Book Image

Opa Application Development

By : Li Wenbo
Book Image

Opa Application Development

By: Li Wenbo

Overview of this book

Opa is a full-stack Open Source web development framework for JavaScript that lets you write secure and scalable web applications. It generates standard Node.js/MongoDB applications, natively supports HTML5 and CSS and automates many aspects of modern web application programming. It handles all aspects of web programming written in one consistent language and compiled to web standards.Opa Application Development is a practical,hands-on guide that provides you with a number of step-by-step exercises. It covers almost all aspects of developing a web application with Opa, which will help you take advantage of the real power of Opa, as well as building a secure, powerful web application rapidly.Opa Application Development dives into all concepts and components required to build a web application with Opa. The first half of this book shows you all of the basic building blocks that you will need to develop an Opa application, including the syntax of Opa, web development aspects, client and server communication and slicing, plugin, database, and so on. By the end of the book you will have yourself created a complete web application along with a game: Pacman!
Table of Contents (18 chapters)
Opa Application Development
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Drawing the text


To display texts on a canvas in Opa, we can use the Canvas.fill_text or Canvas.stroke_text method. We can change the fill style or stroke style by invoking Canvas.set_fill_style or Canvas.set_stroke_style respectively.

To set the font of the text, use the Canvas.set_font function. We should pass the font information to the method; the font information is a string matching the following pattern:

    [font-style] [font-weight] [font-size] [font-family]

The following code draws the word "start" twice, one is filled and the other is stroked, both with font information italic bold 40px verdana:

Canvas.set_fill_style(ctx,{color:Color.red})
Canvas.set_font(ctx,"italic bold 40px verdana")
Canvas.fill_text(ctx,"Start",5,50)
Canvas.set_stroke_style(ctx,{color:Color.red})
Canvas.set_line_width(ctx,2.0)
Canvas.stroke_text(ctx,"Start",200,50)

The result of the preceding code fragment is as follows: