Category Archives: General

manually enabling deflate filter

Oh my, my webhoster has the deflate output filter disabled by default, that enables gzip compression of outgoing content. This is important for huge xml/json data from webservices that travel over mobile networks and easily reduces used bandwith to up to 10%.

Putting this in my .htaccess did the trick:

AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript

You can analyze the traffic with Wireshark, Firebug or use an online tool:

Make sure, your mobile app sets the Accept-Encoding of the request accordingly.


Hardware acceleration on SGS2 with Android 4.0

Starting from Android 3 (API level 11), there is a hardware renderer for 2D graphics, which drastically increases performance. The hardware acceleration was disabled by default and had to be enabled by the developer by declaring in his AndroidManifest.xml file:

<application android:hardwareAccelerated="true" ...>

According to the android documentation, that value changed to true starting with API level 14:

The default value is "true" if you’ve set either minSdkVersion or targetSdkVersion to "14" or higher; otherwise, it’s "false".

This is true for some devices (like the HTC Sensation with Android 4.0.3), but does NOT apply for the Samsung Galaxy S2 with official Android 4.0.3 and 4.0.4.

Applications without above attribute explicitly set to true are not hardware accelerated automatically on that device. On the HTC Sensation they are.

So don’t forget to declare that attribute in your AndroidManifest.xml file, if you want hardware acceleration on all devices.

Users can force-enable the use of GPU rendering in the developer options, which can be used as a workaround with the risk of incompatible applications yielding render errors.

WordMix 2D view must not use hardware acceleration

Currently, the 2D view of my WordMix game uses some features of Canvas, that are incompatible with hardware acceleration and results in display bugs. These glitches did not occur on my Samsung Galaxy S2, because it was not hardware accelerated as stated above, but occured on another device, a HTC Sensation with Android 4. Took me a while to figure out, what exactly was going on, but after declaring

<application android:hardwareAccelerated="false" ...>

fixed it for the time being, until I changed the render code to be hardware accelerated.

android.hardware.faketouch vs. android.hardware.touchscreen

By default, an Android application requires the feature android.hardware.touchscreen, which is then used for filtering in Google Play, so only devices, that have touchscreen capabilities, will be able to install that app.

Besides that, there is a more basic feature, android.hardware.faketouch; android docs state:

If your application requires basic point and click interaction (in other words, it won’t work with only a d-pad controller), you should declare this feature. Because this is the minimum level of touch interaction, your app will also be compatible with devices that offer more complex touch interfaces.

If the application does not require touchscreen features, it is recommended to set android.hardware.touchscreen to not be required, but declare android.hardware.faketouch instead, so I did this for WordMix, which should work with faketouch devices, too:

<uses-feature android:name="android.hardware.touchscreen" android:required="false" />
<uses-feature android:name="android.hardware.faketouch" android:required="true" />

If you do that, check the results on Google Play, which shows the number of supported devices:

  • touchscreen required, faketouch not required: 1500
  • touchscreen not required, faketouch required: 860
  • neither required: 1800

That is odd and not according to the documentation. For example a Samsung GT-S5360 seems to support touchscreen, but not faketouch. The Samsung Galaxy S2 supports both. You can include all devices by setting touchscreen to be not required, which then includes all faketouch devices, but also all devices that have even less input capabilities.

First playable version of Freebloks for Android


I just pushed a first playable version of Freebloks for Android, a port of Freebloks 3D to the Android system. It’s a very early development version and very rough, but you can start a single player game and join a network game and place stones. The user interface still needs a lot of love, but I might push a preview version on Google Play soon. Please get involved on GitHub, if you want to contibute.

Here are two screenshots:


New featured image of WordMix

I tried using the Blender modelling software to create a new featured image for WordMix in Google Play, but I just can’t wrap my head around it. The software has such a horrible UI, that after several hours of trying, I still was unable to create a dice looking object. The learning curve is very flat, I wish I had more time.

This is the result with 3dsmax instead:

The previous image was created with Gimp, based on a screenshot of the game, which I took in a tabet android emulator. It sure did look poorly modified and, compared to the screenshots in Google Play, it did not add anything more:

Creating a custom LSF email router using exim

The University of Applied Sciences Weingarten, as many others, uses an installation of LSF (Lehre Studium Forschung) to manage students, departments and courses.When working at the datacenter of the university, I was part of a project to make the data of the LSF data available to the email system, to make LSF the primary system to connect user accounts with departments or classes. While accounts were primarily managed using LDAP, the system was not flexible enough to hold information about enrolled courses or roles in LSF, like professor, student, assistant, member of department X, etc.

Connecting LSF to the email system

News article: LSF email router

A custom webservice within the LSF framework however, replied a query with a nice plaintext list of user account names, which easily can be mapped to the canonical email adress of each given account. So we have the data, now how do we route the emails?

The datacenter ran two powerful Cisco Ironport appliances, used as MX, filter and first email router. I decided to put the lsf-email-router part on a separate Linux machine, the server, already running exim4 and an instance of mailman for the faculty. The Ironport appliances already routed every mail for subdomain to the lists server.

Special addresses

The exim4 router should detect special LSF email addresses (starting with lsf-), querying LSF for the data, and forward the email to the received list of user accounts, injecting the emails back into the email system to the main mail routers, that resolved account names to actual mailboxes.

