flickity/js/drag.js

Touch, responsive, flickable carousels

// drag
( function( window, factory ) {
  // universal module definition
  /* jshint strict: false */
  if ( typeof define == 'function' && define.amd ) {
    // AMD
    define( [
      './flickity',
      'unidragger/unidragger',
      'fizzy-ui-utils/utils'
    ], function( Flickity, Unidragger, utils ) {
      return factory( window, Flickity, Unidragger, utils );
    });
  } else if ( typeof module == 'object' && module.exports ) {
    // CommonJS
    module.exports = factory(
      window,
      require('./flickity'),
      require('unidragger'),
      require('fizzy-ui-utils')
    );
  } else {
    // browser global
    window.Flickity = factory(
      window,
      window.Flickity,
      window.Unidragger,
      window.fizzyUIUtils
    );
  }

}( window, function factory( window, Flickity, Unidragger, utils ) {

'use strict';

// ----- defaults ----- //

utils.extend( Flickity.defaults, {
  draggable: true,
  dragThreshold: 3,
});

// ----- create ----- //

Flickity.createMethods.push('_createDrag');

// -------------------------- drag prototype -------------------------- //

var proto = Flickity.prototype;
utils.extend( proto, Unidragger.prototype );

// --------------------------  -------------------------- //

var isTouch = 'createTouch' in document;
var isTouchmoveScrollCanceled = false;

proto._createDrag = function() {
  this.on( 'activate', this.bindDrag );
  this.on( 'uiChange', this._uiChangeDrag );
  this.on( 'childUIPointerDown', this._childUIPointerDownDrag );
  this.on( 'deactivate', this.unbindDrag );
  // HACK - add seemingly innocuous handler to fix iOS 10 scroll behavior
  // #457, RubaXa/Sortable#973
  if ( isTouch && !isTouchmoveScrollCanceled ) {
    window.addEventListener( 'touchmove', function() {});
    isTouchmoveScrollCanceled = true;
  }
};

proto.bindDrag = function() {
  if ( !this.options.draggable || this.isDragBound ) {
    return;
  }
  this.element.classList.add('is-draggable');
  this.handles = [ this.viewport ];
  this.bindHandles();
  this.isDragBound = true;
};

proto.unbindDrag = function() {
  if ( !this.isDragBound ) {
    return;
  }
  this.element.classList.remove('is-draggable');
  this.unbindHandles();
  delete this.isDragBound;
};

proto._uiChangeDrag = function() {
  delete this.isFreeScrolling;
};

proto._childUIPointerDownDrag = function( event ) {
  event.preventDefault();
  this.pointerDownFocus( event );
};

// -------------------------- pointer events -------------------------- //

// nodes that have text fields
var cursorNodes = {
  TEXTAREA: true,
  INPUT: true,
  OPTION: true,
};

// input types that do not have text fields
var clickTypes = {
  radio: true,
  checkbox: true,
  button: true,
  submit: true,
  image: true,
  file: true,
};

proto.pointerDown = function( event, pointer ) {
  // dismiss inputs with text fields. #403, #404
  var isCursorInput = cursorNodes[ event.target.nodeName ] &&
    !clickTypes[ event.target.type ];
  if ( isCursorInput ) {
    // reset pointerDown logic
    this.isPointerDown = false;
    delete this.pointerIdentifier;
    return;
  }

  this._dragPointerDown( event, pointer );

  // kludge to blur focused inputs in dragger
  var focused = document.activeElement;
  if ( focused && focused.blur && focused != this.element &&
    // do not blur body for IE9 & 10, #117
    focused != document.body ) {
    focused.blur();
  }
  this.pointerDownFocus( event );
  // stop if it was moving
  this.dragX = this.x;
  this.viewport.classList.add('is-pointer-down');
  // bind move and end events
  this._bindPostStartEvents( event );
  // track scrolling
  this.pointerDownScroll = getScrollPosition();
  window.addEventListener( 'scroll', this );

  this.dispatchEvent( 'pointerDown', event, [ pointer ] );
};

