One of the things which looked so hard, but reveiled using so easy was z3c.traverser. I’m sometimes a bit retarded reading doctests and applying them to my needs. For those who have the same problem, here a small example on how to use the traverser.

The Muffin Traverser

Motivation

Our web application catalogues muffin recipes. Every bloody muffin shop in town has a login to our muffin-application and publishes recipes. To view such a recipe the URLs look like this:

http://muffinsinthehouse.com/shop/recipes/bluemuffin

Now, the customer who operates the site comes to us with a wish: please make the URLs shorter. Each recipe is created with a unique ID and I like to use this id to look up recipes like this:

http://muffinsinthehouse.com/bluemuffin

Implementation

“No worries mate”, you say and use z3c.traverser and implement a custom traverser. The code below shows your custom traverser plugin:

import z3c.traverser.interfaces
import zope.interface
import zope.component
import zope.publisher.interfaces
import zope.app.catalog.interfaces

class MuffinTraverserPlugin(object):
    """Traverser which tries to lookup muffins in the database."""

    zope.interface.implements(
        z3c.traverser.interfaces.ITraverserPlugin)

    def __init__(self, context, request):
        self.context = context
        self.request = request

    def publishTraverse(self, request, name):
        catalog = zope.component.getUtility(
            zope.app.catalog.interfaces.ICatalog)
        result = catalog.searchResults(objectname=name, metatype='Recipe')
        if not result:
            raise zope.publisher.interfaces.NotFound(
                self.context, name, request)
        return result[-1].getObject()

There is nothing really special here, if you know how traversal works in Zope. The plugin is a Multiadapter (a view), which implements z3c.traverser.interfaces.ITraverserPlugin. The object lookup for your muffins is happening in the publishTraverse method. This method either returns the object or raises a NotFound exception if it couldn’t lookup the object. Easy as pie. The catalog is utilised to lookup the object and if its not found a NotFound error is raised.

You register the plug-in with the following ZCML directive:

<adapter
 factory="z3c.traverser.traverser.PluggableTraverser"
 for="zope.traversing.interfaces.IContainmentRoot
 zope.publisher.interfaces.IPublisherRequest"
 />

 <subscriber
 factory=".traversing.MuffinTraverserPlugin"
 for="zope.traversing.interfaces.IContainmentRoot
 zope.publisher.interfaces.IPublisherRequest"
 provides="z3c.traverser.interfaces.ITraverserPlugin"
 />

The first directive “enables” z3c.traverser, the second registers your plugin. After that, try out the custom URL which should work. But wait, if you try to look up other objects in the database, you’ll notice that your traverser deals with them too. That was not the plan, was it?

z3c.traverser provides other plug-ins to deal with folders attributes etc. Don’t lump all those object look-ups into your plug-in! You need to register them additionally:

<subscriber
 factory="z3c.traverser.traverser.ContainerTraverserPlugin"
 for="zope.traversing.interfaces.IContainmentRoot
 zope.publisher.interfaces.IPublisherRequest"
 provides="z3c.traverser.interfaces.ITraverserPlugin"
 />

Try again. This should satisfy the customer.

Comments welcome

For my daily text editing and programming work, I’m using vim. Great editor suitable for almost every purpose.

There is a Firefox add-on out now for changing the browser interface to behave like a vim interface. It advertises itself that you can even throw away your mouse. First I was curious if that’s gonna even work, but it does and I’m very happy with it. Although, I’m still using my mouse for browsing. It saves time not touching the mouse in a few cases, though. A few key features I use every day:

Following links

You press the ‘f‘ key and vimperator hints all links on the current webpage. No you press either the first letters of the link label or a number associated with the link.

Navigating on a website

You can just use the normal arrow keys for browsing, but there is more. As usual you can use ‘j‘ and ‘k‘ for scrolling up and down, as well as ‘space bar‘ for jumping a page down, or ‘gg‘ for jumping to the top, or ‘GG‘ for jumping to the bottom.

Text editing

Remember editing text areas without using your favourite editor? The times are over: Press CTRL+i in insert mode (you’re automatically in insert mode when inserting text on an input field or text area) and vimperator fires up a vim. Very handy for editing large amounts of text in textareas.

