detectElementResize.js

/**
 * Detect Element Resize.
 * https://github.com/sdecima/javascript-detect-element-resize
 * Sebastian Decima
 *
 * Forked from version 0.5.3; includes the following modifications:
 * 1) Guard against unsafe 'window' and 'document' references (to support SSR).
 * 2) Defer initialization code via a top-level function wrapper (to support SSR).
 * 3) Avoid unnecessary reflows by not measuring size for scroll events bubbling from children.
 **/

export default function createDetectElementResize () {
  // Check `document` and `window` in case of server-side rendering
  var _window
  if (typeof window !== 'undefined') {
    _window = window
  } else if (typeof self !== 'undefined') {
    _window = self
  } else {
    _window = this
  }

  var attachEvent = typeof document !== 'undefined' && document.attachEvent;
  var stylesCreated = false;

  if (!attachEvent) {
    var requestFrame = (function(){
      var raf = _window.requestAnimationFrame || _window.mozRequestAnimationFrame || _window.webkitRequestAnimationFrame ||
                function(fn){ return _window.setTimeout(fn, 20); };
      return function(fn){ return raf(fn); };
    })();

    var cancelFrame = (function(){
      var cancel = _window.cancelAnimationFrame || _window.mozCancelAnimationFrame || _window.webkitCancelAnimationFrame ||
                   _window.clearTimeout;
      return function(id){ return cancel(id); };
    })();

    var resetTriggers = function(element){
      var triggers = element.__resizeTriggers__,
        expand = triggers.firstElementChild,
        contract = triggers.lastElementChild,
        expandChild = expand.firstElementChild;
      contract.scrollLeft = contract.scrollWidth;
      contract.scrollTop = contract.scrollHeight;
      expandChild.style.width = expand.offsetWidth + 1 + 'px';
      expandChild.style.height = expand.offsetHeight + 1 + 'px';
      expand.scrollLeft = expand.scrollWidth;
      expand.scrollTop = expand.scrollHeight;
    };

    var checkTriggers = function(element){
      return element.offsetWidth != element.__resizeLast__.width ||
             element.offsetHeight != element.__resizeLast__.height;
    }

    var scrollListener = function(e){
      // Don't measure (which forces) reflow for scrolls that happen inside of children!
      if (
        e.target.className.indexOf('contract-trigger') < 0 &&
        e.target.className.indexOf('expand-trigger') < 0
      ) {
        return
      }

      var element = this;
      resetTriggers(this);
      if (this.__resizeRAF__) cancelFrame(this.__resizeRAF__);
      this.__resizeRAF__ = requestFrame(function(){
        if (checkTriggers(element)) {
          element.__resizeLast__.width = element.offsetWidth;
          element.__resizeLast__.height = element.offsetHeight;
          element.__resizeListeners__.forEach(function(fn){
            fn.call(element, e);
          });
        }
      });
    };

    /* Detect CSS Animations support to detect element display/re-attach */
    var animation = false,
      animationstring = 'animation',
      keyframeprefix = '',
      animationstartevent = 'animationstart',
      domPrefixes = 'Webkit Moz O ms'.split(' '),
      startEvents = 'webkitAnimationStart animationstart oAnimationStart MSAnimationStart'.split(' '),
      pfx  = '';
    {
      var elm = document.createElement('fakeelement');
      if( elm.style.animationName !== undefined ) { animation = true; }

      if( animation === false ) {
        for( var i = 0; i < domPrefixes.length; i++ ) {
          if( elm.style[ domPrefixes[i] + 'AnimationName' ] !== undefined ) {
            pfx = domPrefixes[ i ];
            animationstring = pfx + 'Animation';
            keyframeprefix = '-' + pfx.toLowerCase() + '-';
            animationstartevent = startEvents[ i ];
            animation = true;
            break;
          }
        }
      }
    }

    var animationName = 'resizeanim';
    var animationKeyframes = '@' + keyframeprefix + 'keyframes ' + animationName + ' { from { opacity: 0; } to { opacity: 0; } } ';
    var animationStyle = keyframeprefix + 'animation: 1ms ' + animationName + '; ';
  }

  var createStyles = function() {
    if (!stylesCreated) {
      //opacity:0 works around a chrome bug https://code.google.com/p/chromium/issues/detail?id=286360
      var css = (animationKeyframes ? animationKeyframes : '') +
          '.resize-triggers { ' + (animationStyle ? animationStyle : '') + 'visibility: hidden; opacity: 0; } ' +
          '.resize-triggers, .resize-triggers > div, .contract-trigger:before { content: \" \"; display: block; position: absolute; top: 0; left: 0; height: 100%; width: 100%; overflow: hidden; z-index: -1; } .resize-triggers > div { background: #eee; overflow: auto; } .contract-trigger:before { width: 200%; height: 200%; }',
        head = document.head || document.getElementsByTagName('head')[0],
        style = document.createElement('style');

      style.type = 'text/css';
      if (style.styleSheet) {
        style.styleSheet.cssText = css;
      } else {
        style.appendChild(document.createTextNode(css));
      }

      head.appendChild(style);
      stylesCreated = true;
    }
  }

  var addResizeListener = function(element, fn){
    if (attachEvent) element.attachEvent('onresize', fn);
    else {
      if (!element.__resizeTriggers__) {
        if (_window.getComputedStyle(element).position == 'static') element.style.position = 'relative';
        createStyles();
        element.__resizeLast__ = {};
        element.__resizeListeners__ = [];
        (element.__resizeTriggers__ = document.createElement('div')).className = 'resize-triggers';
        element.__resizeTriggers__.innerHTML = '<div class="expand-trigger"><div></div></div>' +
                                            '<div class="contract-trigger"></div>';
        element.appendChild(element.__resizeTriggers__);
        resetTriggers(element);
        element.addEventListener('scroll', scrollListener, true);

        /* Listen for a css animation to detect element display/re-attach */
        if (animationstartevent) {
          element.__resizeTriggers__.__animationListener__ = function animationListener(e) {
            if(e.animationName == animationName)
              resetTriggers(element);
          };
          element.__resizeTriggers__.addEventListener(
            animationstartevent, element.__resizeTriggers__.__animationListener__
          );
        }
      }
      element.__resizeListeners__.push(fn);
    }
  };

  var removeResizeListener = function(element, fn){
    if (attachEvent) element.detachEvent('onresize', fn);
    else {
      element.__resizeListeners__.splice(element.__resizeListeners__.indexOf(fn), 1);
      if (!element.__resizeListeners__.length) {
          element.removeEventListener('scroll', scrollListener, true);
          if (element.__resizeTriggers__.__animationListener__) {
            element.__resizeTriggers__.removeEventListener(
              animationstartevent, element.__resizeTriggers__.__animationListener__
            );
            element.__resizeTriggers__.__animationListener__ = null;
          }
          try {
            element.__resizeTriggers__ = !element.removeChild(element.__resizeTriggers__);
          } catch (e) {}
      }
    }
  }

  return {
    addResizeListener,
    removeResizeListener
  };
}