Table of Contents for
OpenLayers 3 : Beginner's Guide

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition OpenLayers 3 : Beginner's Guide by Erik Hazzard Published by Packt Publishing, 2015
  1. Cover
  2. Table of Contents
  3. OpenLayers 3 Beginner's Guide
  4. OpenLayers 3 Beginner's Guide
  5. Credits
  6. About the Authors
  7. About the Reviewers
  8. www.PacktPub.com
  9. Preface
  10. What you need for this book
  11. Who this book is for
  12. Sections
  13. Time for action – heading
  14. Conventions
  15. Reader feedback
  16. Customer support
  17. 1. Getting Started with OpenLayers
  18. Advantages of using OpenLayers
  19. What, technically, is OpenLayers?
  20. Anatomy of a web mapping application
  21. Connecting to Google, Bing Maps, and other mapping APIs
  22. Time for action – downloading OpenLayers
  23. Time for action – creating your first map
  24. Where to go for help
  25. OpenLayers issues
  26. OpenLayers source code repository
  27. Getting live news from RSS and social networks
  28. Summary
  29. 2. Key Concepts in OpenLayers
  30. Time for action – creating a map
  31. Time for action – using the JavaScript console
  32. Time for action – overlaying information
  33. OpenLayers' super classes
  34. Key-Value Observing with the Object class
  35. Time for action – using bindTo
  36. Working with collections
  37. Summary
  38. 3. Charting the Map Class
  39. Time for action – creating a map
  40. Map renderers
  41. Time for action – rendering a masterpiece
  42. Map properties
  43. Time for action – target practice
  44. Map methods
  45. Time for action – creating animated maps
  46. Events
  47. Views
  48. Time for action – linking two views
  49. Summary
  50. 4. Interacting with Raster Data Source
  51. Layers in OpenLayers 3
  52. Common operations on layers
  53. Time for action – changing layer properties
  54. Tiled versus untiled layers
  55. Types of raster sources
  56. Tiled images' layers and their sources
  57. Time for action – creating a Stamen layer
  58. Time for action – creating a Bing Maps layer
  59. Time for action – creating tiles and adding Zoomify layer
  60. Image layers and their sources
  61. Using Spherical Mercator raster data with other layers
  62. Time For action – playing with various sources and layers together
  63. Time For action – applying Zoomify sample knowledge to a single raw image
  64. Summary
  65. 5. Using Vector Layers
  66. Time for action – creating a vector layer
  67. How the vector layer works
  68. The vector layer class
  69. Vector sources
  70. Time for action – using the cluster source
  71. Time for action – creating a loader function
  72. Time for action – working with the TileVector source
  73. Time for action – a drag and drop viewer for vector files
  74. Features and geometries
  75. Time for action – geometries in action
  76. Time for action – interacting with features
  77. Summary
  78. 6. Styling Vector Layers
  79. Time for action – basic styling
  80. The style class
  81. Time for action – using the icon style
  82. Have a go hero – using the circle style
  83. Multiple styles
  84. Time for action – using multiple styles
  85. Style functions
  86. Time for action – using properties to style features
  87. Interactive styles
  88. Time for action – creating interactive styles
  89. Summary
  90. 7. Wrapping Our Heads Around Projections
  91. Time for action – using different projection codes
  92. Time for action – determining coordinates
  93. OpenLayers projection class
  94. Transforming coordinates
  95. Time for action – coordinate transforms
  96. Time for action – setting up Proj4js.org
  97. Time for action – reprojecting extent
  98. Time for action – using custom projection with WMS sources
  99. Time for action – reprojecting geometries in vector layers
  100. Summary
  101. 8. Interacting with Your Map
  102. Time for action – converting your local or national authorities data into web mapping formats
  103. Time for action – testing the use cases for ol.interaction.Select
  104. Time for action – more options with ol.interaction.Select
  105. Introducing methods to get information from your map
  106. Time for action – understanding the forEachFeatureAtPixel method
  107. Time for action – understanding the getGetFeatureInfoUrl method
  108. Adding a pop-up on your map
