Wandering Thoughts archives

The solution to the modern X font handling mystery

I wrote last time about my attempts to work out just why xterm was rendering the same font differently on Ubuntu and Fedora. Thanks to comments from Adam Sampson and some additional digging, I now have an answer and some theories. As it happens, the answer illuminates yet more issues with modern X font handling.

In the modern Xft/FreeType/Fontconfig world, fonts are specified more or less as a font name and a size. With most programs that allow explicit specification of the font name you can augment the name with additional attributes, partly to modify the exact font that gets matched and partly to control how it's rendered. All of this is sort of covered in the fontconfig user documentation.

(An example could be 'DejaVu Sans Mono:style=bold:hintstyle=hintslight'. This shows both a modification of the font selection process and a rendering instruction. A similar sort of syntax can be used if you want to find, eg, all of the monospace fonts on the system.)

Fontconfig also has system-wide configuration files, found in /etc/fonts/conf.d/. In most packages that I'm familiar with, the global configuration is a default and explicit specification of things override them. However, this is not the case for fontconfig; at least for some settings, fontconfig's global settings silently override anything you specify explicitly. The only way to override these settings yourself is to have a $HOME/.fonts.conf file (and you can't unset the settings so that you can pick them on the fly, only set them to whatever personal global value you want).

You can probably guess the rest of the story. As spotted by Adam Sampson, Ubuntu's fontconfig package has a global config file that is explicitly forces hinting to be set to hintslight, while Fedora has no config file and is defaulting to hintfull. Because this is set in a global config file you can't override it on the xterm command line, which fooled me into thinking that this setting wasn't the culprit.

(You can include ':hintstyle=hint<whatever>' in a -fa argument all you want, but it is silently ignored.)

Overriding that (with a personal .fonts.conf file that forces hintfull hinting) got Ubuntu rendering to be almost the same as Fedora rendering. The remaining difference turns out to be due to the specific versions and compilation options of my version of FreeType. Interestingly, this is not just a small visual difference; at least under some circumstances the Ubuntu FreeType library renders DejaVu Sans Mono characters a pixel or so taller than my Fedora FreeType library does, meaning that an 80x50 xterm on Ubuntu is visibly taller than a Fedora 80x50 xterm. (They are both the same width.)

I don't know for sure why gnome-terminal, Firefox, and TK applications were unaffected by this, but my theory is that all of them use the Gnome preferences system. Gnome has its own preferences settings for how to render fonts and these appear to completely override fontconfig's views on the subject, so Gnome applications were using the 'right' hinting style for my tastes. I would have probably seen the same rendering of DejaVu Sans Mono in any other Gnome application that used it as the monospace font (a good example is probably gedit).

(Why this happened for some fonts and not for others presumably has to do with how the fonts were hinted, or maybe some fonts specify that they can only be hinted at some levels. I don't know if this means that the fonts that weren't affected are less hinted than DejaVu Sans Mono and so on, or just hinted differently.)

Where is Oracle going with Solaris?

(Disclaimer: rambling ahead.)

Once upon a time, back when Sun was still Sun, it was possible to kind of see what they thought the future market for Solaris was. Solaris wasn't Linux, but they could load it with attractive features (ZFS, DTrace, arguably Zones, etc) to make up for being not-Linux and then sell it for a relatively low price to hook the low end of the market. Arguably Sun skipped the bit where they upsold to more lucrative services later.

(In this view, the free Linux distributions serve as a valuable initial hook for higher end commercial Linuxes like Red Hat Enterprise. A small company is unlikely to buy RHEL right away; instead they can progressively move closer, first with Debian or Ubuntu, then with CentOS, and finally they start paying Red Hat when they get tired of the alternatives. Since very few people were going to jump from a Linux to Solaris, Solaris needed a similar entry-level hook.)

Then Oracle took over Solaris and now I don't understand how they see its future. The initial moves were straightforward: Oracle drastically raised prices and effectively drastically reduced hardware availability. Then of course they killed off other features that made Solaris attractive, like source availability. As far as I can see this took out the bottom end of the Solaris market entirely.

(It's hard to find current pricing for Solaris on non-Oracle hardware. The best I could find on Oracle's own website was $1k per core per year; it's not clear if you can get a better deal through either Dell or HP, which were at one point theoretically reselling Solaris on their own hardware. I couldn't configure a low-end 1U Dell server with Solaris, for what that's worth.)

One possible answer is that Oracle has no real plans for Solaris's future. In this view, they're treating it as a declining asset and milking it to get as much money as possible from those people who have to have Solaris. As the ranks of those people dwindle, Solaris itself will dwindle away with them. Eventually Oracle will politely sunset it and no one will really care. In this view, the relatively high prices for Solaris (and the outrageously high ones for non-Oracle hardware) are somewhat deliberately designed to discourage new customers; the last thing Oracle wants is for Solaris to actually get popular, because then Oracle would have to start spending real money on it.

Another possible answer is that Oracle thinks that Solaris has a viable future on big iron but not on low end hardware. I'm a professional skeptic about big iron in general, so I'm not well placed to evaluate how realistic this is. I think you can make a case that big iron customers are mostly insensitive to both the exact operating system (they care about the apps, which are often layered on top of a database to start with) and the licensing costs, but will value various (theoretical) Solaris virtues like resilience and inspectability with DTrace (especially if Oracle integrates DTrace support into their database products). On the other hand they do care about TCO (and there can be a lot of money involved in that TCO with big iron and Solaris licensing) and I'm not sure Oracle has a good sales pitch for Solaris against the relentless march of cheaper Linuxes.

(I'm not persuaded by the variant of this where Solaris is supposed to be the true home of Oracle's database software, because it requires customers to either like or be neutral to Solaris and its increased costs. If everyone wants to run Oracle on RHEL, it's hard to make Solaris Oracle's true home.)

All of this is mostly but not entirely academic to me, since it seems clear that we have too little money to interest Oracle. Still, I just can't stop wondering; there was a time when Solaris looked like it had a place in the general Unix future.

(You can argue that Solaris still does, in the form of Illumos and distributions using it. Especially as apparently a whole lot of the Sun technical people have left Oracle and settled at various other places that are working on Illumos; this makes Illumos the technical future of Solaris, and the technical future is the interesting one.)

PS: I would probably be better informed about the speculation on this if I actually followed Solaris news. I don't, because it seems very unlikely that anything Solaris news is going to affect us; Oracle would have to perform one of the world's most spectacular sudden reverses in order to be relevant to us again.