feat(svelte): add connectionline and connection functionality

packages/svelte/src/lib/actions/drag/index.ts

@@ -22,7 +22,6 @@ export type NodeDragItem = {
 };
 
 type UseDragParams = {
-	noDragClassName?: string;
 	handleSelector?: string;
 	nodeId?: string;
 	updateNodePositions: (dragItems: NodeDragItem[], d: boolean, p: boolean) => void;
@@ -32,14 +31,7 @@ type UseDragParams = {
 
 export default function drag(
 	nodeRef: Element,
-	{
-		noDragClassName,
-		handleSelector,
-		nodeId,
-		updateNodePositions,
-		nodesStore,
-		transformStore
-	}: UseDragParams
+	{ handleSelector, nodeId, updateNodePositions, nodesStore, transformStore }: UseDragParams
 ) {
 	let dragging = false;
 	let dragItems: NodeDragItem[] = [];
@@ -119,7 +111,7 @@ export default function drag(
 			const target = event.target as HTMLDivElement;
 			const isDraggable =
 				!event.button &&
-				(!noDragClassName || !hasSelector(target, `.${noDragClassName}`, nodeRef)) &&
+				!hasSelector(target, '.nodrag', nodeRef) &&
 				(!handleSelector || hasSelector(target, handleSelector, nodeRef));
 
 			return isDraggable;

packages/svelte/src/lib/components/ConnectionLine/ConnectionLine.svelte

@@ -0,0 +1,46 @@
+<script lang="ts">
+  import cc from 'classcat';
+
+	import { useStore } from '$lib/store';
+	import type { ConnectionLineProps } from '$lib/types';
+
+  type $$Props = ConnectionLineProps;
+
+  const { connectionPathStore, widthStore, heightStore, connectionStore } = useStore();
+</script>
+
+{#if $connectionPathStore}
+  <svg
+    width={$widthStore}
+    height={$heightStore}
+    class="react-flow__connectionline"
+  >
+    <g class={cc(['react-flow__connection', $connectionStore.status])}>
+      <path d={$connectionPathStore} fill="none" class="react-flow__connection-path" />
+    </g>
+  </svg>
+{/if}
+
+<style>
+  .react-flow__connectionline {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    pointer-events: none;
+    overflow: visible;
+    z-index: 1001;
+  }
+
+  .react-flow__connection {
+    pointer-events: none;
+  }
+
+  .react-flow__edge-path,
+  .react-flow__connection-path {
+    stroke: #b1b1b7;
+    stroke-width: 1;
+    fill: none;
+  }
+</style>

packages/svelte/src/lib/components/ConnectionLine/index.ts

@@ -0,0 +1 @@
+export { default as ConnectionLine } from './ConnectionLine.svelte';

