Recent blog entries for e8johan

New Article

I don't know for how long it has been available on-line, but I wrote another article for Qt Quarterly. For your reading pleasure: Designing Delegates.

Syndicated 2008-09-05 13:38:00 from Life of a Developer

Building Qt on a clean Kubuntu

I have to admit it - I always build my own Qt. Because of customers sticking to older versions and myself wanting to have the latest, I currently have 4 flavors of Qt and 3 of QtopiaCore sitting on my laptop.

As I recently invested in a new computer I felt that I had to build Qt + Qtopia on it. The computer was installed with a clean Kubuntu from the start. The problem is that Qt requires some packages to build and finding those packages is (at least for me) a tedious iterative process (make - look what failed - apt-get install it - repeat). So, without further ado, here is a list of packages that you need to get 4.3.4 X11 to build properly:

• build-essential
• libx11-dev
• libxext-dev

So, make sure to apt-get install those before running ./configure && make && make install && echo -e "\a" . At least it keeps you from interrupting your I'm-compiling-thus-working-coffee-break. :-)

Sidenote: I guess Qt 4.4 requires some gstreamer goodies as well, I'll tell you when I get there.

Syndicated 2008-08-22 07:14:00 from Life of a Developer

A tip

The Gigabyte GA-MA78G-DS3H motherboard will not boot with 4 GB on board unless you first update the BIOS. This means that if you buy 2x2GB of RAM, you will need to boot using one DIMM, update the BIOS and then insert the second DIMM. Failing to do so will just bring frustration and anger.

Syndicated 2008-08-17 08:11:00 from Life of a Developer

Commercial Qt on Vista using MinGW

Since I just got my new computer up and running, I wanted to start using Qt. Another new, for me, is Vista, so I decided to get my commercial Qt license up and running using MinGW in Vista. The proved to be a small challenge so I've documented my steps here.

First of all, put your license file in your user directory and try to rename it to .qt-license. Notice that the file explorer won't let you do that. Apparently the only dot denotes the start of the file ending, so in Vista's eyes, a file starting with a dot has no name. The solution is, as always, to use a command prompt and good old ren.

I've downloaded MinGW and the commercial Qt sources for win32. These are installed/extracted into the Coding directory located in my home directory (being C:\Users\Thelin in my case). MinGW lives in Coding\MinGW while Qt is in Coding\qt-win-commercial-src-4.4.1.

Building

Let's continue by using a command prompt and set some environment variables to point out these facts. We need to include MinGW in the PATH variable. Then Qt needs the QTDIR and QMAKESPEC variables to get its foothold.

set PATH=%PATH%;C:\Users\Thelin\Coding\MinGW\bin

set QTDIR=C:\Users\Thelin\Coding\qt-win-commercial-src-4.4.1

set QMAKESPEC=%QTDIR%\mkspecs\win32-g++

As we are used to from Unix, we then configure Qt before building it. This is straight forward, but I've included my configure line for completeness.

configure.exe -debug-and-release -shared -plugin-sql-sqlite -qt-zlib -qt-libpng -qt-libjpeg -no-libtiff -no-gif -no-dsp -no-vcproj -assistant-webkit

The last step of the configuring is the construction of QMake for your configuration. It is good to know that the file pbuilder_pbx.cpp takes ages to build (see TaskTracker #162299). Apparently by design.

When QMake has been built, simply do as told. Run mingw32-make to build Qt. I choose to add the argument -j4 to utilize my CPU cores better. Don't know if it improves the build time much but it makes me feel good.

Now, all that is left is to add %QTDIR%/bin to PATH and to try the Qt demos. However, keep on reading if you want to make the installation easier to use.

set PATH=%PATH%;%QTDIR%\bin

Command Line Conveniences

To make it a bit easier to get up and running with Qt, we will create two batch files. First, qt-vars.bat, that initializes the environment variables as shown in this text (gather all the lines starting with set in a file). To make things fancy, you can create a short-cut to this file. Set it to run cmd /K qt-vars.bat to end up with an intialized command prompt - quite nice.

