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 – optimizing oscillogram drawing


As an exercise, we will modify our oscillogram widget so that it only re-renders the part of its data that is required. The first step is to modify the paint event handling code to fetch information about the region that needs updating and pass it to the method drawing the chart. The changed parts of the code have been highlighted here:

void Widget::paintEvent(QPaintEvent *pe)
{
  QRect exposedRect = pe->rect();
  ...
  drawSelection(&painter, r, exposedRect);
  drawChart(&painter, r, exposedRect);
  painter.restore();
}

The next step is to modify drawSelection() to only draw the part of the selection that intersects with the exposed rectangle. Luckily, QRect offers a method to calculate the intersection for us:

void Widget::drawSelection(QPainter *painter, const QRect &rect, const QRect &exposedRect)
{
    // ...
    QRect selectionRect = rect;
    selectionRect.setLeft(m_pressX);
    selectionRect.setRight(m_releaseX);
 ...