packages/svelte/src/lib/components/Handle/handler.ts

@@ -0,0 +1,210 @@
+import {
+	getHostForElement,
+	calcAutoPan,
+	getEventPosition,
+	pointToRendererPoint,
+	rendererPointToPoint
+} from '@reactflow/utils';
+import type {
+	OnConnect,
+	HandleType,
+	Connection,
+	ConnectionMode,
+	Node,
+	XYPosition,
+	Transform
+} from '@reactflow/system';
+
+import {
+	getClosestHandle,
+	getConnectionStatus,
+	getHandleLookup,
+	getHandleType,
+	isValidHandle,
+	resetRecentHandle,
+	type ConnectionHandle,
+	type ValidConnectionFunc
+} from './utils';
+import { get, type Writable } from 'svelte/store';
+import type { ConnectionData } from '$lib/types';
+
+export function handlePointerDown({
+	event,
+	handleId,
+	nodeId,
+	onConnect,
+	domNode,
+	nodes,
+	connectionMode,
+	connectionRadius,
+	isTarget,
+	transformStore,
+	panBy,
+	updateConnection,
+	cancelConnection,
+	isValidConnection,
+	edgeUpdaterType,
+	onEdgeUpdateEnd
+}: {
+	event: MouseEvent | TouchEvent;
+	handleId: string | null;
+	nodeId: string;
+	onConnect: OnConnect;
+	isTarget: boolean;
+	connectionMode: ConnectionMode;
+	domNode: HTMLDivElement | null;
+	nodes: Node[];
+	connectionRadius: number;
+	isValidConnection: ValidConnectionFunc;
+	transformStore: Writable<Transform>;
+	updateConnection: (connection: Partial<ConnectionData>) => void;
+	cancelConnection: () => void;
+	panBy: (delta: XYPosition) => void;
+	edgeUpdaterType?: HandleType;
+	onEdgeUpdateEnd?: (evt: MouseEvent | TouchEvent) => void;
+}): void {
+	// when react-flow is used inside a shadow root we can't use document
+	const doc = getHostForElement(event.target as HTMLElement);
+	let autoPanId = 0;
+	let prevClosestHandle: ConnectionHandle | null;
+
+	const { x, y } = getEventPosition(event);
+	const clickedHandle = doc?.elementFromPoint(x, y);
+	const handleType = getHandleType(edgeUpdaterType, clickedHandle);
+	const containerBounds = domNode?.getBoundingClientRect();
+
+	if (!containerBounds || !handleType) {
+		return;
+	}
+
+	let prevActiveHandle: Element;
+	let connectionPosition = getEventPosition(event, containerBounds);
+	let autoPanStarted = false;
+	let connection: Connection | null = null;
+	let isValid = false;
+	let handleDomNode: Element | null = null;
+
+	const autoPanOnConnect = true;
+
+	const handleLookup = getHandleLookup({
+		nodes,
+		nodeId,
+		handleId,
+		handleType
+	});
+
+	// when the user is moving the mouse close to the edge of the canvas while connecting we move the canvas
+	const autoPan = (): void => {
+		// @todd add prop
+		if (!autoPanOnConnect) {
+			return;
+		}
+		const [xMovement, yMovement] = calcAutoPan(connectionPosition, containerBounds);
+
+		panBy({ x: xMovement, y: yMovement });
+		autoPanId = requestAnimationFrame(autoPan);
+	};
+
+	updateConnection({
+		position: connectionPosition,
+		nodeId,
+		handleId,
+		handleType,
+		status: null
+	});
+
+	// @todo add prop
+	// onConnectStart?.(event, { nodeId, handleId, handleType });
+
+	function onPointerMove(event: MouseEvent | TouchEvent) {
+		const transform = get(transformStore);
+		connectionPosition = getEventPosition(event, containerBounds);
+
+		prevClosestHandle = getClosestHandle(
+			pointToRendererPoint(connectionPosition, transform, false, [1, 1]),
+			connectionRadius,
+			handleLookup
+		);
+
+		if (!autoPanStarted) {
+			autoPan();
+			autoPanStarted = true;
+		}
+
+		const result = isValidHandle(
+			event,
+			prevClosestHandle,
+			connectionMode,
+			nodeId,
+			handleId,
+			isTarget ? 'target' : 'source',
+			isValidConnection,
+			doc
+		);
+
+		handleDomNode = result.handleDomNode;
+		connection = result.connection;
+		isValid = result.isValid;
+
+		updateConnection({
+			position:
+				prevClosestHandle && isValid
+					? rendererPointToPoint(
+							{
+								x: prevClosestHandle.x,
+								y: prevClosestHandle.y
+							},
+							transform
+					  )
+					: connectionPosition,
+			status: getConnectionStatus(!!prevClosestHandle, isValid)
+		});
+
+		if (!prevClosestHandle && !isValid && !handleDomNode) {
+			return resetRecentHandle(prevActiveHandle);
+		}
+
+		if (connection.source !== connection.target && handleDomNode) {
+			resetRecentHandle(prevActiveHandle);
+			prevActiveHandle = handleDomNode;
+			// @todo: remove the old class names "react-flow__handle-" in the next major version
+			handleDomNode.classList.add('connecting');
+			handleDomNode.classList.toggle('valid', isValid);
+		}
+	}
+
+	function onPointerUp(event: MouseEvent | TouchEvent) {
+		if ((prevClosestHandle || handleDomNode) && connection && isValid) {
+			onConnect?.(connection);
+		}
+
+		// it's important to get a fresh reference from the store here
+		// in order to get the latest state of onConnectEnd
+		// @todo add onConnectEnd prop
+		// getState().onConnectEnd?.(event);
+
+		if (edgeUpdaterType) {
+			onEdgeUpdateEnd?.(event);
+		}
+
+		resetRecentHandle(prevActiveHandle);
+		cancelConnection();
+		cancelAnimationFrame(autoPanId);
+		autoPanStarted = false;
+		isValid = false;
+		connection = null;
+		handleDomNode = null;
+
+		doc.removeEventListener('mousemove', onPointerMove as EventListener);
+		doc.removeEventListener('mouseup', onPointerUp as EventListener);
+
+		doc.removeEventListener('touchmove', onPointerMove as EventListener);
+		doc.removeEventListener('touchend', onPointerUp as EventListener);
+	}
+
+	doc.addEventListener('mousemove', onPointerMove as EventListener);
+	doc.addEventListener('mouseup', onPointerUp as EventListener);
+
+	doc.addEventListener('touchmove', onPointerMove as EventListener);
+	doc.addEventListener('touchend', onPointerUp as EventListener);
+}

