2010. szeptember 15., szerda

Display multiple lines in a single cell of a TStringGrid

Problem/Question/Abstract:

How to display multiple lines in a single cell of a TStringGrid

Solve 1:

It is fairly easy to draw such text in an OnDrawCell handler. However the standard inplace editor of a grid is not well prepared to handle cells higher than one line.

procedure TForm1.StringGrid1DrawCell(Sender: TObject; Col, Row: Integer;
Rect: TRect; State: TGridDrawState);
var
S: string;
drawrect: TRect;
begin
S := (Sender as TStringGrid).Cells[Col, Row];
if Length(S) > 0 then
begin
drawrect := rect;
DrawText((Sender as TStringGrid).canvas.handle, Pchar(S), Length(S), drawrect,
DT_CALCRECT or DT_WORDBREAK or DT_LEFT);
if (drawrect.bottom - drawrect.top) > (Sender as TStringGrid).RowHeights[row] then
(Sender as TStringGrid).RowHeights[row] := (drawrect.bottom - drawrect.top)
else
begin
drawrect.Right := rect.right;
(Sender as TStringGrid).canvas.fillrect(drawrect);
DrawText((Sender as TStringGrid).canvas.handle, Pchar(S), Length(S),
drawrect, DT_WORDBREAK or DT_LEFT);
end;
end;
end;

It will automatically adjust the row height to larger values if needed. The main problem is that it will not automatically decrease the row height if the text would fit into a smaller row. It cannot do that since there may be other cells in the row that need a taller row. You could fix that problem by setting the rowheigh back to the defaultrowheight when you change the cell data for a row, that would trigger a redraw and that in turn would adjust the rowheight to what is needed. It would cause some flicker, though.

Solve 2:

This is a unit that enables word-wrap in a cell of a TStringGrid:

unit Unit1;

interface

uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs, ExtCtrls, Grids;

type
TForm1 = class(TForm)
StringGrid1: TStringGrid;
Panel1: TPanel;
procedure StringGrid1DrawCell(Sender: TObject; Col, Row: Longint;
Rect: TRect; State: TGridDrawState);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{\$R *.DFM}

procedure TForm1.StringGrid1DrawCell(Sender: TObject; Col, Row: Longint;
Rect: TRect; State: TGridDrawState);
var
A: array[0..255] of char;
drawrect: TRect;
begin
StrPCopy(A, (Sender as TStringgrid).Cells[Col, Row]);
if StrLen(A) > 0 then
with (Sender as TStringgrid) do
begin
drawrect := rect;
{Note that the first DrawText uses the DT_CALCRECT flag to calculate a new
value for drawrect. This value is used to set the RowHeights
parameter if necessary.}
DrawText(canvas.handle, A, -1, drawrect, DT_CALCRECT or DT_WORDBREAK or
DT_LEFT);
if (drawrect.bottom - drawrect.top) > RowHeights[Row] then
RowHeights[row] := (drawrect.bottom - drawrect.top)
else
begin
drawrect.right := rect.right;
canvas.fillrect(drawrect);
DrawText(canvas.handle, A, -1, drawrect, DT_WORDBREAK or DT_LEFT);
end;
end;
end;

end.