Qt who is using

Qt Creator creates your project and switches to the Edit view. In the source code editor for the main. The QCoreApplication task handles the entire system startup for an application, and every Qt Console app needs to create one and call its exec method as part of your main method. It sets up Qt's event handler and provides a bunch of porting helpers to determine things such as your application directory, library paths, and other details. Next, let's compile and run the application.

There are several ways to do this. You can:. Click on the green Run arrow below the Help view button on the left to run the application. Click on Start Debugging … from the Debug menu. Click on the green Run arrow with the bug over the arrow in order to debug the application on the left.

If you only want to build the application, you can click on the hammer icon below the Run and Debug icons. When you choose one of these options, Qt Creator invokes the compiler and the linker to build your application. If you choose the Debug option, Qt Creator switches to the Debug view which we will discuss in detail in the next chapter as it starts your application. Once the application starts, you'll see the Hello world!

One of Qt's strengths is its rich collection of GUI elements that you can use to create windowed applications. Try it now:. First, close the current file and project by clicking on Close All Projects and Editors from the File menu.

Then, select the default kit. The New project wizard will prompt you for the name of the class implementing your main window. Skip the version control dialog portion of the wizard. Qt Creator creates a default subclass of the class that provides the platform's basic window in the mainform.

The following screenshot shows a default form as you're editing it in Qt Designer. If you run the application at this point, you'll see an empty window. Instead, double-click on the Forms folder in the project tree the second pane of Qt Creator and then double-click on the mainwindow. Qt Creator switches to the Design view, and you'll see something similar to the next screenshot:. On the left-hand side is a list of the layouts that you can choose to organize widgets, such as spacers, views, containers, buttons, and other widgets; on top of this, there are various edit and layout options.

In the middle is a view of the layout of your application's main window, and to the right are panes with a hierarchy of objects in your main window and the properties of any item that you click on in the main window. Begin by ensuring that you're in the Designer mode:. Where it says Type Here , right-click and choose Remove menu bar. Drag a label under Display Widgets in the left-hand side pane and drop it in the window preview in the center pane. Grab a corner of the label and resize it so that the entire text is shown.

You can also move it around in the window. Note that when you click on the label, the Property field in the lower-right pane is updated to show the properties of your new label.

Drag a button under Buttons in the left-hand side pane and drop it in the window preview in the center pane. With the new button selected, change the objectName field in the Property browser to exitButton.

Right-click on the button and select Go to slot…. A window appears with a list of slots for now, you can think of a slot as something that is triggered on an action; we will discuss them more in Chapter 2 , Building Applications with Qt Creator. Qt Creator returns to the Edit view for your mainwindow. Change it to read as follows:.

Before running your application, let's be sure that you understand the implementation of the MainWindow class. The constructor of the MainWindow class loads the description of the user interface for the main window and sets it up using the Qt Creator-generated class Ui::MainWindow. Double-click on this file in the browser on the left and make sure that it reads as follows:. We'll learn more about signals and slots in the next chapter; for now, it's enough for you to know that you're declaring a private function to be triggered when you click on the button.

Run the application. It should open a single window with the text Hello World! At this point, if you think you want to learn more about Qt Widget applications, go ahead and try dragging other GUI items to the window, or explore the help documentation for Qt Widget applications by switching to the Help view and clicking on Qt GUI from the list of help items. Qt Quick is Qt's newer declarative framework for the user interface, and with this, it's incredibly easy to create fluid applications with animated transitions and flowing user interfaces.

Using Qt Quick, you can describe your user interface using QML, a JavaScript-like language that lets you declare user interface elements and how they relate; the Qt Quick runtime does most of the heavy lifting in the implementation of your application. By now, you can guess how to create a Qt Quick project.

The wizard will ask you one additional question: the Qt Quick version to use. You should simply choose the latest version. Once you walk through the wizard, you end up with a simple application that actually displays Hello World in its own window. Here's the code that it supplies:. If you know JavaScript, the syntax of this might look a little familiar, but it's still different.

