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RGC BASIC — Web IDE (WASM)

The Retro Game Coders IDE embeds the RGC BASIC interpreter as WebAssembly. You get the same language in the browser: edit, run, and share without installing native binaries.

Opening the platform

  1. In the IDE, choose RGC BASIC from the platform selector, or
  2. Use a direct link with query parameters, for example:

ide.retrogamecoders.com/?file=petscii-data.bas&platform=rgc-basic

  • platform=rgc-basic selects the WASM toolchain.
  • file= is the basename of a program bundled with the RGC BASIC preset in the IDE (same filenames as in the rgc-basic repo’s examples/ tree, e.g. gfx_poke_demo.bas, trek.bas). Pattern: https://ide.retrogamecoders.com/?file=<name>.bas&platform=rgc-basic

Documentation links Web IDE next to an example only when that *.bas ships in the IDE preset (the 8bitworkshop presets/rgc-basic/ package).

Output and diagnostics

  • PRINT output, runtime errors, and load-time errors appear in the IDE output / console area.
  • Messages follow the same style as native builds where implemented: BASIC line numbers and Hint: suggestions.

Keyboard and focus

For programs using GET, INKEY$, or INPUT in a canvas / embedded view, click the emulator or canvas first so the browser routes key events to the interpreter. This matches Getting started with the IDE.

Platform and capabilities

PLATFORM$() in Emscripten builds returns "browser" (not the linux-terminal-style strings used on native OS). Native builds return linux-terminal, mac-terminal, windows-terminal, or windows-gfx / linux-gfx / mac-gfx when linked with gfx.

What works in the browser

Feature WASM (typical)
Core BASIC, files in virtual FS (where exposed) Yes
HTTP$ / HTTPSTATUS() Yes — fetch (see below)
SYSTEM / EXEC$ Stubbed — SYSTEM returns -1, EXEC$ returns ""
INKEY$(), GET Yes when the host wires keyboard (IDE / canvas)
Gfx / canvas (PETSCII, bitmap, sprites) When the page uses the canvas host — parity with basic-gfx is documented upstream (docs/gfx-canvas-parity.md).

HTTP$ and HTTPSTATUS

Browser-only (Emscripten). On native basic, HTTP$ returns "" and HTTPSTATUS() returns 0 — use EXEC$("curl …") instead.

Syntax

HTTP$(url$ [, method$ [, body$]])
  • url$ — HTTPS URL (must allow CORS from your page’s origin).
  • method$ — Optional; e.g. "GET", "POST". Omit for default GET-like behaviour (see upstream).
  • body$ — Optional request body for POST/PUT.

HTTP(url) without $ is treated as a call to the same intrinsic as HTTP$ (so HTTP is not mistaken for a user function named HTTP).

HTTPSTATUS() — No arguments. Returns the HTTP status code of the last HTTP$ call, or 0 on failure / non-WASM.

CORS

The remote API must send Cross-Origin Resource Sharing headers that allow your IDE origin. If the request fails, status may be 0 and the body empty — test in browser devtools Network tab.

Example

examples/http_time_london.bas in the repo fetches a public time API (open in Web IDE):

U$ = "https://timeapi.io/api/TimeZone/zone?timeZone=Europe/London"
R$ = HTTP$(U$)
IF HTTPSTATUS() <> 200 THEN PRINT "HTTP error "; HTTPSTATUS(): END

Async / responsiveness

The upstream README notes that WASM uses emscripten_sleep so the tab can paint; tight loops without SLEEP or output can still make the browser report “Page Unresponsive” where basic-gfx feels fine. Prefer periodic SLEEP, or split work — see docs/gfx-canvas-parity.md and examples/wasm_canvas_hang_probe.bas (Web IDE).

Builds in the repo (for contributors)

From rgc-basic (see upstream README):

  • make basic-wasm — Terminal WASM (web/basic.js, web/basic.wasm).
  • make basic-wasm-canvas — Canvas + PETSCII / bitmap / sprites (web/canvas.html, etc.).
  • make basic-wasm-modular — For embedded tutorial pages.

Serve web/ over HTTP and open canvas.html or tutorial.html as documented in web/README.md.

When to use IDE vs native

Situation Prefer
Teaching, sharing a link, no install Web IDE
Pipes, SYSTEM, local paths, automation Terminal basic
Full Raylib window, local PNGs, gamepad basic-gfx

See also