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

[Albert Astals Cid]

A Dissabte, 3 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, Benoit Jacob 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.
> >>
> >> Come on. There's no way at all that the "original" screenshot that I
> >> posted could be satisfactory. Look at the letters, they border on
> >> unreadable. The e look like c, etc.
> >>
> >> There is no way that that screenshot can be acceptable.
> >>
> >> It's not a matter of liking hinting or not. I'm just saying that that
> >> particular screenshot should not happen.
> >>
> >> Thus, what we have here is a BUG. I'd like you to acknowledge that.
> >
> > No.
> > I acknowledge hinting produces bad results in that file
> 
> Good. And Okular forces the use of hinting, hence Okular produces bad
> results in that file.
> 
> > I acknowledge you think hinting make all files look ugly
> 
> No, I never said that.
> 
> For DVI: I said that hinting makes almost all DVI files look ugly,
> that's for sure. Again, here we're talking about DVI, that's a very
> special case.
> 
> For non-DVI: that's not the topic here. I said in *another* thread
> that hinting makes some non-DVI files look ugly, but i didn't say all
> files. Nevertheless, I said that hinting should be disabled, but that,
> again, is another thread, on Poppler, and I won't repeat the arguments
> here.
> 
> > I know some people like to have hinting in their fonts
> 
> In their ___TeX___ fonts ?
> 
> Again here we're talking about DVI files. We're talking about TeX
> fonts. And specifically, the default TeX font. Which is used in a
> large majority of TeX documents.

You are talking about DVI files, i am not, Okular is a multiformat document 
viewer and each option we add has/should apply to all the formats, so if we 
end up adding an option to set if you want hinting or not, it doesn't make 
sense to apply it to pdf rendering and not to dvi, and adding to options is an 
overkill.

> 
> >> There's nothing wrong about having bugs.
> >
> > I know, i fix a lot of bugs, have a look at
> > http://poppler.freedesktop.org/releases.html at least the half of the bug
> > fixes are mind. Actually it's almost the only thing i do lately, so don't
> > accuse me of not accepting bugs.
> 
> Great, actually, like everyone, I know that you are a major KDE and
> Poppler developer and as such you fix a lot of bugs. I never said the
> opposite. I said that you fail to acknowledge _this_ bug.
> 
> It doesn't matter anymore, since you agreed to add an option and to
> default to no hinting.
> 
> >> The next question is how to fix that bug. When I first suggested that
> >> it could be caused by auto-hinting, you told me that there was no
> >> reason why I should claim that, since I was no expert. Fair enough.
> >> Then here I come, making a patch to disable hinting, and bingo!
> >> Suddenly the bug appears fixed.
> >>
> >> Conclusion:
> >>
> >> At least of THAT PARTICULAR font, hinting was a bad thing --- it was
> >> the cause of the bug.
> >
> > Agreed
> 
> Good
> 
> >> Now if this were a PDF document, one could still say, hey! But just
> >> because that particular font looks bad with hinting, doesn't mean that
> >> all fonts will! Well, even with that, Poppler/Cairo is still disabling
> >> hinting and Poppler/Splash still _meant_ to disable auto-hinting. ( By
> >> the way you never addressed this point. )
> >
> > Which point? Poppler/Cairo disabling hinting? Or Poppler/Splash patch?
> 
> The fact that both Poppler/Cairo AND Poppler/Squash meant to disable
> auto-hinting, hence it should have been considered a consensus from
> the onset that Poppler disables auto-hinting, period.
> 
> It is only because of a plain bug in the code (introduced long ago and
> NOT by you) that Poppler/Squash did not disable auto-hinting. That
> never was the intended behavior. Again, the bug was that a feature of
> the runtime configuration and of the font was trying to be detected
> from a preprocessor #define, which wasn't the right thing to test for.
> 
> >> But here we're not talking about PDF documents, we're talking about
> >> DVI, and there it's even 100x more of a no-brainer.
> >>
> >> Because DVI documents, ultimately, are all generated by TeX or PDFTeX,
> >> using TeX fonts. And there aren't too many TeX fonts, almost everybody
> >> uses the standard fonts that are Roman, Computer Modern, and Times.
> >>
> >> That's just 3 fonts to check and I already checked one for you. The
> >> _default_ one (on modern tex distros), i.e., I think, Computer Modern.
> >>
> >> Feel free to check the 2 other ones, but I won't waste more time,
> >> because the truth is that, out of the dozens of DVI documents that I
> >> tried, NONE looked good in Okular.
> >
> > Given your taste.
> >
> > Tastes are like colours, everyone has a favourite one.
> 
> Ah, great. Then, since again we're talking about DVI here, I'll test
> the most recent articles on arXiv.org in various domains, and post
> screenshots here. You'll be the judge.

