Behdad Esfahbod's daily notes on GNOME, Pango, Fedora, Persian Computing, Bob Dylan, and Dan Bern!

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McEs, A Hacker Life
Wednesday, November 25, 2009
 Funny spam

Quite slick actually compared to the average spam I get...

Subject: This is hard for me to say

This is quite hard for me and I haven't been able to let you know up till now (you'd know why if you knew who I was)...but I have a crush on you.
You'll have to find out who I am though (I'm quite shy and this is without a doubt the bravest thing I've ever done). To help you out I made some videos and pictures with your nickname over my body. The photos and videos are kind of risque so I had to make a name at Black Book and put them there. My username in the members area is " behdad.esfahbodandme2009" (it's a free website).
But anyway, get on Black Book and once you are in, take a look for me. I want you to guess who I am and then approach me yourself. Good luck.

Hugs and kisses, Your secret admirer

PS. You'll get no extra help by e-mailing me back, so don't try :P


Wednesday, November 18, 2009
 Pango vs HarfBuzz

Since the rewritten HarfBuzz is shaping up fast and getting lots of Buzz these days, I get asked the same question again and again: "Will HarfBuzz replace Pango?" This post tries to answer that.

Short answer: No, not at all! Pango is here to stay. It will change, but only get better.

Long answer:

Pango provides two levels of API: A low-level and a high-level.

Low level API: What I can the "three pillars of pango":

High-level API: Pango's high-level API consists of the PangoLayout object, aka "here's a piece of text render it in this box I don't care what you do."

Of these, HarfBuzz only does shaping. That is, hb_shape() is functionally equivalent to pango_shape().

API implications: Here is how moving to HarfBuzz affects the Pango API:

Pango Modules: pango_shape() calls into Pango shaper modules to get the actual shaping done. There are two kinds Pango shaper modules depending on what they do (the API is the same, so Pango doesn't differentiate between the two classes):
Now, as HarfBuzz becomes the shaping engine on Linux, all those script-specific modules will be removed and basic-fc will simply call into hb_shape(). That's indeed what the basic-fc.c in the harfbuzz-ng-external does.

Later on, when we add support for native win32, CoreText, Graphite, and m17n to HarfBuzz, all those other modules will also be replaced by HarfBuzz-calling equivalents.

Which one to use: Pango or HarfBuzz? Depends.

PangoLayout is designed to be the 'render this text in this box I don't care how' kind of API. That's a perfect fit for GUI toolkits like GTK+, but not suitable for lots of other uses, for example:
while in many of those cases PangoLayout can be made to work (with much pain, mind you), Pango still provides the lower level API and lots of other bits and pieces to get something going. What it doesn't give full control on however is font selection, which happens to be a deal-breaker for many of those usecases (browsers following CSS rules, etc).

So, each of those kinds of applications need to assess the pros and cons of using Pango vs using HarBuzz and providing all the other bits themselves. For example, HarfBuzz doesn't provide:
There's also a hybrid use possible: to borrow those pieces from Pango on platforms that it's feasable, but drive HarfBuzz directly. It all depends. When in doubt, ask! We have a mailing list.

That said, Firefox will use HarfBuzz as soon as it's ready (there are patches circulating around). Google is using old HarfBuzz for their Webkit and will port to the new one. I'm also attending the Webkit-GTK hackfest in December to port that to the new HarfBuzz. We'll work towards sharing the HarfBuzz-dealing code among Webkit backends.

This is already a long post. Let me finish now. Hope I made it a tiny bit more clear.

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Sunday, November 15, 2009
 On Unexpected Hanging Paradox and applications in law enforcement

[Note: this post has nothing to do with the ongoing executions in Iran.]

Unexpected hanging paradox is a well-known alleged logical paradox about a prisoner's response to an unusual death sentence. To quote Wikipedia, here is the statement of the paradox:
A judge tells a condemned prisoner that he will be hanged at noon on one weekday in the following week but that the execution will be a surprise to the prisoner. He will not know the day of the hanging until the executioner knocks on his cell door at noon that day. Having reflected on his sentence, the prisoner draws the conclusion that he will escape from the hanging. His reasoning is in several parts. He begins by concluding that the "surprise hanging" can't be on a Friday, as if he hasn't been hanged by Thursday, there is only one day left - and so it won't be a surprise if he's hanged on a Friday. Since the judge's sentence stipulated that the hanging would be a surprise to him, he concludes it cannot occur on Friday. He then reasons that the surprise hanging cannot be on Thursday either, because Friday has already been eliminated and if he hasn't been hanged by Wednesday night, the hanging must occur on Thursday, making a Thursday hanging not a surprise either. By similar reasoning he concludes that the hanging can also not occur on Wednesday, Tuesday or Monday. Joyfully he retires to his cell confident that the hanging will not occur at all. The next week, the executioner knocks on the prisoner's door at noon on Wednesday — which, despite all the above, will still be an utter surprise to him. Everything the judge said has come true.

This has intrigued me again and again and I could never come to peace with it. While researching this recently I came across this paper which is a non-exhaustive survey of various tries to model the paradox. Great read.

Today I came across a blog post by Ed Felten called Targeted Copyright Enforcement: Deterring Many Users with a Few Lawsuits. While I find it very disturbing that a scientist like Ed Felten may be helping RIAA better screw people by their copyvio lawsuits, the puzzle and the solution provided are well worth a read. Not irrelevant to the Hanging Paradox, though in this case the reasoning may actually work.

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Wednesday, November 04, 2009
 litl by litl

Finally litl's product is out: it's a webbook. The easel mode looks quite interesting, and reading their website, it looks like the kind of gadget/netbook/appliance I'd be more than happy to have around (in a theoretical family setting, not /me as lone hacker).

But at the starting price of $700, I'm not sure who they are targeting. Sounds like Apple customers... And that does not include the remote or the HDMI cable. And the twinpack offers exactly $0 dollars discount over buying two units separately. I found these very cheap of them. Otherwise it all looks very promising.

While at gadgets, anyone knows whether n900 will have a developer program?

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 HarfBuzz HackFest

Here is a quick update re HarfBuzz:

During May and August I finished rewriting the OpenType Layout engine to use mmap()ed font files. This is in Pango 1.26.x already. Pango and fontconfig also received a lot more optimization love. That deserves a long and separate blogpost. The net result is that the text stack's memory usage is considerably lower now. All this goodness will be in the upcoming Fedora 12.

In October, I attended the 33rd Internationalization and Unicode Conference in San Jose to present the free software text stack (useless slides) as well as present and promote HarfBuzz (useless slides). That was a very fruitful event and I received lots of interest from many major industry players. With the liberal license that we are releasing HarfBuzz under, we expect broad adoption, which is exactly what we are looking for.

This week, Jonathan Kew and myself are having a small HarfBuzz HackFest here in Mozilla's Toronto office. Here's what we have got done so far:
At the rate this is developing, by the end of the week we should have basic shaper (Latin, Cyrillic, CJK, ...) and Arabic+Syriac working perfectly and tackling Indic family. We're closer to 1.0 than you may think!

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