koreader/doc/Hacking.md

Hacking

Developing UI Widgets

If you need to create new UI widgets, utils/wbuilder.lua is your friend. 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.

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 your own UIManager:show show call at the end of utils/wbuilder.lua to test your new widget.