The second batch file that I mentioned before is make.bat. Make it run mingw32-make and place it somewhere in path. If you want to be able to use command line arguments, pass on a few %1 %2 %3 and so on to MinGW. This will allow you to type make -j4, instead of prefixing it with mingw32- every time. You can place this file either in Qt's bin directory, or with the MinGW executables.

Eclipse

Since the Windows command prompt leaves quite alot to wish for, I prefer trying something else for a change. It it possible to use cygwin or other shell replacements, but hey, we're in a graphica environment, so why no try to use something grapical such as Eclipse.

Qt integrates quite well with Eclipse. Start by downloading Eclipse for C/C++, or just the standard edition with and the C/C++ support module. Then download the Qt integration. Commercial license holders will find it in their personal download directory.

Once all the installers have been run, start Eclipse through the Qt Eclipse Integration item on the Windows start menu. Then select File - New - Project... and choose to create Qt application. This will prompt you to specify what Qt version to use in the dialog shown below. Simply point out the version you just built and you are ready to go.



The Qt integration works great - but sometimes you can get a feeling of nausea. For example, it is not clear from the start how to execute the result of your project. But, then you can always revert to the good old command line.

Syndicated 2008-08-10 16:48:00 from Life of a Developer

It has a GUI

In the past, I fiddled with fractals. To force my-self to get started in the right directions, I started from the "other end", i.e. fixing the boring details and such before starting working on the user interface.

Now, my wait is over. The user interface is here, or the basics of it. One can pick fractals through a factory (wait for the plug-ins) and look at fractals. The setting docks are there, but not live and the viewer is just a QLabel i a QScrollArea - not very fancy.


This must be the only general fractal explorer not supporting Julia nor Mandelbrot... :-)

Syndicated 2008-08-08 08:56:00 from Life of a Developer

Foundations of Qt Development re-printed

I was happy to learn that Springer has printed my book, Foundations of Qt Development. Their distribution rights seem to span parts of south east Asia and the middle east. For the rest of us, APress is the preferred source.

In addition to this, the Linux Learning Centre, has decided to use the book as a part of their Qt course. Kudos to Prashanth for making this happen.

Finally, as a side note, real life has recently been too hot to get any hacking done. We've seen about two weeks with 30dgC+ temperatures here, but now it finally rains and temperatures as more comfortable.

Syndicated 2008-08-03 06:37:00 from Life of a Developer

Attracting Fractals

So, more summer and more fractal fun. First of all, now everything is coloured by shaders. A shader, per my definition, picks the colour for any given point/line-segment depending on direction, iterations, or group - where group can be the factor set used (IFS fractals) or angle in predefined steps (L-systems) or just zero (all other fractals).

Below, you can see a maple leaf coloured based on the factor set used to get the specific point.

The latest addition to the number of supported fractals are attractors. Below, you can see a gradient coloured Lorenz attractor from a paralell projection showiing the X and Y axes (ignoring the Z axis).

The introduction of attractors really exposed the lack of properties. The idea is that each fractal provides a range of properties (be it ints, doubles or compex numbers - perhaps also enums). These can then be queried and set from the UI using a standardized interface.

I'm exploring all these fractal types with the goal to create a base class, AbstractFractal, that I can put into a GUI. Then, fractals can be created from plug-ins, where the plug-in factory can get the actual fractals from a set of definition files - hopefully compatible with FractInt (or very similar, so that machine conversion is possible).

Then, all that is left is to create a nice Qt GUI and utilize QtConcurrent to get some performance from it. Also, have a bit of a sit-down and think through the whole memory situation - right now the application is somewhat hungry...

Syndicated 2008-07-26 13:47:00 from Life of a Developer

Fractalicious

Ever since I first played with FractInt, it must have been at least 15 years ago, I've been intrigued by fractals. At first, they seemed like magic to me, but as I learned more maths, I can understand the why, but not always the how.


