item.js

/**
 * Outlayer Item
 */

( function( window ) {

'use strict';

// ----- get style ----- //

var getComputedStyle = window.getComputedStyle;
var getStyle = getComputedStyle ?
  function( elem ) {
    return getComputedStyle( elem, null );
  } :
  function( elem ) {
    return elem.currentStyle;
  };


// extend objects
function extend( a, b ) {
  for ( var prop in b ) {
    a[ prop ] = b[ prop ];
  }
  return a;
}

function isEmptyObj( obj ) {
  for ( var prop in obj ) {
    return false;
  }
  prop = null;
  return true;
}

// http://jamesroberts.name/blog/2010/02/22/string-functions-for-javascript-trim-to-camel-case-to-dashed-and-to-underscore/
function toDash( str ) {
  return str.replace( /([A-Z])/g, function( $1 ){
    return '-' + $1.toLowerCase();
  });
}

// -------------------------- Outlayer definition -------------------------- //

function outlayerItemDefinition( EventEmitter, getSize, getStyleProperty ) {

// -------------------------- CSS3 support -------------------------- //

var transitionProperty = getStyleProperty('transition');
var transformProperty = getStyleProperty('transform');
var supportsCSS3 = transitionProperty && transformProperty;
var is3d = !!getStyleProperty('perspective');

var transitionEndEvent = {
  WebkitTransition: 'webkitTransitionEnd',
  MozTransition: 'transitionend',
  OTransition: 'otransitionend',
  transition: 'transitionend'
}[ transitionProperty ];

// properties that could have vendor prefix
var prefixableProperties = [
  'transform',
  'transition',
  'transitionDuration',
  'transitionProperty'
];

// cache all vendor properties
var vendorProperties = ( function() {
  var cache = {};
  for ( var i=0, len = prefixableProperties.length; i < len; i++ ) {
    var prop = prefixableProperties[i];
    var supportedProp = getStyleProperty( prop );
    if ( supportedProp && supportedProp !== prop ) {
      cache[ prop ] = supportedProp;
    }
  }
  return cache;
})();

// -------------------------- Item -------------------------- //

function Item( element, layout ) {
  if ( !element ) {
    return;
  }

  this.element = element;
  // parent layout class, i.e. Masonry, Isotope, or Packery
  this.layout = layout;
  this.position = {
    x: 0,
    y: 0
  };

  this._create();
}

// inherit EventEmitter
extend( Item.prototype, EventEmitter.prototype );

Item.prototype._create = function() {
  // transition objects
  this._transn = {
    ingProperties: {},
    clean: {},
    onEnd: {}
  };

  this.css({
    position: 'absolute'
  });
};

// trigger specified handler for event type
Item.prototype.handleEvent = function( event ) {
  var method = 'on' + event.type;
  if ( this[ method ] ) {
    this[ method ]( event );
  }
};

Item.prototype.getSize = function() {
  this.size = getSize( this.element );
};

/**
 * apply CSS styles to element
 * @param {Object} style
 */
Item.prototype.css = function( style ) {
  var elemStyle = this.element.style;

  for ( var prop in style ) {
    // use vendor property if available
    var supportedProp = vendorProperties[ prop ] || prop;
    elemStyle[ supportedProp ] = style[ prop ];
  }
};

 // measure position, and sets it
Item.prototype.getPosition = function() {
  var style = getStyle( this.element );
  var layoutOptions = this.layout.options;
  var isOriginLeft = layoutOptions.isOriginLeft;
  var isOriginTop = layoutOptions.isOriginTop;
  var x = parseInt( style[ isOriginLeft ? 'left' : 'right' ], 10 );
  var y = parseInt( style[ isOriginTop ? 'top' : 'bottom' ], 10 );

  // clean up 'auto' or other non-integer values
  x = isNaN( x ) ? 0 : x;
  y = isNaN( y ) ? 0 : y;
  // remove padding from measurement
  var layoutSize = this.layout.size;
  x -= isOriginLeft ? layoutSize.paddingLeft : layoutSize.paddingRight;
  y -= isOriginTop ? layoutSize.paddingTop : layoutSize.paddingBottom;

  this.position.x = x;
  this.position.y = y;
};

// set settled position, apply padding
Item.prototype.layoutPosition = function() {
  var layoutSize = this.layout.size;
  var layoutOptions = this.layout.options;
  var style = {};

  if ( layoutOptions.isOriginLeft ) {
    style.left = ( this.position.x + layoutSize.paddingLeft ) + 'px';
    // reset other property
    style.right = '';
  } else {
    style.right = ( this.position.x + layoutSize.paddingRight ) + 'px';
    style.left = '';
  }

  if ( layoutOptions.isOriginTop ) {
    style.top = ( this.position.y + layoutSize.paddingTop ) + 'px';
    style.bottom = '';
  } else {
    style.bottom = ( this.position.y + layoutSize.paddingBottom ) + 'px';
    style.top = '';
  }

  this.css( style );
  this.emitEvent( 'layout', [ this ] );
};


