feat(svelte): add drag n drop example

packages/svelte/src/example-components/Header/Header.svelte

@@ -2,6 +2,7 @@
   import { goto } from '$app/navigation';
 
   const routes = [
+    'drag-n-drop',
     'overview',
     'stress',
     'usesvelteflow',

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

@@ -12,10 +12,9 @@
   import { KeyHandler } from '$lib/components/KeyHandler';
   import { ConnectionLine } from '$lib/components/ConnectionLine';
   import { useStore } from '$lib/store';
-  import type { SvelteFlowProps, SvelteFlowEvents } from './types';
+  import type { SvelteFlowProps } from './types';
 
   type $$Props = SvelteFlowProps;
-  type $$Events = SvelteFlowEvents;
 
   export let id: $$Props['id'] = '1';
   export let fitView: $$Props['fitView'] = undefined;
@@ -98,6 +97,9 @@
   style={style}
   class={cc(['svelte-flow', className])}
   data-testid="rf__wrapper"
+  on:dragover
+  on:drop
+  {...$$restProps}
 >
   <KeyHandler {selectionKey} {deleteKey} />
   <Zoom {initialViewport}>

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

@@ -1,3 +1,4 @@
+import type { DOMAttributes } from 'svelte/elements';
 import type {
   Connection,
   ConnectionLineType,
@@ -17,7 +18,7 @@ import type {
   IsValidConnection
 } from '$lib/types';
 
-export type SvelteFlowProps = {
+export type SvelteFlowProps = DOMAttributes<HTMLDivElement> & {
   id?: string;
   nodeTypes?: NodeTypes;
   edgeTypes?: EdgeTypes;
@@ -37,19 +38,17 @@ export type SvelteFlowProps = {
 
   connectionLineType?: ConnectionLineType;
   isValidConnection?: IsValidConnection;
-};
 
-export type SvelteFlowEvents = {
-  'node:click': CustomEvent<Node>;
-  'node:mouseenter': CustomEvent<Node>;
-  'node:mousemove': CustomEvent<Node>;
-  'node:mouseleave': CustomEvent<Node>;
-  'edge:click': CustomEvent<Edge>;
-  'connect:start': CustomEvent<OnConnectStartParams>;
-  connect: CustomEvent<Connection>;
-  'connect:end': CustomEvent<OnConnectStartParams>;
-  'pane:click': CustomEvent;
-  'pane:contextmenu': CustomEvent;
+  'on:node:click'?: CustomEvent<Node>;
+  'on:node:mouseenter'?: CustomEvent<Node>;
+  'on:node:mousemove'?: CustomEvent<Node>;
+  'on:node:mouseleave'?: CustomEvent<Node>;
+  'on:edge:click'?: CustomEvent<Edge>;
+  'on:connect:start'?: CustomEvent<OnConnectStartParams>;
+  'on:connect'?: CustomEvent<Connection>;
+  'on:connect:end'?: CustomEvent<OnConnectStartParams>;
+  'on:pane:click'?: CustomEvent;
+  'on:pane:contextmenu'?: CustomEvent;
 };
 
 export type SvelteFlowSlots = {

packages/svelte/src/lib/hooks/useSvelteFlow.ts

@@ -1,9 +1,10 @@
-import type { Viewport, ZoomInOut } from '@reactflow/system';
+import type { Project, Viewport, XYPosition, ZoomInOut } from '@reactflow/system';
 
 import { useStore } from '$lib/store';
 import type { FitViewOptions } from '$lib/types';
 import { get, writable, type Writable } from 'svelte/store';
 import type { SvelteFlowStore } from '$lib/store/types';
+import { pointToRendererPoint } from '@reactflow/utils';
 
 export function useSvelteFlow(): {
   zoomIn: ZoomInOut;
@@ -12,9 +13,10 @@ export function useSvelteFlow(): {
   viewport: Writable<Viewport>;
   nodes: SvelteFlowStore['nodes'];
   edges: SvelteFlowStore['edges'];
+  project: Project;
 } {
   // how to get the new context here? fit view doesn't work, because the store is not updated (uses old nodes store)
-  const { zoomIn, zoomOut, fitView, transform, nodes, edges } = useStore();
+  const { zoomIn, zoomOut, fitView, snapGrid: snapGridStore, transform, nodes, edges } = useStore();
 
   const transformValues = get(transform);
   const viewportWritable = writable({
@@ -35,6 +37,10 @@ export function useSvelteFlow(): {
     zoomIn,
     zoomOut,
     fitView,
+    project: (position: XYPosition) => {
+      const snapGrid = get(snapGridStore);
+      return pointToRendererPoint(position, get(transform), snapGrid !== null, snapGrid || [1, 1]);
+    },
     nodes,
     edges,
     viewport: viewportWritable

