velox-renderer

Skia rendering backends, events and HMR for the Velox UI framework.

Overview

velox-renderer owns everything between a styled VNode and pixels: backend selection, window and event loops, offscreen Skia rasterisation, hit testing and input editing, accessibility trees, viewport/DPI maths, and the HMR client. It depends on velox-core, velox-dom and velox-style, and every heavyweight dependency is behind a feature flag — with no features the crate compiles to a fast stub backend and pulls in no windowing or GPU stack at all. The feature set is the crate's real user-facing API.

Features

Feature-flagged backends — default stub backend (no optional dependencies), skia, svg, and skia-native (winit + skia-safe + EGL/GL)
Windowed render loop — run_window_vnode_skia (and its HMR variant) opens a window and drives layout, paint and events
Immediate-mode paint — Skia rasterisation of a styled VNode every frame
Offscreen rendering — RGBA and PNG output at an explicit DPI scale
Event dispatch — click/input/change, keyboard and mouse events, point-in-box hit testing, and semantic EditAction text editing
Accessibility — build_a11y_tree walks the laid-out tree into roles, names and rects
Viewport/DPI maths — a single rounding authority (physical_from_logical) plus the Viewport type
HMR client — reconnecting client thread, HmrMessage protocol on port 31313

Installation

cargo add velox-renderer                # stub backend, no features
cargo add velox-renderer --features skia-native   # native Skia window

Feature	What it turns on
`default`	Empty — the stub backend, no optional dependencies, fast to compile.
`skia`	Selects the Skia backend path: `BACKEND = "skia"`, `SelectedRenderer = skia_backend::SkiaRenderer`, and a compile-only `skia_backend` module with no native dependencies (so the API surface builds without Skia).
`svg`	`dep:resvg 0.48` — rasterisation of SVG images (`<img src="*.svg">`).
`skia-native`	The real backend: `dep:skia-safe 0.91.1`, `dep:winit 0.28`, `dep:raw-window-handle 0.5`, `dep:egl 0.2`, `dep:glow 0.12`, `dep:softbuffer 0.3`, plus `skia` and `svg`. Unlocks the window loops, GPU surface, offscreen PNG/RGBA rendering, and `skia_backend::SkiaRenderer` with a live `surface`.

The always-on dependencies are velox-core, velox-dom, velox-style, log 0.4, bytemuck 1, serde 1, serde_json 1.0.

Quick start

With no features enabled the crate is a stub you can still build against:

use velox_dom::{h, text};
use velox_renderer::{backend_name, build_a11y_tree};

let vnode = h("button", (), vec![text("Save")]);
assert_eq!(backend_name(), "stub");

let tree = build_a11y_tree(&vnode, 800, 600);
println!("{}x{} root", tree.root.rect.w, tree.root.rect.h);

With --features skia-native, run_window_vnode_skia opens a window and drives the render/event loop — a complete program using it lives in examples/counter.

Documentation

API reference: docs.rs/velox-renderer
Book: Renderer — backends, features and rendering

Workspace crates

Velox is a workspace of six published crates. This crate is marked (this crate).

Crate	What it provides	Documentation
velox-core	Reactive primitives: signals, effects, lifecycle hooks	docs.rs
velox-dom	`VNode` types, block + flex layout, positioning, overflow	docs.rs
velox-style	CSS parsing, selectors, cascade; styles applied to `VNode`	docs.rs
velox-renderer · this crate	Rendering backends, event dispatch, hit testing	docs.rs
velox-sfc	Single-file component compiler (pest grammar) → Rust	docs.rs
veloxc	The CLI and dev server	docs.rs

Status

Published on crates.io at 0.1.1.

Working today: Skia immediate-mode paint, event hit-testing, the skia-native windowed backend, offscreen RGBA/PNG rendering, and accessibility trees. Notes:

default compiles to a stub backend with no native dependencies — opt in with skia-native when you're ready. Expect a heavy first build: the Skia stack is large.
The render loop is immediate-mode: no retained tree, no previous frame to compare, no patch applier. See docs/internal/RECONCILER.md.
Falls back to headless rendering with VELOX_HEADLESS=1 or when no compositor is available.

License

Licensed under MIT OR Apache-2.0.

velox-renderer 0.1.2