If you see this post, my WordPress blog is gone.
My Blog now uses Hugo. I really like formats like Markdown and AsciiDoc. These formats are expressive, and you can edit them with every editor you want and don’t need expensive licenses, like for Word or similar. Another advantage is that you define what should happen by writing and not by clicking a button and hoping the program does what you intended to do.
Continue readingSometimes you just want a newer version than ubuntu ships. This code will update cmake to version 3.11.1 or any other version you want.
Continue readingThese steps are for all those people who hate to sign the Virtualbox modules every time and don’t want to disable UEFI.
Continue readingI just encountered the problem that I have to type two passwords at startup, for two encrypted disks. My first disk is encrypted through the Ubuntu installer. After some searching I found the perfect solution for that task. In german, it’s called “Schlüsselableitung”, in English derived keys. But perfect solutions often have a big issue why they don’t work, like here. I’m using Ubuntu 16.04 which uses ´systemd´, and that has problems with derived keys. So I found the second most perfect solution for me, using a key-file. Some people argue that this is a security issue, but the derived key is also obtainable with root rights, just like a key-file. And by the way, your private keys of your certificates are also stored on that disks and nearly nobody complains about that.
Continue readingThe one thing that confuses the most people in the beginning is the
Signal & Slot mechanism of Qt. But it’s actually not that difficult to
understand. In general Signals & Slots are used to loosely connect
classes. Illustrated by the keyword emit, Signals are used to
broadcast a message to all connected Slots. If no Slots are connected,
the message “is lost in the wild”. So a connection between Signals &
Slots is like a TCP/IP connection with a few exceptions, but this
metaphor will help you to get the principle. A Signal is an outgoing
port and a Slot is an input only port and a Signal can be connected to
multiple Slots.
If you come from plain vanilla C++, you only know the C++ Standard
Library with its containers like std::vector. If you know how to use
them, you can accomplish your tasks pretty fast. But if you’re coming
from another language, the naming might be a bit odd. The Qt containers
offer both, C++ style and Java style naming of methods. So coming from
another language the Qt one’s might be easier to use.
Everyone that knows me, knows that I love the Qt framework. Before I started programming in C++, Java was my primary programming language. I love the generics (yes, some of you will hate me for that opinion right now) and reflection. During my Java-time I used them very often to increase reusability. But while studying we had to learn C++ and I hated it in the beginning. It felt so old and so stiff compared to Java. But in one lecture we used Qt, and it was even more terrible - in the beginning. Signals, Slots, QWidgets, … it was too much. After working with it for some time it felt better. What I really liked about Qt from the beginning was the Qt Designer. For the first time I was able to have fancy ui’s in C++ and don’t have to bother with a C api. In Java, I had a graphical editor for Swing. So creating ui’s was now as easy as in Java, maybe a bit easier. But the results with Qt are much better and fancier. After some reading and experimentation I began to understand how Signals and Slots work. From now on I really liked Qt. It was awesome. It was so easy to accomplish tasks, and it still is. If you build an application with an ui and some heavy stuff to calculate, or simply said two threads to communicate, it is very easy with Qt. Just use Signals and Slots to communicate between the threads and the Qt framework will deal with all the synchronization stuff (If you use them properly). You can also use Signals and Slots to loosely couple objects. The sender-object that emitted the Signal, does not know where it is going and the receiver-object does not know where it came from. So you easily exchange components, just like with dependency injection. If I write an application and use the C++ standard library and Qt, I can be sure that it will compile and run on all the mayor platforms. A few months ago I switched from Windows to Linux. The reason why I did that can be found here Warum ich zu Linux wechsle if you can read German. I was so excited when I opened the project file of my Qt project. I developed the whole project in Windows and with a click of the “Compile & Run” button it was running under Linux. But the portability is not the only advantage. You have a huge Library with many classes solving different problems. If you want to use for example Network, no problem, just use it. The same goes for JSON support, XML, SQL, Bluetooth, OpenGL and many more. It’s just so convenient, you don’t have to search for a library, try to compile it and link it to your project, Qt does all that for you. So you don’t have to reinvent the wheel every time. At the beginning I mentioned reflection in Java. You can use reflection in Qt with the help of moc (Meta Object Compiler). So every class that inherits from QObject knows what class it is and other information at runtime.
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