Warning: Experimental project

EPGI: Exotically Parallel Graphical Interface

epgi is a Rust library for building user interfaces.

epgi's design is heavily influenced by existing frameworks like React and Flutter.

• Declarative. Compose declarative widgets and the runtime will efficiently reconcile and update the tree.
• Component-based. Widgets are encapsulated with their own states. They can be re-used and composed into complex UIs.
• Hooks. All states and effects are managed by Hooks. (Similar to React Hook)
• Concurrency. The framework performs updates in a concurrent manner to avoid blocking. It provides both the Suspense APIs for IO-bound scenarios and the Transition APIs for CPU-bound scenarios.

Besides, the capabilities from the Rust language and its ecosystem enables us to move further.

• Parallel. epgi uses the rayon library to achieve maximum parallelism during every phases inside the pipeline, including building, layout, and painting.
• High performance. Hot paths are carefully written to minimize heap allocation, runtime polymorphism and locks.
• GPU-accelerated. The default 2D rendering backend, vello, is a Rust library with WebGPU-based 2D rendering.
• Static type safety. Widgets are bound by its protocol type. Mismatching two unrelated widget results in compile-time error.
• Extensibility and composability beyond 2D. The layout protocol can be easily extended to, and composite with, 3D scenes and TUIs.
• (Almost) Unsafe-free. The project witnessed a single-digit trivially-provable unsafe usages. We leave most of the optimizations in the hands of compilers for Safe Rust.

Project status

"Rocket science" demo

This demo showcases Suspense and Transition API. As well as explicit animation and implicit animation.

Hello.World.2024-07-06.23-57-10.mp4

"Bouncing blocks" demo

This demo tests parallel performance characteristics when rendering 40k interactive & animated widgets, to compare against a Flutter mimic.

Hello.World.2024-07-08.03-07-26.mp4

N_thread	build+layout(low, ms)	paint(low, ms)	raster(ms)	FPS(high)
1	31.9	9.0	1.5	20.3
2	19.8	9.2	1.4	28.5
4	12.4	8.9	1.5	37.6
8	8.4	9.1	1.5	45.1
16	7.0	9.5	1.4	47.4
Flutter Desktop	NA due to impl diff	~16	~28	16

*: Tested on 8-core Intel i7-12700K, Win 11. Built in release mode. Flutter desktop imitate app is built on profile mode.

**: Currently, paint phase is not parallelized

Objectives

Completed:

• A minimal example is running
• Sync parallel reconcilliation
• Provider and consumer
• Basic hook system
  • use_state, use_memo, use_effect, use_reducer
• Suspense and transition
• Async parallel reconcilliation
• Basic hit-test system
• Basic text widgets
• Basic layout widgets
• Prototype animation support

Planned:

• Documentation
• Tests
• Pointer interaction
• Keyboard
• Widget libraries
  • Material design

Organization of Repo

• epgi-core: Core functionalities to spin up epgi's scheduler and pipeline. Does not assume canvas type, backend, or embeddings.
• epgi-2d: Basic definitions and utilies for 2D affine canvas rendering. Default to use vello as backend.
• epgi-winit: Integrations to run epgi on winit.
• epgi-common: Basic widget library to enabling building a minimal 2D UI.
• epgi-material: Material design widget library for epgi.
• epgi-3d: Basic definitions and utilies for 3D rendering. Default to use bevy as backend.
• epgi: Re-export for common library users' convenience.
• epgi-glazier: Integrations to run epgi on glazier. (Abandoned following Xilem's decision)

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.