The GNOME Platform, Awn, and the Cloud

Benjamin Otte recently wrote about desktop-web integration in the GNOME desktop. It's kind of interesting that he calls himself "not web enabled", given that he's the main developer of the swfdec library and associated applications. I agree with most of what he wrote, but there are a few comments I would like to make.

Benjamin asks:

Why does dconf (or GConf) not store my settings in the cloud so it uses the same settings on my university login?

As I understand it, this is one of the features of Conduit. There's a bug in Awn regarding config synchronization via Conduit. I'm probably going to look into how that works when I resume work on the config interface for libdesktop-agnostic.

There is an erroneous statement in his post:

We don't even have a http library that knows cookies.

libsoup has had (non-persistent) cookie support since 2.23.1, and persistent support will be in 2.26.0.

And then there's the main point:

[GNOME is] doing a very bad job at integrating the web into the desktop. Apart from epiphany (and the weather applet), what application does GNOME ship that speak http?

I believe there are two main reasons for this: One is GNOME developers are not "web-enabled". [...] The other, related reason is that we don't have the software to do this.

In Awn-land, we have several web-enabled applets:

• arss
• comics
• digg
• lastfm
• meebo
• pandora
• rtm
• weather
• webapplet

In particular, webapplet is a work in progress framework, which will allow what is essentially an applet version of Mozilla Prism. It currently uses WebKit as the backend, although there is also a Gecko-based backend planned. The rest of the applets listed are written in Python. In particular, the digg, meebo, pandora, and rtm applets use the gtkmozembed Python bindings to view the respective websites. Here lies one of the problems of the web-enabling the GNOME platform. This library is acknowledged to be less than ideal. If you look at the source code of the applets, you'll see that there are some ugly hacks in order to make them work properly on Ubuntu systems. Webapplet is slated to replace that ugliness.

One of my side projects is a status aggregator applet. It's supposed to aggregate all of these social networking status feeds and also to sync all of your personal statuses. One of said social networking websites returns complex, site-specific HTML that obviously needs to be sanitized/canonicalized. The easiest (but not necessarily most memory-efficient) method of performing that task is to use the DOM. There is not currently a DOM library for the GNOME platform. There is a libgdom3 project (written in Vala) which I believe is being / will be used by the gnome2-globalmenu project, but it is unfinished. There is also an old, unmaintained library called gdome2 based on libxml2. I'm not even sure if anyone actually uses that library anymore (its last release was in 2003). I avoided using gtkmozembed and friends based on the experiences described above. I settled on a promising feature request for WebKit: a GObject/C DOM binding. (As an aside, the WebKit bug linked is a fascinating case study on several levels: conflicting coding standards, conflicting developer personalities, and some interesting coding/reviewing.) It's very nice - I can manipulate document fragments as if I were using JavaScript in a web page, among other things. I eagerly await that feature being committed to WebKit trunk.It is an important stepping stone when it comes to working with the web.

Another side project that I'm currently working on is a developer dashboard applet. It's kind of like the previous applet, except as applied to software projects. I was originally going to write it in Vala, which meant that I would have to write an interface to (at least) the Launchpad API, which meant implementing at least three specifications in Vala: OAuth, URI templates, and WADL. I finished the first two (I haven't yet decided whether to release my URI templates implementation as a separate library - the implementation plus the test app is 451 source lines of code), and WADL is a very complex specification. So, I decided to postpone working on the WADL library and instead am currently working on a prototype applet using Python and launchpadlib. Implementations for those three specifications and many others (including AtomPub) should be included in the GNOME platform if it wants to be web-enabled.

RFC 5023

The Atom Publishing Protocol has finally been published as RFC 5023.

Whew.

Hurrah! Congrats to the authors/contributors!

Website finally updated, hooray!

After years of malnourishment and two weeks of development, my little old static website (now using a smaller domain name!) is live. The old website, like the new website, was created via a templating system. However, the former website's templating system was homegrown using PHP4 classes (disgusting, I know...but that's all I could use at the time). Even more disgusting about my system was that it was HTML comment directives plus a regular expression parser. I was so young and naïve, and I hadn't taken a compilers class yet. So this time around, I said "screw it" and went with a) my favorite language, Python, and b) the template software that I had been using for my Trac-AtomPub plugin (yes, not -atompp anymore, per the lengthy discussion on the atom-protocol mailing list).

The Journey

As the new website was a chance to experiment with new things, I decided to take the plunge and use HTML5 to markup my website. And with any sort of experimental technology, there were many problems.

First, I tried to use the genshihtml5 plugin, but strangely enough the code was a bit buggy (e.g., it was missing an import), and I could never figure out how to get it to output proper HTML5 while still removing end tags from tags which don't need them, e.g. <link/>, while retaining them for tags which require one, e.g., <script/>.

Next, I tried to use html5lib's Genshi-Stream-based tree walker. For some reason, it simply would not output any data. I don't remember all of the details, but I do remember inserting a lot of print statements in html5lib to see if I could find the bad piece.

Finally, I gave up and made Genshi just output XHTML plus the extra HTML5 tags. I figured that all of the debugging trouble simply wasn't worth it for the timeframe I had envisioned.

(As an aside, I do plan on submitting the patches that I've made as a result of this...exercise (for lack of a better word) so that they can be integrated in future releases of the respective software.)