Opening URLs

Just press ‘o‘ to open a new url, or ‘O‘ to use the current URL. You can easily open the url in a tab by using ‘t‘ or ‘T‘ instead. You can use yank and paste as well. Just pressing ‘y‘ on an opened web site, yanks the URL. If you’re already a URL in the buffer, press ‘p‘ and the browser opens the link (like the middle mouse click). Very handy.

You can also use tab for completing commands or URLs. For example you want to open the website you opened yesterday, but you only remember a few letters, You type: ‘o‘, enter ‘foo‘ and press tab. Vimperator shows a list of URLs matching your string. You can now tab and enter to the match and open the URL.

Navigating between tabs … err… buffers

Jumping between tabs is like jumping between buffers in vim. Use CTRL+n or CTRL+n for jumping to the next and previous tabs. It’s similar to jumping in the history of visited pages: use CTRL+i or CTRL+o for back or forward in the history.

That are the commands are use almost everyday for browsing. There is support for more features like macros and quickmarks and so forth. So if you’re using vim everyday, give it a go. IMHO it’s worth the speed for browsing you get.

Before I forget: In case you need help to the features, use ‘:help‘ as usual for browsing the online help.

I watched Trawlermen on SBS yesterday. The documentary is about the work of a number of trawler crews based in Peterhead/Ireland. I have two quotes from the documentary which I found really interesting. It can be applied probably to any other business including writing software.

The skipper said: “Without my crew I’m nothing, because I can’t catch the fish all by myself.” The crew in turn said: “We have to trust the decisions made by the skipper. He leads us to the best fishing grounds which in turn brings the most money for the fish.”

So for now, all the people out there who think they can always do it better on their own, think about this documentary.

My working desktop setup used XMonad as a window manager and a terminal using GNU screen. In XMonad, I was using dzen as a small panel in the top corner for displaying useful information (mail, clock, battery status, etc). Dzen just display a text string. This can also be printed by a program. I wrote myself a simple python script, for doing that part like the example shows below:

gocept:INBOX(1)  private: -- | Friday, 19.12.2008 10:44:15 (AUS 20:44, CAN 3:44)

Now I switched to use XMonad in GNOME. Dzen is gone and I was looking for an alternative to display the information printed by my script. After a bit of googling, I found a very nice howto about GNU screen. Screen offers a harstatus and a caption line to display information. I tweaked my screenrc to use the python script in the caption line.

Have a look at my simple python script or my screenrc. Use it on your own risk of course

I stumbled over a strange svn problem today, while merging the xml2po branch into TRUNK:

svn: Working copy path 'ChangeLog.pre-2-4' does not exist in repository

photo by zen Sutherland on flickr.com

I found two possible solutions in the net, but none of them seemed to work:

1. “edit the “.svn/entries” file, and look for an incorrect revision=”0″ attribute, and set it to the correct value.” ( see http://www.axlrosen.net/stuff/svnproblem.html)
2. “At this point, the only way I found to repair my working copy was to delete the directory containing the problematic file, check it out again [...]” (see http://svn.haxx.se/dev/archive-2006-03/0795.shtml)

I checked the ‘entries’ file, but couldn’t spot a ‘revision’ attribute at all. Solution two wouldn’t work, or I had to wipe out the whole gimp-help-2 module.

What I did now is to remove the files temporary (aprox. 10 files) and try again. I got the merge working afterwards. Although it is cumbersome, because you won’t spot the erroneus file in a dry run.

I just upgraded from Ubuntu Hardy to Ubuntu Intrepid. As always – there is something totally wrong going on after an upgrade. My network didn’t work anymore (solved, because of openvpn created wrong routes), my sound was flaky because of pulseaudio (just turned it off) and Flash applets in Firefox were flickering.

I solved the latter problem now, by just using the Firefox 3 from Ubuntu. I had a local installed Firefox 3 which was probably older than the version in Ubuntu. That solved the problem and flash applets aren’t flickering anymore.