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

@@ -292,6 +292,7 @@ export function createStore(params: CreateStoreParams): SvelteFlowStore {
     store.fitViewOnInitDone.set(false);
     store.selectionRect.set(null);
     store.selectionRectMode.set(null);
+    store.snapGrid.set(null);
 
     resetSelectedElements();
     cancelConnection();

packages/svelte/src/routes/drag-n-drop/+page.svelte

@@ -0,0 +1,52 @@
+<script lang="ts">
+  import { createNodes, createEdges, SvelteFlowProvider } from '../../lib/index';
+
+  import Flow from './Flow.svelte';
+  
+  const nodes = createNodes(
+    [
+      {
+        id: '1',
+        type: 'input',
+        data: { label: 'Input Node' },
+        position: { x: 150, y: 5 }
+      },
+      {
+        id: '2',
+        type: 'default',
+        data: { label: 'Node' },
+        position: { x: 0, y: 150 }
+      },
+      {
+        id: '3',
+        type: 'output',
+        data: { label: 'Output Node' },
+        position: { x: 300, y: 150 }
+      }
+    ],
+    { origin: [0.5, 0.5] }
+  );
+
+  const edges = createEdges([
+    {
+      id: '1-2',
+      type: 'default',
+      source: '1',
+      target: '2',
+      label: 'Edge Text'
+    },
+    {
+      id: '1-3',
+      type: 'smoothstep',
+      source: '1',
+      target: '3'
+    }
+  ]);
+</script>
+
+<SvelteFlowProvider
+  {nodes}
+  {edges}
+>
+  <Flow />
+</SvelteFlowProvider>

packages/svelte/src/routes/drag-n-drop/Flow.svelte

@@ -0,0 +1,65 @@
+<script lang="ts">
+  import SvelteFlow, {
+    Controls,
+    Background,
+    BackgroundVariant,
+    Minimap,
+    useSvelteFlow,
+    type Node
+  } from '../../lib/index';
+  import Sidebar from './Sidebar.svelte';
+
+  const svelteFlow = useSvelteFlow();
+
+  const onDragOver = (event: DragEvent) => {
+    event.preventDefault();
+
+    console.log(event)
+
+    if (event.dataTransfer) {
+      event.dataTransfer.dropEffect = 'move';
+    }
+  };
+
+  const onDrop = (event: DragEvent) => {
+    event.preventDefault();
+
+    if (!event.dataTransfer) {
+      return null;
+    }
+
+    const type = event.dataTransfer.getData('application/svelteflow');
+    const position = svelteFlow.project({
+      x: event.clientX,
+      y: event.clientY - 40,
+    });
+    const newNode: Node = {
+      id: `${Math.random()}`,
+      type,
+      position,
+      data: { label: `${type} node` },
+    };
+
+    svelteFlow.nodes.update(nds => nds.concat(newNode));
+  };
+</script>
+
+<main>
+  <SvelteFlow
+    fitView
+    on:dragover={onDragOver}
+    on:drop={onDrop}
+  >
+    <Controls />
+    <Background variant={BackgroundVariant.Dots} />
+    <Minimap />
+  </SvelteFlow>
+  <Sidebar />
+</main>
+
+<style>
+  main {
+    height: 100%;
+    display: flex;
+  }
+</style>

packages/svelte/src/routes/drag-n-drop/Sidebar.svelte

@@ -0,0 +1,59 @@
+<script lang="ts">
+  import {
+    useSvelteFlow
+  } from '../../lib/index';
+
+  const onDragStart = (event: DragEvent, nodeType: string) => {
+    if (!event.dataTransfer) {
+      return null;
+    }
+
+    event.dataTransfer.setData('application/svelteflow', nodeType);
+    event.dataTransfer.effectAllowed = 'move';
+  };
+
+  const { zoomIn, zoomOut, fitView, viewport, nodes } = useSvelteFlow();
+</script>
+
+<aside>
+  <div class="label">You can drag these nodes to the pane on the left.</div>
+  <div class="input-node node" on:dragstart={(event) => onDragStart(event, 'input')} draggable={true}>
+    Input Node
+  </div>
+  <div
+    class="default-node node"
+    on:dragstart={(event) => onDragStart(event, 'default')}
+    draggable={true}
+  >
+    Default Node
+  </div>
+  <div
+    class="output-node node"
+    on:dragstart={(event) => onDragStart(event, 'output')}
+    draggable={true}
+  >
+    Output Node
+  </div>
+</aside>
+
+<style>
+  .label {
+    margin: 0.5rem 0 .25rem 0;
+  }
+
+  aside {
+    width: 20vw;
+    background: #f4f4f4;
+    padding: 0.4rem 0.8rem;
+    font-size: 12px;
+  }
+
+  .node {
+    margin-bottom: 0.5rem;
+    border: 1px solid #111;
+    padding: .5rem 1rem;
+    font-weight: 700;
+    border-radius: 3px;
+    cursor: grab;
+  }
+</style>