Introduction
QGIS has been built using the comprehensive graphical user interface framework called Qt. Both QGIS and Qt have Python APIs. In this chapter, we'll learn how to interact with the user in order to collect and display information outside the default QGIS interface. Qt has excellent documentation of its own. Since QGIS is built on top of Qt, all of this documentation applies to QGIS. Note that it is now possible to build QGIS with Qt version 5, which has a different API. Most packaged distributions of QGIS use Qt4, which is the focus of this book. You can find the Qt documentation at https://www.qt.io/developers/.