Happy 2013!

January 2nd, 2013 No comments

I think the new one is going to be even better…

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How to change the Trash shortcut in Ubuntu 11.10 oneiric ocelot

November 6th, 2011 3 comments

Unity’s default shortcut to use <Super>+T to open the trash has been bugging me for some time, mostly because it conflicts with my open terminal shortcut. Judging from the questions I found by googling, I don’t seem to be the only person who would like to configure it.

Turns out, there is no easy way. Although there are two different places where I can configure keyboard shortcuts, none of them can be used to change the shortcut used to open the trash window. It’s kind of odd how this is a shortcut at all. I mean, how often do I actually look into the trashcan to see what’s in there? That’s not even remotely close to being a common operation.

The cumbersome way

This being free software, there is of course another way, which you might or might not consider to be worth doing, that is downloading the source-code for a package, change it and compile it into a .deb package again (If you don’t know how to do that, consult the link I provided below).

Turns out changing the source code was really easy. Simple searching for “trash, I soon found “plugins/unityshell/src/TrashLauncherIcon.cpp” where I found the following code:

TrashLauncherIcon::TrashLauncherIcon(Launcher* IconManager)
  : SimpleLauncherIcon(IconManager)
  , proxy_("org.gnome.Nautilus", "/org/gnome/Nautilus", "org.gnome.Nautilus.FileOperations")
  tooltip_text = _("Trash");
  SetQuirk(QUIRK_VISIBLE, true);
  SetQuirk(QUIRK_RUNNING, false);

I changed the last line to set ‘x’ as the shortcut and build the package, which turned out to be multiple .deb files of which I found the right one by unpacking them into a temp directory and looking for the TrashLauncherIcon symbol.

I’m not sure the amount of work required to do this is really worth it, especially considering that I have to redo it every time the unity package is updated again, but for now I’m really satisfied.


Update: Added bugtracker URL for this.

Update2: Build and uploaded new .deb for new version (12.11.2011)

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The people are just disturbing governance

October 3rd, 2010 No comments

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Generating List<Something> from JSON with svenson

September 9th, 2010 No comments

Often you’ll find yourself wanting to parse a JSON into a Java collection but want the values inside the collection to be of a specific type. Nothing easier than that.

import org.svenson.JSONParser;
// Getting a list containing your own type Something.
// Assume json to be a String containing the JSON dataset.
JSONParser parser = new JSONParser();
parser.addTypeHint("[]", Something.class);
List<Something> someThings = parser.parse(List.class, json);
// someThings will be a ArrayList instance by default. You can change
// that by changing the mappings for interfaces by calling
// org.svenson.JSONParser.setInterfaceMappings(Map<Class, Class>)

Parsing into a map is not much more complicated either

JSONParser jsonParser = new JSONParser();
jsonParser.addTypeHint(new RegExPathMatcher("\\.(f1|f2)"), Something.class);
Map<String,Object> someThings = jsonParser.parse(Map.class, json);

If we want to have our Something type for more than a single field, we need to setup a matcher. Here you see an example of a RegExPathMatcher that makes sure that both the keys “f1″ and “f2″ of the map we receive will be converted to Something, while all other fields are not.

If you want to convert all map properties to Something, the RegExPathMatcher would be like this

    … new RegExPathMatcher("\\..*") …

This would match every JSON path that starts with a property. If you don’t like RegularExpressions, or are on some kind of diet on them, you can also construct a more complex matcher tree from the compositable Matchers like this

JSONParser jsonParser = new JSONParser();
jsonParser.addTypeHint(new OrMatcher(
    new PrefixPathMatcher(".f1"),
    new PrefixPathMatcher(".f2")), Something.class);
Map<String,Object> someThings = jsonParser.parse(Map.class, json);

Update: Due to me fucking up both the Prefix-/Suffix- matchers as well as their tests, the last example will only really work with the current svenson trunk/future svenson 1.3.8

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Thrust 2010

July 24th, 2010 No comments

Thrust 2010 gameplay screenshot

Those of you who playtested it know it already, for all the others, I’d like to announce the first release of Thrust 2010. It’s a HTML5/canvas game inspired by the old C64 classic, redone for mouse-driven interface. So far it contains 6 levels of agility / shooting fun. Don’t give up if you are having a hard time controlling the ship at first. Just keep trying, don’t speed and keep it under control. People keep telling me it’s difficult to control and I guess that’s true and to some degree even intended, but I’m also sure that you get much better at it over time.


Gelernter nonsense

June 26th, 2010 1 comment

No english translation yet.

