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    Game Programming Using Qt: Beginner's Guide
    Game Programming Using Qt: Beginner's Guide
    Game Programming Using Qt: Beginner's Guide
    Ebook1,127 pages9 hours

    Game Programming Using Qt: Beginner's Guide

    By Wysota Witold and Haas Lorenz

    ()

    Read preview

    About this ebook

    A complete guide to designing and building fun games with Qt and Qt Quick 2 using associated toolsets

    About This Book

    - Learn to create simple 2D to complex 3D graphics and games using all possible tools and widgets available for game development in Qt
    - Understand technologies such as QML, Qt Quick, OpenGL, and Qt Creator, and learn the best practices to use them to design games
    - Learn Qt with the help of many sample games introduced step-by-step in each chapter

    Who This Book Is For

    If you want to create great graphical user interfaces and astonishing games with Qt, this book is ideal for you. Any previous knowledge of Qt is not required, however knowledge of C++ is mandatory.

    What You Will Learn

    - Install Qt on your system
    - Understand the basic concepts of every Qt game and application
    - Develop 2D object-oriented graphics using Qt Graphics View
    - Build multiplayer games or add a chat function to your games with Qt's Network module
    - Script your game with Qt Script
    - Program resolution-independent and fluid UI using QML and Qt Quick
    - Control your game flow as per the sensors of a mobile device
    - See how to test and debug your game easily with Qt Creator and Qt Test

    In Detail

    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.

    Style and approach

    This is an easy-to-follow, example-based, comprehensive introduction to all the major features in Qt. The content of each chapter is explained and organized around one or multiple simple game examples to learn Qt in a fun way.
    LanguageEnglish
    PublisherPackt Publishing
    Release dateJan 29, 2016
    ISBN9781782168881
    Game Programming Using Qt: Beginner's Guide

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      Book preview

      Game Programming Using Qt - Wysota Witold

      Table of Contents

      Game Programming Using Qt

      Credits

      About the Authors

      About the Reviewers

      www.PacktPub.com

      Support files, eBooks, discount offers, and more

      Why subscribe?

      Free access for Packt account holders

      Preface

      What this book covers

      What you need for this book

      Who this book is for

      Sections

      Time for action – heading

      What just happened?

      Pop quiz – heading

      Have a go hero – heading

      Conventions

      Reader feedback

      Customer support

      Downloading the example code

      Downloading the color images of this book

      Errata

      Piracy

      Questions

      1. Introduction to Qt

      The cross-platform programming

      What just happened?

      Qt Platform Abstraction

      Supported platforms

      A journey through time

      New in Qt 5

      Restructured codebase

      Qt Essentials

      Qt Add-ons

      Qt Quick 2.0

      Meta-objects

      C++11 support

      Choosing the right license

      An open source license

      A commercial license

      Summary

      2. Installation

      Installing the Qt SDK

      Time for action – installing Qt using an online installer

      What just happened?

      Setting up Qt Creator

      Time for action – loading an example project

      What just happened?

      Time for action – running the Affine Transformations project

      What just happened?

      Building Qt from sources

      Time for action – setting up Qt sources using Git

      What just happened?

      Time for action – configuring and building Qt

      What just happened?

      Summary

      3. Qt GUI Programming

      Windows and dialogs

      Creating a Qt project

      Time for action – creating a Qt Desktop project

      What just happened?

      Adding child widgets to a window

      Managing widget content

      Time for action – implementing a tic-tac-toe game board

      What just happened?

      Qt meta-objects

      Signals and slots

      Pop quiz – making signal-slot connections

      Time for action – functionality of a tic-tac-toe board

      Properties

      Declaring a property

      Using a property

      Time for action – adding properties to the board class

      What just happened?

      Designing GUIs

      Time for action – designing the game configuration dialog

      What just happened?

      Time for action – polishing the dialog

      Accelerators and label buddies

      The tab order

      Signals and slots

      What just happened?

      Using designer forms

      Direct approach

      The multiple-inheritance approach

      The single inheritance approach

      Time for action – the logic of the dialog

      An application's main window

      The Qt resource system

      Time for action – the main window of the application

      What just happened?

      Time for action – adding a pull-down menu

      What just happened?

      Time for action – creating a toolbar

      What just happened?

      Time for action – filling in the central widget

      What just happened?

      Time for action – putting it all together

      What just happened?

