Force and Edited Cell to keep focus if not valid

VCL TMS VCL UI Pack
1
I try to implement a grid where an edited cell behave as follow:
- before exiting an edited  cell, the grid check if this cell match some constraints.
- If the value match the constraints you can leave the cell.
- if the value doesn't match the constraints, the cell MUST keep the focus.

For my example, I build a grid (2x2) where when Col=1 I have an edNumeric editor Type.
On the CellValidate event, I have this code :
//------------------------------------------------------------------------------
procedure TForm2.GridCellValidate(Sender: TObject; ACol, ARow: Integer;
  var Value: string; var Valid: Boolean);
//------------------------------------------------------------------------------
var
  i:Integer;
begin
  if Value='' then valid:=True
  else begin
    i:=StrToInt(value);
    case aRow of
      0: Valid:= (i mod 2)=0;
      1: Valid:= (i mod 2)=1;
    end;
  end;
end;

Which set valid to True if you type an even value for row 0 and an odd value for row 1.

When I try to leave my edited cell with Up/down key and this code set Valid variable to False. The Cell keep the focus and I remain in the cell. 
But If i click into another cell, and Valid is false, my grid cancel the edit AND exit the cell.

2

You can block the mouse to move the focused cell by implementing OnSelectCell.

Example:


Add at form level a variable lastval to store the last validation result.

procedure TForm3.AdvStringGrid1CellValidate(Sender: TObject; ACol,
  ARow: Integer; var Value: string; var Valid: Boolean);
begin
  if Length(Value) > 2 then
    valid := false;
  lastval := valid;
end;

procedure TForm3.AdvStringGrid1SelectCell(Sender: TObject; ACol, ARow: Integer;
  var CanSelect: Boolean);
begin
  CanSelect := lastval;
  if not lastval then
    AdvStringGrid1.ShowInplaceEdit;
end;