Clay (short for C Layout) is a high performance 2D UI layout library

Original Article ↗ Hacker News Discussion ↗

Overview & Purpose

  • Clay is a single-header, dependency-free C library for 2D UI layout, intended as a high‑performance immediate‑mode layout engine.
  • Commenters like the API design, documentation quality, and examples; some compare it favorably to microui and similar game/graphics UIs.
  • Several people see it as especially well‑suited to custom tools (e.g., IDEs, editors) and game UIs rather than general desktop/web apps.

Platforms, Bindings & Integrations

  • Works with rendering backends like Raylib; users confirm a Raylib example in the repo.
  • Using it with LÖVE (Love2D) or Lua is considered feasible via FFI/binding generators.
  • Running on microcontrollers such as ESP32 is viewed as possible if a custom renderer is written.

Accessibility & Input Concerns

  • Multiple commenters emphasize that real difficulty in UI systems is not layout but:
    • Cross‑platform input (mouse, touch, gamepad, keyboard).
    • Accessibility: screen reader integration, focus management, narration behavior.
  • A retained model is described as necessary even for immediate‑mode APIs to support accessibility well.
  • Existing projects like AccessKit, libAgar, and LVGL are mentioned as related but with varying accessibility coverage.

Website / HTML Demo Issues

  • The official Clay site (HTML demo using Clay for layout) draws heavy criticism:
    • Keyboard scrolling and PageUp/PageDown initially broken; later partially fixed.
    • Screen readers cannot interpret the page: everything is in generic <div>s, anchors are empty overlays, no semantic hierarchy.
    • Some users report total blank pages or crashes in Firefox/Chrome/Android; others see sluggish behavior.
    • Mouse wheel scrolling is reported as slow or janky; pinch‑zoom on mobile breaks layout.

Performance Discussion

  • Library claims “fast enough to recompute UI every frame.”
  • Several users report stuttering and poor scrolling performance on modern hardware; others report smooth 120fps.
  • The author attributes slowness to the demo renderer, not the layout algorithm, but the discrepancy across machines/browsers remains unclear.

Alternative Layout Models & Debates

  • Some commenters prefer constraint‑based systems (e.g., Cassowary, Auto Layout) and wish for more declarative “this goes relative to that” syntax.
  • Others point out maintainability and complexity issues of full constraint solvers for large apps.
  • Comparisons are drawn with Qt, GTK, CSS flexbox/grid, and historical tools like Interface Builder and “springs and struts.”