      Have a go hero – extending the game

      Pop quiz – using widgets

      Summary

      4. Qt Core Essentials

      Text handling

      Manipulating strings

      Encoding and decoding text

      Basic string operations

      The string search and lookup

      Dissecting strings

      Converting between numbers and strings

      Using arguments in strings

      Regular expressions

      Time for action – a simple quiz game

      What just happened?

      Extracting information out of a string

      Finding all pattern occurrences

      Data storage

      Files and devices

      Traversing directories

      Getting access to the basic file

      Devices

      Time for action – implementing a device to encrypt data

      What just happened?

      Have a go hero – a GUI for the Caesar cipher

      Text streams

      Data serialization

      Binary streams

      Time for action – serialization of a custom structure

      What just happened?

      XML streams

      Time for action – implementing an XML parser for player data

      What just happened?

      Have a go hero – an XML serializer for player data

      JSON files

      Time for action – the player data JSON serializer

      Time for action – implementing a JSON parser

      What just happened?

      QSettings

      Pop quiz – Qt core essentials

      Summary

      5. Graphics with Qt

      Raster painting

      Painter attributes

      Widget painting

      Time for action – custom-painted widgets

      What just happened?

      Time for action – transforming the viewport

      What just happened?

      Time for action – drawing an oscillogram

      Input events

      Time for action – making oscillograms selectable

      Have a go hero – reacting only to the left mouse button

      Working with images

      Loading

      Modifying

      Painting

      Painting text

      Static text

      Rich text

      Optimized drawing

      Time for action – optimizing oscillogram drawing

      What just happened?

      Have a go hero – implementing a double-buffered oscillogram

      Time for action – developing the game architecture

      What just happened?

      Time for action – implementing the game board class

      What just happened?

      Time for action – understanding the ChessView class

      What just happened?

      Time for action – rendering the pieces

      What just happened?

      Time for action – making the chess game interactive

      What just happened?

      Time for action – connecting the game algorithm

      What just happened?

      Have a go hero – implementing the UI around the chess board

      Have a go hero – connecting a UCI-compliant chess engine

      OpenGL

      Introduction to OpenGL with Qt

      Time for action – drawing a triangle using Qt and OpenGL

      Time for action – scene-based rendering

      What just happened?

      Time for action – drawing a textured cube

      Have a go hero – animating a cube

      Modern OpenGL with Qt

      Shaders

      Time for action – shaded objects

      GL buffers

      Off-screen rendering

      Summary

      6. Graphics View

      Graphics View architecture

      Items

      Parent child relationship

      Appearance

      Time for action – creating a black, rectangular item

      What just happened?

      Time for action – reacting to an item's selection state

      What just happened?

      Time for action – making the item's size definable

      What just happened?

      Have a go hero – customizing the item

      Standard items

      Coordinate system of the items

      Time for action – creating items with different origins

      What just happened?

      Time for action – rotating an item

      What just happened?

      Have a go hero – applying multiple transformations

      Scenes

      Adding items to the scene

      Time for action – adding an item to a scene

      What just happened?

      Interacting with items on the scene

      Rendering

      Time for action – rendering the scene's content to an image

      What just happened?

      Have a go hero – rendering only specific parts of a scene

      Coordinate system of the scene

      Time for action – transforming parent items and child items

      What just happened?

      Have a go hero – playing with the z value

      View

      Time for action – putting it all together!

      What just happened?

      Showing specific areas of the scene

      Transforming the scene

      Time for action – creating an item where transformations can easily be seen

      What just happened?

      Time for action – implementing the ability to scale the scene

      What just happened?

      Time for action – implementing the ability to move the scene

      What just happened?

      Time for action – taking the zoom level into account

      What just happened?

      Questions you should keep in mind

      The jumping elephant or how to animate the scene

      The game play

      The player item

      Time for action – creating an item for Benjamin

      What just happened?

      The playing field

      The scene

      Time for action – making Benjamin move

      What just happened?

      Parallax scrolling

      Time for action – moving the background

      What just happened?

      Have a go hero – adding new background layers

      QObject and items

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

      Property animations

      Time for action – using animations to move items smoothly

      What just happened?

      Have a go hero – letting the scene handle Benjamin's jump

      Time for action – keeping multiple animations in sync

      What just happened?

      Item collision detection

      Time for action – making the coins explode

      What just happened?