// transform translate function
var translate = is3d ?
  function( x, y ) {
    return 'translate3d(' + x + 'px, ' + y + 'px, 0)';
  } :
  function( x, y ) {
    return 'translate(' + x + 'px, ' + y + 'px)';
  };


Item.prototype._transitionTo = function( x, y ) {
  this.getPosition();
  // get current x & y from top/left
  var curX = this.position.x;
  var curY = this.position.y;

  var compareX = parseInt( x, 10 );
  var compareY = parseInt( y, 10 );
  var didNotMove = compareX === this.position.x && compareY === this.position.y;

  // save end position
  this.setPosition( x, y );

  // if did not move and not transitioning, just go to layout
  if ( didNotMove && !this.isTransitioning ) {
    this.layoutPosition();
    return;
  }

  var transX = x - curX;
  var transY = y - curY;
  var transitionStyle = {};
  // flip cooridinates if origin on right or bottom
  var layoutOptions = this.layout.options;
  transX = layoutOptions.isOriginLeft ? transX : -transX;
  transY = layoutOptions.isOriginTop ? transY : -transY;
  transitionStyle.transform = translate( transX, transY );

  this.transition({
    to: transitionStyle,
    onTransitionEnd: {
      transform: this.layoutPosition
    },
    isCleaning: true
  });
};

// non transition + transform support
Item.prototype.goTo = function( x, y ) {
  this.setPosition( x, y );
  this.layoutPosition();
};

// use transition and transforms if supported
Item.prototype.moveTo = supportsCSS3 ?
  Item.prototype._transitionTo : Item.prototype.goTo;

Item.prototype.setPosition = function( x, y ) {
  this.position.x = parseInt( x, 10 );
  this.position.y = parseInt( y, 10 );
};

// ----- transition ----- //

/**
 * @param {Object} style - CSS
 * @param {Function} onTransitionEnd
 */

// non transition, just trigger callback
Item.prototype._nonTransition = function( args ) {
  this.css( args.to );
  if ( args.isCleaning ) {
    this._removeStyles( args.to );
  }
  for ( var prop in args.onTransitionEnd ) {
    args.onTransitionEnd[ prop ].call( this );
  }
};

/**
 * proper transition
 * @param {Object} args - arguments
 *   @param {Object} to - style to transition to
 *   @param {Object} from - style to start transition from
 *   @param {Boolean} isCleaning - removes transition styles after transition
 *   @param {Function} onTransitionEnd - callback
 */
Item.prototype._transition = function( args ) {
  // redirect to nonTransition if no transition duration
  if ( !parseFloat( this.layout.options.transitionDuration ) ) {
    this._nonTransition( args );
    return;
  }

  var _transition = this._transn;
  // keep track of onTransitionEnd callback by css property
  for ( var prop in args.onTransitionEnd ) {
    _transition.onEnd[ prop ] = args.onTransitionEnd[ prop ];
  }
  // keep track of properties that are transitioning
  for ( prop in args.to ) {
    _transition.ingProperties[ prop ] = true;
    // keep track of properties to clean up when transition is done
    if ( args.isCleaning ) {
      _transition.clean[ prop ] = true;
    }
  }

  // set from styles
  if ( args.from ) {
    this.css( args.from );
    // force redraw. http://blog.alexmaccaw.com/css-transitions
    var h = this.element.offsetHeight;
    // hack for JSHint to hush about unused var
    h = null;
  }
  // enable transition
  this.enableTransition( args.to );
  // set styles that are transitioning
  this.css( args.to );

  this.isTransitioning = true;

};

var itemTransitionProperties = transformProperty && ( toDash( transformProperty ) +
  ',opacity' );

Item.prototype.enableTransition = function(/* style */) {
  // only enable if not already transitioning
  // bug in IE10 were re-setting transition style will prevent
  // transitionend event from triggering
  if ( this.isTransitioning ) {
    return;
  }

  // make transition: foo, bar, baz from style object
  // TODO uncomment this bit when IE10 bug is resolved
  // var transitionValue = [];
  // for ( var prop in style ) {
  //   // dash-ify camelCased properties like WebkitTransition
  //   transitionValue.push( toDash( prop ) );
  // }
  // enable transition styles
  // HACK always enable transform,opacity for IE10
  this.css({
    transitionProperty: itemTransitionProperties,
    transitionDuration: this.layout.options.transitionDuration
  });
  // listen for transition end event
  this.element.addEventListener( transitionEndEvent, this, false );
};

