...show Window Contents while dragging?

procedure ShowContents(Value: Boolean);
begin
  SystemParametersInfo(SPI_SETDRAGFULLWINDOWS, Ord(Value), nil, 0);
end;

// To Show window contents while dragging:

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowContents(True);
end;

// To disable this option call the function:

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowContents(False);
end;