Book Image

Building Mapping Applications with QGIS

By : Erik Westra
Book Image

Building Mapping Applications with QGIS

By: Erik Westra

Overview of this book

Table of Contents (16 chapters)
Building Mapping Applications with QGIS
About the Author
About the Reviewers
Free Chapter
Getting Started with QGIS

Chapter 5. Using QGIS in an External Application

In Chapter 1, Getting Started with QGIS, we looked briefly at a standalone Python program built using PyQt and the PyQGIS library. In this chapter, we will use the same technique to build a complete turnkey mapping application using PyQGIS. Along the way, we will:

  • Design and build a simple but complete standalone mapping application

  • Learn how to use a wrapper script to handle the platform-specific dependencies before our Python program is run

  • Define our application's user interface in a separate Python module so that we keep our UI separate from the application's business logic

  • Dynamically show and hide map layers based on the user's preference

  • Learn how to use a rule-based renderer to selectively display features based on the map's current zoom level

  • See how data-defined properties can be used to calculate the font size to use for a label based on the feature's attributes

  • Implement Google Maps style panning and zooming