feat: freeze edges while dragging associated nodes

packages/demo-app-ts/src/demos/stylesDemo/Styles.tsx

@@ -666,6 +666,47 @@ export const EdgeStyles = withTopologySetup(() => {
   return null;
 });
 
+export const FreezedEdge = withTopologySetup(() => {
+  useComponentFactory(defaultComponentFactory);
+  useComponentFactory(stylesComponentFactory);
+  const nodes: NodeModel[] = createGroupNodes('edges-group');
+  const edges: EdgeModel[] = [];
+
+  const middleNodeIndex = nodes.length - 1;
+  nodes.forEach((item, index) => {
+    if (index === middleNodeIndex) {
+      return;
+    }
+    const endIndex = index < nodes.length - 2 ? index + 1 : 0;
+    edges.push({
+      id: `edge-${index}-${endIndex}`,
+      type: 'edge',
+      source: nodes[index].id,
+      target: nodes[endIndex].id,
+      edgeStyle: EDGE_STYLES[index % EDGE_STYLE_COUNT],
+      data: { freezeEdgeDuringNodeDrag: true }
+    });
+    edges.push({
+      id: `edge-${middleNodeIndex}-${index}`,
+      type: 'edge',
+      source: nodes[middleNodeIndex].id,
+      target: nodes[index].id,
+      edgeStyle: EdgeStyle.default,
+      data: { freezeEdgeDuringNodeDrag: true }
+    });
+  });
+
+  useModel({
+    graph: {
+      id: 'g1',
+      type: 'graph'
+    },
+    nodes,
+    edges
+  });
+  return null;
+});
+
 export const EdgeAnimationStyles = withTopologySetup(() => {
   useComponentFactory(defaultComponentFactory);
   useComponentFactory(stylesComponentFactory);
@@ -977,16 +1018,19 @@ export const StyleEdges: React.FunctionComponent = () => {
         <Tab eventKey={0} title={<TabTitleText>Edge Styles</TabTitleText>}>
           <EdgeStyles />
         </Tab>
-        <Tab eventKey={1} title={<TabTitleText>Animated Edges</TabTitleText>}>
+        <Tab eventKey={1} title={<TabTitleText>Freeze Edge When Dragging Node</TabTitleText>}>
+          <FreezedEdge />
+        </Tab>
+        <Tab eventKey={2} title={<TabTitleText>Animated Edges</TabTitleText>}>
           <EdgeAnimationStyles />
         </Tab>
-        <Tab eventKey={2} title={<TabTitleText>Edge Terminal Types</TabTitleText>}>
+        <Tab eventKey={3} title={<TabTitleText>Edge Terminal Types</TabTitleText>}>
           <EdgeTerminalStyles />
         </Tab>
-        <Tab eventKey={3} title={<TabTitleText>Edge Terminal Status</TabTitleText>}>
+        <Tab eventKey={4} title={<TabTitleText>Edge Terminal Status</TabTitleText>}>
           <EdgeTerminalStatusStyles />
         </Tab>
-        <Tab eventKey={4} title={<TabTitleText>Edge Terminal Tags</TabTitleText>}>
+        <Tab eventKey={5} title={<TabTitleText>Edge Terminal Tags</TabTitleText>}>
           <EdgeTerminalTagStyles />
         </Tab>
       </Tabs>

packages/demo-app-ts/src/demos/stylesDemo/stylesComponentFactory.tsx

@@ -23,7 +23,8 @@ import {
   groupDropTargetSpec,
   graphDropTargetSpec,
   NODE_DRAG_TYPE,
-  CREATE_CONNECTOR_DROP_TYPE
+  CREATE_CONNECTOR_DROP_TYPE,
+  edgeDropTargetSpec
 } from '@patternfly/react-topology';
 import StyleNode from './StyleNode';
 import StyleGroup from './StyleGroup';
@@ -132,7 +133,11 @@ const stylesComponentFactory: ComponentFactory = (
           collect: (monitor) => ({
             dragging: monitor.isDragging()
           })
-        })(withContextMenu(() => defaultMenu)(withSelection()(StyleEdge)))
+        })(
+          withDndDrop<Node, any, { droppable?: boolean; hover?: boolean; canDrop?: boolean }, EdgeProps>(
+            edgeDropTargetSpec
+          )(withContextMenu(() => defaultMenu)(withSelection()(StyleEdge)))
+        )
       );
     default:
       return undefined;

