# all files / Github/diagram-js/lib/features/dragging/ Dragging.js

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83.33% Branches 55/66
72.22% Functions 13/18
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     /* global TouchEvent */

    var round = Math.round;

    import { assign } from 'min-dash';

    import {
      event as domEvent
    } from 'min-dom';

    import {
      getOriginal,
      toPoint,
      stopPropagation
    } from '../../util/Event';

    import {
      set as cursorSet,
      unset as cursorUnset
    } from '../../util/Cursor';

    import {
      install as installClickTrap
    } from '../../util/ClickTrap';

    import {
      delta as deltaPos
    } from '../../util/PositionUtil';

    var DRAG_ACTIVE_CLS = 'djs-drag-active';

    function preventDefault(event) {
      event.preventDefault();
    }

    function isTouchEvent(event) {
      // check for TouchEvent being available first
      // (i.e. not available on desktop Firefox)
      return typeof TouchEvent !== 'undefined' && event instanceof TouchEvent;
    }

    function getLength(point) {
      return Math.sqrt(Math.pow(point.x, 2) + Math.pow(point.y, 2));
    }

    /**
     * A helper that fires canvas localized drag events and realizes
     * the general "drag-and-drop" look and feel.
     *
     * Calling {@link Dragging#activate} activates dragging on a canvas.
     *
     * It provides the following:
     *
     *   * emits life cycle events, namespaced with a prefix assigned
     *     during dragging activation
     *   * sets and restores the cursor
     *   * sets and restores the selection
     *   * ensures there can be only one drag operation active at a time
     *
     * Dragging may be canceled manually by calling {@link Dragging#cancel}
     * or by pressing ESC.
     *
     *
     * ## Life-cycle events
     *
     * Dragging can be in three different states, off, initialized
     * and active.
     *
     * (1) off: no dragging operation is in progress
     * (2) initialized: a new drag operation got initialized but not yet
     *                  started (i.e. because of no initial move)
     * (3) started: dragging is in progress
     *
     * Eventually dragging will be off again after a drag operation has
     * been ended or canceled via user click or ESC key press.
     *
     * To indicate transitions between these states dragging emits generic
     * life-cycle events with the `drag.` prefix _and_ events namespaced
     * to a prefix choosen by a user during drag initialization.
     *
     * The following events are emitted (appropriately prefixed) via
     * the {@link EventBus}.
     *
     * * `init`
     * * `start`
     * * `move`
     * * `end`
     * * `ended` (dragging already in off state)
     * * `cancel` (only if previously started)
     * * `canceled` (dragging already in off state, only if previously started)
     * * `cleanup`
     *
     *
     * @example
     *
     * function MyDragComponent(eventBus, dragging) {
     *
     *   eventBus.on('mydrag.start', function(event) {
     *     console.log('yes, we start dragging');
     *   });
     *
     *   eventBus.on('mydrag.move', function(event) {
     *     console.log('canvas local coordinates', event.x, event.y, event.dx, event.dy);
     *
     *     // local drag data is passed with the event
     *     event.context.foo; // "BAR"
     *
     *     // the original mouse event, too
     *     event.originalEvent; // MouseEvent(...)
     *   });
     *
     *   eventBus.on('element.click', function(event) {
     *     dragging.init(event, 'mydrag', {
     *       cursor: 'grabbing',
     *       data: {
     *         context: {
     *           foo: "BAR"
     *         }
     *       }
     *     });
     *   });
     * }
     */
    export default function Dragging(eventBus, canvas, selection) {

      var defaultOptions = {
        threshold: 5,
        trapClick: true
      };

      // the currently active drag operation
      // dragging is active as soon as this context exists.
      //
      // it is visually _active_ only when a context.active flag is set to true.
      var context;

      /* convert a global event into local coordinates */
      function toLocalPoint(globalPosition) {

        var viewbox = canvas.viewbox();

        var clientRect = canvas._container.getBoundingClientRect();

        return {
          x: viewbox.x + (globalPosition.x - clientRect.left) / viewbox.scale,
          y: viewbox.y + (globalPosition.y - clientRect.top) / viewbox.scale
        };
      }

      // helpers

      function fire(type, dragContext) {
        dragContext = dragContext || context;

        var event = eventBus.createEvent(
          assign(
            {},
            dragContext.payload,
            dragContext.data,
            { isTouch: dragContext.isTouch }
          )
        );

