feat: create flowcharts from a generic element using elbow arrows (#8329)

Co-authored-by: Mark Tolmacs <mark@lazycat.hu>
Co-authored-by: dwelle <5153846+dwelle@users.noreply.github.com>

packages/excalidraw/scene/Scene.ts

@@ -377,6 +377,10 @@ class Scene {
   }
 
   insertElementsAtIndex(elements: ExcalidrawElement[], index: number) {
+    if (!elements.length) {
+      return;
+    }
+
     if (!Number.isFinite(index) || index < 0) {
       throw new Error(
         "insertElementAtIndex can only be called with index >= 0",
@@ -403,7 +407,11 @@ class Scene {
   };
 
   insertElements = (elements: ExcalidrawElement[]) => {
-    const index = elements[0].frameId
+    if (!elements.length) {
+      return;
+    }
+
+    const index = elements[0]?.frameId
       ? this.getElementIndex(elements[0].frameId)
       : this.elements.length;
 

packages/excalidraw/scene/export.ts

@@ -242,6 +242,7 @@ export const exportToCanvas = async (
       // empty disables embeddable rendering
       embedsValidationStatus: new Map(),
       elementsPendingErasure: new Set(),
+      pendingFlowchartNodes: null,
     },
   });
 

packages/excalidraw/scene/types.ts

@@ -16,6 +16,7 @@ import type {
   SocketId,
   UserIdleState,
   Device,
+  PendingExcalidrawElements,
 } from "../types";
 import type { MakeBrand } from "../utility-types";
 
@@ -33,6 +34,7 @@ export type StaticCanvasRenderConfig = {
   isExporting: boolean;
   embedsValidationStatus: EmbedsValidationStatus;
   elementsPendingErasure: ElementsPendingErasure;
+  pendingFlowchartNodes: PendingExcalidrawElements | null;
 };
 
 export type SVGRenderConfig = {