Outlook Drag and Drop deletes Messages in Outlook ("move" instead of "copy") in Chrome

[ThomasSteschulat]

Hey Tewr! There is a bug in chrome that when someone drop a message from outllook (here Outlook 2016) on a droptarget in a browser (here blazor app with tewr.blazorfilereader) the message in outlook is deleted. It will be "moved" instead of "copied". The bug is documented here: chrome outlook drop In Comment 16 someone has a solution for this: Solution: Indeed you have to set dataTransfer.dropEffect = 'copy' ... but you have to set it to dragenter and dragover also, not only on the drop event. Then you can drag / drop emails without them going to the deleted folder :) tada!

My question is how to achive this dataTransfer.dropEffect = 'copy' in your blazor filereader package.

Can you help me out here?

Thomas

[ThomasSteschulat]

Hi @Tewr , we have put the dataTransfer.dropEffect = "copy" in the RegisterDropEvent Method and that works for now

  public RegisterDropEvents = (element: HTMLElement, additive: boolean): boolean => {
    this.LogIfNull(element);
    const handler = (ev: DragEvent) => {
        this.PreventDefaultHandler(ev);
        if (ev.target instanceof HTMLElement) {
            let list = ev.dataTransfer.files;
            if (additive) {
                const existing = this.elementDataTransfers.get(element);
                if (existing !== undefined && existing.length > 0) {
                    list = new FileReaderComponent.ConcatFileList(existing, list);
                }
            }

            this.elementDataTransfers.set(element, list);
        }
    };

    const handlerDragOver = (ev: DragEvent) => {
        this.PreventDefaultHandler(ev);
        **ev.dataTransfer.dropEffect = "copy";**
    };

    this.dragElements.set(element, handler);
    element.addEventListener("drop", handler);
    element.addEventListener("dragover", handlerDragOver);
    return true;
}

Perhaps you can make it useable as a parameter!?

Regards Thomas

[Tewr]

I'll have to think about a proper api here, just exposing this as a flag would be oddly specific. But the current API is indeed lacking extension points. I'm thinking some kind of simple plugin structure, I'll have to tinker a bit.

[ThomasSteschulat]

Great! I think that setting "copy" as Standard makes sense. There may be only a few situations where "move" makes sense. But first of all... its a bug in chrome :-)

And btw... great Work!

[Tewr]

So I've tinkered a bit in this branch/PR #170. There is a small "expert" api where you can plug in your own javascript method or snippet in the event handlers. Also I wrote an extension method that adresses your specific need using that API.

You would set it up using the extension method like this (for context, see here):

 await dropReference.RegisterDropEventsAsync(o => o.SetDragOverDataTransferDropEffect(DropEffect.Copy));

Let me know what you think and also if you could try it out as I don't have Outlook installed and I havent really checked for any other application that reads the dropEffect value.