feat(create): show connection preview during creation

Diagram will display connection preview when appending
a shape.

BREAKING CHANGES:

When appending a shape to existing element, the layouter will
receive a connection without waypoints, source, target and with
only { source, target } hints. Make sure your layouter handles
such case.

lib/features/create/CreateConnectPreview.js

@@ -0,0 +1,152 @@
+import {
+  append as svgAppend,
+  attr as svgAttr,
+  classes as svgClasses,
+  create as svgCreate,
+  remove as svgRemove,
+  clear as svgClear
+} from 'tiny-svg';
+
+
+var LOW_PRIORITY = 740;
+
+/**
+ * Shows a connection preview during element creation.
+ *
+ * @param {didi.Injector} injector
+ * @param {EventBus} eventBus
+ * @param {Canvas} canvas
+ * @param {GraphicsFactory} graphicsFactory
+ * @param {ElementFactory} elementFactory
+ */
+export default function CreateConnectPreview(injector, eventBus, canvas, graphicsFactory, elementFactory) {
+
+  // optional components
+
+  var connectionDocking = injector.get('connectionDocking', false);
+  var layouter = injector.get('layouter', false);
+
+
+  // visual helpers
+
+  function createConnectVisual() {
+
+    var visual = svgCreate('g');
+    svgAttr(visual, {
+      'pointer-events': 'none'
+    });
+
+    svgClasses(visual).add('djs-dragger');
+
+    svgAppend(canvas.getDefaultLayer(), visual);
+
+    return visual;
+  }
+
+  // move integration
+
+  eventBus.on('create.move', LOW_PRIORITY, function(event) {
+
+    var context = event.context,
+        source = context.source,
+        shape = context.shape,
+        connectVisual = context.connectVisual,
+        canExecute = context.canExecute,
+        connect = canExecute && canExecute.connect,
+        getConnection = context.getConnection,
+        connection;
+
+
+    if (!getConnection) {
+      getConnection = context.getConnection = Cacher(function(attrs) {
+        return elementFactory.create('connection', attrs);
+      });
+    }
+
+    if (!connectVisual) {
+      connectVisual = context.connectVisual = createConnectVisual();
+    }
+
+    svgClear(connectVisual);
+
+    if (!connect) {
+      return;
+    }
+
+    connection = getConnection(connectionAttrs(connect));
+
+    // monkey patch shape position for intersection to work
+    shape.x = Math.round(event.x - shape.width / 2);
+    shape.y = Math.round(event.y - shape.height / 2);
+
+    if (layouter) {
+      connection.waypoints = [];
+
+      connection.waypoints = layouter.layoutConnection(connection, {
+        source: source,
+        target: shape
+      });
+    } else {
+      connection.waypoints = [
+        { x: source.x + source.width / 2, y: source.y + source.height / 2 },
+        { x: event.x, y: event.y }
+      ];
+    }
+
+    if (connectionDocking) {
+      connection.waypoints = connectionDocking.getCroppedWaypoints(connection, source, shape);
+    }
+
+    graphicsFactory.drawConnection(connectVisual, connection);
+  });
+
+
+  eventBus.on('create.cleanup', function(event) {
+    var context = event.context;
+
+    if (context.connectVisual) {
+      svgRemove(context.connectVisual);
+    }
+  });
+
+}
+
+CreateConnectPreview.$inject = [
+  'injector',
+  'eventBus',
+  'canvas',
+  'graphicsFactory',
+  'elementFactory'
+];
+
+
+
+// helpers //////////////
+
+function connectionAttrs(connect) {
+
+  if (typeof connect === 'boolean') {
+    return {};
+  } else {
+    return connect;
+  }
+}
+
+
+function Cacher(createFn) {
+
+  var entries = {};
+
+  return function(attrs) {
+
+    var key = JSON.stringify(attrs);
+
+    var e = entries[key];
+
+    if (!e) {
+      e = entries[key] = createFn(attrs);
+    }
+
+    return e;
+  };
+}