Item.prototype.transition = Item.prototype[ transitionProperty ? '_transition' : '_nonTransition' ];

// ----- events ----- //

Item.prototype.onwebkitTransitionEnd = function( event ) {
  this.ontransitionend( event );
};

Item.prototype.onotransitionend = function( event ) {
  this.ontransitionend( event );
};

// properties that I munge to make my life easier
var dashedVendorProperties = {
  '-webkit-transform': 'transform',
  '-moz-transform': 'transform',
  '-o-transform': 'transform'
};

Item.prototype.ontransitionend = function( event ) {
  // disregard bubbled events from children
  if ( event.target !== this.element ) {
    return;
  }
  var _transition = this._transn;
  // get property name of transitioned property, convert to prefix-free
  var propertyName = dashedVendorProperties[ event.propertyName ] || event.propertyName;

  // remove property that has completed transitioning
  delete _transition.ingProperties[ propertyName ];
  // check if any properties are still transitioning
  if ( isEmptyObj( _transition.ingProperties ) ) {
    // all properties have completed transitioning
    this.disableTransition();
  }
  // clean style
  if ( propertyName in _transition.clean ) {
    // clean up style
    this.element.style[ event.propertyName ] = '';
    delete _transition.clean[ propertyName ];
  }
  // trigger onTransitionEnd callback
  if ( propertyName in _transition.onEnd ) {
    var onTransitionEnd = _transition.onEnd[ propertyName ];
    onTransitionEnd.call( this );
    delete _transition.onEnd[ propertyName ];
  }

  this.emitEvent( 'transitionEnd', [ this ] );
};

Item.prototype.disableTransition = function() {
  this.removeTransitionStyles();
  this.element.removeEventListener( transitionEndEvent, this, false );
  this.isTransitioning = false;
};

/**
 * removes style property from element
 * @param {Object} style
**/
Item.prototype._removeStyles = function( style ) {
  // clean up transition styles
  var cleanStyle = {};
  for ( var prop in style ) {
    cleanStyle[ prop ] = '';
  }
  this.css( cleanStyle );
};

var cleanTransitionStyle = {
  transitionProperty: '',
  transitionDuration: ''
};

Item.prototype.removeTransitionStyles = function() {
  // remove transition
  this.css( cleanTransitionStyle );
};

// ----- show/hide/remove ----- //

// remove element from DOM
Item.prototype.removeElem = function() {
  this.element.parentNode.removeChild( this.element );
  this.emitEvent( 'remove', [ this ] );
};

Item.prototype.remove = function() {
  // just remove element if no transition support or no transition
  if ( !transitionProperty || !parseFloat( this.layout.options.transitionDuration ) ) {
    this.removeElem();
    return;
  }

  // start transition
  var _this = this;
  this.on( 'transitionEnd', function() {
    _this.removeElem();
    return true; // bind once
  });
  this.hide();
};

Item.prototype.reveal = function() {
  delete this.isHidden;
  // remove display: none
  this.css({ display: '' });

  var options = this.layout.options;
  this.transition({
    from: options.hiddenStyle,
    to: options.visibleStyle,
    isCleaning: true
  });
};

Item.prototype.hide = function() {
  // set flag
  this.isHidden = true;
  // remove display: none
  this.css({ display: '' });

  var options = this.layout.options;
  this.transition({
    from: options.visibleStyle,
    to: options.hiddenStyle,
    // keep hidden stuff hidden
    isCleaning: true,
    onTransitionEnd: {
      opacity: function() {
        // check if still hidden
        // during transition, item may have been un-hidden
        if ( this.isHidden ) {
          this.css({ display: 'none' });
        }
      }
    }
  });
};

Item.prototype.destroy = function() {
  this.css({
    position: '',
    left: '',
    right: '',
    top: '',
    bottom: '',
    transition: '',
    transform: ''
  });
};

return Item;

}

// -------------------------- transport -------------------------- //

if ( typeof define === 'function' && define.amd ) {
  // AMD
  define( [
      'eventEmitter/EventEmitter',
      'get-size/get-size',
      'get-style-property/get-style-property'
    ],
    outlayerItemDefinition );
} else if (typeof exports === 'object') {
  // CommonJS
  module.exports = outlayerItemDefinition(
    require('wolfy87-eventemitter'),
    require('get-size'),
    require('desandro-get-style-property')
  );
} else {
  // browser global
  window.Outlayer = {};
  window.Outlayer.Item = outlayerItemDefinition(
    window.EventEmitter,
    window.getSize,
    window.getStyleProperty
  );
}

})( window );