feat: decouple DI from businessObject

In the diagram `di` is now accessed via the diagram element, not the
business object. This has the benefit that elements in multiple diagrams
can easily be represented.

Related to #1472

BREAKING CHANGE:

* Instead of referencing the `di` from the business object, reference it
  from the diagram element representing it.

lib/BaseViewer.js

@@ -528,19 +528,6 @@ BaseViewer.prototype.clear = function() {
     return;
   }
 
-  // remove businessObject#di binding
-  //
-  // this is necessary, as we establish the bindings
-  // in the BpmnTreeWalker (and assume none are given
-  // on reimport)
-  this.get('elementRegistry').forEach(function(element) {
-    var bo = element.businessObject;
-
-    if (bo && bo.di) {
-      delete bo.di;
-    }
-  });
-
   // remove drawn elements
   Diagram.prototype.clear.call(this);
 };

lib/draw/BpmnRenderUtil.js

@@ -43,7 +43,7 @@ export function isCollection(element) {
 }
 
 export function getDi(element) {
-  return element.businessObject.di;
+  return element.di;
 }
 
 export function getSemantic(element) {

lib/import/BpmnImporter.js

@@ -26,17 +26,18 @@ import {
 } from './Util';
 
 
-function elementData(semantic, attrs) {
+function elementData(semantic, di, attrs) {
   return assign({
     id: semantic.id,
     type: semantic.$type,
-    businessObject: semantic
+    businessObject: semantic,
+    di: di
   }, attrs);
 }
 
-function getWaypoints(bo, source, target) {
+function getWaypoints(di, source, target) {
 
-  var waypoints = bo.di.waypoint;
+  var waypoints = di.waypoint;
 
   if (!waypoints || waypoints.length < 2) {
     return [ getMid(source), getMid(target) ];
@@ -92,10 +93,8 @@ BpmnImporter.$inject = [
  * Add bpmn element (semantic) to the canvas onto the
  * specified parent shape.
  */
-BpmnImporter.prototype.add = function(semantic, parentElement) {
-
-  var di = semantic.di,
-      element,
+BpmnImporter.prototype.add = function(semantic, di, parentElement) {
+  var element,
       translate = this._translate,
       hidden;
 
@@ -107,21 +106,22 @@ BpmnImporter.prototype.add = function(semantic, parentElement) {
   if (is(di, 'bpmndi:BPMNPlane')) {
 
     // add a virtual element (not being drawn)
-    element = this._elementFactory.createRoot(elementData(semantic));
+    element = this._elementFactory.createRoot(elementData(semantic, di));
 
     this._canvas.setRootElement(element);
   }
 
   // SHAPE
   else if (is(di, 'bpmndi:BPMNShape')) {
 
-    var collapsed = !isExpanded(semantic),
+    var collapsed = !isExpanded(semantic, di),
         isFrame = isFrameElement(semantic);
+
     hidden = parentElement && (parentElement.hidden || parentElement.collapsed);
 
-    var bounds = semantic.di.bounds;
+    var bounds = di.bounds;
 
-    element = this._elementFactory.createShape(elementData(semantic, {
+    element = this._elementFactory.createShape(elementData(semantic, di, {
       collapsed: collapsed,
       hidden: hidden,
       x: Math.round(bounds.x),
@@ -159,11 +159,11 @@ BpmnImporter.prototype.add = function(semantic, parentElement) {
 
     hidden = parentElement && (parentElement.hidden || parentElement.collapsed);
 
-    element = this._elementFactory.createConnection(elementData(semantic, {
+    element = this._elementFactory.createConnection(elementData(semantic, di, {
       hidden: hidden,
       source: source,
       target: target,
-      waypoints: getWaypoints(semantic, source, target)
+      waypoints: getWaypoints(di, source, target)
     }));
 
     if (is(semantic, 'bpmn:DataAssociation')) {
@@ -190,7 +190,7 @@ BpmnImporter.prototype.add = function(semantic, parentElement) {
 
   // (optional) LABEL
   if (isLabelExternal(semantic) && getLabel(element)) {
-    this.addLabel(semantic, element);
+    this.addLabel(semantic, di, element);
   }
 
 
@@ -239,12 +239,12 @@ BpmnImporter.prototype._attachBoundary = function(boundarySemantic, boundaryElem
 /**
  * add label for an element
  */
-BpmnImporter.prototype.addLabel = function(semantic, element) {
+BpmnImporter.prototype.addLabel = function(semantic, di, element) {
   var bounds,
       text,
       label;
 
-  bounds = getExternalLabelBounds(semantic, element);
+  bounds = getExternalLabelBounds(di, element);
 
   text = getLabel(element);
 
