bpmn-js/lib/features/snapping/BpmnSnappingUtil.js

import {
  getOrientation
} from 'diagram-js/lib/layout/LayoutUtil';


export function getBoundaryAttachment(position, targetBounds) {

  var orientation = getOrientation(position, targetBounds, -15);

  if (orientation !== 'intersect') {
    return orientation;
  } else {
    return null;
  }
}


// participant snapping box implementation //////////////////////

import { is } from '../../util/ModelUtil';

import {
  asTRBL
} from 'diagram-js/lib/layout/LayoutUtil';

import {
  collectLanes,
  getLanesRoot
} from '../modeling/util/LaneUtil';

var abs = Math.abs,
    min = Math.min,
    max = Math.max;


function addToTrbl(trbl, attr, value, choice) {

  var current = trbl[attr];

  // make sure to set the value if it does not exist
  // or apply the correct value by comparing against
  // choice(value, currentValue)
  trbl[attr] = current === undefined ? value : choice(value, current);
}

function addMin(trbl, attr, value) {
  return addToTrbl(trbl, attr, value, min);
}

function addMax(trbl, attr, value) {
  return addToTrbl(trbl, attr, value, max);
}


var LANE_MIN_HEIGHT = 60,
    LANE_MIN_WIDTH = 300,
    LANE_RIGHT_PADDING = 20,
    LANE_LEFT_PADDING = 50,
    LANE_TOP_PADDING = 20,
    LANE_BOTTOM_PADDING = 20;


export function getParticipantSizeConstraints(laneShape, resizeDirection, balanced) {

  var lanesRoot = getLanesRoot(laneShape);

  var isFirst = true,
      isLast = true;

  // max top/bottom size for lanes

  var allLanes = collectLanes(lanesRoot, [ lanesRoot ]);

  var laneTrbl = asTRBL(laneShape);

  var maxTrbl = {},
      minTrbl = {};

  if (/e/.test(resizeDirection)) {
    minTrbl.right = laneTrbl.left + LANE_MIN_WIDTH;
  } else
  if (/w/.test(resizeDirection)) {
    minTrbl.left = laneTrbl.right - LANE_MIN_WIDTH;
  }

  allLanes.forEach(function(other) {

    var otherTrbl = asTRBL(other);

    if (/n/.test(resizeDirection)) {

      if (otherTrbl.top < (laneTrbl.top - 10)) {
        isFirst = false;
      }

      // max top size (based on next element)
      if (balanced && abs(laneTrbl.top - otherTrbl.bottom) < 10) {
        addMax(maxTrbl, 'top', otherTrbl.top + LANE_MIN_HEIGHT);
      }

      // min top size (based on self or nested element)
      if (abs(laneTrbl.top - otherTrbl.top) < 5) {
        addMin(minTrbl, 'top', otherTrbl.bottom - LANE_MIN_HEIGHT);
      }
    }

    if (/s/.test(resizeDirection)) {

      if (otherTrbl.bottom > (laneTrbl.bottom + 10)) {
        isLast = false;
      }

      // max bottom size (based on previous element)
      if (balanced && abs(laneTrbl.bottom - otherTrbl.top) < 10) {
        addMin(maxTrbl, 'bottom', otherTrbl.bottom - LANE_MIN_HEIGHT);
      }

      // min bottom size (based on self or nested element)
      if (abs(laneTrbl.bottom - otherTrbl.bottom) < 5) {
        addMax(minTrbl, 'bottom', otherTrbl.top + LANE_MIN_HEIGHT);
      }
    }
  });


  // max top/bottom/left/right size based on flow nodes

  var flowElements = lanesRoot.children.filter(function(s) {
    return !s.hidden && !s.waypoints && (is(s, 'bpmn:FlowElement') || is(s, 'bpmn:Artifact'));
  });

  flowElements.forEach(function(flowElement) {

    var flowElementTrbl = asTRBL(flowElement);

    if (isFirst && /n/.test(resizeDirection)) {
      addMin(minTrbl, 'top', flowElementTrbl.top - LANE_TOP_PADDING);
    }

    if (/e/.test(resizeDirection)) {
      addMax(minTrbl, 'right', flowElementTrbl.right + LANE_RIGHT_PADDING);
    }

    if (isLast && /s/.test(resizeDirection)) {
      addMax(minTrbl, 'bottom', flowElementTrbl.bottom + LANE_BOTTOM_PADDING);
    }

    if (/w/.test(resizeDirection)) {
      addMin(minTrbl, 'left', flowElementTrbl.left - LANE_LEFT_PADDING);
    }
  });


  return {
    min: minTrbl,
    max: maxTrbl
  };
}