        // default integration
        Iif (eventBus.fire('drag.' + type, event) === false) {
          return false;
        }

        return eventBus.fire(dragContext.prefix + '.' + type, event);
      }

      // event listeners

      function move(event, activate) {
        var payload = context.payload,
            displacement = context.displacement;

        var globalStart = context.globalStart,
            globalCurrent = toPoint(event),
            globalDelta = deltaPos(globalCurrent, globalStart);

        var localStart = context.localStart,
            localCurrent = toLocalPoint(globalCurrent),
            localDelta = deltaPos(localCurrent, localStart);

        // activate context explicitly or once threshold is reached
        if (!context.active && (activate || getLength(globalDelta) > context.threshold)) {

          // fire start event with original
          // starting coordinates

          assign(payload, {
            x: round(localStart.x + displacement.x),
            y: round(localStart.y + displacement.y),
            dx: 0,
            dy: 0
          }, { originalEvent: event });

          Iif (false === fire('start')) {
            return cancel();
          }

          context.active = true;

          // unset selection and remember old selection
          // the previous (old) selection will always passed
          // with the event via the event.previousSelection property
          Eif (!context.keepSelection) {
            payload.previousSelection = selection.get();
            selection.select(null);
          }

          // allow custom cursor
          if (context.cursor) {
            cursorSet(context.cursor);
          }

          // indicate dragging via marker on root element
          canvas.addMarker(canvas.getRootElement(), DRAG_ACTIVE_CLS);
        }

        stopPropagation(event);

        Eif (context.active) {

          // update payload with actual coordinates
          assign(payload, {
            x: round(localCurrent.x + displacement.x),
            y: round(localCurrent.y + displacement.y),
            dx: round(localDelta.x),
            dy: round(localDelta.y)
          }, { originalEvent: event });

          // emit move event
          fire('move');
        }
      }

      function end(event) {
        var previousContext,
            returnValue = true;

        Eif (context.active) {

          if (event) {
            context.payload.originalEvent = event;

            // suppress original event (click, ...)
            // because we just ended a drag operation
            stopPropagation(event);
          }

          // implementations may stop restoring the
          // original state (selections, ...) by preventing the
          // end events default action
          returnValue = fire('end');
        }

        if (returnValue === false) {
          fire('rejected');
        }

        previousContext = cleanup(returnValue !== true);

        // last event to be fired when all drag operations are done
        // at this point in time no drag operation is in progress anymore
        fire('ended', previousContext);
      }

      // cancel active drag operation if the user presses
      // the ESC key on the keyboard

      function checkCancel(event) {

        if (event.which === 27) {
          preventDefault(event);

          cancel();
        }
      }

      // prevent ghost click that might occur after a finished
      // drag and drop session

      function trapClickAndEnd(event) {

        var untrap;

        // trap the click in case we are part of an active
        // drag operation. This will effectively prevent
        // the ghost click that cannot be canceled otherwise.
        if (context.active) {

          untrap = installClickTrap(eventBus);

          // remove trap after minimal delay
          setTimeout(untrap, 400);

          // prevent default action (click)
          preventDefault(event);
        }

        end(event);
      }

      function trapTouch(event) {
        move(event);
      }

      // update the drag events hover (djs.model.Base) and hoverGfx (Snap<SVGElement>)
      // properties during hover and out and fire {prefix}.hover and {prefix}.out properties
      // respectively

      function hover(event) {
        var payload = context.payload;

        payload.hoverGfx = event.gfx;
        payload.hover = event.element;

        fire('hover');
      }

      function out(event) {
        fire('out');

        var payload = context.payload;

        payload.hoverGfx = null;
        payload.hover = null;
      }

      // life-cycle methods

      function cancel(restore) {
        var previousContext;

        if (!context) {
          return;
        }

        var wasActive = context.active;

        if (wasActive) {
          fire('cancel');
        }

        previousContext = cleanup(restore);

        if (wasActive) {
          // last event to be fired when all drag operations are done
          // at this point in time no drag operation is in progress anymore
          fire('canceled', previousContext);
        }
      }

      function cleanup(restore) {
        var previousContext,
            endDrag;

        fire('cleanup');

        // reset cursor
        cursorUnset();

        if (context.trapClick) {
          endDrag = trapClickAndEnd;
        } else {
          endDrag = end;
        }