Several adresses and queries were prepared, which can be easily extended, for example:

  • lsf-einrichtung-XXX@… (department XXX)
  • lsf-veranstaltung-xyz@… (all members of course xyz)
  • lsf-einrichtung-XXX-funktion-YYY@… (department XXX, role YYY)
  • lsf-veranstaltung-XYZ-20112@… (members of course xyz of winter semester 2011/12)
  • lsf-studiengang-XY@… (all students of the field XY)

A complete list of available dynamic addresses can be found in the service portal:

The custom script

Two ninjas created a short perl script to be called from exim4, that did the following tasks:

  1. Separate the parts of the email address and check for validity
  2. Determine cache file for the special list and exit script, if cache file is younger than 6 hours. This is done to not query the webservice more often than necessary and using 6h old data was acceptable in this case.
  3. If the cache file does not exist or is older, the LSF webservice is queried for the list of accounts. On success, the cache file is created or updated.
  4. On failure, the LSF might be down, but the email system shouldn’t. If a cache file exists and is younger than 1 week, use it anyway.
  5. If the cache file is too old, delete it and fail. Do not use cached file that is too old but rather fail routing the email, which will result in a mailer daemon message back to the sender.
  6. The perl script exits with an error code 0 or 1 to indicate success or failure.

Now we have a cache file with valid email addresses, or we don’t.

The exim configuration

Integrating the perl script into exim, using exim4’s splitted config, was demeaningly easy, but was actually the tricky part (file /etc/exim4/conf.d/router/475-lsf-router):

    driver = redirect
    local_part_prefix = lsf-
    file = ${run{/usr/bin/perl /etc/exim4/ \
           --lsflist $local_part_prefix$local_part} \
           {/var/cache/lsf-router/$local_part_prefix$local_part} \

This router entry works as a redirect router, giving it a file to expand email adresses from. Like a boss, we used exim’s ${run} string expansion to run our script every time an email is routed that maches the lsf- local part prefix of the address. Depending on the success or failure of the ran command, the expansion returns one of two strings. On success, the used filename is the whole local part of the destination address, on failure it is a non-existing path, which will result in a permanent routing failure.

Voilà, our LSF email router is done and working. Sending an email to lsf-veranstaltung-XYZ@… results in the email being routed to the Linux box, the script will be run to refresh the cache for the special email address, querying LSF at most every 6 hours, expanding the data and exim will forward the email to all user accounts.

It’s like using mailman for managing university courses and departments – except that it’s great.

For further information, feel free to contact me or

See also:

kwin-style-crystal repository on GitHub

I prepared a public repository on GitHub with all the code of the crystal window decoration, from crystal-0.5 for KDE-3.2 to the current crystal-2.2.0 for KDE-4.9 beta.

Please feel free to contribute:

There are also ongoing discussions about integrating the crystal window decoration into the official KDE SC, moving all development into the offical KWin tree, next to the current default Oxygen deco.

Currently all major distributions ship optional binary crystal packages. If not, see the official crystal project page on

Crystal-2.1.1 casting shadows ahead

I just added shadow support in Crystal-2.1.1 (for KDE 4.8) and Crystal-2.2.0 (for KDE 4.9), as well as some minor fixes. Since KDE 4.8 the window decoration itself is responsible for rendering shadows when compositing. Because Crystal uses an unstable kwin API to support tabbing, versions before 2.2.0 are unable to compile, which has the exact same features than 2.1.1.

The shadows aren’t the prettiest but better than none. Hopefully I’ll have time to do further improvements, refactoring, increased speed, stability and graphical improvements.

I hope to get a stable crystal release, which would blend in well with the rest of KDE SC.

Get crystal from the project page on or wait for your distribution to catch up:

WordMix Pro going 3D

WordMix in the Google Play Store

WordMix Pro arrived in the Google Play Store. While WordMix will stay free of charge, selling a pro-version will support the developing of the game and helpkeeping the free version adfree. So far the Pro version does not have much to offer but some more background images for the game. I do not intend to make the gameplay differ between the free and the payed version.

A 3D OpenGL interface for the game is under development and will be available in the pro-version soon.

Check out the first screenshot:

Chicken Tournament source code on GitHub!

I finally published the source code of my biggest game so far Chicken Tournament, which I created about 10 years ago in C++. Starting in 2002, at the age of 18, it took me 13 month to create the game and a lot of my blood went into the game, and I’m still proud of the result. Over the years many people asked me for the source code or parts of it to study, and I never hesitated showing the code around, but never wanted to actually make it OpenSource.

Now the complete source code of the game (excluding source of the models and the video so far) is available on GitHub and contains the resources, the game logic, libraries and the Microsoft Visual C++ 6 project. Along the source, the DirectX7-SDK is needed to successfully create a binary.

The game is not under development anymore and big changed are unlikely to happen. Please respect my work.

Porting Freebloks to Android

I’m currently trying to port the Freebloks game to Android. The core of the game is actually pretty easy to convert from POSIX C to Java for Android and I’m already done migrating the client code and the model, so my app is able to establish a connection to a remote server and display the state of the game.

The display is still very simple, only meant to visualize the state of the core and there is no user interaction possible yet but I plan to port the OpenGL interface too, which does need some rewriting of the logic.

I’m working on keeping the network protocol intact so you can use play together with people using Freebloks 3D in Windows, Linux or MacOSX.

I hope to have a test version around for download, as soon as I have the server portion ported too, so one can play it without connecting over the data connection.