feat: added keyboard compatibility shim for p5.js v1.x to v2.x

[kunstewi]

Background

p5.js v2.x dropped several legacy keyboard APIs that many existing sketches depend on specifically the named numeric keyCode constants (e.g. LEFT_ARROW, RIGHT_ARROW) and the event.keyCode property on keyCode. This PR adds a compatibility shim inside src/data.js that transparently restores that behavior so v1.x sketches run on v2.x without any source changes.

A v1.x sketch like this:

function draw() {
  background(220);
  if (keyCode === RIGHT_ARROW) background(0);
  else if (keyCode === LEFT_ARROW) background(100);
}

silently breaks on v2.x because:

• RIGHT_ARROW, LEFT_ARROW, etc. are no longer defined globals
  keyCode no longer holds the legacy numeric value (v2.x uses string-based key/code)

• keyIsDown() only accepts the new string format.

Changes Made

• p5.prototype.LEFT_ARROW = 37 (+ 13 others) - Restores the 14 legacy named key constants as globals.
• CODE_TO_KEYCODE lookup table - Maps modern event.code strings → legacy numeric keyCodes as a fallback.
• fn._onkeydown override - Resolves and writes the correct numeric keyCode onto the p5 instance on every keydown; tracks held keys in _pressedKeyCodes
• fn._onkeyup override - Mirror of _onkeydown removes key from the pressed-keys set on release.
• fn.keyIsDown override - Lets keyIsDown()accept both numeric (v1.x: keyIsDown(37)) and string (v2.x: keyIsDown('ArrowLeft')) arguments.

The overrides all delegate to the original v2.x handlers after patching, so no existing v2.x behavior is broken.

Testing

• made a temporary test.html where i imported p5 minified 2.x version and linked the data.js file to test things out.
• I have created a new repo where you can find the test.html file and test things out. here
• or you can check the live html website here. click on the canvas to focus then use right and left arrow key to see the changes.

without the keyboard compatibility code

tests not passing

example code not working
https://github.com/user-attachments/assets/fd9ec047-ce15-452e-836d-97e4ea12498e

with the kyboard compatibility code

tests passing

example code working

Screen.Recording.2026-02-22.at.3.04.06.PM.mov

AI disclosure

• used antigravity to find problems and propose solutions
• generated code using claude opus 4.6 thinking
• reviewed and tested code before pushing

closes #26

hey @ksen0 could you please take a look, and propose changes or let me know if i am moving in the right direction.

Thanks for your time.

[ksen0]

Ah, hm, @kunstewi maybe this is a good signal that the backwards compatibility vars actually should be in events.js? Although initially I described in the issue that it should be data, it's true that other keyboard backwards compatibility support is already in events and should be kept consistent.

Apologies this took so long to get to. If you move the vars over that would be good, I'll do my best to test and merge asap. Feel free to @ on the discord contribute channel if needed! thanks for working on this.

[kunstewi]

thanks Kit (@ksen0) I have added the requested changes, I have added the keyboard compatibility layer in the events.js and kept touch and mouse in the data.js as it is.