      Setting up the playing field

      Have a go hero – extending the game

      A third way of animation

      Widgets inside Graphics View

      Optimization

      A binary space partition tree

      Caching the item's paint function

      Optimizing the view

      Pop quiz – mastering Graphics View

      Summary

      7. Networking

      QNetworkAccessManager

      Downloading files over HTTP

      Time for action – downloading a file

      Have a go hero – extending the basic file downloader

      Error handling

      Time for action – displaying a proper error message

      Downloading files over FTP

      Downloading files in parallel

      The finished signal

      Time for action – writing the OOP conform code using QSignalMapper

      What just happened?

      The error signal

      The readyRead signal

      The downloadProgress method

      Time for action – showing the download progress

      What just happened?

      Using a proxy

      Connecting to Google, Facebook, Twitter, and co.

      Time for action – using Google's Distance Matrix API

      Time for action – constructing the query

      Time for action – parsing the server's reply

      Have a go hero – choosing XML as the reply's format

      Controlling the connectivity state

      QNetworkConfigurationManager

      QNetworkConfiguration

      QNetworkSession

      QNetworkInterface

      Communicating between games

      Time for action – realizing a simple chat program

      The server – QTcpServer

      Time for action – setting up the server

      What just happened?

      Time for action – reacting on a new pending connection

      What just happened?

      Time for action – forwarding a new message

      Have a go hero – using QSignalMapper

      Time for action – detecting a disconnect

      What just happened?

      The client

      Time for action – setting up the client

      What just happened?

      Time for action – receiving text messages

      Time for action – sending text messages

      Have a go hero – extending the chat with a user list

      Improvements

      Using UDP

      Time for action – sending a text via UDP

      Have a go hero – connecting players of the Benjamin game

      Pop quiz – test your knowledge

      Summary

      8. Scripting

      Why script?

      The basics of Qt Script

      Evaluating JavaScript expressions

      Time for action – creating a Qt Script editor

      What just happened?

      Time for action – sandboxed script evaluation

      What just happened?

      Integrating Qt and Qt Script

      Exposing objects

      Time for action – employing scripting for npc AI

      What just happened?

      Have a go hero – extending the Dungeons & Dragons game

      Exposing functions

      Exposing C++ functions to scripts

      Exposing script functions to C++

      Time for action – storing the script

      What just happened?

      Time for action – providing an initialization function

      What just happened?

      Time for action – implementing the heartbeat event

      What just happened?

      Have a go hero – defending against attacks

      Using signals and slots in scripts

      Have a go hero – triggering defense using signals and slots

      Creating Qt objects in scripts

      Error recovery and debugging

      Extensions

      The other Qt JavaScript environment

      Alternatives to JavaScript

      Python

      Time for action – writing a Qt wrapper for embedding Python

      What just happened?

      Time for action – converting data between C++ and Python

      What just happened?

      Have a go hero – implementing the remaining conversions

      Time for action – calling functions and returning values

      What just happened?

      Have a go hero – wrapping Qt objects into Python objects

      Pop quiz – scripting

      Summary

      9. Qt Quick Basics

      Fluid user interfaces

      Declarative UI programming

      Element properties

      Group properties

      Object hierarchies

      Time for action – creating a button component

      What just happened?

      Time for action – adding button content

      What just happened?

      Time for action – sizing the button properly

      What just happened?

      Time for action – making the button a reusable component

      What just happened?

      Event handlers

      Mouse input

      Time for action – making the button clickable

      What just happened?

      Time for action – visualizing button states

      What just happened?

      Time for action – notifying the environment about button states

      What just happened?

      Touch input

      Time for action – dragging an item around

      What just happened?

      Time for action – rotating and scaling a picture by pinching

      What just happened?

      Have a go hero – rotating and scaling with a mouse

      Keyboard input

      Have a go hero – practicing key-event propagation

      Using components in Qt Quick

      Time for action – a simple analog clock application

      What just happened?

      Time for action – adding needles to the clock

      What just happened?

      Time for action – making the clock functional

      What just happened?

      Dynamic objects

      Using components in detail

      Creating objects on request

      Delaying item creation

      Accessing your item's component functionality

      Imperative painting

      Time for action – preparing Canvas for heartbeat visualization

      What just happened?

      Time for action – drawing a heartbeat

      What just happened?

      Time for action – making the diagram more colorful

      What just happened?

      Qt Quick and C++

      Creating QML objects from C++

      Pulling QML objects to C++

      Pushing C++ objects to QML

      Time for action – self-updating car dashboard

      What just happened?

      Time for action – grouping engine properties

      What just happened?

      Extending QML

      Registering classes as QML elements

      Time for action – making CarInfo instantiable from QML

      What just happened?

