Documentation › BROWSER

Browser and litehtml Porting Notes

LeonOS now ships browser.elf, a classic IE-style browser shell. Upstream litehtml is present as a Git submodule under third_party/litehtml; the browser currently links a freestanding C litehtml_core adapter while the full C++ litehtml runtime prerequisites are still being built.

Current Browser

userland/apps/browser/main.c is a freestanding C application that uses the existing GUI, libc, launch, filesystem, and network ABIs.

Current features:

• IE-style menu/toolbar/address layout with toast status messages.
• Times New Roman as the browser's Latin font, with SimSun as the Chinese fallback; both are loaded at runtime from external font files rather than embedded in browser.elf.
• Bilingual about:leonos start page.
• http:// and https:// navigation through the libc HTTP client on top of TCP sockets. HTTPS uses TLS 1.2 with certificate, hostname, and system-clock validation.
• Chrome-compatible desktop User-Agent, Accept, and language headers for sites that reject unknown clients.
• Local .html and .htm file loading.
• Download-link handoff: links ending in common binary/media/archive suffixes launch downloadmgr.elf, which saves the response to the current user's Downloads directory.
• A userland/apps/browser/litehtml_core.c document layout layer for headings, paragraphs and block sections, lists, blockquotes, table rows/cells, breaks, horizontal rules, image placeholders with alt text, entities, links, per-cell table alignment, and basic inline styles (strong/b, em/i, code).
• A small CSS v1 parser for <style> blocks, inline style="", and up to four HTTP or HTTPS <link rel="stylesheet"> stylesheets per page. It covers simple tag/class/id selectors plus color, background-color, font-weight, font-style, text-decoration, text-align, left indent properties, and basic borders.
• HTTP toast reporting, response content-type handling, bounded redirects, chunked transfer decoding, final URL reporting, and truncation indicators.
• Link hit testing, relative URL resolution, Back, Forward, Refresh, Home, and mouse-wheel scrolling.
• Inline form support: form, text/email/search/url/tel/number/password/hidden inputs, checkbox/radio controls, single-choice select/option, one-line textarea, placeholder text, submit/reset inputs and buttons, disabled/read-only states, GET and POST, and application/x-www-form-urlencoded bodies. Select controls cycle through options when clicked.
• Resize-aware reflow.

Current limits:

• No JavaScript.
• No inline image loading. Image links can be downloaded and opened with imageview.elf when saved as BMP or PNG.
• No full CSS cascade, box model, floats, flex/grid, or media queries.
• HTTP uses HTTP/1.1 over TCP sockets with Connection: close; HTTPS uses a TLS 1.2 client profile backed by Mbed TLS and the bundled CA roots. Cookies, cache, compression, and true streaming downloads are not implemented yet.

The repository owns the font build inputs: system/fonts/times.ttf is copied to /usr/share/fonts/leonos/times-new-roman.ttf, and system/fonts/simsun.ttc is packaged as /usr/share/fonts/leonos/simsun.ttc. Local and GitHub Actions builds use these same repository files.

litehtml Status

Upstream litehtml is checked out as:

• submodule path: third_party/litehtml
• upstream URL: https://github.com/litehtml/litehtml.git
• current recorded commit: b9e89f0b9494ff9a5f008800af35503efabddf59

The current upstream tree is C++ and depends heavily on STL types and library facilities such as strings, vectors, maps, smart pointers, variants, algorithms, and bundled Gumbo parser support. LeonOS userland is still freestanding C with a small libc and no C++ runtime or STL build path.

Because of that, the browser app currently owns a small C core with a deliberately narrow surface. The replacement point is the document layout layer: URL loading, navigation history, window chrome, status reporting, and launch integration should remain useful when the full C++ litehtml container becomes available.

Next Porting Steps

To integrate real litehtml, do these in order:

1. Add a userland C++ build mode to the GNU Make build system (mk/userland.mk and the component graph).
2. Provide a minimal C++ runtime surface for constructors, destructors, allocation, exceptions-disabled builds, and required ABI helpers.
3. Port or provide an STL subset/libc++ profile that satisfies litehtml.
4. Build Gumbo and upstream litehtml as userland libraries from third_party/litehtml.
5. Replace litehtml_core.c with a LeonOS litehtml container that maps text measurement, drawing, colors, clipping, mouse hit testing, and file/network resource fetches to the existing GUI and network APIs.
6. Keep the browser shell, navigation, address bar, history, and app-launch integration stable while swapping the document engine.

User Integration

The browser is registered as:

• /usr/lib/leonos/apps/browser/browser.elf
• launch alias: browser
• default app for .html and .htm

Download and image companion apps are registered as:

• /usr/lib/leonos/apps/downloadmgr/downloadmgr.elf, launch alias downloadmgr
• /usr/lib/leonos/apps/imageview/imageview.elf, launch alias imageview
• default app for .bmp, .dib, and .png

The generated icon is /usr/lib/leonos/apps/browser/browser.bmp, following the existing same-directory/same-basename application icon convention.