Undo for objects created programmatically

[Artomov_Vitalii (Vitalii Artomov)]

Hi, I see a strange diagram reaction to the undo action. I create block programmatically (TDiagramBlock.Create) and then remove it to new position, just using the mouse cursor on the screen. If I then click undo action, the block becomes invisible (or deleted?), but logically, it should have just returned to its start position. If I create block using standard DiagramButtons container — all works fine.

What am I doing wrong? I am attaching the test, but I think that the question is already clear.

undo_example.zip (53.9 KB)

[Artomov_Vitalii (Vitalii Artomov)]

By the way, the FDiagram.ClearUndoStack method helped if I call it after creating the block. If this is the correct solution, perhaps it needs to be added to the help documentation, in the "Working with diagram programatically" section?

[wlandgraf (Wagner Landgraf)]

You should always call PushUndoStack to "save a snapshot" that you want to revert to when you can undo:

procedure TForm1.Button1Click(Sender: TObject);
var
  Block: TDiagramBlock;
begin
  Block := TDiagramBlock.Create(Self);
  Block.Diagram := Diagram1;
  Block.Color := clWhite;
  Diagram1.PushUndoStack('block create');
end;

[Artomov_Vitalii (Vitalii Artomov)]

Thanks a lot, Wagner!