  109. Time for action – introducing ol.Overlay with a static example
  110. Time for action – using ol.Overlay dynamically with layers information
  111. Time for action – using ol.interaction.Draw to share new information on the Web
  112. Time for action – using ol.interaction.Modify to update drawing
  113. Understanding interactions and their architecture
  114. Time for action – configuring default interactions
  115. Discovering the other interactions
  116. Time for action – using ol.interaction.DragRotateAndZoom
  117. Time for action – making rectangle export to GeoJSON with ol.interaction.DragBox
  118. Summary
  119. 9. Taking Control of Controls
  120. Adding controls to your map
  121. Time for action – starting with the default controls
  122. Controls overview
  123. Time for action – changing the default attribution styles
  124. Time for action – finding your mouse position
  125. Time for action – configuring ZoomToExtent and manipulate controls
  126. Creating a custom control
  127. Time for action – extending ol.control.Control to make your own control
  128. Summary
  129. 10. OpenLayers Goes Mobile
  130. Using a web server
  131. Time for action – go mobile!
  132. The Geolocation class
  133. Time for action – location, location, location
  134. The DeviceOrientation class
  135. Time for action – a sense of direction
  136. Debugging mobile web applications
  137. Debugging on iOS
  138. Debugging on Android
  139. Going offline
  140. Time for action – MANIFEST destiny
  141. Going native with web applications
  142. Time for action – track me
  143. Summary
  144. 11. Creating Web Map Apps
  145. Using geospatial data from Flickr
  146. Time for action – getting Flickr data
  147. A simple application
  148. Time for Action – adding data to your map
  149. Styling the features
  150. Time for action – creating a style function
  151. Creating a thumbnail style
  152. Time for action – switching to JSON data
  153. Time for action – creating a thumbnail style
  154. Turning our example into an application
  155. Time for action – adding the select interaction
  156. Time for action – handling selection events
  157. Time for action – displaying photo information
  158. Using real time data
  159. Time for action – getting dynamic data
  160. Wrapping up the application
  161. Time for action – adding dynamic tags to your map
  162. Deploying an application
  163. Creating custom builds
  164. Creating a combined build
  165. Time for action – creating a combined build
  166. Creating a separate build
  167. Time for action – creating a separate build
  168. Summary
  169. A. Object-oriented Programming – Introduction and Concepts
  170. Going further
  171. B. More details on Closure Tools and Code Optimization Techniques
  172. Introducing Closure Library, yet another JavaScript library
  173. Time for action – first steps with Closure Library
  174. Making custom build for optimizing performance
  175. Time for action – playing with Closure Compiler
  176. Applying your knowledge to the OpenLayers case
  177. Time for action - running official examples with the internal OpenLayers toolkit
  178. Time for action - building your custom OpenLayers library
  179. Syntax and styles
  180. Time for action – using Closure Linter to fix JavaScript
  181. Summary
  182. C. Squashing Bugs with Web Debuggers
  183. Time for action – opening Chrome Developer Tools
  184. Explaining Chrome Developer debugging controls
  185. Time for action – using DOM manipulation with OpenStreetMap map images
  186. Time for action – using breakpoints to explore your code
  187. Time for action – playing with zoom button and map copyrights
  188. Using the Console panel
  189. Time for action – executing code in the Console
  190. Time for action – creating object literals
  191. Time for action – interacting with a map
  192. Improving Chrome and Developer Tools with extensions
  193. Debugging in other browsers
  194. Summary
  195. D. Pop Quiz Answers
  196. Chapter 5, Using Vector Layers
  197. Chapter 7, Wrapping Our Heads Around Projections
  198. Chapter 8, Interacting with Your Map
  199. Chapter 9, Taking Control of Controls
  200. Chapter 10, OpenLayers Goes Mobile
  201. Appendix B, More details on Closure Tools and Code Optimization Techniques
  202. Appendix C, Squashing Bugs with Web Debuggers
  203. Index

