koreader/doc/Hacking.md

Hacking

Developing UI Widgets

utils/wbuilder.lua is your friend, if you need to create new UI widgets. It sets up a minimal environment to bootstrap KOReader's UI framework to avoid starting the whole reader. This gives you quick feedback loop while iterating through your widget changes. It's also a handy tool for debugging widget issues.

To get a taste of how it works, try running this command at the root of KOReader's source tree:

./kodev wbuilder

It will spawn up an emulator window with a grid and simple timer widget for demonstration.

You can add more UIManager:show call at the end of utils/wbuilder.lua to test your new widgets.