packages/demo-app-ts/src/demos/topologyPackageDemo/DemoContext.tsx

@@ -22,7 +22,8 @@ export class DemoModel {
     showStatus: false,
     showAnimations: false,
     showTags: false,
-    terminalTypes: false
+    terminalTypes: false,
+    freezeEdgeDuringNodeDrag: false
   };
   protected creationCountsP: { numNodes: number; numEdges: number; numGroups: number; nestedLevel: number } = {
     numNodes: 6,

packages/demo-app-ts/src/demos/topologyPackageDemo/DemoEdge.tsx

@@ -37,6 +37,7 @@ const DemoEdge: React.FunctionComponent<DemoEdgeProps> = ({ element, ...rest })
       endTerminalStatus={options.showStatus && NODE_STATUSES[data.index % NODE_STATUSES.length]}
       tag={options.showTags ? data.tag : undefined}
       tagStatus={options.showStatus && NODE_STATUSES[data.index % NODE_STATUSES.length]}
+      freezeEdgeDuringNodeDrag={options.freezeEdgeDuringNodeDrag}
     />
   );
 };

packages/demo-app-ts/src/demos/topologyPackageDemo/OptionsContextBar.tsx

@@ -202,6 +202,19 @@ const OptionsContextBar: React.FC = observer(() => {
         >
           Tags
         </SelectOption>
+        <SelectOption
+          value="Freeze Edge During Node Drag"
+          hasCheckbox
+          isSelected={options.edgeOptions.freezeEdgeDuringNodeDrag}
+          onClick={() =>
+            options.setEdgeOptions({
+              ...options.edgeOptions,
+              freezeEdgeDuringNodeDrag: !options.edgeOptions.freezeEdgeDuringNodeDrag
+            })
+          }
+        >
+          Freeze Edge During Node Drag
+        </SelectOption>
       </SelectList>
     );
     const edgeOptionsToggle = (toggleRef: React.Ref<MenuToggleElement>) => (

packages/demo-app-ts/src/demos/topologyPackageDemo/generator.ts

@@ -99,6 +99,7 @@ export interface GeneratorEdgeOptions {
   showAnimations?: boolean;
   showTags?: boolean;
   terminalTypes?: boolean;
+  freezeEdgeDuringNodeDrag?: boolean;
 }
 
 const createNode = (index: number): NodeModel => ({

packages/module/src/components/edges/DefaultEdge.tsx

@@ -1,4 +1,4 @@
-import { useLayoutEffect } from 'react';
+import { useLayoutEffect, useRef } from 'react';
 import { observer } from 'mobx-react';
 import {
   Edge,
@@ -71,6 +71,8 @@ interface DefaultEdgeProps {
   canDrop?: boolean;
   /** Flag if the node is the current drop target */
   dropTarget?: boolean;
+  /** Flag indicating if an edge endpoint is currently being dragged */
+  endpointDragging?: boolean;
   /** Flag indicating if the element is selected. Part of WithSelectionProps */
   selected?: boolean;
   /** Function to call when the element should become selected (or deselected). Part of WithSelectionProps */
@@ -79,6 +81,13 @@ interface DefaultEdgeProps {
   onContextMenu?: (e: React.MouseEvent) => void;
   /** Flag indicating that the context menu for the edge is currently open  */
   contextMenuOpen?: boolean;
+  /**
+   * When true, the edge path and terminals stay visually fixed (last position) while
+   * an associated node is being dragged. When false or omitted, the edge updates
+   * during drag as before. Can be set per edge via this prop, element state, or
+   * in the model as edge data: `data: { freezeEdgeDuringNodeDrag: true }`.
+   */
+  freezeEdgeDuringNodeDrag?: boolean;
 }
 
 type DefaultEdgeInnerProps = Omit<DefaultEdgeProps, 'element'> & { element: Edge };
@@ -92,6 +101,7 @@ const DefaultEdgeInner: React.FunctionComponent<DefaultEdgeInnerProps> = observe
     dndDropRef,
     canDrop,
     dropTarget,
+    endpointDragging,
     edgeStyle,
     animationDuration,
     onShowRemoveConnector,
@@ -111,12 +121,23 @@ const DefaultEdgeInner: React.FunctionComponent<DefaultEdgeInnerProps> = observe
     className,
     selected,
     onSelect,
-    onContextMenu
+    onContextMenu,
+    freezeEdgeDuringNodeDrag
   }) => {
+    const freezeDuringDrag =
+      freezeEdgeDuringNodeDrag ??
+      (element.getData() as { freezeEdgeDuringNodeDrag?: boolean } | undefined)?.freezeEdgeDuringNodeDrag ??
+      false;
+
     const [hover, hoverRef] = useHover();
     const edgeRef = useCombineRefs(hoverRef, dndDropRef);
     const startPoint = element.getStartPoint();
     const endPoint = element.getEndPoint();
+    const edgeDRef = useRef<string | null>(null);
+    const startPointRef = useRef<Point | null>(null);
+    const endPointRef = useRef<Point | null>(null);
+    const targetStartPointRef = useRef<Point | null>(null);
+    const targetEndPointRef = useRef<Point | null>(null);
 
