From a56dcd7948cf060876f8282677001ec60c804248 Mon Sep 17 00:00:00 2001
From: Alex | Kronox <alexander_vogt@outlook.de>
Date: Tue, 27 Jan 2026 14:22:53 +0100
Subject: [PATCH 1/2] fix file drop

---
 frontend/webEditor/src/serialize/di.config.ts |  4 +
 .../webEditor/src/serialize/dropListener.ts   | 83 +++++++++++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 frontend/webEditor/src/serialize/dropListener.ts

diff --git a/frontend/webEditor/src/serialize/di.config.ts b/frontend/webEditor/src/serialize/di.config.ts
index 4c1c0f4a..493081b5 100644
--- a/frontend/webEditor/src/serialize/di.config.ts
+++ b/frontend/webEditor/src/serialize/di.config.ts
@@ -9,6 +9,7 @@ import { SaveJsonFileCommand } from "./saveJsonFile";
 import { SaveDfdAndDdFileCommand } from "./saveDfdAndDdFile";
 import { AnalyzeCommand } from "./analyze";
 import { LoadFromUrlCommand } from "./LoadUrl";
+import { JsonDropHandler, LoadDroppedFileCommand } from "./dropListener";
 
 export const serializeModule = new ContainerModule((bind, unbind, isBound, rebind) => {
     const context = { bind, unbind, isBound, rebind };
@@ -20,6 +21,9 @@ export const serializeModule = new ContainerModule((bind, unbind, isBound, rebin
     configureCommand(context, SaveJsonFileCommand);
     configureCommand(context, SaveDfdAndDdFileCommand);
     configureCommand(context, AnalyzeCommand);
+    configureCommand(context, LoadDroppedFileCommand);
+
+    bind(TYPES.MouseListener).to(JsonDropHandler);
 
     rebind(TYPES.IModelFactory).to(DfdModelFactory);
 });
diff --git a/frontend/webEditor/src/serialize/dropListener.ts b/frontend/webEditor/src/serialize/dropListener.ts
new file mode 100644
index 00000000..c781a701
--- /dev/null
+++ b/frontend/webEditor/src/serialize/dropListener.ts
@@ -0,0 +1,83 @@
+import { inject, injectable } from "inversify";
+import { ActionDispatcher, ILogger, MouseListener, SModelElementImpl, TYPES } from "sprotty";
+import { Action } from "sprotty-protocol";
+import { FileData, LoadJsonCommand } from "./loadJson";
+import { SavedDiagram } from "./SavedDiagram";
+import { SETTINGS } from "../settings/Settings";
+import { ConstraintRegistry } from "../constraint/constraintRegistry";
+import { FileName } from "../fileName/fileName";
+import { LabelTypeRegistry } from "../labels/LabelTypeRegistry";
+import { LoadingIndicator } from "../loadingIndicator/loadingIndicator";
+import { EditorModeController } from "../settings/editorMode";
+
+@injectable()
+export class JsonDropHandler extends MouseListener {
+    constructor(@inject(TYPES.ILogger) private readonly logger: ILogger) {
+        super();
+    }
+
+    drop(_target: SModelElementImpl, ev: DragEvent): Promise<Action>[] {
+        this.logger.log(this, "Drop event detected", ev);
+
+        // Prevent default behavior which would open the file in the browser
+        ev.preventDefault();
+
+        const file = ev.dataTransfer?.files[0];
+        if (!file) {
+            return [];
+        }
+
+        if (file.type !== "application/json") {
+            alert("Diagram file must be in JSON format");
+            return [];
+        }
+
+        return [file.text().then((t) => LoadDroppedFileAction.create(file.name, JSON.parse(t)))];
+    }
+}
+
+interface LoadDroppedFileAction extends Action {
+    file: FileData<SavedDiagram>;
+}
+
+namespace LoadDroppedFileAction {
+    export const KIND = "loadDroppedFileAction";
+    export function create(fileName: string, content: SavedDiagram): LoadDroppedFileAction {
+        return {
+            kind: KIND,
+            file: {
+                fileName,
+                content,
+            },
+        };
+    }
+}
+
+export class LoadDroppedFileCommand extends LoadJsonCommand {
+    static readonly KIND = LoadDroppedFileAction.KIND;
+
+    constructor(
+        @inject(TYPES.Action) private readonly action: LoadDroppedFileAction,
+        @inject(TYPES.ILogger) logger: ILogger,
+        @inject(LabelTypeRegistry) labelTypeRegistry: LabelTypeRegistry,
+        @inject(ConstraintRegistry) constraintRegistry: ConstraintRegistry,
+        @inject(SETTINGS.Mode) editorModeController: EditorModeController,
+        @inject(TYPES.IActionDispatcher) actionDispatcher: ActionDispatcher,
+        @inject(FileName) fileName: FileName,
+        @inject(LoadingIndicator) loadingIndicator: LoadingIndicator,
+    ) {
+        super(
+            logger,
+            labelTypeRegistry,
+            constraintRegistry,
+            editorModeController,
+            actionDispatcher,
+            fileName,
+            loadingIndicator,
+        );
+    }
+
+    protected async getFile(): Promise<FileData<SavedDiagram> | undefined> {
+        return this.action.file;
+    }
+}

From aff4bc20a8ac50ae7c3d0ad1fa3f1442868a6b8e Mon Sep 17 00:00:00 2001
From: Alex | Kronox <alexander_vogt@outlook.de>
Date: Tue, 27 Jan 2026 14:25:36 +0100
Subject: [PATCH 2/2] move event prevention after file type check

---
 frontend/webEditor/src/serialize/dropListener.ts | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/frontend/webEditor/src/serialize/dropListener.ts b/frontend/webEditor/src/serialize/dropListener.ts
index c781a701..c6bc62cb 100644
--- a/frontend/webEditor/src/serialize/dropListener.ts
+++ b/frontend/webEditor/src/serialize/dropListener.ts
@@ -19,19 +19,18 @@ export class JsonDropHandler extends MouseListener {
     drop(_target: SModelElementImpl, ev: DragEvent): Promise<Action>[] {
         this.logger.log(this, "Drop event detected", ev);
 
-        // Prevent default behavior which would open the file in the browser
-        ev.preventDefault();
-
         const file = ev.dataTransfer?.files[0];
         if (!file) {
             return [];
         }
 
         if (file.type !== "application/json") {
-            alert("Diagram file must be in JSON format");
             return [];
         }
 
+        // Prevent default behavior which would open the file in the browser
+        ev.preventDefault();
+
         return [file.text().then((t) => LoadDroppedFileAction.create(file.name, JSON.parse(t)))];
     }
 }