packages/svelte/src/lib/components/Handle/index.svelte

@@ -1,21 +1,77 @@
 <script lang="ts">
 	import { getContext } from 'svelte';
   import cc from 'classcat';
-	import { type HandleType, Position } from '@reactflow/system';
+	import {  Position, type Connection, type HandleProps } from '@reactflow/system';
+	import { isMouseEvent } from '@reactflow/utils';
 
-  export let type: HandleType = 'source';
-  export let position: Position = Position.Top;
-  export let id: string | null = null;
-  
+	import { handlePointerDown } from './handler';
+	import { useStore } from '$lib/store';
+
+  type $$Props = HandleProps;
+
+  export let type: $$Props['type'] = 'source';
+  export let position: $$Props['position'] = Position.Top;
+  export let id: $$Props['id'] = undefined;
+  export let isConnectable: $$Props['isConnectable'] = true;
+  export let isValidConnection: $$Props['isValidConnection'] = (_: Connection) => true;
   let className: string | null = null;
   export { className as class };
 
   const isTarget = type === 'target';
-  const nodeId = getContext('rf_nodeid');
+  const nodeId = getContext<string>('rf_nodeid');
+  const handleId = id || null;
+
+  const {
+    connectionModeStore,
+    domNodeStore,
+    nodesStore,
+    connectionRadiusStore,
+    transformStore,
+    addEdge,
+    panBy,
+    cancelConnection,
+    updateConnection
+  } = useStore();
+
+  function onConnectExtended(params: Connection) {
+      addEdge(params);
+      // @todo add props
+      // onConnectAction?.(edgeParams);
+      // onConnect?.(edgeParams);
+    };
+
+  function onPointerDown(event: MouseEvent | TouchEvent)  {
+      const isMouseTriggered = isMouseEvent(event);
+
+      if ((isMouseTriggered && event.button === 0) || !isMouseTriggered) {
+        handlePointerDown({
+          event,
+          handleId,
+          nodeId,
+          isTarget,
+          connectionRadius: $connectionRadiusStore,
+          domNode: $domNodeStore,
+          nodes: $nodesStore,
+          connectionMode: $connectionModeStore,
+          transformStore,
+          isValidConnection: isValidConnection!,
+          onConnect: onConnectExtended,
+          updateConnection,
+          cancelConnection,
+          panBy,
+        });
+      }
+
+      // if (isMouseTriggered) {
+      //   onMouseDown?.(event);
+      // } else {
+      //   onTouchStart?.(event);
+      // }
+    };
 </script>
 