      Custom Qt Quick items

      OpenGL items

      Time for action – creating a regular polygon item

      What just happened?

      Have a go hero – creating a supporting border for RegularPolygon

      Painted items

      Time for action – creating an item for drawing outlined text

      What just happened?

      Summary

      10. Qt Quick

      Bringing life into static user interfaces

      Animating elements

      Generic animations

      Time for action – scene for an action game

      What just happened?

      Time for action – animating the sun's horizontal movement

      What just happened?

      Composing animations

      Time for action – making the sun rise and set

      What just happened?

      Non-linear animations

      Time for action – improving the path of the sun

      What just happened?

      Property value sources

      Time for action – adjusting the sun's color

      What just happened?

      Time for action – furnishing sun animation

      What just happened?

      Have a go hero – animating the sun's rays

      Behaviors

      Time for action – animating the car dashboard

      What just happened?

      States and transitions

      More animation types

      Quick game programming

      Game loops

      Time for action – character navigation

      What just happened?

      Time for action – another approach to character navigation

      What just happened?

      Have a go hero – polishing the animation

      Time for action – generating coins

      What just happened?

      Sprite animation

      Time for action – implementing simple character animation

      What just happened?

      Time for action – animating characters using sprites

      What just happened?

      Time for action – adding jumping with sprite transitions

      What just happened?

      Have a go hero – making Benjamin wiggle his tail in anticipation

      Parallax scrolling

      Time for action – revisiting parallax scrolling

      What just happened?

      Have a go hero – vertical parallax sliding

      Collision detection

      Time for action – collecting coins

      What just happened?

      Notes on collision detection

      Eye candy

      Auto-scaling user interfaces

      Graphical effects

      Have a go hero – the blur parallax scrolled game view

      Particle systems

      Tuning the emitter

      Rendering particles

      Making particles move

      Time for action – vanishing coins spawning particles

      What just happened?

      Summary

      A. Pop Quiz Answers

      Chapter 3, Qt GUI Programming

      Pop quiz – making signal-slot connections

      Pop quiz – using widgets

      Chapter 4, Qt Core Essentials

      Pop quiz – Qt core essentials

      Chapter 6, Graphics View

      Pop quiz – mastering Graphics View

      Chapter 7, Networking

      Pop quiz – testing your knowledge

      Chapter 8, Scripting

      Pop quiz – scripting

      Chapter 11, Miscellaneous and Advanced Concepts

      Pop quiz – testing your knowledge

      Index

      Game Programming Using Qt

      Game Programming Using Qt

      Copyright © 2016 Packt Publishing

      All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

      Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the authors, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

      Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

      First published: January 2016

      Production Reference: 1210116

      Published by Packt Publishing Ltd.

      Livery Place

      35 Livery Street

      Birmingham B3 2PB, UK.

      ISBN 978-1-78216-887-4

      www.packtpub.com

      Credits

      Authors

      Witold Wysota

      Lorenz Haas

      Reviewers

      Simone Angeloni

      Rahul De

      Pooya Eimandar

      Shaveen Kumar

      M. Cihan Özer

      Acquisition Editor

      Vinay Argekar

      Content Development Editor

      Pooja Mhapsekar

      Technical Editor

      Mrunmayee Patil

      Copy Editor

      Neha Vyas

      Project Coordinator

      Sanjeet Rao

      Proofreader

      Safis Editing

      Indexer

      Monica Ajmera Mehta

      Graphics

      Disha Haria

      Jason Monterio

      Production Coordinator

      Conidon Miranda

      Cover Work

      Conidon Miranda

      About the Authors

      Witold Wysota is a software architect and developer living in Poland. He started his adventure with Qt in 2004 when he joined QtForum.org and started answering questions about programming with Qt. Shortly afterwards, he became part of the moderator group of the forum. In 2006, together with the moderator team, he established QtCentre.org, which quickly became the largest community-driven support site devoted to Qt. For a number of years, he conducted commercial, academic, and public trainings and workshops and has been giving lectures on Qt, Qt Quick, and related technologies. He is a certified Qt developer and was a member of Qt Education Advisory Board with Nokia, where he helped prepare materials in order to use Qt in educational activities.

      Witold was also a technical reviewer for Foundations of Qt Development, Johan Thelin, Apress Publishing, a book about Qt 4, and an author of a couple of articles on programming with Qt.

      In real life, he is a passionate adept of Seven Star Praying Mantis, a traditional style of Chinese martial arts.

      I would like to thank all the people who have worked on Qt's development over the years for creating such a great programming framework, which was the main force that helped me to shape my programming career.

