Disallow dragging other things over the notebook

Fix #99257

src/vs/workbench/contrib/notebook/browser/view/renderers/cellRenderer.ts

@@ -51,6 +51,7 @@ import { CodeCellViewModel } from 'vs/workbench/contrib/notebook/browser/viewMod
 import { MarkdownCellViewModel } from 'vs/workbench/contrib/notebook/browser/viewModel/markdownCellViewModel';
 import { CellViewModel } from 'vs/workbench/contrib/notebook/browser/viewModel/notebookViewModel';
 import { CellKind, NotebookCellRunState, NotebookCellMetadata } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { containsDragType } from 'vs/workbench/browser/dnd';
 
 const $ = DOM.$;
 
@@ -513,6 +514,8 @@ interface CellDragEvent {
 }
 
 export class CellDragAndDropController extends Disposable {
+	private static DATA_TYPE = 'vscode_notebook_cell';
+
 	// TODO@roblourens - should probably use dataTransfer here, but any dataTransfer set makes the editor think I am dropping a file, need
 	// to figure out how to prevent that
 	private currentDraggedCell: ICellViewModel | undefined;
@@ -619,6 +622,15 @@ export class CellDragAndDropController extends Disposable {
 	}
 
 	private onCellDragover(event: CellDragEvent): void {
+		if (!event.browserEvent.dataTransfer) {
+			return;
+		}
+
+		if (!this.currentDraggedCell || !containsDragType(event.browserEvent, CellDragAndDropController.DATA_TYPE)) {
+			event.browserEvent.dataTransfer.dropEffect = 'none';
+			return;
+		}
+
 		if (this.isScrolling || this.currentDraggedCell === event.draggedOverCell) {
 			this.setInsertIndicatorVisibility(false);
 			return;
@@ -691,6 +703,8 @@ export class CellDragAndDropController extends Disposable {
 				return;
 			}
 
+			event.dataTransfer.setData(CellDragAndDropController.DATA_TYPE, 'true');
+
 			this.currentDraggedCell = templateData.currentRenderedCell!;
 			this.currentDraggedCell.dragging = true;