Pidili: a declarative Pillow-based display library for smartscreens

[hchargois]

I made a simple display library that tries to address the shortcomings of using the library/lcd's widgets that paint themselves directly to the screen.

It makes it easy to create a scene (widget tree) declaratively on every frame, and pass it to a renderer/differ combo that renders the scene and sends only the required patches to the screen efficiently.

Want to move a widget around? Just create it in a different location in the next scene, the library will figure out the patches that need to be painted. Want to remove a widget? Just omit it in the next scene, the library will figure it out. A widget changed size (e.g. a text widget with a smaller content), no big deal, the library will figure it out.

If you're familiar with React, or the Elm architecture, or immediate-mode UIs in general, that should make sense to you (and if not, I encourage you to go read up on these fascinating concepts).

The renderer itself is optimized to not re-render (to the internal buffer) widgets that don't change from one scene to the next. Moreover, the rendered buffer itself is diffed, i.e. at pixel level. This means that, for example, if a progress bar has changed from 49% to 51%, it will be re-rendered to the internal buffer, but only a small patch of pixels near the middle of the bar is sent to the screen, not the whole bar. Depending on the kind of widgets that are displayed, this can make the screen look very fast. See the video in the repo.

Here is the repo, check it out!

https://github.com/hchargois/pidili