Add DBLookupCombobox to Delphi DBGrid - delphi

Question

I'd like to add DBLookupComboboxes to certain columns in a DBGrid. There is a nice article on About.com on how to do this here. The problem is that with a table having many columns, if you select from the DBLookupCombobox in one column and then try to scroll left, the combobox will move left too as shown in the included images. How can the About.com code can be changed to prevent this behavior? A web search showed two others complaining of the exact same problem with no solution. Note that I want to use a DBLookupCombobox to show a name but enter the id, so using a simple picklist will not do.
procedure TForm1.DBGrid1ColExit(Sender: TObject);
begin
if DBGrid1.SelectedField.FieldName = DBLookupComboBox1.DataField then
DBLookupComboBox1.Visible := False
end;
procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
DataCol: Integer; Column: TColumn; State: TGridDrawState);
begin
if (gdFocused in State) then
begin
if (Column.Field.FieldName = DBLookupComboBox1.DataField) then
with DBLookupComboBox1 do
begin
Left := Rect.Left + DBGrid1.Left + 2;
Top := Rect.Top + DBGrid1.Top + 2;
Width := Rect.Right - Rect.Left;
Width := Rect.Right - Rect.Left;
Height := Rect.Bottom - Rect.Top;
Visible := True;
end;
end
end;
procedure TForm1.DBGrid1KeyPress(Sender: TObject; var Key: Char);
begin
if (key = Chr(9)) then Exit;
if (DBGrid1.SelectedField.FieldName = DBLookupComboBox1.DataField) then
begin
DBLookupComboBox1.SetFocus;
SendMessage(DBLookupComboBox1.Handle, WM_Char, word(Key), 0);
end
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
with DBLookupComboBox1 do
begin
DataSource := DataSource1; // -> AdoTable1 -> DBGrid1
ListSource := DataSource2;
DataField := 'resource_id'; // from AdoTable1 - displayed in the DBGrid
KeyField := 'id';
ListField := 'resource_name; id';
Visible := False;
end;
DataSource2.DataSet := AdoQuery1;
AdoQuery1.Connection := AdoConnection1;
AdoQuery1.SQL.Text := 'SELECT id,resource_name FROM resources';
AdoQuery1.Open;
end;

Answer 1

Here is one solution using a neat hack from François.
type
// Hack to redeclare your TDBGrid here without the the form designer going mad
TDBGrid = class(DBGrids.TDBGrid)
procedure WMHScroll(var Msg: TWMHScroll); message WM_HSCROLL;
end;
TForm1 = class(TForm)
[...]
procedure TDBGrid.WMHScroll(var Msg: TWMHScroll);
begin
if Form1.DBGrid1.SelectedField.FieldName = Form1.DBLookupComboBox1.DataField then begin
case Msg.ScrollCode of
SB_LEFT,SB_LINELEFT,SB_PAGELEFT: begin
Form1.DBGrid1.SelectedIndex := Form1.DBGrid1.SelectedIndex-1;
Form1.DBLookupComboBox1.Visible := False;
end;
SB_RIGHT,SB_LINERIGHT,SB_PAGERIGHT: begin
Form1.DBGrid1.SelectedIndex := Form1.DBGrid1.SelectedIndex+1;
Form1.DBLookupComboBox1.Visible := False;
end;
end;
end;
inherited; // to keep the expected behavior
end;