var touchStartEvents = {
  touchstart: true,
  MSPointerDown: true
};

var focusNodes = {
  INPUT: true,
  SELECT: true
};

proto.pointerDownFocus = function( event ) {
  // focus element, if not touch, and its not an input or select
  if ( !this.options.accessibility || touchStartEvents[ event.type ] ||
      focusNodes[ event.target.nodeName ] ) {
    return;
  }
  var prevScrollY = window.pageYOffset;
  this.element.focus();
  // hack to fix scroll jump after focus, #76
  if ( window.pageYOffset != prevScrollY ) {
    window.scrollTo( window.pageXOffset, prevScrollY );
  }
};

proto.canPreventDefaultOnPointerDown = function( event ) {
  // prevent default, unless touchstart or <select>
  var isTouchstart = event.type == 'touchstart';
  var targetNodeName = event.target.nodeName;
  return !isTouchstart && targetNodeName != 'SELECT';
};

// ----- move ----- //

proto.hasDragStarted = function( moveVector ) {
  return Math.abs( moveVector.x ) > this.options.dragThreshold;
};

// ----- up ----- //

proto.pointerUp = function( event, pointer ) {
  delete this.isTouchScrolling;
  this.viewport.classList.remove('is-pointer-down');
  this.dispatchEvent( 'pointerUp', event, [ pointer ] );
  this._dragPointerUp( event, pointer );
};

proto.pointerDone = function() {
  window.removeEventListener( 'scroll', this );
  delete this.pointerDownScroll;
};

// -------------------------- dragging -------------------------- //

proto.dragStart = function( event, pointer ) {
  this.dragStartPosition = this.x;
  this.startAnimation();
  window.removeEventListener( 'scroll', this );
  this.dispatchEvent( 'dragStart', event, [ pointer ] );
};

proto.pointerMove = function( event, pointer ) {
  var moveVector = this._dragPointerMove( event, pointer );
  this.dispatchEvent( 'pointerMove', event, [ pointer, moveVector ] );
  this._dragMove( event, pointer, moveVector );
};

proto.dragMove = function( event, pointer, moveVector ) {
  event.preventDefault();

  this.previousDragX = this.dragX;
  // reverse if right-to-left
  var direction = this.options.rightToLeft ? -1 : 1;
  var dragX = this.dragStartPosition + moveVector.x * direction;

  if ( !this.options.wrapAround && this.slides.length ) {
    // slow drag
    var originBound = Math.max( -this.slides[0].target, this.dragStartPosition );
    dragX = dragX > originBound ? ( dragX + originBound ) * 0.5 : dragX;
    var endBound = Math.min( -this.getLastSlide().target, this.dragStartPosition );
    dragX = dragX < endBound ? ( dragX + endBound ) * 0.5 : dragX;
  }

  this.dragX = dragX;

  this.dragMoveTime = new Date();
  this.dispatchEvent( 'dragMove', event, [ pointer, moveVector ] );
};

proto.dragEnd = function( event, pointer ) {
  if ( this.options.freeScroll ) {
    this.isFreeScrolling = true;
  }
  // set selectedIndex based on where flick will end up
  var index = this.dragEndRestingSelect();

  if ( this.options.freeScroll && !this.options.wrapAround ) {
    // if free-scroll & not wrap around
    // do not free-scroll if going outside of bounding slides
    // so bounding slides can attract slider, and keep it in bounds
    var restingX = this.getRestingPosition();
    this.isFreeScrolling = -restingX > this.slides[0].target &&
      -restingX < this.getLastSlide().target;
  } else if ( !this.options.freeScroll && index == this.selectedIndex ) {
    // boost selection if selected index has not changed
    index += this.dragEndBoostSelect();
  }
  delete this.previousDragX;
  // apply selection
  // TODO refactor this, selecting here feels weird
  // HACK, set flag so dragging stays in correct direction
  this.isDragSelect = this.options.wrapAround;
  this.select( index );
  delete this.isDragSelect;
  this.dispatchEvent( 'dragEnd', event, [ pointer ] );
};

proto.dragEndRestingSelect = function() {
  var restingX = this.getRestingPosition();
  // how far away from selected slide
  var distance = Math.abs( this.getSlideDistance( -restingX, this.selectedIndex ) );
  // get closet resting going up and going down
  var positiveResting = this._getClosestResting( restingX, distance, 1 );
  var negativeResting = this._getClosestResting( restingX, distance, -1 );
  // use closer resting for wrap-around
  var index = positiveResting.distance < negativeResting.distance ?
    positiveResting.index : negativeResting.index;
  return index;
};