 <div
-  data-handleid={id}
+  data-handleid={handleId}
   data-nodeid={nodeId}
   data-handlepos={position}
   data-id={`${nodeId}-${id}-${type}`}
@@ -23,12 +79,16 @@
     'react-flow__handle',
     `react-flow__handle-${position}`,
     'nodrag',
+    'nopan',
     className,
     position
   ])}
   class:source={!isTarget}
   class:target={isTarget}
-  >
+  class:connectable={isConnectable}
+  on:mousedown={onPointerDown}
+  on:touchstart={onPointerDown}
+>
   <slot />
 </div>
 
@@ -46,6 +106,11 @@
     border-radius: 100%;
   }
 
+  .connectable {
+    pointer-events: all;
+    cursor: crosshair;
+  }
+
   .bottom {
     top: 100%;
     left: 50%;

packages/svelte/src/lib/components/Handle/utils.ts

@@ -0,0 +1,188 @@
+import { internalsSymbol, ConnectionMode, type ConnectionStatus } from '@reactflow/system';
+import type { Connection, HandleType, XYPosition, Node, NodeHandleBounds } from '@reactflow/system';
+import { getEventPosition } from '@reactflow/utils';
+
+export type ConnectionHandle = {
+	id: string | null;
+	type: HandleType;
+	nodeId: string;
+	x: number;
+	y: number;
+};
+
+export type ValidConnectionFunc = (connection: Connection) => boolean;
+
+// this functions collects all handles and adds an absolute position
+// so that we can later find the closest handle to the mouse position
+export function getHandles(
+	node: Node,
+	handleBounds: NodeHandleBounds,
+	type: HandleType,
+	currentHandle: string
+): ConnectionHandle[] {
+	return (handleBounds[type] || []).reduce<ConnectionHandle[]>((res, h) => {
+		if (`${node.id}-${h.id}-${type}` !== currentHandle) {
+			res.push({
+				id: h.id || null,
+				type,
+				nodeId: node.id,
+				x: (node.positionAbsolute?.x ?? 0) + h.x + h.width / 2,
+				y: (node.positionAbsolute?.y ?? 0) + h.y + h.height / 2
+			});
+		}
+		return res;
+	}, []);
+}
+
+export function getClosestHandle(
+	pos: XYPosition,
+	connectionRadius: number,
+	handles: ConnectionHandle[]
+): ConnectionHandle | null {
+	let closestHandle: ConnectionHandle | null = null;
+	let minDistance = Infinity;
+
+	handles.forEach((handle) => {
+		const distance = Math.sqrt(Math.pow(handle.x - pos.x, 2) + Math.pow(handle.y - pos.y, 2));
+		if (distance <= connectionRadius && distance < minDistance) {
+			minDistance = distance;
+			closestHandle = handle;
+		}
+	});
+
+	return closestHandle;
+}
+
+type Result = {
+	handleDomNode: Element | null;
+	isValid: boolean;
+	connection: Connection;
+};
+
+const nullConnection: Connection = {
+	source: null,
+	target: null,
+	sourceHandle: null,
+	targetHandle: null
+};
+
+// checks if  and returns connection in fom of an object { source: 123, target: 312 }
+export function isValidHandle(
+	event: MouseEvent | TouchEvent,
+	handle: Pick<ConnectionHandle, 'nodeId' | 'id' | 'type'> | null,
+	connectionMode: ConnectionMode,
+	fromNodeId: string,
+	fromHandleId: string | null,
+	fromType: string,
+	isValidConnection: ValidConnectionFunc,
+	doc: Document | ShadowRoot
+) {
+	const isTarget = fromType === 'target';