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Annotating DOM nodes with JSON, Part 2

June 3rd, 2010 No comments

It’s been a while since I wrote Annotating DOM nodes with JSON and in retrospective I can say that I never really used the method described in a real life project. Now I’d like to present another method of decorating DOM nodes with JSON based on classes. This one I actually implemented in OpenSAGA to have arbitrary metadata from some of the OpenSAGA Widgets.

I didn’t really like the idea of misusing onclick for the purpose of meta-data and thought about a better way of doing it. Browsing the w3 HTML specs I came upon the fact that classes can be any character separated by spaces. So for use-cases where I only needed one meta-data value I used classes like

<div class="refId:id-1234">
    DIV content

A use-case specific prefix is used to mark a class as meta-data container containing the string after the prefix. The code to evaluate this in javascript is very easy

 * Returns the class value with the given prefix using the giving separator
 * @param {DOMElement} elem DOM element to fetch metadata from
 * @param {String} name of the classval value
 * @param {String} separator to use between name and value. Default is ":"
function classval(elem, name, separator)
    var match = new RegExp("\\b" + name + (separator || ":") + "([^ ]*)($| )")
    if (match)
        return match[1];
    return null;
// assume divElement to be DOM element of the div
var refId = classval(divElement, "refId");

I thought about going for a more elaborate prefix scheme to support nested metadata but in the end decided against it because I already have a nicely supported format for exchanging data between server and client: JSON. So I tried to come up with a scheme of using arbitrary JSON for the metadata decoration.

Only problem: Spaces are not valid inside classes, so I needed a method to encode and decode JSON into valid classes. The method should not totally mangle the JSON to keep readability and maybe write the encoded variant by hand for simple cases.


  • HTML encode the JSON-String
  • Replace spaces with underlines and underlines with \u005f

The replacement of underlines is valid because underlines can only occur inside quoted JSON strings so they can just be replaced by their escaped unicode value \u005f.

Here is the java code to do the escaping. Since it’s basically a combination of string replacement and HTML encoding this should be easily doable in any server-side language:

    public String escapeDecoration(String s)
        String escaped = StringEscapeUtils.escapeHtml(s);

        StringBuilder sb = new StringBuilder(escaped.length());
        for (int i = 0; i < escaped.length() ; i++)
            char c = escaped.charAt(i);
                case '_':
                case ' ':

        return sb.toString();

The escape method uses the escapeHTML method from Apache commons-lang's StringEscapeUtil. Going the other way in javascript is not that complicated either:

 * Decodes the given string containing HTML entities.
function htmlDecode(s)
    var helper = document.createElement("SPAN");
    helper.innerHTML = s;
    return helper.innerHTML;

 * Returns the JSON decoration of the given element.
 * @param {DOMElement} DOM element
 * @param {String} decorator classval name, default is "deco".
function decoration(elem, name)
    var value, data, result;

    value = classval(elem, name || "deco");
    if (value)
       // get raw data from DOM element
       data = value.replace(/_/g, " ");
       // replace HTML entities with the original characters
       data = htmlDecode(data);
       // evaluate JSON
       result = eval("("+data+")");
    return result || {};

In order to achieve a better readability of escaped JSON, I also used svenson's ability to deviate from the JSON standard by using single quotes instead of double quotes. Just comparing

<div id="tst2" class="deco:{'foo':'xxx\u005f_yyy','baz':[1,3,5,7,9]}">
JSON annotation


<div id="tst2" class="deco:{&quot;foo&quot;:&quot;xxx\u005f_yyy&quot;,&quot;baz&quot;:[1,3,5,7,9]}">
JSON annotation

should demonstrate that single quotes are not only much better readable, but also shorter. If you use eval() evaluate the JSON string, the single quotes are no problem at all. If you want json2.js / native JSON-parsing, you might have to replace the quote chars before parsing.


HTML test page with both metadata strategies

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Playing around with RaphaelJS

May 30th, 2010 1 comment

Recently I stumbled across what I later found out is known as Morley’s trisector theorem.

“Trisect the angles of any triangle and you’ll find an equilateral triangle at its heart.”

A Better Nature

This inspired me to do some javascript coding with the help of RaphaelJS (a very nice crossbrowser graphics library) . It’s been a while since I last wrote any real geometry stuff but I got it in the end.

Start interactive demo for Morley’s trisector theorem.


