Blitz: A lightweight, modular, extensible web renderer

Blitz is a "native" HTML/CSS renderer built to support the "Dioxus Native" project. It is effectively a lightweight webview except that the JavaScript engine is replaced with a native Rust API which allows Rust reactivity / state management libraries like Dioxus to interface with it directly.

Talk to us in: the #native channel in the Dioxus Discord

It currenly has two frontends:

• An HTML/markdown frontend that can render an HTML string. This is useful for previewing HTML and/or markdown files but currently lacks interactivity.
• A Dioxus frontend that can render a Dioxus VirtualDom. This has full interactivity support via Dioxus's event handling.

Blitz builds upon:

• Stylo (Firefox's parallel browser-grade CSS engine) for CSS resolution
• Vello + WGPU for rendering
• Taffy for box-level layout
• Parley for text/inline-level layout
• AccessKit for accessibility
• Winit for windowing and input handling

Note: This repo contains a new version of Blitz which uses Stylo. The source code for the old version is still available on the legacy branch but is not under active development.

Screenshots

The Dioxus renderer:

The HTML renderer (rendering google.com):

Trying it out

1. Clone this repo
2. Run an example:
   • cargo run --example google
   • cargo run --example url https://myurl.com
   • Other example available
   • Add --release for better runtime performance
3. Press Ctrl/Cmd + + / Ctrl/Cmd + - to change the scaling, press F1 to show layout rectangles

Goals

Blitz is designed to render HTML and CSS - we don't want to support the entirety of browser features (or at least we want to make all such "extra" features opt-in). In our opinion, the browser is bloated for the basic usecase of rendering HTML/CSS.

We do intend to support:

• Modern HTML layout (flexbox, grid, table, block, inline, absolute/fixed, etc).
• Advanced CSS (complex selectors, media queries, css variables)
• HTML Form controls
• Accessibility using AccessKit
• Extensibility via custom widgets

Notably we don't provide features like webrtc, websockets, bluetooth, localstorage, etc. In a native app, much of this functionality can be fulfilled using regular Rust crates and doesn't need to be coupled with the renderer.

We don't yet have Blitz bindings for other languages (JavaScript, Python, etc) but would accept contributions along those lines.

Architecture

Blitz consists of a core DOM abstraction (blitz-dom), and several modular pieces which provide functionality like networking, rendering, windows, and state management. These pieces can be combined together to make a cohesive web engine.

Crates

Core:

• blitz-traits: Minimal crate containing types and traits to allow the other crates to interoperate without depending on each other
• blitz-dom: The core DOM abstraction that includes style resolution and layout but not drawing/painting. Combines the best of Stylo and Taffy that allows you to build extendable dom-like structures.

Modules:

• blitz-renderer-vello: Adds a Vello/WGPU based renderer to blitz-dom

• blitz-net: Networking that can fetch resources over http, from the file-system or from encoded data URIs.

• dioxus-native: This crate should contain just a dioxus integration layer for Blitz. However, it currently contains all of the following functionality:

  • DioxusDocument - A dioxus integration layer for Blitz
  • HtmlDocument - An HTML rendering layer for Blitz
  • Window - A winit-based "shell" for running Blitz applications in a window.

  These different parts will be split into separate crates in future.

Status

Blitz is currently experimental. We are actively working on bringing into a usable state but we would not yet recommend building apps with it.

TODO

• Core DOM tree abstraction
• Parse styles using html5ever
• Compute styles for html5ever document
• Compute layout with Taffy
• Render using WGPU

Rendering

• Render to window
• Render to image
• Gradients
• Border/Outline
• Raster images (png, jpeg, etc)
• Zoom
• SVG
  • External SVGs (basic support)
  • Inline SVGs
• Shadows
• Animations/Transitions
• Standard form controls (Checkbox/Dropdown/slider/etc)
• Custom widgets
• Shadow elements

Layout

• Inline (partial support - implementation still immature)
• Block
• Flexbox
• Grid
  • Named grid lines
  • Subgrid
• Table
• Z-index
• Additional CSS features
  • box-sizing: content-box
  • calc()
  • position: static
  • direction: rtl
  • transform

Text

• Font loading
  • System font loading
  • Web font loading
• Text
  • Shaping / Bidi
  • Layout / line breaking
  • Font size / line height
  • Text color
  • Bold / Italic
  • Underline / Strikethrough
• Text selection

Input

• Scrolling
  • The root view
  • Any overflow: scroll element
• Hover detection
• Click handling
• Text input

Performance

• Hot reloading
• Scrolling without re-resolving style and layout
• Style caching
• Layout caching

Other

• Multiwindow
• Accessibility tree
• Focus
• Devtools
• Hooks for context menu
• use_wgpu_context() to grab an element as an arbitrary render surface

License

This project is dual licensed under the Apache 2.0 and MIT licenses

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in stylo-dioxus by you, shall be licensed as MIT, without any additional terms or conditions.