/**
 * given resting X and distance to selected cell
 * get the distance and index of the closest cell
 * @param {Number} restingX - estimated post-flick resting position
 * @param {Number} distance - distance to selected cell
 * @param {Integer} increment - +1 or -1, going up or down
 * @returns {Object} - { distance: {Number}, index: {Integer} }
 */
proto._getClosestResting = function( restingX, distance, increment ) {
  var index = this.selectedIndex;
  var minDistance = Infinity;
  var condition = this.options.contain && !this.options.wrapAround ?
    // if contain, keep going if distance is equal to minDistance
    function( d, md ) { return d <= md; } : function( d, md ) { return d < md; };
  while ( condition( distance, minDistance ) ) {
    // measure distance to next cell
    index += increment;
    minDistance = distance;
    distance = this.getSlideDistance( -restingX, index );
    if ( distance === null ) {
      break;
    }
    distance = Math.abs( distance );
  }
  return {
    distance: minDistance,
    // selected was previous index
    index: index - increment
  };
};

/**
 * measure distance between x and a slide target
 * @param {Number} x
 * @param {Integer} index - slide index
 */
proto.getSlideDistance = function( x, index ) {
  var len = this.slides.length;
  // wrap around if at least 2 slides
  var isWrapAround = this.options.wrapAround && len > 1;
  var slideIndex = isWrapAround ? utils.modulo( index, len ) : index;
  var slide = this.slides[ slideIndex ];
  if ( !slide ) {
    return null;
  }
  // add distance for wrap-around slides
  var wrap = isWrapAround ? this.slideableWidth * Math.floor( index / len ) : 0;
  return x - ( slide.target + wrap );
};

proto.dragEndBoostSelect = function() {
  // do not boost if no previousDragX or dragMoveTime
  if ( this.previousDragX === undefined || !this.dragMoveTime ||
    // or if drag was held for 100 ms
    new Date() - this.dragMoveTime > 100 ) {
    return 0;
  }

  var distance = this.getSlideDistance( -this.dragX, this.selectedIndex );
  var delta = this.previousDragX - this.dragX;
  if ( distance > 0 && delta > 0 ) {
    // boost to next if moving towards the right, and positive velocity
    return 1;
  } else if ( distance < 0 && delta < 0 ) {
    // boost to previous if moving towards the left, and negative velocity
    return -1;
  }
  return 0;
};

// ----- staticClick ----- //

proto.staticClick = function( event, pointer ) {
  // get clickedCell, if cell was clicked
  var clickedCell = this.getParentCell( event.target );
  var cellElem = clickedCell && clickedCell.element;
  var cellIndex = clickedCell && this.cells.indexOf( clickedCell );
  this.dispatchEvent( 'staticClick', event, [ pointer, cellElem, cellIndex ] );
};

// ----- scroll ----- //

proto.onscroll = function() {
  var scroll = getScrollPosition();
  var scrollMoveX = this.pointerDownScroll.x - scroll.x;
  var scrollMoveY = this.pointerDownScroll.y - scroll.y;
  // cancel click/tap if scroll is too much
  if ( Math.abs( scrollMoveX ) > 3 || Math.abs( scrollMoveY ) > 3 ) {
    this._pointerDone();
  }
};

// ----- utils ----- //

function getScrollPosition() {
  return {
    x: window.pageXOffset,
    y: window.pageYOffset
  };
}

// -----  ----- //

return Flickity;

}));