@@ -254,7 +254,7 @@ BpmnImporter.prototype.addLabel = function(semantic, element) {
     bounds = this._textRenderer.getExternalLabelBounds(bounds, text);
   }
 
-  label = this._elementFactory.createLabel(elementData(semantic, {
+  label = this._elementFactory.createLabel(elementData(semantic, di, {
     id: semantic.id + '_label',
     labelTarget: element,
     type: 'label',

lib/import/BpmnTreeWalker.js

@@ -4,17 +4,10 @@ import {
   forEach
 } from 'min-dash';
 
-import Refs from 'object-refs';
-
 import {
   elementToString
 } from './Util';
 
-var diRefs = new Refs(
-  { name: 'bpmnElement', enumerable: true },
-  { name: 'di', configurable: true }
-);
-
 /**
  * Returns true if an element has the given meta-model type
  *
@@ -48,6 +41,8 @@ export default function BpmnTreeWalker(handler, translate) {
   // prerequisites are drawn
   var deferred = [];
 
+  var diMap = {};
+
   // Helpers //////////////////////
 
   function contextual(fn, ctx) {
@@ -76,17 +71,17 @@ export default function BpmnTreeWalker(handler, translate) {
     }
 
     // call handler
-    return handler.element(element, ctx);
+    return handler.element(element, diMap[element.id], ctx);
   }
 
   function visitRoot(element, diagram) {
-    return handler.root(element, diagram);
+    return handler.root(element, diMap[element.id], diagram);
   }
 
   function visitIfDi(element, ctx) {
 
     try {
-      var gfx = element.di && visit(element, ctx);
+      var gfx = diMap[element.id] && visit(element, ctx);
 
       handled(element);
 
@@ -109,16 +104,15 @@ export default function BpmnTreeWalker(handler, translate) {
     var bpmnElement = di.bpmnElement;
 
     if (bpmnElement) {
-      if (bpmnElement.di) {
+      if (diMap[bpmnElement.id]) {
         logError(
           translate('multiple DI elements defined for {element}', {
             element: elementToString(bpmnElement)
           }),
           { element: bpmnElement }
         );
       } else {
-        diRefs.bind(bpmnElement, 'di');
-        bpmnElement.di = di;
+        diMap[bpmnElement.id] = di;
       }
     } else {
       logError(
@@ -175,6 +169,7 @@ export default function BpmnTreeWalker(handler, translate) {
     }
 
     // load DI from selected diagram only
+    diMap = {};
     handleDiagram(diagram);
 
 

lib/import/Importer.js

@@ -49,12 +49,12 @@ export function importBpmnDiagram(diagram, definitions, bpmnDiagram) {
 
     var visitor = {
 
-      root: function(element) {
-        return importer.add(element);
+      root: function(element, di) {
+        return importer.add(element, di);
       },
 
-      element: function(element, parentShape) {
-        return importer.add(element, parentShape);
+      element: function(element, di, parentShape) {
+        return importer.add(element, di, parentShape);
       },
 
       error: function(message, context) {

lib/util/DiUtil.js

@@ -1,21 +1,24 @@
 import {
   is,
-  getBusinessObject
+  getBusinessObject,
+  getDi
 } from './ModelUtil';
 
 import {
   forEach
 } from 'min-dash';
 
 
-export function isExpanded(element) {
+export function isExpanded(element, di) {
 
   if (is(element, 'bpmn:CallActivity')) {
     return false;
   }
 
   if (is(element, 'bpmn:SubProcess')) {
-    return getBusinessObject(element).di && !!getBusinessObject(element).di.isExpanded;
+    di = di || getDi(element);
+
+    return di && !!di.isExpanded;
   }
 
   if (is(element, 'bpmn:Participant')) {

lib/util/LabelUtil.js

@@ -116,15 +116,14 @@ export function getExternalLabelMid(element) {
  * Returns the bounds of an elements label, parsed from the elements DI or
  * generated from its bounds.
  *
- * @param {BpmnElement} semantic
+ * @param {BpmndDi} di
  * @param {djs.model.Base} element
  */
-export function getExternalLabelBounds(semantic, element) {
+export function getExternalLabelBounds(di, element) {
 
   var mid,
       size,
       bounds,
-      di = semantic.di,
       label = di.label;
 
   if (label && label.bounds) {

lib/util/ModelUtil.js

@@ -22,4 +22,15 @@ export function is(element, type) {
  */
 export function getBusinessObject(element) {
   return (element && element.businessObject) || element;
+}
+
+/**
+ * Return the di object for a given element.
+ *
+ * @param  {djs.model.Base} element
+ *
+ * @return {ModdleElement}
+ */
+export function getDi(element) {
+  return element && element.di;
 }