TODO.md

Vello GPU Rendering Backend

Cargo.toml

• Add vello feature flag: vello = ["dep:vello", "dep:parley", "dep:image"]
• Add vello = { version = "0.7", optional = true }
• Add parley = { version = "0.7", optional = true }
• Add dev-deps: pollster = "0.4", winit = "0.30", wgpu = "27"
• Add [[example]] name = "render_vello" with required-features = ["vello"]

lib.rs

• Add #[cfg(feature = "vello")] pub mod vello_backend;

vello_backend.rs — Struct + Constructors

• VelloContainer struct (scene, font_ctx, layout_ctx, fonts, clip_stack, images, viewport, etc.)
• new(width, height) / new_with_scale(width, height, scale)
• scene(&self) / into_scene(self) / clear(&mut self)
• resize(&mut self, width, height)
• load_image_data(&mut self, url, data) — decode + store as peniko::Image
• scale_factor(&self) getter

vello_backend.rs — Font Management

• FontData internal struct (family, size, weight, style, metrics)
• create_font — store metadata, measure metrics via parley Layout
• delete_font — remove from HashMap
• text_width — build parley Layout, return layout.width()

vello_backend.rs — Text Drawing

• draw_text — build parley Layout, iterate glyph runs, scene.draw_glyphs()

vello_backend.rs — Fill / Gradient / Image

• draw_solid_fill — scene.fill() with solid brush on rounded rect
• draw_linear_gradient — Gradient::new_linear().with_stops() → scene.fill()
• draw_radial_gradient — Gradient::new_radial().with_stops() → scene.fill()
• draw_conic_gradient — Gradient::new_sweep().with_stops() → scene.fill()
• draw_image — scene.draw_image() with transform

vello_backend.rs — Borders + Clipping

• draw_borders — build kurbo::BezPath per side, scene.stroke() with dash patterns
• draw_list_marker — disc/circle/square fills, numbered via draw_text
• set_clip — scene.push_layer(Mix::Clip, ...) or push_clip_layer
• del_clip — scene.pop_layer()

vello_backend.rs — Remaining Trait Methods

• set_caption / set_base_url / on_anchor_click / set_cursor
• get_viewport — return stored viewport
• get_media_features — return features with scale-adjusted resolution
• transform_text — uppercase/lowercase/capitalize
• load_image / get_image_size

vello_backend.rs — Headless Helper

• render_to_rgba(html, width, height) — wgpu headless → RGBA buffer
• render_to_rgba_scaled(html, width, height, scale) — same with scale factor

Example

• render_vello.rs — winit window, wgpu surface, vello::Renderer::render_to_surface()

Verification

• cargo check --features vello compiles
• Example renders sample HTML in a window