Nah, i don't have that much time, and you've "won" already. Spend your time 
doing something else.

> 
> > Though lots of people like the taste of lobster and not much the taste of
> > kidneys. And that's why we provide configuration options and try to find
> > the lobster to set it as default.
> 
> OK, we're making some progress here.
> 
> >> > 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.
> >>
> >> As long as "no hinting" is the default, I am happy. This is useless
> >> for DVI but may be useful for PDF, for the reasons explained above.
> >
> > Exact
> 
> OK
> 
> >> You run no risk of getting hordes of angry users slamming you for
> >> this. For if you had any exposure to potential angry users, you would
> >> already have been slammed quite a bit by the users who are unhappy
> >> about the current state of Okular. I mean, Okular currently messes the
> >> rendering of, say, all DVI files (unconditionally) and perhaps half of
> >> PDF files (at least on Ubuntu and openSUSE).
> >
> > I have experienced both, i won't bother seraching and giving you the
> > addresses but i have received mails from people saying:
> >  * I want subpixel hinting and you are a useless man for not programming
> > it * I don't want subpixel hinting and you are a useless man for not
> > removing it (even we don't do subpixel hinting)
> >  * I want hinting and you are a useless man for not programming it (even
> > it seems it's enabled)
> >  * I do not want hinting and you are a useless man for not programming it
> 
> First, the situation is NOT symmetrical. Hinting is not a neutral
> choice, like choosing between the color blue and red. Hinting is the
> solution that adds extra complexity and requires extra code.
> 
> Second, what my screenshots really show is bugs in the auto-hinter.
> When you look at the first word, "ABSTRACT", and the top of the
> letters are at different heights, well that's a bug.
> 
> So, to users who demand hinting, you could just have said: good that
> hinting works for you, but it is completely broken in other cases, so
> we can't make it default.

I could not because i didn't know it was a problem.

> 
> > So yes, i've received quite a lot of hate mail regarding this issue and
> > the tone of your mails isn't really helping much.
> 
> I've only started being defensive in my 2 last emails. Before that,
> the tone of my mails was 100% friendly. You, on the other hand, have
> aggressed me ever since your first reply on kde-devel.

It wasn't my intention, if you feel that saying that if you are not a font 
expert you can't conclude hinting is the root cause of a given problem is an 
attack, i'm sorry, it wasn't meant to be.

> 
> > So to recap:
> >  * No Hinting is the default for 4.4 and the setting can be changed via
> > the GUI
> >  * Hinting is the default for 4.4.3 and the setting can't be changed via
> > the GUI
> 
> Good.

Now please be patient, that won't happen today or maybe it will, but don't 
take it for granted, i've lots of things in my todo.

> 
> > Do you agree on that or you prefer to continue with the flaming?
> 
> I agree with that.
> 
> I hate having entered in a flamewar with you and I don't want this to
> come off as a bad experience for either of us.

We're all friends here making KDE better, right?

Albert

> 
> Benoit
> _______________________________________________
> Okular-devel mailing list
> Okular-devel at kde.org
> https://mail.kde.org/mailman/listinfo/okular-devel
>