Setting background color of selected row on TStrin

Question

I have a TStringGrid where the selected row (max 1, no multi-select) should always have a different background colo(u)r.

I set the DefaultDrawing property to false, and provide a method for the OnDrawCell event, shown below - but it is not working. I can't even describe exactly how it is not working; I supect that if I could I would already have solved the problem. Suffice it to say that instead of having complete rows all with the same background colour it is a mish-mash. Muliple rows have some cells of the "Selected" colour and not all cells of the cselected row have the selected colour.

Note that I compare the cell's row with the strnggrid's row; I can't check the cell state for selected since only cell of the selected row is selected.

procedure TForm1.DatabaseNamesStringGridDrawCell(Sender: TObject;
                                                 ACol, ARow: Integer;
                                                 Rect: TRect;
                                                 State: TGridDrawState);

  var cellText :String;
begin
   if gdFixed in State then
      DatabaseNamesStringGrid.Canvas.Brush.Color := clBtnFace
   else
   if ARow = DatabaseNamesStringGrid.Row then
      DatabaseNamesStringGrid.Canvas.Brush.Color := clAqua
   else
      DatabaseNamesStringGrid.Canvas.Brush.Color := clWhite;

   DatabaseNamesStringGrid.Canvas.FillRect(Rect);
   cellText := DatabaseNamesStringGrid.Cells[ACol, ARow];
   DatabaseNamesStringGrid.Canvas.TextOut(Rect.Left + 2, Rect.Top + 2, cellText);
end;

Answer 1

This works for me

procedure TFmain.yourStringGrid(Sender: TObject; ACol, ARow: Integer; Rect: TRect;
  State: TGridDrawState);
var
  md: integer;
begin
  with yourStringGrid do 
    begin
           if yourStringGrid,Row = ARow then
              Canvas.Brush.Color:= clYellow  //your highlighted color
           else begin
                 md := Arow mod 2;
                 if md <> 0 then Canvas.Brush.Color:= $00BADCC1 else //your alternate color
                 Canvas.Brush.Color:= clwhite;
           end;
           Canvas.FillRect(Rect);
           Canvas.TextOut(L, Rect.top + 4, cells[ACol, ARow]);
        end;
end;

Refresh the grid

procedure TFmain.yourStringGridClick(Sender: TObject);
begin
  yourStringGrid.Refresh;
end;

Note: Has a little latency, but otherwise works great.
(Used in Delphi XE2)

Answer 2

if you are trying of paint the selected row or cell with a different color you must check for the gdSelected value in the state var.

procedure TForm1.DatabaseNamesStringGridDrawCell(Sender: TObject;
                                                 ACol, ARow: Integer;
                                                 Rect: TRect;
                                                 State: TGridDrawState);
var
  AGrid : TStringGrid;
begin
   AGrid:=TStringGrid(Sender);

   if gdFixed in State then //if is fixed use the clBtnFace color
      AGrid.Canvas.Brush.Color := clBtnFace
   else
   if gdSelected in State then //if is selected use the clAqua color
      AGrid.Canvas.Brush.Color := clAqua
   else
      AGrid.Canvas.Brush.Color := clWindow;

   AGrid.Canvas.FillRect(Rect);
   AGrid.Canvas.TextOut(Rect.Left + 2, Rect.Top + 2, AGrid.Cells[ACol, ARow]);
end;

Answer 3

Do you have run-time themes enabled? Run-time themes override any colour scheme you try to enforce for Windows Vista and up.

Answer 4

When a new cell is selected in a stringgrid only the previous and the new selected cell are invalidated. Thus the remaining cells of the previous and new row are not redrawn, giving the effect you describe.

One workaround would be to call InvalidateRow for both affected rows, but this is a protected method and you have to find a way to reach this method from an OnSelectCell event handler. Depending on your Delphi version there are different ways to accomplish that.

The cleanest way would be to derive from TStringGrid, but in most cases this is not feasible. With a newer Delphi version you can use a class helper to achieve this. Otherwise you have to rely on the usual protected hack.