A couple of years ago I set out to write a fractal exploration application called Frakter. To be honest, it sucked pretty much, but it was an attempt. The nice things about it where:

• Fractals where kept in external scripts, so that the application could be extended.
• Colouring was done using special colour maps that could be loaded and saved.
• It used a background thread to render the fractals.
• It had a zooming history that one could type right into to find interesting ranges in the complex numbers realm.

Now and then I visit Paul Bourke's great collection of fractals (and loads of other stuff too). Each time, I feel an urge to write something that can handle everything that he shows.

I want to be able to fit all different types of fractals into a class tree that I can write a GUI around. The data carried from the fractals to the UI would be enough to do basic 2D rendering, 3D rendering, psychedelic colouring, and so on.


I've had a couple of half hearted attempts this far, but now I started from the other direction, i.e. starting with the fractal types I never get to otherwise.


Right now I've implemented IFS and L-systems. The implementation is not even an attempt at being efficient and uses loads and loads and loads of memory, but it works. The next step is to create a colouring class that one can inherit to do the funky stuff. Last value, current value and current iteration, fractal specific category are the "input values" I plan to use. Right now, fractal specific category, is "last used transformation set" when dealing with IFS, for L-systems, it is zero.

Syndicated 2008-07-23 15:41:00 from Life of a Developer

VB Porting Issues

Dear Lazy-web,

I was hoping that someone out there remembers good old VB4. I have an issue when helping out to port a VB4 system to XP. The thing is that I've got a really old system for managing club members and race results that is used by the local bicycle club. I did not write this system, and I'm helping them for free. Anyhow, it uses VB4 + Crystal Reports 1.x.

Installing these tools on Windows XP works on some machines, but not all. For instance, Swedish XP installations seems to crash Crystal Reports (somewhere in ntdll.dll). Just starting the app, that is.

Does anyone know what is causing this and how to circumvent it? I would be very pleased...

Syndicated 2008-07-16 19:28:00 from Life of a Developer

Standard Template Library - readable?

Since I called some STL code readable, I've recieved numerous mails and comments. Fellow Qt/KDE-er dhaumann added his 0.02 EUR to the pile and showed the nicety of template specialization.

Today I thought I'd follow up on some more comments.

First of all, my personal opinion is that C++ is just as readable as most other languages. Even in this case. What can be less readable are the horrendus error messages that one can end up with. I've even compiled a small list of error messages and what they really mean in plain English, but this does not - of course - help in ugly template cases. (Yes, the css of digitalfanatics.org is ugly and somewhat broken...)

Back to readability. Even plain English cannot express the two operations that I suggested in a short way. Both cases results in fairly long sentences. Also, try to formally parse and express such sentences with more "interesting" transformation functions.

"For every item in the source list, add 42 to it and replace it in the source list."

"For every item in the source list, add 42 to it and append it to the end of the destination list."

As the commenter zwabel pointed out, in the put-the-result-in-another-list a simple foreach loop showing the actual operation is good enough and reads better. I agree, but that kind of break my do-everything-on-a-line-thesis.

Titus Brown pointed out that I do too much on a single line. I have to disagree with this - looping and doing something on each item is simple enough.

Then I had lots of suggestions that I say that C++ isn't functional, but I use a functional style in my example. I'm not sure that I agree. My impression of the STL is that it can perform a number of functions on lists that I'm interested in, for instance.

• Iterating (for_each)
• Filtering (remove_if)
• Searching (find_if)
• Processing (transform)

To make these operations flexible, they accept a functor - either a predicate or an actual transformation operation. This isn't really functional programming in my eyes, even if it can be used for functional programming. To me, it is just a set of ways to perform iterations and common tasks.

Anyway, some fun thought that have poped up while discussing this topic. What if we combine these operations with the QtConcurrent framework. I have not tried the framework myself, but I was in Munich and listened to Morten's presentation of it, and to me it looks like it could be done. What is missing is a nice set of flexible map and filter functions, binders and such goodies that the STL carries.

Syndicated 2008-07-08 18:01:00 from Life of a Developer