all files / lib/features/dragging/ HoverFix.js

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87.5% Branches 7/8
100% Functions 11/11
94.87% Lines 37/39
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import {
  closest as domClosest
} from 'min-dom';
 
import {
  toPoint
} from '../../util/Event';
 
var HIGH_PRIORITY = 1500;
 
 
/**
 * Browsers may swallow certain events (hover, out ...) if users are to
 * fast with the mouse.
 *
 * @see http://stackoverflow.com/questions/7448468/why-cant-i-reliably-capture-a-mouseout-event
 *
 * The fix implemented in this component ensure that we
 *
 * 1) have a hover state after a successive drag.move event
 * 2) have an out event when dragging leaves an element
 *
 * @param {EventBus} eventBus
 * @param {Dragging} dragging
 * @param {ElementRegistry} elementRegistry
 */
export default function HoverFix(eventBus, dragging, elementRegistry) {
 
  var self = this;
 
  /**
   * We wait for a specific sequence of events before
   * emitting a fake drag.hover event.
   *
   * Event Sequence:
   *
   * drag.start
   * drag.move
   * drag.move >> ensure we are hovering
   */
  eventBus.on('drag.start', function(event) {
 
    eventBus.once('drag.move', function() {
 
      eventBus.once('drag.move', function(event) {
 
        self.ensureHover(event);
      });
    });
 
  });
 
 
  /**
   * We make sure that drag.out is always fired, even if the
   * browser swallows an element.out event.
   *
   * Event sequence:
   *
   * drag.hover
   * (element.out >> sometimes swallowed)
   * element.hover >> ensure we fired drag.out
   */
  eventBus.on('drag.init', function() {
 
    var hover, hoverGfx;
 
    function setDragHover(event) {
      hover = event.hover;
      hoverGfx = event.hoverGfx;
    }
 
    function unsetHover() {
      hover = null;
      hoverGfx = null;
    }
 
    function ensureOut() {
 
      if (!hover) {
        return;
      }
 
      var element = hover,
          gfx = hoverGfx;
 
      hover = null;
      hoverGfx = null;
 
      // emit synthetic out event
      dragging.out({
        element: element,
        gfx: gfx
      });
    }
 
    eventBus.on('drag.hover', setDragHover);
    eventBus.on('element.out', unsetHover);
    eventBus.on('element.hover', HIGH_PRIORITY, ensureOut);
 
    eventBus.once('drag.cleanup', function() {
      eventBus.off('drag.hover', setDragHover);
      eventBus.off('element.out', unsetHover);
      eventBus.off('element.hover', ensureOut);
    });
 
  });
 
 
  /**
   * Make sure we are god damn hovering!
   *
   * @param {Event} dragging event
   */
  this.ensureHover = function(event) {
 
    if (event.hover) {
      return;
    }
 
    var originalEvent = event.originalEvent,
        position,
        target,
        element,
        gfx;
 
    if (!(originalEvent instanceof MouseEvent)) {
      return;
    }
 
    position = toPoint(originalEvent);
 
    // damn expensive operation, ouch!
    target = document.elementFromPoint(position.x, position.y);
 
    gfx = getGfx(target);
 
    Iif (gfx) {
      element = elementRegistry.get(gfx);
 
      dragging.hover({ element: element, gfx: gfx });
    }
  };
 
}
 
HoverFix.$inject = [
  'eventBus',
  'dragging',
  'elementRegistry'
];
 
 
// helpers /////////////////////
 
function getGfx(target) {
  return domClosest(target, 'svg, .djs-element', true);
}