StarWeb dev log #5

Lua support!

Every tab gets its own ScriptEngine, a sandboxed Lua 5.4 interpreter. A custom allocator caps its memory, an instruction hook kills it when it runs past its time budget, and require, dofile, and loadfile don’t exist in there. It’s untrusted code from whatever page you loaded.

Scripts get a DOM API: getElementById, querySelector, innerText, get/setAttribute, addEventListener, console.log, alert, setTimeout/setInterval, requestAnimationFrame. There’s a location object too, so scripts can navigate, but only to moon:// URLs.

Yes, there is <canvas>. getContext("2d") gives you fillRect, paths, arcs, fillText, but scripts never touch the screen directly; every call gets recorded into a list of CanvasOps and the renderer draws the list. To test all of it, I wrote a raycaster (www/game.lua), a small maze you can walk around in, running entirely as a page script.

external scripts and keyboard input

<script src="..."> works, not just inline scripts. The fetcher downloads them so the engine sees them in document order. Keyboard input works too; keys get polled from GLFW and sent to the active tab, so document.addEventListener("keydown", ...) does something. That’s how the raycaster gets its controls.

The main loop also stopped redrawing at 60fps when nothing’s happening. It sleeps until something needs a frame: a fetch, a playing video, a pending timer, or requestAnimationFrame. Good for the battery. (My MacBook 2015 was on fire when the browser ran. That’s how I noticed lol)

Also, from now on I will be posting more devlogs because im done with the core stuff. Rupnil () said not to make them that big and commit more.