Book Image

Mastering Qt 5 - Second Edition

By : Guillaume Lazar, Robin Penea
Book Image

Mastering Qt 5 - Second Edition

By: Guillaume Lazar, Robin Penea

Overview of this book

Qt 5.11 is an app development framework that provides a great user experience and develops full capability applications with Qt Widgets, QML, and even Qt 3D. Whether you're building GUI prototypes or fully-fledged cross-platform GUI applications with a native look and feel, Mastering Qt 5 is your fastest, easiest, and most powerful solution. This book addresses various challenges and teaches you to successfully develop cross-platform applications using the Qt framework, with the help of well-organized projects. Working through this book, you will gain a better understanding of the Qt framework, as well as the tools required to resolve serious issues, such as linking, debugging, and multithreading. You'll start off your journey by discovering the new Qt 5.11 features, soon followed by exploring different platforms and learning to tame them. In addition to this, you'll interact with a gamepad using Qt Gamepad. Each chapter is a logical step for you to complete in order to master Qt. By the end of this book, you'll have created an application that has been tested and is ready to be shipped.
Table of Contents (16 chapters)

Fading in the picture

When the user opens a picture, we want to fade in the image by playing with its opacity. The QLabel or QWidget classes do not provide an opacity property. However, we can add a visual effect to any QWidget using QGraphicsEffect. For this animation, we will use QGraphicsOpacityEffect to provide an opacity property.

Here is a schema to describe the role of each one:

In our case, the QWidget class is our QLabel and the QGraphicsEffect class is QGraphicsOpacityEffect. Qt provides the graphics effect system to alter the rendering of a QWidget class. The QGraphicsEffect abstract class has a pure virtual method, draw(), that is implemented by each graphic effect.

We can now update MainWindow.h according to the next snippet:

#include <QPropertyAnimation> 
#include <QGraphicsOpacityEffect> 
class MainWindow : public QMainWindow