+	const handleDomNode = doc.querySelector(
+		`.react-flow__handle[data-id="${handle?.nodeId}-${handle?.id}-${handle?.type}"]`
+	);
+	const { x, y } = getEventPosition(event);
+	const handleBelow = doc.elementFromPoint(x, y);
+	const handleToCheck = handleBelow?.classList.contains('react-flow__handle')
+		? handleBelow
+		: handleDomNode;
+
+	const result: Result = {
+		handleDomNode: handleToCheck,
+		isValid: false,
+		connection: nullConnection
+	};
+
+	if (handleToCheck) {
+		const handleType = getHandleType(undefined, handleToCheck);
+		const handleNodeId = handleToCheck.getAttribute('data-nodeid');
+		const handleId = handleToCheck.getAttribute('data-handleid');
+
+		const connection: Connection = {
+			source: isTarget ? handleNodeId : fromNodeId,
+			sourceHandle: isTarget ? handleId : fromHandleId,
+			target: isTarget ? fromNodeId : handleNodeId,
+			targetHandle: isTarget ? fromHandleId : handleId
+		};
+
+		result.connection = connection;
+
+		// in strict mode we don't allow target to target or source to source connections
+		const isValid =
+			connectionMode === ConnectionMode.Strict
+				? (isTarget && handleType === 'source') || (!isTarget && handleType === 'target')
+				: handleNodeId !== fromNodeId || handleId !== fromHandleId;
+
+		if (isValid) {
+			result.isValid = isValidConnection(connection);
+		}
+	}
+
+	return result;
+}
+
+type GetHandleLookupParams = {
+	nodes: Node[];
+	nodeId: string;
+	handleId: string | null;
+	handleType: string;
+};
+
+export function getHandleLookup({ nodes, nodeId, handleId, handleType }: GetHandleLookupParams) {
+	return nodes.reduce<ConnectionHandle[]>((res, node) => {
+		if (node[internalsSymbol]) {
+			const { handleBounds } = node[internalsSymbol];
+			let sourceHandles: ConnectionHandle[] = [];
+			let targetHandles: ConnectionHandle[] = [];
+
+			if (handleBounds) {
+				sourceHandles = getHandles(
+					node,
+					handleBounds,
+					'source',
+					`${nodeId}-${handleId}-${handleType}`
+				);
+				targetHandles = getHandles(
+					node,
+					handleBounds,
+					'target',
+					`${nodeId}-${handleId}-${handleType}`
+				);
+			}
+
+			res.push(...sourceHandles, ...targetHandles);
+		}
+		return res;
+	}, []);
+}
+
+export function getHandleType(
+	edgeUpdaterType: HandleType | undefined,
+	handleDomNode: Element | null
+): HandleType | null {
+	if (edgeUpdaterType) {
+		return edgeUpdaterType;
+	} else if (handleDomNode?.classList.contains('target')) {
+		return 'target';
+	} else if (handleDomNode?.classList.contains('source')) {
+		return 'source';
+	}
+
+	return null;
+}
+
+export function resetRecentHandle(handleDomNode: Element): void {
+	handleDomNode?.classList.remove('valid', 'connecting');
+}
+
+export function getConnectionStatus(isInsideConnectionRadius: boolean, isHandleValid: boolean) {
+	let connectionStatus = null;
+
+	if (isHandleValid) {
+		connectionStatus = 'valid';
+	} else if (isInsideConnectionRadius && !isHandleValid) {
+		connectionStatus = 'invalid';
+	}
+
+	return connectionStatus as ConnectionStatus;
+}