Playing on hubdub.com is fun.

I’m playing on hubdub.com from time to time. It’s a funny online game of a prediction stock market. People creating questions for upcoming events and you can bet how this event will proceed in real.

For example: Who will be the new American president? Obama or McCain? Now it comes to all the news who’ve been floating around. Who will make it. That pushes the chances between Obama and McCain to various percentages. Say, for example, you start  at a 12% probability that Obama makes it, while everyone sets on McCain. The more likely Obama will win the race the more money you will make if you sell your stocks. If you wait until the end when the question is settled, you earn the most money.

But don’t forget: It’s all play money

I did a 10km walk up the Brocken (1141m high, highest peak in my state) and a 20km walk. I want to share some experiences with the outside world about the five fingers:

1. Take it easy
   Train your feet to walk barefoot. Don’t start with too long walks. Not only that you hurt your feet, you could also get blisters while walking (vibram five fingers classic).
2. Wet feet getting colder much faster
   Don’t let them get wet, and your feet are getting colder even faster. They could stay cold.
3. Sun heats you up
   It’s better to walk in the sun. Your body temperature get’s warmer as well as the feet.
4. Avoid walking on concrete
   My walks on concrete were awful so far. Maybe it’s a training thing, maybe not. I’d rather avoid it.
5. Minimum temperature
   If the outside temperature is colder than 9°C, your feet are getting colder much faster which you can’t compensate with warm clothes covering the body. Though the rubber sole isolates very good between the foot and the icy ground.
6. Hiking
   If you’re up for hiking, be sure you practices enough before. You should be aware that you can cut your feet at sharp things (not from the sole – from the top). Check if not poisonous animals can cause problems (e.g. Australia).

GIMP Help Browser using webkit.

… and the Manual will be next.

The current plan is to release the last tarball of the manual suitable for the GIMP 2.4 release a.s.a.p. It should still be installed by most of the desktops until GIMP 2.6 is provided by the distributions.

We’re currently still working heavily to migrate most of the translations from DocBook/XML to po/gettext. The biggest problem for us is the missing 1:1 mapping between reference language to a translation. We’re trying to minimize the site effects when splitting the translations and using xml2po’s reuse option for a content migration. Ulf D. Ehlert wrote a Python script, which will splitt the reference language from the translation “as good as possible”.

As long this script is ready and we’re able to migrate, we’re up to speed to document GIMP 2.6.

The autumn and winter is approaching in Europe. I was walking most of the days barefoot in summer. It would be cool to still walk barefoot even when the weather becomes colder. It looks like there is a chance of doing this: vibram five fingers.

Theuni started with the five fingers. I ordered myself a pair of five fingers classic from barefoot.com with the size of 46; tried them and recognized, that they not fit. barefoot.com didn’t had a bigger size in stock, found one pair at globetrotter.de and ordered a 47. The five fingers homepage has a good introduction on how you measure the size you should order.

So, my key points are:

1. is it really different to walk in those shoes from walking barefoot?
2. can you still wear those shoes in autumn, maybe in winter?

Difference between walking barefoot

So to summarize from the first walk: it is different. I wouldn’t believed it. You still have to adopt on wearing those shoes.

You can sense the ground under your feet. You feel that the ground is cold. Your feet feel kind of numb. For example, if you walk barefoot through gravel it feels really uncomfortable (depending on the gravel). If you use the shoes, it’s much easier because of the vibram sole catches most of the stones. But you still sense that you’re walking through gravel. If you’re walking through grass, you sense that the grass is cold and soft, but you can’t feel the grass on your feet.

Wearing five fingers during cold times

It was 9.0 ℃ when I took a walk today. I sensed the cold ground under my feet (especially when walking through grass). Though I was wearing thick clothes to keep the body warm and it turned out to be working. After 5 Minutes the feet were getting warmer and were well temperatured. I will continue doing this even when the temperatures drop. I really want to know when it is to cold to not take a walk “barefoot”.

General

In general I like to wear them. It’s a great alternative in times where it’s not possible to walk barefoot. I’d like to test the five fingers sprint. I can imagine to take them for running.