Adding consistency to Kivy's Python UI tools
Kivy has a wonderful set of built-in widgets that can be extended in numerous ways. They have very useful behaviors, but their look and feel may not integrate well with your App or the platforms you are targeting. Kivy doesn’t support theming out of the box right now, but if you poke around enough, there are a range of options you can use to customize the default look of widgets without having to define your own inherited versions of them.
I’ll first introduce you to Kivy’s image atlases, which are less mysterious than they sound, and are important groundwork for understanding theming in Kivy. Then you’ll learn two different ways to do manual theming in Kivy, with an eye to future automation.
To understand theming, you must first understand atlases. An atlas is essentially a collection of distinct images combined into a single image file for loading efficiency. A JSON file describes the location of the separate images inside that master image file so that Kivy can access them directly. If you’ve ever worked with CSS sprites, you know exactly what I’m talking about. If you haven’t, the following example should explain everything.
Recharging the Python standard library
It’s unfortunate that the official About Python page still describes Python’s standard library as having “batteries included.” Sure, some of those old standbys will keep your project going and going, but many of them are leaking acid all over the place. Guido Van Rossum, head developer of Python, has said “the stdlib offerings … are not very convenient and may not support popular idioms very well.” Five years ago, I always assumed the Python library contained the “best of breed” for all packages. These days, I tend to think the opposite.
To counteract this minor flaw, I keep a small “personal standard library.” I keep a pip requirements file listing all the packages I use in every project. A simple script automatically installs that file whenever I create a virtualenv for a new project. With the pip download cache enabled, this is a near-painless process.