packages/svelte/src/lib/container/SvelteFlow.svelte

@@ -11,6 +11,7 @@
   import UserSelection from '$lib/components/UserSelection/index.svelte';
   import NodeSelection from '$lib/components/NodeSelection/index.svelte';
   import { KeyHandler } from '$lib/components/KeyHandler';
+  import { ConnectionLine } from '$lib/components/ConnectionLine';
 	import type { SvelteFlowProps } from '$lib/types';
 
   type $$Props = SvelteFlowProps;
@@ -26,7 +27,7 @@
   let className: $$Props['class'] = undefined;
   export { className as class };
 
-  let domNode: Element;
+  let domNode: HTMLDivElement;
 
   const store = createStore({
     fitView,
@@ -41,6 +42,7 @@
     const { width, height } = domNode.getBoundingClientRect();
     store.widthStore.set(width);
     store.heightStore.set(height);
+    store.domNodeStore.set(domNode);
 
     // @todo: is this a svelte way for two way binding?
     store.nodesStore.subscribe((ns) => {
@@ -69,6 +71,7 @@
     <Pane>
       <Viewport>
         <EdgeRenderer />
+        <ConnectionLine />
         <div class="react-flow__edgelabel-renderer" />
         <NodeRenderer />
         <NodeSelection />

packages/svelte/src/lib/store/index.ts

@@ -12,19 +12,32 @@ import {
 	type D3SelectionInstance,
 	type ViewportHelperFunctionOptions,
 	type SelectionRect,
-	type Node as RFNode
+	type Node as RFNode,
+	type Connection,
+	ConnectionMode,
+	type XYPosition,
+	type CoordinateExtent,
+	ConnectionLineType
 } from '@reactflow/system';
-import { fitView, getConnectedEdges, getD3Transition, getDimensions } from '@reactflow/utils';
+import {
+	fitView as fitViewUtil,
+	getConnectedEdges,
+	getD3Transition,
+	getDimensions,
+	addEdge as addEdgeUtil
+} from '@reactflow/utils';
+import { zoomIdentity } from 'd3-zoom';
 
 import { getHandleBounds } from '../../utils';
 import { getEdgePositions, getHandle, getNodeData } from '$lib/container/EdgeRenderer/utils';
 import DefaultNode from '$lib/components/nodes/DefaultNode.svelte';
 import InputNode from '$lib/components/nodes/InputNode.svelte';
 import OutputNode from '$lib/components/nodes/OutputNode.svelte';
-import type { EdgeTypes, NodeTypes, Node, Edge, WrapEdgeProps } from '$lib/types';
+import type { EdgeTypes, NodeTypes, Node, Edge, WrapEdgeProps, ConnectionData } from '$lib/types';
 import BezierEdge from '$lib/components/edges/BezierEdge.svelte';
 import StraightEdge from '$lib/components/edges/StraightEdge.svelte';
 import SmoothStepEdge from '$lib/components/edges/SmoothStepEdge.svelte';
+import { getBezierPath, getSmoothStepPath, getStraightPath } from '@reactflow/edge-utils';
 
 export const key = Symbol();
 
@@ -58,8 +71,14 @@ type SvelteFlowStore = {
 	deleteKeyPressedStore: Writable<boolean>;
 	nodeTypesStore: Writable<NodeTypes>;
 	edgeTypesStore: Writable<EdgeTypes>;
+	domNodeStore: Writable<HTMLDivElement | null>;
+	connectionRadiusStore: Writable<number>;
+	connectionModeStore: Writable<ConnectionMode>;
+	connectionStore: Writable<ConnectionData>;
+	connectionPathStore: Readable<string | null>;
 	setNodes: (nodes: Node[]) => void;
 	setEdges: (edges: Edge[]) => void;
+	addEdge: (edge: Edge | Connection) => void;
 	zoomIn: (options?: ViewportHelperFunctionOptions) => void;
 	zoomOut: (options?: ViewportHelperFunctionOptions) => void;
 	fitView: (options?: ViewportHelperFunctionOptions) => boolean;
@@ -71,6 +90,17 @@ type SvelteFlowStore = {
 	updateNodeDimensions: (updates: NodeDimensionUpdate[]) => void;
 	resetSelectedElements: () => void;
 	addSelectedNodes: (ids: string[]) => void;
+	panBy: (delta: XYPosition) => void;
+	updateConnection: (connection: Partial<ConnectionData>) => void;
+	cancelConnection: () => void;
+};
+
+const initConnectionData = {
+	nodeId: null,
+	handleId: null,
+	handleType: null,
+	position: null,
+	status: null
 };
 
 export function createStore({
@@ -112,6 +142,11 @@ export function createStore({
 		default: edgeTypes.default || BezierEdge
 	});
 	const transformStore = writable(transform);
+	const connectionModeStore = writable(ConnectionMode.Strict);
+	const domNodeStore = writable(null);
+	const connectionStore = writable<ConnectionData>(initConnectionData);
+	const connectionRadiusStore = writable(25);
+	const connectionLineTypeStore = writable(ConnectionLineType.Bezier);
 
 	let fitViewOnInitDone = false;
 
