mojibaka/canvas.js

✨ Browser emoji support detection toolkit

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.prepareCanvasContext = prepareCanvasContext;
exports.canDrawCharacter = canDrawCharacter;
exports.getCharacterWidth = getCharacterWidth;
var DRAW_SIZE = 32;

function newContext() {
  var canvas = document.createElement('canvas');
  canvas.width = canvas.height = DRAW_SIZE * 2;
  return canvas.getContext('2d');
}

function prepareCanvasContext(context) {
  if (!context) {
    context = newContext();
    context.fillStyle = "#000";
    context.font = DRAW_SIZE + 'px "Apple Color Emoji","Segoe UI","Segoe UI Emoji","Segoe UI Symbol",Arial';
  } else {
    context.clearRect(0, 0, DRAW_SIZE * 2, DRAW_SIZE * 2);
  }

  return context;
}

function canDrawCharacter(character, context) {
  context = prepareCanvasContext(context);
  context.fillText(character, 0, DRAW_SIZE);

  return context.getImageData(DRAW_SIZE / 2 + 2, DRAW_SIZE / 2, 1, 1).data[0] !== 0;
}

function getCharacterWidth(character, context) {
  context = prepareCanvasContext(context);

  return context.measureText(character).width;
}
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