      I would also like to thank Lorenz for helping me with the book as well as the team at Packt Publishing for having a magnitude of patience for me during the process of the creation of this book.

      Lorenz Haas is a passionate programmer who started his Qt career with Qt 3. Thrilled by Qt's great community, especially the one at QtCentre.org, he immersed himself in this framework, became one of the first certified Qt developers and specialists, and turned his love for Qt into his profession.

      Lorenz is now working at a medium-sized IT company based in Erlangen, Germany, as a lead software architect. He mainly develops machine controls and their user interfaces as well as general solutions for the industry sector. Additionally, he runs his own small consultancy and programming business called Histomatics (http://www.histomatics.de).

      A few years ago, he started contributing to Qt Creator. He added a couple of refactoring options that you probably rely on a regular basis if you use Qt Creator. He is also the author of the Beautifier plugin.

      I would like to thank Witold who guided me through my first steps into the Qt world back in the days and who still assists me with any problems that arise. I am also very grateful to him for taking me on board for this book writing project. He's an excellent teacher and tutor!

      Secondly, I would like to thank the team at Packt Publishing, who helped and guided us through the entire process of writing this book.

      About the Reviewers

      Simone Angeloni is a software developer and consultant with over a decade of experience in C++ and scripting languages. He is a passionate gamer, but an even more passionate modder and game designer.

      He is currently working for Crytek GmbH and developing the UI of the free-to-play, award-winning video game Warface. Before this, he was realizing configuration systems for railway signaling and creating standalone applications with Qt. Later, he worked with universities and the National Institute of Nuclear Physics to realize fast data acquisition for particle accelerators.

      Recently, he founded Clockwise Interactive, a game company that is currently working on the production of its first title.

      Rahul De is a 23-year-old systems and server-side engineer from Kolkata, India. He recently graduated from the Vellore Institute of Technology with a bachelor of technology degree in computer science and now works with ThoughtWorks. Being a tech and open source enthusiast and a proper geeks geek, Rahul took up programming at a very young age and quickly matured from developing small-time native applications for desktops to maintaining servers, writing compilers, building IDEs, and enhancing Qt. His latest pet projects involve Medusa—a JIT compiler for Python using Qt, which aims to provide up to a 1500 percent boost for Python projects.

      Being an avid gamer, he has already dabbled quite a bit with various engines such as Unreal and Cry. He likes to play and develop games in his spare time.

      Pooya Eimandar was born on 7th January 1986. He graduated in computer science and has a hardware engineering degree from Shomal University. He is also the author of DirectX 11.1 Game Programming, Packt Publishing.

      He began his career working on various 3D simulation applications. In 2010, he founded BaziPardaz Game Studio, and since then, he has been leading an open source game engine (https://persianengine.codeplex.com/) at Bazipardaz.

      He is currently working on a playout and CG editor tool for Alalam News Network. You can find more information about him at http://PooyaEimandar.com/.

      Shaveen Kumar is a computer scientist and engineer. He graduated from Carnegie Mellon University in 2013 with a master's degree in entertainment technology and is working at Google. He works there as a graphics engineer and technical artist. His main interests are in GPU programming, parallel computing, game engine development, robotics, and computer vision.

      More information about his work can be found at http://www.shaveenk.com.

      M. Cihan Özer is a game developer and researcher in computer graphics. He started his career in game development and worked for several mobile and game companies.

      He got his bachelor's degree from Ankara University, Turkey, and he is currently an MS student at Université de Montréal, Canada. Cihan's work focuses on realistic rendering and interactive techniques.

      I would like to thank the authors of this book. It will help a lot of people who want to learn Qt and work with it. Also, I would like to thank the great people at Packt Publishing for giving me the opportunity to review this book.

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      Preface

      As a leading cross-platform toolkit for all significant desktop, mobile, and embedded platforms, Qt is becoming more popular by the day. This book will help you learn the nitty-gritty of Qt and will equip you with the necessary toolsets to build apps and games. This book is designed as a beginner's guide to take programmers that are new to Qt from the basics, such as objects, core classes, widgets, and so on, and new features in version 5.4, to a level where they can create a custom application with best practices when it comes to programming with Qt.