@@ -172,10 +207,84 @@ export function createStore({
 			.filter((e) => e !== null) as WrapEdgeProps[];
 	});
 
+	const oppositePosition = {
+		[Position.Left]: Position.Right,
+		[Position.Right]: Position.Left,
+		[Position.Top]: Position.Bottom,
+		[Position.Bottom]: Position.Top
+	};
+
+	const connectionPathStore = derived(
+		[connectionStore, connectionLineTypeStore, connectionModeStore, nodesStore, transformStore],
+		([
+			$connectionStore,
+			$connectionLineTypeStore,
+			$connectionModeStore,
+			$nodesStore,
+			$transformStore
+		]) => {
+			if (!$connectionStore.nodeId) {
+				return null;
+			}
+
+			const fromNode = $nodesStore.find((n) => n.id === $connectionStore.nodeId);
+			const fromHandleBounds = fromNode?.[internalsSymbol]?.handleBounds;
+			const handleBoundsStrict = fromHandleBounds?.[$connectionStore.handleType || 'source'] || [];
+			const handleBoundsLoose = handleBoundsStrict
+				? handleBoundsStrict
+				: fromHandleBounds?.[$connectionStore.handleType === 'source' ? 'target' : 'source']!;
+			const handleBounds =
+				$connectionModeStore === ConnectionMode.Strict ? handleBoundsStrict : handleBoundsLoose;
+			const fromHandle = $connectionStore.handleId
+				? handleBounds.find((d) => d.id === $connectionStore.handleId)
+				: handleBounds[0];
+			const fromHandleX = fromHandle
+				? fromHandle.x + fromHandle.width / 2
+				: (fromNode?.width ?? 0) / 2;
+			const fromHandleY = fromHandle ? fromHandle.y + fromHandle.height / 2 : fromNode?.height ?? 0;
+			const fromX = (fromNode?.positionAbsolute?.x ?? 0) + fromHandleX;
+			const fromY = (fromNode?.positionAbsolute?.y ?? 0) + fromHandleY;
+			const fromPosition = fromHandle?.position;
+			const toPosition = fromPosition ? oppositePosition[fromPosition] : undefined;
+
+			const pathParams = {
+				sourceX: fromX,
+				sourceY: fromY,
+				sourcePosition: fromPosition,
+				targetX: (($connectionStore.position?.x ?? 0) - $transformStore[0]) / $transformStore[2],
+				targetY: (($connectionStore.position?.y ?? 0) - $transformStore[1]) / $transformStore[2],
+				targetPosition: toPosition
+			};
+
+			let path = '';
+
+			if ($connectionLineTypeStore === ConnectionLineType.Bezier) {
+				// we assume the destination position is opposite to the source position
+				[path] = getBezierPath(pathParams);
+			} else if ($connectionLineTypeStore === ConnectionLineType.Step) {
+				[path] = getSmoothStepPath({
+					...pathParams,
+					borderRadius: 0
+				});
+			} else if ($connectionLineTypeStore === ConnectionLineType.SmoothStep) {
+				[path] = getSmoothStepPath(pathParams);
+			} else {
+				[path] = getStraightPath(pathParams);
+			}
+
+			return path;
+		}
+	);
+
 	function setEdges(edges: Edge[]) {
 		edgesStore.set(edges);
 	}
 