     useLayoutEffect(() => {
       if (hover && !dragging) {
@@ -175,6 +196,23 @@ const DefaultEdgeInner: React.FunctionComponent<DefaultEdgeInnerProps> = observe
     const tagScale = hover && !(detailsLevel === ScaleDetailsLevel.high) ? Math.max(1, 1 / scale) : 1;
     const tagPositionScale = hover && !(detailsLevel === ScaleDetailsLevel.high) ? Math.min(1, scale) : 1;
 
+    const shouldFreeze = freezeDuringDrag && endpointDragging;
+
+    if (
+      !shouldFreeze ||
+      !edgeDRef.current ||
+      !startPointRef.current ||
+      !endPointRef.current ||
+      !targetStartPointRef.current ||
+      !targetEndPointRef.current
+    ) {
+      edgeDRef.current = d;
+      startPointRef.current = bendpoints[0] || endPoint;
+      endPointRef.current = startPoint;
+      targetStartPointRef.current = bendpoints[bendpoints.length - 1] || startPoint;
+      targetEndPointRef.current = endPoint;
+    }
+
     return (
       <Layer id={dragging || hover ? TOP_LAYER : undefined}>
         <g
@@ -190,7 +228,11 @@ const DefaultEdgeInner: React.FunctionComponent<DefaultEdgeInnerProps> = observe
             onMouseEnter={onShowRemoveConnector}
             onMouseLeave={onHideRemoveConnector}
           />
-          <path className={linkClassName} d={d} style={{ animationDuration: `${edgeAnimationDuration}s` }} />
+          <path
+            className={linkClassName}
+            d={edgeDRef.current}
+            style={{ animationDuration: `${edgeAnimationDuration}s` }}
+          />
           {showTag && (
             <g transform={`scale(${hover ? tagScale : 1})`}>
               <DefaultConnectorTag
@@ -211,6 +253,8 @@ const DefaultEdgeInner: React.FunctionComponent<DefaultEdgeInnerProps> = observe
             terminalType={startTerminalType}
             status={startTerminalStatus}
             highlight={dragging || hover}
+            startPoint={shouldFreeze ? startPointRef.current : undefined}
+            endPoint={shouldFreeze ? endPointRef.current : undefined}
           />
           <DefaultConnectorTerminal
             className={endTerminalClass}
@@ -221,6 +265,8 @@ const DefaultEdgeInner: React.FunctionComponent<DefaultEdgeInnerProps> = observe
             terminalType={endTerminalType}
             status={endTerminalStatus}
             highlight={dragging || hover}
+            startPoint={shouldFreeze ? targetStartPointRef.current : undefined}
+            endPoint={shouldFreeze ? targetEndPointRef.current : undefined}
           />
           {children}
         </g>

packages/module/src/components/factories/components/componentUtils.ts

@@ -278,17 +278,31 @@ const edgeDragSourceSpec = (
   })
 });
 
+const edgeEndpointIsDragging = (monitor: any, props: EdgeComponentProps) => {
+  if (!monitor.isDragging()) {
+    return false;
+  }
+  if (monitor.getItemType() === NODE_DRAG_TYPE) {
+    return (
+      monitor.getItem().element.id === props.element.getSource().getId() ||
+      monitor.getItem().element.id === props.element.getTarget().getId()
+    );
+  }
+  return false;
+};
+
 const edgeDropTargetSpec: DropTargetSpec<any, any, { droppable: boolean; dropTarget: boolean; canDrop: boolean }, any> =
   {
     accept: [NODE_DRAG_TYPE],
     canDrop: (item, monitor, props) =>
       !!props &&
       (props.element as Edge).getSource().getId() !== item.id &&
       (props.element as Edge).getTarget().getId() !== item.id,
-    collect: (monitor) => ({
+    collect: (monitor, props) => ({
       droppable: monitor.isDragging(),
       dropTarget: monitor.isOver(),
-      canDrop: monitor.canDrop()
+      canDrop: monitor.canDrop(),
+      endpointDragging: edgeEndpointIsDragging(monitor, { element: props.element as Edge })
     })
   };