      With a brief introduction on how to create an application and prepare a working environment for both desktop and mobile platforms, we will dive deeper into the basics of creating graphical interfaces and Qt's core concepts of data processing and display before you try to create a game. As you progress through the chapters, you'll learn to enrich your games by implementing network connectivity and employing scripting. Delve into Qt Quick, OpenGL, and various other tools to add game logic, design animation, add game physics, and build astonishing UIs for games. Toward the end of this book, you'll learn to exploit mobile device features, such as accelerators and sensors, to build engaging user experiences.

      What this book covers

      Chapter 1, Introduction to Qt, will familiarize you with the standard behavior that is required when creating cross-platform applications as well as show you a bit of history of Qt and how it evolved over time with an emphasis on the most recent architectural changes in Qt.

      Chapter 2, Installation, will guide you through the process of installing a Qt binary release for desktop platforms, setting up the bundled IDE, and looking at various configuration options related to cross-platform programming.

      Chapter 3, Qt GUI Programming, will show you how to create classic user interfaces with the Qt Widgets module. It will also familiarize you with the process of compiling applications using Qt.

      Chapter 4, Qt Core Essentials, will familiarize you with the concepts related to data processing and display in Qt—file handling in different formats, Unicode text handling and displaying user-visible strings in different languages, and regular expression matching.

      Chapter 5, Graphics with Qt, describes the whole mechanism related to creating and using graphics in Qt in 2D and 3D. It also presents multimedia capabilities for audio and video (capturing, processing, and output)

      Chapter 6, Graphics View, will familiarize you with 2D-object-oriented graphics in Qt. You will learn how to use built-in items to compose the final results as well as create your own items supplementing what is already available and possibly animate them.

      Chapter 7, Networking, will demonstrate the IP networking technologies that are available in Qt. It will teach you how to connect to TCP servers, implement a reliable server using TCP, and implement an unreliable server using UDP.

      Chapter 8, Scripting, shows you the benefits of scripting in applications. It will teach you how to employ a scripting engine for a game by using JavaScript. It will also suggest some alternatives to JavaScript for scripting that can be easily integrated with Qt.

      Chapter 9, Qt Quick Basics, will teach you to program resolution-independent fluid user interfaces using a QML declarative engine and Qt Quick 2 scene graph environment. In addition, you will learn how to implement new graphical items in your scenes.

      Chapter 10, Qt Quick, will show you how to bring dynamics to various aspects of a UI. You will see how to create fancy graphics and animations in Qt Quick by using the particle engine, GLSL shaders and built-in animation, and state machine capabilities, and you will learn how to use these techniques in games.

      Chapter 11, Miscellaneous and Advanced Concepts, covers the important aspects of Qt programming that didn't make it into the other chapters but may be important for game programming. This chapter is available online at the link https://www.packtpub.com/sites/default/files/downloads/Advanced_Concepts.pdf.

      What you need for this book

      All you need for this book is a Windows machine with the latest version of Qt installed. The examples presented in this book are based on Qt 5.4.

      Qt can be downloaded from http://www.qt.io/download-open-source/.

      Who this book is for

      The expected readers of this book will be application and UI developers/programmers who have basic/intermediate functional knowledge of C++. The target audience also includes C++ programmers. No previous experience with Qt is required for you to read this book. Developers with up to a year of Qt experience will also benefit from the topics covered in this book.

      Sections

      In this book, you will find several headings that appear frequently (Time for action, What just happened?, Pop quiz, and Have a go hero).

      To give clear instructions on how to complete a procedure or task, we use these sections as follows:

      Time for action – heading

      Action 1

      Action 2

      Action 3

      Instructions often need some extra explanation to ensure they make sense, so they are followed with these sections:

      What just happened?

      This section explains the working of the tasks or instructions that you have just completed.

      You will also find some other learning aids in the book, for example:

      Pop quiz – heading

      These are short multiple-choice questions intended to help you test your own understanding.

      Have a go hero – heading

      These are practical challenges that give you ideas to experiment with what you have learned.

      Conventions

      You will also find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

      Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: This API is centered on QNetworkAccessManager, which handles the complete communication between your game and the Internet.

      A block of code is set as follows:

      QNetworkRequest request;

      request.setUrl(QUrl(http://localhost/version.txt));

      request.setHeader(QNetworkRequest::UserAgentHeader, MyGame);

      m_nam->get(request);

      When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

      void FileDownload::downloadFinished(QNetworkReply *reply) {   const QByteArray content = reply->readAll();

       

        m_edit->setPlainText(content);

        reply->deleteLater();

       

      }

      Any command-line input or output is written as follows:

      git clone git://code.qt.io/qt/qt5.git cd qt5 perl init-repository

      New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: On the Select Destination Location screen, click on Next to accept the default destination.

