7Of6wP74k7fKUwXTw?feat=dire
>> >> >>ctl ink
>> >> >>
>> >> >> Here are some comments before one objects that disabling hinting is
>> >> >> just a matter of taste, etc.
>> >> >>
>> >> >> First, it's obvious that the "original" screenshot linked above is
>> >> >> horrible and that the "fixed" is the one that looks good.
>> >> >>
>> >> >> Second, it is a consensus on the Poppler/PDF side that one should use
>> >> >> no hinting, and then, there's no reason why DVI should be any
>> >> >> different. To summarize the situation on the PDF side:
>> >> >> * poppler/cairo (hence Evince) 's code completely disables hinting
>> >> >> * poppler/splash (hence Okular) 's code _meant_ to completely disable
>> >> >> hinting (actually only auto-hinting, but in the context of DVI that's
>> >> >> really the same because almost all DVI files use Type 1 fonts, and
>> >> >> bytecode only exists in TrueType fonts). It was a clear bug in the
>> >> >> code, where it was clear that the code didn't do what it intended,
>> >> >> that resulted in hinted fonts being used.
>> >> >>
>> >> >> Third, the old KDVI used to not do any hinting, I'm completely sure
>> >> >> of that because I've spent hundreds of hours looking at documents in
>> >> >> it. I remember distinctly the (imho beautiful) slightly fuzzy look of
>> >> >> the TeX fonts in it, that is characteristic of non-hinted text,
>> >> >> although at that time I didn't know about hinting. That said, I used
>> >> >> "svn annotate" to see who enabled hinting in the C++ code, and it
>> >> >> turns out to be Stefan Kebekus himself in an old revision
>> >> >> (240000-something). I am puzzled about that, but I still maintain
>> >> >> that KDVI didn't use hinting on all the Linux systems that I tried.
>> >> >> My best guess is that Stefan Kebekus _thought_ that he had enabled
>> >> >> hinting but for some reason it wasn't used. I haven't investigated
>> >> >> further as this is quite intricate, and of course I only have
>> >> >> Okular's code at hand, I haven't looked at the actual KDVI code.
>> >> >>
>> >> >> OK to commit?
>> >> >
>> >> > No, actually what it is clear that *you* don't like hinting, and you
>> >> > have a certain amount of followers, the problem is that typically
>> >> > people that is happy with a setting is not much active defending it
>> >> > because they are happy in their sofas.
>> >> >
>> >> > My suggestion is adding a configuration option that lets the user
>> >> > choose between "No Hinting", "Hinting" and "Hinting as set in KDE
>> >> > settings". For KDE 4.3.x we can add it, it set in "Hinting" and the
>> >> > only configuration option will be thought non GUI as we can't add
>> >> > translatable texts. For KDE 4.4.x we can default to "No Hinting" if
>> >> > others here (basically Pino, Brad, Tokoe) agree.
>> >>
>> >> I'm not one of those three, but I'll just chime in anyway and say that
>> >> I agree with Benoit that, at least in the example he gave, it's very
>> >> obvious that the non-hinted version looks much better. I'm not trying
>> >> to troll here, but come on, in some places the hinted one is hardly
>> >> readable, the characters are all jumpy; e.g. the 'T' in the very first
>> >> word. I don't know if this is a bug in the hinting or just the way
>> >> it's supposed to look.
>> >>
>> >> Anyway, this doesn't make me a "follower" of Benoit; I'm just calling
>> >> it like I see it ;)
>> >
>> > That's one PDF in one hundred, and i've already felt too many times
>> > people hating me becuase I changed something I considered mintor but was
>> > critical for them, so for me it's a setting all the way.
>>
>> You miss the point, it's not a PDF, it's a DVI, and that makes all the
>> difference, because as I explained in my previous email, 95% of DVI
>> files use the same TeX font, so if I show you a bad screenshot with
>> this font, it's to be taken seriously.
>>
>> Albert, seriously. I've fixed one of the top bugs in Okular, that
>> makes it useless to half of people as far as PDF is concerned, and to
>> everybody as far as DVI is concerned, and you don't even acknowledge
>> the bug.
>
> Man, you are starting to repeat yourself
>
>> Let alone say thank you. Instead, you answer like I'm just an
>> angry user who wants to steer Okular his own way. The bug wasn't hard
>> to fix, you just need to acknowledge that while hinting can
>> *sometimes* increase the crispness, it *always* degrades the fidelity
>> of the rendering, and, regardless of "sometimes" versus "always", in
>> the PARTICULAR setting of a PDF/DVI viewer, it should be OBVIOUS that
>> fidelity is more important than crispness.
>
> You want a thanks?
>
> THANKS
>  THANKS
>  THANKS

Sigh. Am I really ridiculous, as you imply, for having expected a
little "thanks" ?

> Here you have three, please try to be constructive.

Constructive?
 - I fix a bug in poppler and one in Okular
 - I provide explanations of my findings
 - I provide rationalizations of my opinions
what more can i do. seriously?

> We have reached the situation in which it seems hinting is the culprit for
> some bad font rendering.

Yes.

> Trust me in the fact that i know some people like
> hinting, if you can't trust me, bad luck, but i'm the core developer here.

Again, here I was submitting a patch that affects only DVI rendering.
Only TeX fonts. I explained in the previous mail how this makes all
the difference.

> I even gave you the default value, but you want to win so much that you don't
> even want the option to exist? I don't really see what your problem is.

I never said that. As soon as I read about your proposal to introduce
the option, I was satisfied. It is useless for DVI, but it doesn't
disturb me. And I understand that you want only one GUI for
configuration, not one per file format. All is OK and for the rest, I
was only replying point by point to your replies.

Again, let's not end this discussion on bad feelings. I don't know how
such a technical discussion about patches could lead to bad moods but
let's make sure it's over now. I never meant to offend you or attack
you personnally, I was only criticizing existing code.

Thanks for listening,
Benoit