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Scripting JSON

May 16th, 2010 No comments

Doing a lot of web stuff and fiddling around with CouchDB, I really got to like JSON as versatile format for things. Installing the JSONView extension for firefox really helps with working with JSON in the browser, but what I’ve been missing so far is an easy way to deal with JSON from bash scripts. Fiddling around with the very interesting NodeJS, I came up with a small node js script that makes JSON handling much easier, the JSON command: It reads a JSON object from stdin and feeds it to a javascript function body with “v” and NodeJS’ “sys” as parameters. The return value of the function is written to stdout. If it was a string, it is written as-is, if it is another object it will be pretty-JSONified.

Simple Example

$ curl -s http://localhost:5984/test | json "return v;"
 "db_name": "test",
 "doc_count": 0,
 "doc_del_count": 0,
 "update_seq": 0,
 "purge_seq": 0,
 "compact_running": false,
 "disk_size": 79,
 "instance_start_time": "1274021449672284",
 "disk_format_version": 5

Use curl to fetch the status of CouchDB database “test” from the local CouchDB node and then just pretty print it by returning the implicit value v.

$ curl -s http://localhost:5984/test | json "return v.disk_size;"

Just print the disk_size of CouchDB database “test”. You can use all the modern JavaScript functions v8 offers plus the implicit “sys” object that lets you log stuff to stderr or inspect objects. A little script that I find highly useful:

# Delete all jcouchdb test databases
DBS=$(curl -s http://localhost:5984/_all_dbs | \
json 'return v.filter( function(db) { return db.indexOf("jcouchdb") == 0; }).join("\n");')

for i in $DBS
 curl -X DELETE http://localhost:5984/$i

Filter the list of database to only contain those that start with “jcouchdb”, then loop over them to delete.


Update: Added “return v;” as default function. now also supports “-h” and “–help”.

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Installing Ubuntu 10.04

May 16th, 2010 1 comment

I was kind of looking forward to the new Ubuntu 10.04 aka Lucid Lynx. New LTS version with promising features and a good occasion to redo my badly partitioned desktop computer. I had not thought of the additional space requirements of a 64 bit Linux, so the partitioned 8GB for the root system were not really enough.

Seeing that the new incompatible MythTV version in 10.04 would require me to do at least my desktop and the mediahub computer in one go, I did not do the install immediately but put it on my TODO list. So my first actual exposure to Ubuntu 10.04 was last week, when I tried to get it installed on my new company laptop.

First their were strange issues with the computer not booting anymore. After some searching I discovered that Grub was creating a /boot/grub/grub.cfg file that was somehow broken, because it kept changing its name every time I listed it from the Grub shell. Suddenly its name would be «grub.cfgw» or even stranger something like «grub.cfg ☺~_.q». The issue could be fixed by booting from the cd in rescue mode, moving the “grub.cfg” to “grub.cfg.bogus” and copying it back. Maybe just touching it would have been enough, too.

But then I was facing hard crashes related to the intel video driver which could just not be fixed. Either randomly or consistently every time I either had an external monitor connected at bootup or connected it afterwards and pressed “Detect monitors”, the laptop would crash hard and needed to be force-shutoff.

I tried finding a way to fix it, tried reverting back to 9.10, changing to newer driver versions, nothing helped. So in the end, I had to give up and give the laptop back to our IT guys.


Given those troubles I was kind of afraid of rolling it out in my local LAN. But it was nearly problem-free. On my desktop computer, the graphics  mode was kind of borked. Linux believed to be correctly displaying a 1680×1050 display while the monitor seemd to disagree and switch to some 1680×900 mode that would cut off the lower part of the desktop. That issue vanished with the proprietary nvidia drivers though. The graphics pad was auto-discovered flawlessly. The only thing that was missing was actually to select the rubber tool for the rubber tip and save that. Since I have two sound cards in the desktop, I blacklisted the driver for the on-board sound-card by creating a /etc/modprobe.d/blacklist-intel-sound.conf with

blacklist snd_hda_intel

to not have to ease audio device configuration. After that only the one correct sound card is visible to Linux and I don’t need to configure ALSA and Pulse etc to use the correct device. Configuring the gnome multi-media and MythTV to use both Pulse Audio solved the issue of MythTV blocking Rhythmbox or Flash from playing sound even in paused mode.

The installation on the Eee Box B202 was also almost trouble free. Initially I had problems with MythTV because I forgot to install the mythtv-database package which led to the database not being created in MySQL (D’oh). Then MySQL wasn’t listening on all IPs ( because it need to be restarted. The remote control of my DVB-T stick ( TerraTec Cinergy DT USB XS Diversity , newer hardware-rev) needed its usual

options dvb_usb_dib0700 dvb_usb_dib0700_ir_proto=0

which I wrote into a newly created /etc/modprobe.d/terratec-remote.conf.

All in all much less trouble than I feared.

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