The tool Qt Linguist and its companions lupdate , lrelease and lconvert make it easy to translate applications to locale languages. Qt supports most languages and writing systems that are in use today. For a complete listing see the corresponding manual pages. Qt also comes with an interactive graphical tool called Qt Designer which functions as a code generator for Widgets based GUIs.

Qt Designer can be used stand-alone but is also integrated into Qt Creator. QML is a declarative object description language that integrates Javascript for procedural programming. Qt is far more than a GUI toolkit. For a full list of official Qt modules, see the All Modules page in the Qt documentation.

Also, see Inqlude. These are not part of Qt but are provided by various third parties. Riverbank Computing for example provides commercial and free software Python bindings PyQt.

The offline installer is a platform-specific package that includes all Qt modules and add-ons relevant for the platform. Due to the official policy changes, open source offline installers are not available any more since Qt 5. If you have a commercial license, then you can provide the credentials during the installation process. You can locate your license key in your Qt account web portal. The Qt Company provides users with a dual-licensing option. As a beginner, you can get started with an open source license to explore Qt.

If you are working for a company, then discuss with your manager or Information Technology IT or legal team to procure a commercial license or to understand legal obligations. You will see a Thank you page after you click on the download option. At this stage, you can find the installer in your download folder. Now, let's start the installation process on Windows! Proceed as follows:. We will be focusing on the most popular Linux distribution, Ubuntu.

You can follow the same steps as mentioned previously to download the online installer from the Qt website. At the time of writing the book, there was no Ubuntu or Debian package available for Qt 6 as the respective maintainers have stepped down.

Hence, you may not get the Qt 6 package from the terminal. If you are a macOS user, then you can also install the same way as discussed for the earlier platforms. You can follow the same steps mentioned previously to download the online installer from the Qt website.

Qt has a dependency on Xcode. To install Qt on your Mac, you will need Xcode installed on your machine, otherwise, it will refuse to install. If you are an Apple developer, then your Mac may have Xcode installed. If you don't have Xcode installed on your machine, then you may proceed to install Xcode's Command Line Tools instead of Xcode. This will save time and storage space on your machine:. Once Qt is installed, you can modify the components—including updating, adding, and removing components—using the Maintenance Tool under the installation directory.

The directory structure remains the same for all desktop platforms. The installation directory contains folders and files, as shown in the following screenshot on Windows :. Let's begin with the maintenance process! You can add, remove, and update modules using the Maintenance Tool.

Please note that on clicking the Uninstall button, all the Qt components will be removed from your system; you will have to reinstall Qt if you want to use them again.

Click on Cancel if you don't intend to remove the Qt components from your system, as illustrated in the following screenshot. If you intend to remove the existing version and use a newer version of Qt, then select the Add or remove components option, as discussed earlier.

This will remove older Qt modules and free up your disk space:. In this section, we learned about modifying an existing Qt installation through the Maintenance Tool. Now, let's learn how to build and install Qt from the source code. If you want to build the framework and tools yourself or experiment with the latest unreleased code, then you can build Qt from the source code.

If you are a commercial customer, then you can download the Source Packages from your Qt account portal. Platform-specific building instructions are discussed in the upcoming subsections. You can also clone from the GitHub repository, and check out the desired branch. At the time of authoring this book, the Qt 6 branch remained inside the Qt 5 super module.

The qt5. Ensure that you install the latest versions of Git, Perl, and Python on your machine. To install Qt 6 on Windows from source code, follow these next steps:. Your Windows machine is now ready to use Qt.

To build the source package on Linux distributions, run the following set of instructions on your terminal:. If you use a different shell, modify your environment variables accordingly. Qt is now ready to be used on your Linux machine. To install Qt on your Mac, you will need Xcode installed on your machine. If you don't have Xcode installed on your machine, then you may proceed to install Xcode's Command Line Tools :. In this section, we learned how to install Qt from source on your favorite platform.