Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By : Joel Lawhead
Book Image

QGIS Python Programming Cookbook, Second Edition - Second Edition

By: Joel Lawhead

Overview of this book

QGIS is a desktop geographic information system that facilitates data viewing, editing, and analysis. Paired with the most efficient scripting language—Python, we can write effective scripts that extend the core functionality of QGIS. Based on version QGIS 2.18, this book will teach you how to write Python code that works with spatial data to automate geoprocessing tasks in QGIS. It will cover topics such as querying and editing vector data and using raster data. You will also learn to create, edit, and optimize a vector layer for faster queries, reproject a vector layer, reduce the number of vertices in a vector layer without losing critical data, and convert a raster to a vector. Following this, you will work through recipes that will help you compose static maps, create heavily customized maps, and add specialized labels and annotations. As well as this, we’ll also share a few tips and tricks based on different aspects of QGIS.
Table of Contents (16 chapters)
QGIS Python Programming Cookbook - Second Edition
About the Author
About the Reviewer
Customer Feedback

Keeping dialogs on top

It's easy to lose track of windows that pop up in front of QGIS. As soon as the user changes focus to move the main QGIS application window, your dialog can disappear behind it, forcing the user to rearrange their whole desktop to find the smaller window again. Fortunately, Qt has a window setting called hint, which allows you to force a window to stay on top. This type of dialog is called a modal dialog. In this recipe, we'll create a message dialog using hint.

Getting ready

Open the QGIS Python console by selecting the Plugins menu and then clicking on Python Console.

How to do it...

In this recipe, we will create a simple message dialog and set it to stay on top, as follows:

  1. First, we import the Qt GUI and QGIS core libraries:

            from PyQt4.QtGui import * 
            from PyQt4.QtCore import * 
  2. Next, we create the text for our message:

            msg = "This window will always stay on top." 
  3. Now, we create our dialog and specify the message and hint: