6. Advanced Graphics – Shaders and Rendering | Kivy Cookbook

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Kivy Cookbook

By : Hugo Solis, Solis

2.5 (2)

Kivy Cookbook

2.5 (2)

By: Hugo Solis, Solis

Overview of this book

Kivy is an open-source Python library for rapid development of applications that make use of innovative user interfaces, such as multi-touch apps. It is a promising Python framework to develop UI and UX apps in a cross-platform environment, under the Python philosophy. Kivy Cookbook is a practical book that will guide you through the Kivy framework to develop apps and get your apps ready for distribution in App Store and Android devices. You will start off with installing Kivy and building your interfaces. You will learn how to work the accelerometer and create custom events. Then, you will understand how to use the basics, buttons, labels and text inputs and manipulate the widget tree. Next, you will be able to work with manipulating instructions, create an atlas and layouts. Moving on, you will learn packing for Windows and packing for iOS, and use TestDrive. By the end of the book, you will have learnt in detail the relevant features and tools in Kivy and how to create portable packages to distribute your apps in the most used platforms.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Conventions

Reader feedback

Customer support

Free Chapter

1. Kivy and the Kv Language

1. Kivy and the Kv Language

Introduction

Installing Kivy

Building your interfaces

Declaring properties within a class

Relating Python code and the Kv language

Referencing widgets

Accessing widgets defined inside the Kv language in your Python code

Reusing styles in multiple widgets

Designing with the Kv language

Running your code

Using Kivy garden

2. Input, Motion, and Touch

2. Input, Motion, and Touch

Introduction

Using the mouse

Evolving to the touchscreen

Working with the accelerometer

Using the gyroscope

The differences between the touch and motion events

Recognizing touch shapes

Detecting multitapping

Grabbing touch events

Recording gestures

3. Events

3. Events

Introduction

Scheduling a one-time event

Scheduling a repetitive event

Triggering events

Defining widget events

Creating custom events

Attaching callbacks

Declaring a property

Compounding properties

4. Widgets

4. Widgets

Introduction

Using the basics: buttons, labels, and text inputs

Manipulating the widget tree

Traversing the tree

Using swappable widgets

Organizing with layouts

Using FloatLayout

Using BoxLayout

Using GridLayout

Using StackLayout

Using RelativeLayout

Using AnchorLayout

Working with ActionBar

5. Graphics – Canvas and Instructions

5. Graphics – Canvas and Instructions

Introduction

Separating with the screen manager

Using drawing instructions

Using context instructions

Working with manipulating instructions

Rotating, translating, and scaling the canvas

Modifying with multitouching

Storing and retrieving the coordinate space context

Introducing animations

6. Advanced Graphics – Shaders and Rendering

6. Advanced Graphics – Shaders and Rendering

Introduction

Using Carousel

Creating and using Atlas

Creating layouts

Editing shaders

Creating widgets

Creating your own shader

Rendering in a Framebuffer

Optimizing graphics

7. The API in Detail

7. The API in Detail

Introduction

Getting to know the API

Using the asynchronous data loader

Logging objects

Parsing

Applying utils

Leveraging the factory object

Working with audio

Working with video

Working with a camera

Using spelling

Adding effects

Advanced text manipulation

8. Packaging our Apps for PC

8. Packaging our Apps for PC

Introduction

Packaging for Windows

Including multimedia for Windows

Running apps in Windows

Packaging for Mac OS

Including multimedia for Mac OS

Running apps in Mac OS

Packaging for Linux

Including multimedia for Linux

Running apps in Linux

9. Kivy for Mobile Devices

9. Kivy for Mobile Devices

Introduction

Packaging for iOS

Resizing the screen into iOS

Leveraging mobile features in iOS

Preparing for the App Store

Packaging for Android

Resizing the screen into Android

Leveraging mobile features in Android

Index

Index

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Creating widgets

Actually, this topic has been almost covered in the last chapters, but now we can give graphics to our widgets. The following recipe will create a widget where the user can create graphics ad lib. When the user performs a touch in the widget, the app will draw a yellow point, and if he maintains the touch and moves it, the app will draw a yellow path for the movement.

Getting ready

We are going to work with the touch directive in this recipe. It is useful to read Differencing between Touch and Motion events recipe in Chapter 2, Input, Motion, and Touch.

How to do it…

We are going to use just one Python file to complete the task where we will define the method of our created widget. Follow these steps of the recipe:

Import the usual Kivy packages.
Define the MyWidget class instanced as a widget.
Define the on_touch_down() callback for the class.
In the method, add canvas, Color, and Ellipse to the widget.
Also add the initial point of the line to be drawn.
Define the on_touch_move...

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