implement onSelectionChanged

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

@@ -1,6 +1,6 @@
 <script lang="ts" generics="NodeType extends Node = Node, EdgeType extends Edge = Edge">
   import type { Edge, Node } from '$lib/types';
-  import { getContext, setContext, onDestroy } from 'svelte';
+  import { getContext, setContext, onDestroy, untrack } from 'svelte';
   import type { HTMLAttributes } from 'svelte/elements';
   import { ConnectionLineType, PanOnScrollMode } from '@xyflow/system';
 
@@ -110,6 +110,15 @@
     }
   } satisfies StoreContext<NodeType, EdgeType>);
 
+  // handle selection change
+  $effect(() => {
+    const params = { nodes: store.selectedNodes, edges: store.selectedEdges };
+    untrack(() => props.onselectionchanged)?.(params);
+    for (const handler of store.selectionChangedHandlers.values()) {
+      handler(params);
+    }
+  });
+
   onDestroy(() => {
     store.reset();
   });

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

@@ -52,6 +52,7 @@
     onclickconnectstart,
     onclickconnectend,
     oninit,
+    onselectionchanged,
     clickConnect,
     fitView,
     fitViewOptions,

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

@@ -36,7 +36,8 @@ import type {
   OnBeforeConnect,
   OnBeforeDelete,
   IsValidConnection,
-  OnBeforeReconnect
+  OnBeforeReconnect,
+  OnSelectionChanged
 } from '$lib/types';
 
 import type { Component } from 'svelte';
@@ -391,6 +392,8 @@ export type SvelteFlowProps<
      * If you have custom connection logic its preferred to use this callback over the
      * `isValidConnection` prop on the handle component for performance reasons.
      */
+    /** Toggles ability to make connections via clicking the handles */
+    clickConnect?: boolean;
     isValidConnection?: IsValidConnection;
     /** This event handler is called when the user begins to pan or zoom the viewport */
     onmovestart?: OnMoveStart;
@@ -434,8 +437,8 @@ export type SvelteFlowProps<
     onclickconnectstart?: OnConnectStart;
     /** A connection is finished by clicking on a handle */
     onclickconnectend?: OnConnectEnd;
-    /** Toggles ability to make connections via clicking the handles */
-    clickConnect?: boolean;
     /** This handler gets called when the flow is finished initializing */
     oninit?: () => void;
+    /** This event handler gets called when the selected nodes & edges change */
+    onselectionchanged?: OnSelectionChanged<NodeType, EdgeType>;
   };