      Note

      Warnings or important notes appear in a box like this.

      Tip

      Tips and tricks appear like this.

      Reader feedback

      Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of.

      To send us general feedback, simply e-mail <[email protected]>, and mention the book's title in the subject of your message.

      If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide at www.packtpub.com/authors.

      Customer support

      Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

      Downloading the example code

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      Downloading the color images of this book

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      Errata

      Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you could report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting http://www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded to our website or added to any list of existing errata under the Errata section of that title.

      To view the previously submitted errata, go to https://www.packtpub.com/books/content/support and enter the name of the book in the search field. The required information will appear under the Errata section.

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      Questions

      If you have a problem with any aspect of this book, you can contact us at <[email protected]>, and we will do our best to address the problem.

      Chapter 1. Introduction to Qt

      In this chapter, you will learn what Qt is and how it evolved. We will pay special attention to the differences between Qt's major versions 4 and 5. Finally, you will learn to decide on which of the available Qt licensing schemes to choose for our projects.

      The cross-platform programming

      Qt is an application programming framework that is used to develop cross-platform applications. What this means is that software written for one platform can be ported and executed on another platform with little or no effort. This is obtained by limiting the application source code to a set of calls to routines and libraries available to all the supported platforms, and by delegating all tasks that may differ between platforms (such as drawing on the screen and accessing system data or hardware) to Qt. This effectively creates a layered environment (as shown in the following figure), where Qt hides all platform-dependent aspects from the application code:

      Of course, at times we need to use some functionality that Qt doesn't provide. In such situations, it is important to use conditional compilation like the one used in the following code:

      #ifdef Q_OS_WIN32

      // Windows specific code

      #elif defined(Q_OS_LINUX) || defined(Q_OS_MAC)

      // Mac and Linux specific code

      #endif

      Tip

      Downloading the example code

      You can download the example code files from your account at http://www.packtpub.com for all the Packt Publishing books you have purchased. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register there to have the files e-mailed directly to you.

      What just happened?

      Before the code is compiled, it is first fed to a preprocessor that may change the final text that is going to be sent to a compiler. When it encounters a #ifdef directive, it checks for the existence of a label that will follow (such as Q_OS_WIN32), and only includes a block of code in compilation if the label is defined. Qt makes sure to provide proper definitions for each system and compiler so that we can use them in such situations.

      Tip

      You can find a list of all such macros in the Qt reference manual under the term QtGlobal.

      Qt Platform Abstraction

      Qt itself is separated into two layers. One is the core Qt functionality that is implemented in a standard C++ language, which is essentially platform-independent. The other is a set of small plugins that implement a so-called Qt Platform Abstraction (QPA) that contains all the platform-specific code related to creating windows, drawing on surfaces, using fonts, and so on. Therefore, porting Qt to a new platform in practice boils down to implementing the QPA plugin for it, provided the platform uses one of the supported standard C++ compilers. Because of this, providing basic support for a new platform is work that can possibly be done in a matter of hours.

      Supported platforms

      The framework is available for a number of platforms, ranging from classical desktop environments through embedded systems to mobile phones. The following table lists down all the platforms and compiler families that Qt supports at the time of writing. It is possible that when you are reading this, a couple more rows could have been added to this table:

      A journey through time

      The development of Qt was started in 1991 by two Norwegians—Eirik Chambe-Eng and Haavard Nord, who were looking to create a cross-platform GUI programming toolkit. The first commercial client of Trolltech (the company that created the Qt toolkit) was the European Space Agency. The commercial use of Qt helped Trolltech sustain further development. At that time, Qt was available for two platforms—Unix/X11 and Windows; however, developing with Qt for Windows required buying a proprietary license, which was a significant drawback in porting the existing Unix/Qt applications.

      A major step forward was the release of Qt Version 3.0 in 2001, which saw the initial support for Mac as well as an option to use Qt for Unix and Mac under a liberal GPL license. Still, Qt for Windows was only available under a paid license. Nevertheless, at that time, Qt had support for all the important players in the market—Windows, Mac, and Unix desktops, with Trolltech's mainstream product and Qt for embedded Linux.

