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Details

Resolve ch unit for pseudo-elements; re-promote balance-before-after-002

The ch measurement previously ran only in the main element loop, so
::before/::after/::first-line/::first-letter fell back to the 0.5em
approximation for `ch`. Factor "resolve font longhands early + measure
the 0 advance" into a shared `resolve_fonts_and_measure_ch` helper and
call it from the main cascade, compute_pseudo_styles, and
apply_pseudo_declarations (which backs ::first-line/::first-letter). The
Pass-3 skip of those longhands now goes through a shared
`is_early_font_longhand` predicate. Net: removes the duplicated early-pass
logic the main loop carried and closes the pseudo-element gap.

text-wrap-balance-before-after-002 draws its text via `content:` generated
content; with accurate ch now applied to both the test and reference
pseudo-elements, they align within reftest tolerance. This reverts the
demote from the previous commit — the failure was pseudo-element ch, not
text-wrap:balance as first attributed. WPT 1747 -> 1748, failures=0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-06-06 07:07:07 -04:00

_bmad

Add BMAD framework, planning artifacts, and architecture decision document

2026-03-12 15:13:06 -04:00

_bmad-output

Add focus management and keyboard navigation with tabindex ordering and review fixes (Story 4.7)

2026-04-02 16:51:55 -04:00

.agents/skills

Add BMAD framework, planning artifacts, and architecture decision document

2026-03-12 15:13:06 -04:00

.cargo

Move some hidden files from docs directory to root of project (they were in docs dir accidentally)

2026-01-31 01:10:13 -05:00

.claude/commands

Improve investigate skill; dump failed scripts to output dir not /tmp

2026-05-31 00:51:00 -04:00

.gitea/workflows

Get gitea action running

2026-02-04 00:18:21 -05:00

crates

Resolve ch unit for pseudo-elements; re-promote balance-before-after-002

2026-06-06 07:07:07 -04:00

docs

Implement 8 spec-compliant CSS fixes; +63 WPT tests (1677→1740)

2026-06-06 06:06:14 -04:00

investigations

Fix inline-flex auto width to shrink-to-fit (F-001)

2026-06-05 16:39:17 -04:00

scripts

Implement Symbol, WeakMap, and Proxy with comprehensive test coverage

2026-02-25 11:08:36 -05:00

src

Phase 0: Initial Implementation

2026-01-28 22:47:48 -05:00

tests

Resolve ch unit for pseudo-elements; re-promote balance-before-after-002

2026-06-06 07:07:07 -04:00

.gitignore

Add persistent investigation reports with fix tracking

2026-03-02 22:29:57 -05:00

AGENTS.md

Update some docs - Add CSS2.1 & HTML Implementation checklists

2026-03-01 23:44:21 -05:00

Cargo.lock

Resolve CSS ch unit via measured '0' advance; +7 WPT tests (1740→1747)

2026-06-06 06:58:10 -04:00

Cargo.toml

F-021: use unicode-ident for exact Unicode identifier conformance

2026-05-31 19:46:51 -04:00

CLAUDE.md

Add JS262_FILTER env var for running individual test262 tests

2026-03-18 22:29:05 -04:00

deny.toml

Initial commit

2026-01-28 21:41:46 -05:00

justfile

Widen cross-context sizing differential (slice 2)

2026-06-03 08:30:06 -04:00

README.md

Add --js flag to app_browser for executing JavaScript from stdin or file

2026-03-18 15:37:20 -04:00

rust-toolchain.toml

Initial commit

2026-01-28 21:41:46 -05:00

README.md

rust_browser

A modular, experimental web browser engine and desktop shell written in Rust.

This repository is organized as a Cargo workspace with focused crates for HTML/CSS parsing, DOM, style, layout, rendering, networking, and a desktop app shell.

Current Status

rust_browser is under active development. The project prioritizes:

correctness before performance
deterministic behavior and testability
clear crate boundaries for long-term maintainability

Implemented today includes:

HTML parsing and DOM construction
CSS parsing, selector matching, and core style computation
block/inline layout, flexbox support, table support (partial)
display-list generation and CPU rasterization path
local file and HTTP loading
golden tests and WPT-based external conformance harnessing

Workspace Layout

Top-level crates in crates/:

app_browser: desktop app binary (app_browser)
browser_runtime: navigation/session/runtime orchestration
web_api: browser-facing API surface
js, js_vm, js_parser: JavaScript stack
dom, html, css, selectors, style: document/style pipeline
layout, display_list, render, graphics: layout and rendering pipeline
net, storage, image, fonts: resource and media subsystems
platform: platform integration
shared: shared types/utilities

See docs/browser_project_structure_modularization_guide.md for dependency layering and crate ownership rules.

Prerequisites

Rust toolchain from rust-toolchain.toml (currently stable)
just command runner

Install just if needed:

cargo install just

Build

cargo build -p app_browser

Run

Show CLI help:

cargo run -p app_browser -- --help

Open a URL in windowed mode:

cargo run -p app_browser -- https://example.com

Render an input file/URL to layout and display-list dumps:

cargo run -p app_browser -- --render tests/goldens/fixtures/001-empty.html

Render and emit PNG:

cargo run -p app_browser -- --render tests/goldens/fixtures/001-empty.html --png

Execute JavaScript from a file:

cargo run -p app_browser -- --js script.js

Execute JavaScript from stdin (useful for quick debugging):

echo 'console.log(1 + 2)' | cargo run -p app_browser -- --js

Pipeline Overview

The browser pipeline is intentionally staged and deterministic:

browser_runtime receives a navigation request and tracks lifecycle/history state.
net loads content (HTTP or file) and returns response bytes.
html parses markup into a dom document tree.
css parses stylesheets and selectors matches rules to DOM nodes.
style computes final values (UA + author + inline cascade).
layout builds and resolves the layout tree (box geometry/flow).
display_list converts layout output into backend-agnostic draw commands.
render rasterizes draw commands to pixels, and platform presents them in a window.

In --render mode, steps 3-7 are written to artifact dumps (.layout.txt and .dl.txt) to make regressions easy to diff and review in tests.

Development Commands

Primary workflow commands are defined in justfile:

just fmt: check formatting
just lint: run clippy (warnings denied)
just test: run workspace tests + WPT manifest expectation test
just policy: enforce unsafe/dependency/file-size policy checks
just metrics: report project metrics
just ci: run full local CI pipeline (fmt, lint, test, policy, metrics)
just regen-wpt: regenerate expected WPT outputs
just import-wpt ...: import WPT reftests into fixture form
just wpt-status ...: summarize WPT status

Testing Strategy

Testing combines multiple layers:

unit tests in crate source modules
integration tests in tests/
golden rendering regression tests (tests/goldens)
external conformance fixtures and WPT harnessing (tests/external/wpt)

Details: docs/browser_testing_strategy_high_level_to_detailed.md.

Architecture Notes

Initial architecture is deliberately conservative:

interpreter-first semantics
deterministic single-threaded core pipeline
worker threads for I/O-oriented work
display-list abstraction between layout/paint and rendering backend

Details: docs/browser_architecture_initial_exploration.md.

Contributing

General expectations in this repo:

keep crate boundaries clean (no cross-layer leaks)
avoid introducing unsafe outside approved crates
add regression tests for bug fixes
run just ci before sending changes