Actual usage of new HTML5 tags was...interesting to debug. If you're writing HTML5 and not XHTML5, and you're viewing the page in Firefox, this is what the DOM tree looks like (according to Firebug):

<figure _moz-userdefined="" />
<img src="..." alt="..." />
<legend>...</legend>

For comparison, this is what it looks like when rendered as XHTML5:

<figure>
<img src="..." alt="..." />
<legend>...</legend>
</figure>

That completely broke my CSS files, as I was using child/descendant rules utilizing the new tags. This sort of thing is why I love using Firebug.

Testing

I've really only thoroughly tested this website on Firefox 2.x (Windows & Linux). I just checked it on Opera 9.20 (Linux) and a relatively old development version of Gtk-Webcore (AKA WebKit), and the only bug that I see (in both of them, strangely) is some sort of CSS error in calculating the spacing for the <dd/> box for "Special Skills" in my CV.

Future

Future plans include packing both the CSS and the JavaScript, via csstidy and packer, respectively. Right now there are several bugs with regards to integrating the two applications with my build system. csstidy interprets white-space values incorrectly, particularly the vendor-specific values. I'm currently trying to integrate packer via this nifty little python module that uses ctypes to create an interface with Mozilla's Spidermonkey JavaScript engine. Unfortunately, there's a recursive reference somewhere in base2, and the module is choking on it, so I have to figure out how to resolve that (if possible). Another future plan involves making the site fully dynamic in that the page layout stays the same, while background XMLHttpRequests retrieve the page contents when internal links are clicked. Obviously the current behavior would be retained as a fallback.

Anyhow, there are more details about how I made my website on the colophon. Bug reports, suggestions and feature requests are welcome!

Re: Genshi Filters for Venus; Genshi + Trac-AtomPP

This news is excellent. One of my side projects (although, it was pretty low on my list) was to figure out how to use Genshi templates in Venus. I started out by copying the Django template code/unit tests and adapted them for Genshi. However, I got stuck getting some of the unit tests to pass (_item_title and _config_context). Perhaps sometime this weekend I can see how this particular implementation works.

Speaking of Genshi, I just noticed that they had released version 0.4. Hopefully, this will help me resolve the last APE error in my Trac-AtomPP plugin — adding app:edited elements to relevant entries and sorting by that property.

While I'm thinking about it (this really seems to be turning into a stream of consciousness post), I'm not exactly sure how to page the collection efficiently, considering that Trac creates the wiki page list via a generator. Right now I'm just putting everything into one feed, but obviously that doesn't scale very well.

trac-atompp progress; APE questions

I'm working on (among other things) finishing up wiki support in my trac-atompp plugin. I'm nearly done, I think. In order to make sure it's "valid", I'm using Tim Bray's APE (albeit from CVS). However, I've got a few questions about some of the errors:

8. ! 53 of 53 entries in Page 1 of Entry collection lack app:date elements.

From the source, it looks like it should actually say app:edited. But, why is it giving an error? According to draft 14, section 10.2, Atom Entry elements in Collection documents SHOULD contain one "app:edited" element, and MUST NOT contain more than one. Perhaps the messages should conform to RFC 2119 instead of lumping in all of the SHOULDs with the MUSTs, or something.

49. ? Can't update new entry with PUT: No Content [Dialog]
50. ! Couldn't delete the entry that was posted: No Content [Dialog]

I don't really understand why HTTP status code 204 (No Content) isn't allowed for either PUT or DELETE, seeing as RFC 2616 says that it is a perfectly valid response for both actions.

Trac-AtomPP progress, 2007-01-23

I finally got myself out of my Trac plugin coding slump. Genshi is really making this a whole lot easier; I don't really know why I was manually generating XML from trees in the first place.

I am very grateful for the existence of Joe Gregorio's Atom Publishing Protocol test suite. There are only a couple of nits about it — first, it doesn't seem to play well with Multi-version installs of wxPython (seems to require 2.6, perhaps 2.5 [I only have 2.4 and 2.6 on my computer]), so I cooked up a really simple patch for that. Secondly, my wiki collection feed generates some warnings via Feed Validator, but in the logging pane, it records them as errors. Since it doesn't affect the functionality, I merely consider that a minor usability bug. But, this really doesn't seem to be meant for end users, so...whatever.

Anyway, for my capstone, I'm only working on the wiki part. GET is done, and POST is nearly done. DELETE is done in theory (haven't tested it out yet), and PUT still needs to be converted. POST and PUT now require some implementation of ElementTree to be installed, in order to parse the Atom Entry input. As an aside, ElementTree's find*() methods are really poor substitutes for XPath. Also, this implementation utilizes the Atom MIME type parameter draft whenever possible.

Reminder: Bazaar URL is: http://bzr.malept.com/trac-atompp

Bits and Pieces

• If I'm lucky, I'll have my win32 autotools patch in PyGTK 2.8.0. Yay!
• Being used to the linux terminal, I missed the usage of Home, End, and Delete. Fortunately, I found a mailing list post to enable them on MSYS's RXVT.
• I'm probably going to write myself an AtomPP-based client in PyGTK. I need practice coding in things other than shell and m4, anyway.

[Edit: typoes]