      In 2005, Qt 4.0 was released, which was a real breakthrough for a number of reasons. First, the Qt API was completely redesigned, which made it cleaner and more coherent. Unfortunately, at the same time, it made the existing Qt-based code incompatible with 4.0, and many applications needed to be rewritten from scratch or required much effort to be adapted to the new API. It was a difficult decision, but from the time perspective, we can see it was worth it. Difficulties caused by changes in the API were well countered by the fact that Qt for Windows was finally released under GPL. Many optimizations were introduced that made Qt significantly faster. Lastly, Qt, which was a single library until now, was divided into a number of modules:

      This allowed programmers to only link to the functionality that they used in their applications, reducing the memory footprint and dependencies of their software.

      In 2008, Trolltech was sold to Nokia, which at that time was looking for a software framework to help it expand and replace its Symbian platform in the future. The Qt community became divided, some people were thrilled, others worried after seeing Qt's development get transferred to Nokia. Either way, new funds were pumped into Qt, speeding up its progress and opening it for mobile platforms—Symbian and then Maemo and MeeGo.

      For Nokia, Qt was not considered a product of its own, but rather a tool. Therefore, they decided to introduce Qt to more developers by adding a very liberal LGPL license that allowed the usage of the framework for both open and closed source development.

      Bringing Qt to new platforms and less powerful hardware required a new approach to create user interfaces and to make them more lightweight, fluid, and eye candy. Nokia engineers working on Qt came up with a new declarative language to develop such interfaces—the Qt Modeling Language (QML) and a Qt runtime for it called Qt Quick.

      The latter became the primary focus of the further development of Qt, practically stalling all nonmobile-related work, channeling all efforts to make Qt Quick faster, easier, and more widespread. Qt 4 was already in the market for 7 years and it became obvious that another major version of Qt had to be released. It was decided to bring more engineers to Qt by allowing anyone to contribute to the project.

      Nokia did not manage to finish working on Qt 5.0. As a result of an unexpected turn over of Nokia toward different technology in 2011, the Qt division was sold in mid-2012 to the Finnish company Digia that managed to complete the effort and release Qt 5.0 in December of the same year.

      New in Qt 5

      The API of Qt 5 does not differ much from that of Qt 4. Therefore, Qt 5 is almost completely source compatible with its predecessor, which means that we only need a minimal effort to port the existing applications to Qt 5. This section gives a brief introduction to the major changes between versions 4 and 5 of Qt. If you are already familiar with Qt 4, this can serve as a small compendium of what you need to pay attention to if you want to use the features of Qt 5 to their fullest extent.

      Restructured codebase

      The biggest change compared to the previous major release of Qt and the one that is immediately visible when we try to build an older application against Qt 5 is that the whole framework was refactored into a different set of modules. Because it expanded over time and became harder to maintain and update for the growing number of platforms that it supported, a decision was made to split the framework into much smaller modules contained in two module groups—Qt Essentials and Qt Add-ons. A major decision relating to the split was that each module could now have its own independent release schedule.

      Qt Essentials

      The Essentials group contains modules that are mandatory to implement for every supported platform. This implies that if you are implementing your system using modules from this group only, you can be sure that it can be easily ported to any other platform that Qt supports. Some of the modules are explained as follows:

      The QtCore module contains the most basic Qt functionality that all other modules rely on. It provides support for event processing, meta-objects, data I/O, text processing, and threading. It also brings a number of frameworks such as the animation framework, the State Machine framework, and the plugin framework.

      The Qt GUI module provides basic cross-platform support to build user interfaces. It is much smaller compared with the same module from Qt 4, as the support for widgets and printing has been moved to separate modules. Qt GUI contains classes that are used to manipulate windows that can be rendered using either the raster engine (by specifying QSurface::RasterSurface as the surface type) or OpenGL (QSurface::OpenGLSurface). Qt supports desktop OpenGL as well as OpenGL ES 1.1 and 2.0.

      The Qt Network module brings support for IPv4 and IPv6 networking using TCP and UDP as well as by controlling the device connectivity state. Compared to Qt 4, this module improves IPv6 support, adds support for opaque SSL keys (such as hardware key devices) and UDP multicast, and assembles MIME multipart messages to be sent over HTTP. It also extends support for DNS lookups.

      Qt Multimedia allows programmers to access audio and video hardware (including cameras and FM radio) to record and play multimedia content.

      Qt SQL brings a framework that is used to manipulate SQL databases in an abstract way.

      Qt WebKit is a port of the WebKit 2 web browser engine to Qt. It provides classes to display and manipulate web content and integrates with your desktop application.

      Qt Widgets extends the GUI module with the ability to create a user interface using widgets, such as buttons, edit boxes, labels, data views, dialog boxes, menus, and toolbars that are arranged using a special layout engine. It also contains the implementation of

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