Programming Python, Second Edition

Advanced GUI Coding Techniques

If you read Chapter 8, you know that the code used to construct non-trivial GUIs can become large if we make each widget by hand. Not only do we have to manually link up all the widgets, but there are dozens of options to be set and remember. If we stick to this strategy, GUI programming often becomes an exercise in typing, or at least in cut-and-paste text editor operations.

GuiMixin: Shared Behavior in “Mixin” Classes

Rather than doing each step by hand, a better idea is to wrap or automate as much of the GUI construction process as possible. One approach is to code functions that provide typical widget configurations; for instance, we could define a button function to handle configuration details and support most of the buttons we draw.

Alternatively, we can implement common methods in a class and inherit them everywhere they are needed. Such classes are commonly called mixin classes, because their methods are “mixed in” with other classes. Mixins serve to package generally useful tools as methods. The concept is almost like importing a module, but mixin classes can access the subject instance, self, to utilize per-instance state and inherited methods. The script in Example 9-1 shows how.

Example 9-1. PP2E\Gui\Tools\guimixin.py

######################################################## # a "mixin" class for other frames: common methods for # canned-dialogs, spawning programs, etc; must be mixed # with a class derived from Frame for its quit method ...