How to automatically drop down the lookup list in a TDBGrid

Problem/Question/Abstract:

I'm trying to do this: On enter in a cell of a DBGrid that is of fkLookup FieldKind type show the lookup list immediately without clicking on the little button that appears when I click in the cell.

Answer:

Solve 1:

Here is a sample how to drop down the lookup list automatically when the user enters a column and the OnColEnter event is fired.

procedure TForm1.DBGrid1ColEnter(Sender: TObject);
const
  MyFieldName: string = 'SomeFieldName';
var
  I: Integer;
  MyGrid: TCustomDBGrid;
begin
  MyGrid := Sender as TCustomDBGrid;
  if MyGrid.SelectedField.FullName = MyFieldName then
  begin
    { Put the grid in edit mode. }
    MyGrid.EditorMode := True;
    { TCustomGrid.InplaceEditor is declared as protected property and
                cannot be addressed directly.
                 Since the inplace editor window is a child window of the grid,
                we can find it. }
    for I := 0 to MyGrid.ControlCount - 1 do
    begin
      if MyGrid.Controls[I] is TInplaceEdit then
        { Simulate an Alt+DownArrow key stroke }
        PostMessage(TWinControl(MyGrid.Controls[I]).Handle, WM_KEYDOWN,
          VK_DOWN, $20000000);
      Break;
    end;
  end;
end;


Solve 2:

In the OnColEnter event, send an Alt-DownArrow keystroke:

{ ... }
if DBGrid1.SelectedField.FieldName = 'fieldname' then
begin
  DBGrid1.EditorMode := True;
  keybd_event(VK_MENU, MapVirtualKey(VK_MENU, 0), 0, 0);
  keybd_event(VK_DOWN, MapVirtualKey(VK_DOWN, 0), 0, 0);
  keybd_event(VK_DOWN, 0, KEYEVENTF_KEYUP, 0);
  keybd_event(VK_MENU, 0, KEYEVENTF_KEYUP, 0)
end;

Or use a cracker class to expose TCustomGrid.InplaceEditor:

type
  TCrackGrid = class(TDBGrid);
  { ... }

procedure TForm1.DBGrid1ColEnter(Sender: TObject);
begin
  with TCrackGrid(DBGrid1) do
    if SelectedField.FieldName = 'fieldname' then
    begin
      EditorMode := True;
      {send Alt-DownArrow keystroke}
      PostMessage(InplaceEditor.Handle, WM_KEYDOWN, VK_DOWN, $20000000)
    end;
end;