Updated April 4, 2023
Introduction to Linux QT
QT is defined as an app development framework that is intended for cross-platform development activities. The development activities include developing apps for mobile, desktop, and embedded applications. The QT framework supports Linux and platforms like Windows, iOS, Android, OS X, and many others. Though for the matter of the article, we will discuss an end to end about QT only keeping Linux in mind. Some of the organizations widely use QT for their app development, and these include Siemens, AMD, Telegram, etc. last bit of intro for QT is that this framework is written in C++, and hence the apps written on it can be compiled through any standard C++ compiler.
How does Linux QT work?
Before learning about the working of Linux QT, let us understand how to pronounce it! QT is pronounced as “cute”. It is an app development framework, as we talked about when we were looking at the definition, but one needs to also know that the QT framework is not a programming language and instead just only a framework written in C++. After the compiler is written in C++, a pre-processor or other words, compiler, known as MOC (Meta-Object Compiler), is used for extension of the C++ language and its features.
Now let us understand how QT works. A developer writes the code for all utilities of the app in the QT framework. Once the codes are developed and validated for their logic, one needs to run the compiler. Before the source files reach the compiler, the Meta Object Compiler parses all the source files which are written in the Qt framework; the extended version of C++, standard complaint C++ source codes are generated for compilation. For the compilation of the framework itself or the application or libraries using it, any standard C++ complaint compiler can be used as they are capable of reading the C++ complaint codes generated by the QT framework.
Now the next important thing for us to know is how a QT program is compiled. In QT, though there is a system known as QT creator that invokes the build system, it is interesting and important to know the compilation of QT programs. In the case of smaller programs, it becomes very easy to perform the compilation manually by creating the object files and then linking them in a particular fashion to achieve the desired result, but the challenge in a larger program where the command line is hard to write.
In Linux, the programs are compiled by the use of makefile, where all the command lines are described for execution and in larger projects, making the makefile is tedious. To solve the problem of making the makefile, a build system comes bound with QT, known as qmake, which performs the job of making the makefile. The makefile prepared using qmake includes the meta-object extraction phase, which is responsible for the extension of C++ in the QT framework. Now summing up the compilation which happens in 3 phases:
- .pro file is created, which describes the project which needs to compile.
- Makefile is generated using the qmake.
- The program is then built using make.
How to use Linux QT?
For building QT on any platform, the below-listed steps are followed. Now, since this article is particularly for Linux, let us walk through the process of building or using QT on a Linux system.
- Source code archive is downloaded.
The easiest and most convenient way to download the QT is by browsing for the download server and then navigating to the appropriate directory. After navigation, the official source code is found as the system specification and then downloaded. Some people also prefer the Linux command line for downloading the file, using the wget command.
- The source code is extracted to a working directory.
The next step is to untar the tar.gz file to the working directory. Syntax for the same is: tar xzf <filename>.tar.gz
- The development packages and other build dependencies are installed for QT.
The next step, and the most time-consuming one, in the process is to find all the related dependencies. Once you have the list, just an apt-get command will enable you to install the libraries in the Linux system.
- QT is configured for desired options and made sure that all dependencies are met.
This step will help identify the options that will be enabled and then create the make files required for the build. The syntax for initiation is by running a shell script by ./configure.
- QT build is started
In this step, the build is performed by running the command make.
- The new version is installed and tested.
The final version is to test the new version of QT and is done by running
sudo make install
Advantages and disadvantages
Below are the advantages and disadvantages of Linux QT:
Advantages
- Quite a mature platform vetted by major players in application development.
- Well-designed framework. Some might argue it to be the best-designed framework.
- The user base for QT is quite exemplary.
- The documentation is well written.
- Stability on the major platforms.
- The cross-platform way of working enables many kinds of stuff that desktop application often needs to do.
Disadvantages
- As it is written in C++, some people who don’t use C++ might find it clumsy at an aesthetic level.
- The use of a MOC adds a bit of complexity.
- QT doesn’t reply on standard libraries, and as a result, many times, wheels must be reinvented. For example, making a string class again!
- A lot of ownership change has happened for QT; hence the future is still debatable!
Features
There are a lot of features available for QT, majorly bucketed into 4 categories. They are (along with examples of each:
- Design Tools
Example: QT Design Studio, QT designer, QT quick Designer
- Development Tools
Example: QT QmlLive, GammaRay, Emulator
- Framework Essentials:
Example: QT Core, QT GUI, QT Multimedia
- Framework Add-on
Example: Active QT, QT Canvas 3D, QT Android Extras
Conclusion
With the different aspects being touched upon by this article, we by now have a clear picture of QT and the essential aspects of this framework. The next steps lie in the hand of the reader to try out these steps and create something exciting as an application to use!
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