Graphics Reference
In-Depth Information
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 be-
fore 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
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