+	function addEdge(edgeParams: Edge | Connection) {
+		const edges = get(edgesStore);
+		edgesStore.set(addEdgeUtil(edgeParams, edges));
+	}
+
 	function setNodes(nodes: Node[]) {
 		nodesStore.update((currentNodes) => {
 			const nextNodes = nodes.map((n) => {
@@ -254,7 +363,7 @@ export function createStore({
 		const { zoom: d3Zoom, selection: d3Selection } = get(d3Store);
 
 		fitViewOnInitDone =
-			fitViewOnInitDone || (fitViewOnInit && !!d3Zoom && !!d3Selection && _fitView());
+			fitViewOnInitDone || (fitViewOnInit && !!d3Zoom && !!d3Selection && fitView());
 
 		nodesStore.set(nextNodes);
 	}
@@ -274,14 +383,14 @@ export function createStore({
 		}
 	}
 
-	function _fitView() {
+	function fitView() {
 		const { zoom: d3Zoom, selection: d3Selection } = get(d3Store);
 
 		if (!d3Zoom || !d3Selection) {
 			return false;
 		}
 
-		return fitView(
+		return fitViewUtil(
 			{
 				nodes: get(nodesStore) as RFNode[],
 				width: get(widthStore),
@@ -373,6 +482,52 @@ export function createStore({
 		);
 	}
 
+	function panBy(delta: XYPosition) {
+		const { zoom: d3Zoom, selection: d3Selection } = get(d3Store);
+		const transform = get(transformStore);
+		const width = get(widthStore);
+		const height = get(heightStore);
+
+		if (!d3Zoom || !d3Selection || (!delta.x && !delta.y)) {
+			return;
+		}
+
+		const nextTransform = zoomIdentity
+			.translate(transform[0] + delta.x, transform[1] + delta.y)
+			.scale(transform[2]);
+
+		const extent: CoordinateExtent = [
+			[0, 0],
+			[width, height]
+		];
+
+		const constrainedTransform = d3Zoom?.constrain()(nextTransform, extent, [
+			[Number.NEGATIVE_INFINITY, Number.NEGATIVE_INFINITY],
+			[Number.POSITIVE_INFINITY, Number.POSITIVE_INFINITY]
+		]);
+		d3Zoom.transform(d3Selection, constrainedTransform);
+	}
+
+	function updateConnection(connectionUpdate: Partial<ConnectionData> | null) {
+		const currentConnectionData = get(connectionStore);
+		const nextConnectionData = currentConnectionData
+			? {
+					...initConnectionData,
+					...currentConnectionData,
+					...connectionUpdate
+			  }
+			: {
+					...initConnectionData,
+					...connectionUpdate
+			  };
+
+		connectionStore.set(nextConnectionData);
+	}
+
+	function cancelConnection() {
+		updateConnection(initConnectionData);
+	}
+
 	return {
 		nodesStore,
 		edgesStore,
@@ -391,15 +546,24 @@ export function createStore({
 		selectionMode,
 		nodeTypesStore,
 		edgeTypesStore,
+		connectionModeStore,
+		domNodeStore,
+		connectionStore,
+		connectionRadiusStore,
+		connectionPathStore,
 		setNodes,
 		setEdges,
+		addEdge,
 		updateNodePositions,
 		updateNodeDimensions,
 		zoomIn,
 		zoomOut,
-		fitView: _fitView,
+		fitView,
 		resetSelectedElements,
-		addSelectedNodes
+		addSelectedNodes,
+		panBy,
+		updateConnection,
+		cancelConnection
 	};
 }
 

packages/svelte/src/lib/types/general.ts

@@ -1,11 +1,21 @@
 import type { Node, NodeTypes } from './nodes';
-import type { Edge } from './edges';
 import type { ShortcutModifierDefinition } from '@svelte-put/shortcut';
+import type { Edge, HandleType, XYPosition } from '@reactflow/system';
 
 export type KeyModifier = ShortcutModifierDefinition;
 export type KeyDefinitionObject = { key: string; modifier?: KeyModifier };
 export type KeyDefinition = string | KeyDefinitionObject;
 
+export type ConnectionData = {
+	position: XYPosition | null;
+	nodeId: string | null;
+	handleId: string | null;
+	handleType: HandleType | null;
+	status: string | null;
+};
+
+export type ConnectionLineProps = {};
+
 export type SvelteFlowProps = {
 	nodes: Node[];
 	edges: Edge[];