        // reset dom listeners
        domEvent.unbind(document, 'mousemove', move);

        domEvent.unbind(document, 'dragstart', preventDefault);
        domEvent.unbind(document, 'selectstart', preventDefault);

        domEvent.unbind(document, 'mousedown', endDrag, true);
        domEvent.unbind(document, 'mouseup', endDrag, true);

        domEvent.unbind(document, 'keyup', checkCancel);

        domEvent.unbind(document, 'touchstart', trapTouch, true);
        domEvent.unbind(document, 'touchcancel', cancel, true);
        domEvent.unbind(document, 'touchmove', move, true);
        domEvent.unbind(document, 'touchend', end, true);

        eventBus.off('element.hover', hover);
        eventBus.off('element.out', out);

        // remove drag marker on root element
        canvas.removeMarker(canvas.getRootElement(), DRAG_ACTIVE_CLS);

        // restore selection, unless it has changed
        var previousSelection = context.payload.previousSelection;

        if (restore !== false && previousSelection && !selection.get().length) {
          selection.select(previousSelection);
        }

        previousContext = context;

        context = null;

        return previousContext;
      }

      /**
       * Initialize a drag operation.
       *
       * If `localPosition` is given, drag events will be emitted
       * relative to it.
       *
       * @param {MouseEvent|TouchEvent} [event]
       * @param {Point} [localPosition] actual diagram local position this drag operation should start at
       * @param {String} prefix
       * @param {Object} [options]
       */
      function init(event, relativeTo, prefix, options) {

        // only one drag operation may be active, at a time
        if (context) {
          cancel(false);
        }

        if (typeof relativeTo === 'string') {
          options = prefix;
          prefix = relativeTo;
          relativeTo = null;
        }

        options = assign({}, defaultOptions, options || {});

        var data = options.data || {},
            originalEvent,
            globalStart,
            localStart,
            endDrag,
            isTouch;

        if (options.trapClick) {
          endDrag = trapClickAndEnd;
        } else {
          endDrag = end;
        }

        if (event) {
          originalEvent = getOriginal(event) || event;
          globalStart = toPoint(event);

          stopPropagation(event);

          // prevent default browser dragging behavior
          Iif (originalEvent.type === 'dragstart') {
            preventDefault(originalEvent);
          }
        } else {
          originalEvent = null;
          globalStart = { x: 0, y: 0 };
        }

        localStart = toLocalPoint(globalStart);

        if (!relativeTo) {
          relativeTo = localStart;
        }

        isTouch = isTouchEvent(originalEvent);

        context = assign({
          prefix: prefix,
          data: data,
          payload: {},
          globalStart: globalStart,
          displacement: deltaPos(relativeTo, localStart),
          localStart: localStart,
          isTouch: isTouch
        }, options);

        // skip dom registration if trigger
        // is set to manual (during testing)
        if (!options.manual) {

          // add dom listeners

          Iif (isTouch) {
            domEvent.bind(document, 'touchstart', trapTouch, true);
            domEvent.bind(document, 'touchcancel', cancel, true);
            domEvent.bind(document, 'touchmove', move, true);
            domEvent.bind(document, 'touchend', end, true);
          } else {
            // assume we use the mouse to interact per default
            domEvent.bind(document, 'mousemove', move);

            // prevent default browser drag and text selection behavior
            domEvent.bind(document, 'dragstart', preventDefault);
            domEvent.bind(document, 'selectstart', preventDefault);

            domEvent.bind(document, 'mousedown', endDrag, true);
            domEvent.bind(document, 'mouseup', endDrag, true);
          }

          domEvent.bind(document, 'keyup', checkCancel);

          eventBus.on('element.hover', hover);
          eventBus.on('element.out', out);
        }

        fire('init');

        if (options.autoActivate) {
          move(event, true);
        }
      }

      // cancel on diagram destruction
      eventBus.on('diagram.destroy', cancel);

      // API

      this.init = init;
      this.move = move;
      this.hover = hover;
      this.out = out;
      this.end = end;

      this.cancel = cancel;

      // for introspection

      this.context = function() {
        return context;
      };

      this.setOptions = function(options) {
        assign(defaultOptions, options);
      };
    }

    Dragging.$inject = [
      'eventBus',
      'canvas',
      'selection'
    ];