Appendix B. More details on Closure Tools and Code Optimization Techniques

Closure Tools are a set of utilities used for web development. It is mainly supported by Google, but is open source under the Apache License Version 2.0, a well-established permissive license. The name Closure Tools hides under it a lot of subtools, which will make your life as an apprentice developer easier. It includes a JavaScript optimizer, a JavaScript library, a templating library, a style checker and style fixer, and at last, a stylesheet language. Just to illustrate how powerful this set can be, think that most Google JavaScript applications, such as Gmail or Google Maps, use these components.

Why are we introducing you to these tools?

The OpenLayers 3 library itself depends on the Closure Library, the JavaScript library attached to Closure Tools. Its main goal is to leverage cross-browser support. You also know you can write your application in pure JavaScript.

However, you can also consider Closure for advanced uses like creating your own component such as controls and buttons with special behavior inherited from an existing OpenLayers component. You will also get some useful UI components. It is also a good toolset to achieve better file compression when you want an efficient web mapping application, using the Closure Compiler, another utility from the Closure Tools bundle.

We will not review all Closure Tools but only the most useful. Specifically, we will cover the following topics:

  • Understanding the Closure Tools concepts
  • How to use the Closure Library and a small review of the main components' families
  • Why Closure Compiler is different from others compiler tools
  • How to use it with Closure Library and with other JavaScript libraries. Application of Closure Tools in OpenLayers for improving our way of developing web-mapping applications
  • The use of the already hidden workflow in OpenLayers code that relies on Closure Tools
  • Best practices for creating readable code and how to detect and fix errors using both Closure style checker and style fixer

The Closure Tools philosophy

If you have ever done a bit of web development, and in particular, JavaScript, you must have heard about jQuery, the most popular JavaScript library with more than 50 percent of the worldwide websites using it. To not reinvent the wheel, the OpenLayers development team chose Closure Library rather than jQuery. Why was this decision made? For a better understanding, you need a bit of history of the Web.

Ensuring optimum performance

In the olden days, there wasn't a lot of JavaScript. All applications were created using simple HTML and CSS. There was dynamic content when reloading a full page using a server-side such as PHP or Java. However, people wanted a smoother web navigation experience. With the way AJAX works it was possible, as illustrated in the following figure, and people began to focus more and more on the client-side:

Ensuring optimum performance

The main two problems associated with this evolution are:

  • The more files you have, the more your browser will wait to display pages. The issue here comes from the processing cost to ask for the file, wait for it and then use it. This behavior is called latency. For example, imagine you are at the checkout counter at the supermarket; if ten clients buy one apple, the billing will take longer, than if one client buys ten apples.
  • The second drawback of this evolution is that browsers have to load more and more resources such as images, CSS, and JavaScript.
  • The bigger the files are, the longer it will take to retrieve and process the content. The main cause for this is the limited bandwidth. For example, when you are cooking pasta, the more water you put in, the longer you have to wait for the pasta to cook.

When you are at home, you don't really suffer from bandwidth restriction, but in other cases, you will always suffer from high latency. If you are planning to work on mobile support with limited bandwidth, high latency, and a browser with limited memory, it can be a pain.

A good part of the solution lies in compression.

You have three levels of compression available for JavaScript, depending on technology:

  • Combine without compacting all JavaScript in one file
  • Combine and compact all JavaScript in one file
  • Combine, compact, and obfuscate the code

For performance, the last method will work the best, and the Closure Library is the only JavaScript library able to work this way, when combined with Closure Compiler.

Closure Tools, in particular, Closure Library and Closure Compiler are among the best tools to deal with this case.

Although both tools are tightly related, we will review the most useful functions related to Google Closure Library and later explain how to use Closure Compiler to optimize code.