pointer-trap

A "niche" wrapper for chrisdickinson's pointer-lock module.

If you've ever played a windowed game, and the pointer isn't locked within the screen, you may occasionally click outside the window by mistake. This is super annoying if it happens in a tight spot, so here's a drop-in fix for the problem.

Installation

npm install pointer-trap

Usage

stream = require('pointer-trap')(element)

Returns a readable stream, which emits the current position of the mouse (relative to the element you've attached it to). The user can click on the element to enable pointer lock - when not trapped, the stream will fall back to the data it can get from the element's mousemove event.

stream.on('data', callback)

Emitted periodically, passing stream.pos to the callback.

stream.on('attain', callback)

Called each time the pointer is trapped.

stream.on('release', callback)

Called when each time the pointer is released.

stream.pos

The current position of the mouse, as of the last update. If you're using a game loop, you'll get better results reading it directly this way.

stream.trapped

A boolean value, set to true when the pointer is trapped.

var canvas = document.createElement('cavas')
var trap = require('pointer-trap')(canvas)
var ticker = require('ticker')(60, canvas)
var x = 0
var y = 0

// either on tick...
ticker.on('tick', function() {
  x = trap.pos.x
  y = trap.pos.y
})

// or on capture...
trap.on('data', function(pos) {
  x = pos.x
  y = pos.y
})

var ctx = canvas.getContext('2d')
ticker.on('draw', function() {
  canvas.width  = window.innerWidth
  canvas.height = window.innerHeight
  ctx.fillStyle = trap.trapped ? '#0f0' : '#f00'
  ctx.fillRect(x - 4, y - 4, 8, 8)
})