No drop support from Outlook New

[did-vmonroig]

Dropping files from Outlook New (version 1.2025.617.100) does not fire TDropComboTarget.OnDrop event. Same code works with previous Outlook versions (now called Classic) and other mail clients like Thunderbird. I've tried also OutlookDemo with no luck.

[landrix]

The new Outlook is a web app. There will be a problem there. I don't know what to do at the moment.

[did-vmonroig]

I've read about it and it seems problematic with nearly every desktop application. I think there is nothing to do at this moment, until Microsoft fixes the drag and drop functionality in Outlook New.

https://techcommunity.microsoft.com/blog/outlook/things-to-look-forward-to-in-the-new-outlook-for-windows/3975602
https://www.microsoft.com/en-us/microsoft-365/roadmap?filters=Outlook%2CDesktop&searchterms=drag+drop

[andersmelander]

First step would be to use the Drop Source Analyzer example to determine what data formats Outlook New supplies in the drop. I don't have access to Outlook New myself so I can't do it for you.

My guess would be that it supplies the FileContents and FileDescriptor formats with IStream as the medium - i.e. virtual files. Dragging to one of the VirtualFile examples should confirm this.

[OlliWW]

This is, what the Drop Source Analyer finds out, when you drop a file from a Outlook New Client.

Update:
You need to Enable Async Transfer to make it drop in the first place

[andersmelander]

Okay, so it supplies the CF_HDROP clipboard format (which should contain a filename) but returns an error when we try to actually read the data.
If you click on the CF_HDROP line it might display the actual error message in the preview pane; It depends on where in the process the error occurs.

The three next clipboard formats has to do with the drag cursor and the last is a custom format that can contain anything.

According to the stackoverflow post linked below, where they actually got drag from Outlook New to work in Delphi, one needs to use asynchronous data transfer.
The drag and drop component suite does support async transfer but it's disabled by default. To enable it, simple set AllowAsyncTransfer=True on the drop target. Be aware that during an async transfer, the OnDrop event handler is executed in the context of a background thread so one needs to check for that and handle it. See the AsyncTarget example.

The Drop Source Analyzer example unfortunately doesn't support async transfer, so we can't use that to confirm that it works. I'll see if I can do something about that.

• How to handle drag and drop of emails and attachments from New Outlook to native (Delphi) application?

[andersmelander]

Update:
You need to Enable Async Transfer to make it drop in the first place

I see our posts crossed :-)

[OlliWW]

What worked for me is:

• Enabled: "Async Transfer"
• Use a FileDataFormatAdapter and just copy the file

procedure TForm4.DropComboTarget1Drop(Sender: TObject; ShiftState: TShiftState; APoint: TPoint; var Effect: LongInt);
var
  i1: Integer;
begin
  if (DataFormatAdapter1.DataFormat <> nil)
  and (DataFormatAdapter1.DataFormat is TFileDataFormat) then
  begin
    Memo1.Lines.Assign((DataFormatAdapter1.DataFormat as TFileDataFormat).Files);
    for i1 := 0 to (DataFormatAdapter1.DataFormat as TFileDataFormat).Files.Count - 1 do
    begin
      TFile.Copy((DataFormatAdapter1.DataFormat as TFileDataFormat).Files[i1], 'C:\DroppedFiles\' + TPath.GetFileName((DataFormatAdapter1.DataFormat as TFileDataFormat).Files[i1]));
    end;
  end;
end;

This is the error i got on "CF_HDROP":

[andersmelander]

Excellent!

However, don't do this:

Memo1.Lines.Assign((DataFormatAdapter1.DataFormat as TFileDataFormat).Files);

since that isn't safe to do from a thread.

Also, one minor thing that has nothing to do with the topic, is that once you have determined that (DataFormatAdapter1.DataFormat is TFileDataFormat) then there's no need to use as like this: (DataFormatAdapter1.DataFormat as TFileDataFormat).
Simple use a cast instead: TFileDataFormat(DataFormatAdapter1.DataFormat). It's much more efficient.

[andersmelander]

@OlliWW Can I bother you to give the updated Source Analyzer from my repo a go at a Outlook New drop. It works with the async sources I've tested it with but I'd like it confirmed that it also works with Outlook New.

[OlliWW]

Sure 💯

Here are the results:
If i use "synchronous" mode, its the same behavior as before.
CF_HDROP => Failed to retreive data from Drop Source

If I use "Asynchronous" Mode CF_HDROP has Data in it (Filename to the temporary *.eml file in users\appdata...):