lib/features/create/index.js

@@ -3,6 +3,7 @@ import SelectionModule from '../selection';
 import RulesModule from '../rules';
 
 import Create from './Create';
+import CreateConnectPreview from './CreateConnectPreview';
 
 
 export default {
@@ -11,5 +12,9 @@ export default {
     SelectionModule,
     RulesModule
   ],
-  create: [ 'type', Create ]
+  __init__: [
+    'createConnectPreview'
+  ],
+  create: [ 'type', Create ],
+  createConnectPreview: [ 'type', CreateConnectPreview ]
 };

test/spec/features/create/CreateSpec.js

@@ -224,6 +224,97 @@ describe('features/create - Create', function() {
 
   });
 
+  describe('display', function() {
+
+    it('should display connection preview', inject(function(create, elementRegistry, dragging) {
+
+      // given
+      var parentGfx = elementRegistry.getGraphics('parentShape');
+
+      // when
+      create.start(canvasEvent({ x: 0, y: 0 }), newShape, childShape);
+
+      dragging.move(canvasEvent({ x: 175, y: 175 }));
+      dragging.hover({ element: parentShape, gfx: parentGfx });
+      dragging.move(canvasEvent({ x: 400, y: 200 }));
+
+      var ctx = dragging.context();
+
+      // then
+      expect(ctx.data.context.connectVisual).to.exist;
+      expect(svgClasses(ctx.data.context.connectVisual).has('djs-dragger')).to.be.true;
+    }));
+
+
+    it('should not display preview if connection is disallowed',
+      inject(function(create, elementRegistry, dragging, createRules) {
+
+        // given
+        createRules.addRule('connection.create', 8000, function() {
+          return false;
+        });
+
+        var parentGfx = elementRegistry.getGraphics('parentShape');
+
+        // when
+        create.start(canvasEvent({ x: 0, y: 0 }), newShape, childShape);
+
+        dragging.move(canvasEvent({ x: 175, y: 175 }));
+        dragging.hover({ element: parentShape, gfx: parentGfx });
+        dragging.move(canvasEvent({ x: 400, y: 200 }));
+
+        var ctx = dragging.context();
+
+        // then
+        expect(ctx.data.context.connectVisual.childNodes).to.be.have.lengthOf(0);
+      })
+    );
+  });
+
+  describe('cleanup', function() {
+
+    it('should remove connection preview on dragging end', inject(function(create, elementRegistry, dragging) {
+
+      // given
+      var parentGfx = elementRegistry.getGraphics('parentShape');
+
+      // when
+      create.start(canvasEvent({ x: 0, y: 0 }), newShape, childShape);
+
+      dragging.move(canvasEvent({ x: 175, y: 175 }));
+      dragging.hover({ element: parentShape, gfx: parentGfx });
+      dragging.move(canvasEvent({ x: 400, y: 200 }));
+
+      var ctx = dragging.context();
+
+      dragging.end();
+
+      // then
+      expect(ctx.data.context.connectVisual.parentNode).not.to.exist;
+    }));
+
+
+    it('should remove connection preview on dragging cancel', inject(function(create, elementRegistry, dragging) {
+
+      // given
+      var parentGfx = elementRegistry.getGraphics('parentShape');
+
+      // when
+      create.start(canvasEvent({ x: 0, y: 0 }), newShape, childShape);
+
+      dragging.move(canvasEvent({ x: 175, y: 175 }));
+      dragging.hover({ element: parentShape, gfx: parentGfx });
+      dragging.move(canvasEvent({ x: 400, y: 200 }));
+
+      var ctx = dragging.context();
+
+      dragging.cancel();
+
+      // then
+      expect(ctx.data.context.connectVisual.parentNode).not.to.exist;
+    }));
+  });
+
 
   describe('rules', function() {