Book Image

Getting Started with Qt 5

By : Benjamin Baka
Book Image

Getting Started with Qt 5

By: Benjamin Baka

Overview of this book

Qt is a cross-platform application framework and widget toolkit that is used to create GUI applications that can run on different hardware and operating systems. The main aim of this book is to introduce Qt to the reader. Through the use of simple examples, we will walk you through building blocks without focusing too much on theory. Qt is a popular tool that can be used for building a variety of applications, such as web browsers, media players such as VLC, and Adobe Photoshop. Following Qt installation and setup, the book dives straight into helping you create your first application. You will be introduced to Widgets, Qt's interface building block, and the many varieties that are available for creating GUIs. Next, Qt's core concept of signals and slots are well illustrated with sufficient examples. The book further teaches you how to create custom widgets, signals and slots, and how to communicate useful information via dialog boxes. To cap everything off, you will be taken through writing applications that can connect to databases in order to persist data. By the end of the book, you should be well equipped to start creating your own Qt applications and confident enough to pick up more advanced Qt techniques and materials to hone your skills.
Table of Contents (8 chapters)

Custom signals

In previous chapters, we saw how to use slots and create custom slots to implement some functionality in response to a signal being emitted. Now, in this section, we will look at how to create custom signals that can be emitted and connected to other slots.

To create a custom signal, one needs to declare a method signature and mark it as a signal with the aid of the Q_OBJECT macro. When declared, signals don't have a return type, but they can accept parameters.

Let's get our feet wet with a project. As usual, a new folder should be created with the three (3) files, namely, main.cpp, mainwindow.cpp, and mainwindow.h.

In this example, we shall override mousePressEvent and emit a custom signal that will be connected to a slot to perform a number of updates on a window.

In the mainwindow.h file, insert the following lines of code: