Objective

Make UI rendering optional.

Quite a few people have been experimenting with using Bevy UI for layout and interaction but replacing the rendering with bevy_prototype_lyon or whatever. It's awkward to do though as there is no way to disable the existing UI rendering requiring users to create their own custom node bundles and components. Also, you can't replace the UI's shader and a number of other things.

This PR makes the setup and initialization of UI rendering for the RenderApp optional. Then you can do whatever you want by replacing build_ui_render with your own function. For instance, one that loads a custom shader.

The UI layout and interaction components are still updated as normal.

Solution

Add a field enable_rendering to UiPlugin.
Only call build_ui_render and initialize the UiPipeline if enable_rendering is false.

I thought about implementing a "bevy_ui_render" feature but suspect everything is too tightly coupled atm and it would be very fragile. Similar to the struggles with the "bevy_text" feature but worse.

Changelog

UiPlugin

• Added a bool field enable_rendering.
• Only calls build_ui_render and initializes the UiPipeline if enable_rendering is true.

Migration Guide

UiPlugin has a new field enable_rendering. If set to false, the UI's rendering systems won't be added to the RenderApp and no UI elements will be drawn. The layout and interaction components will still be updated as normal.