Book Image

Game Programming Using Qt: Beginner's Guide

By : Lorenz Haas, Witold Wysota, Witold Wysota, Lorenz Haas
Book Image

Game Programming Using Qt: Beginner's Guide

By: Lorenz Haas, Witold Wysota, Witold Wysota, Lorenz Haas

Overview of this book

Qt is the leading cross-platform toolkit for all significant desktop, mobile, and embedded platforms and is becoming more popular by the day, especially on mobile and embedded devices. Despite its simplicity, it's a powerful tool that perfectly fits game developers’ needs. Using Qt and Qt Quick, it is easy to build fun games or shiny user interfaces. You only need to create your game once and deploy it on all major platforms like iOS, Android, and WinRT without changing a single source file. The book begins with a brief introduction to creating an application and preparing a working environment for both desktop and mobile platforms. It then dives deeper into the basics of creating graphical interfaces and Qt core concepts of data processing and display before you try creating a game. As you progress through the chapters, you’ll learn to enrich your games by implementing network connectivity and employing scripting. We then delve into Qt Quick, OpenGL, and various other tools to add game logic, design animation, add game physics, and build astonishing UI for the games. Towards the final chapters, you’ll learn to exploit mobile device features such as accelerators and sensors to build engaging user experiences. If you are planning to learn about Qt and its associated toolsets to build apps and games, this book is a must have.
Table of Contents (18 chapters)
Game Programming Using Qt
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Time for action – using properties, signals, and slots with items


So let's alter the Player class to use QObject:

class Player : public QObject, public QGraphicsPixmapItem {
  Q_OBJECT

All you have to do is to add QObject as a base class and add the Q_OBJECT macro. Now you can use signals and slots with items too. Be aware that QObject must be the first base class of an item.

Tip

If you want an item that inherits from QObject and QGraphicsItem, you can directly inherit QGraphicsObject. Moreover, this class defines and emits some useful signals such as xChanged() when the x coordinate of the item has changed or scaleChanged() when the item is scaled.

Note

A word of warning: Only use QObject with items if you really need its capabilities. QObject adds a lot of overhead to the item, which will have a noticeable impact on performance when you have many items. So use it wisely and not only because you can.

Let us go back to our player item. After adding QObject, we define a property called m_jumpFactor...