fps.js

var gamejs = require('gamejs');

var conf = require('./config');

exports.FpsDisplay = function() {
   // fps counter
   var lastDurations = [];
   var fpsFont = new gamejs.font.Font();
   var fpsWarningFont = new gamejs.font.Font('20px monospace');
   var fpsAvg = 99;
   this.lowCPU = false;

   this.update = function(msDuration) {
      // fps
      lastDurations.push(msDuration);
      if (lastDurations.length > 60) {
         var sum = 0;
         lastDurations = lastDurations.splice(0, 10);
         lastDurations.forEach(function(ld) {
            sum += ld;
         });
         fpsAvg = Math.ceil(1000 / (sum / lastDurations.length));
      }
   };

   this.draw = function(display) {
      if (fpsAvg < 14) this.lowCPU = true;

      if (this.lowCPU) {
         display.blit(fpsFont.render('Low CPU mode! ' + fpsAvg, '#ff33ff'), [conf.SCREEN_WIDTH - 100, 5]);
      }
      return;
   };

   return this;
};