Posted by webmaster Guido on July 06, 2006
In Reply to Re: Making a grid with FG/BG setable colors posted by Lee Hallin P12462 on
July 02, 2006
Here's some code to play with :)
1. Add a Delphi TStringGrid component to the form. In the Object Inspector, set the following properties:
ColCount : default 5 or whatever number you prefer
2. In the implementation part of the unit, before the first procedure or function, declare two dynamic arrays that will hold the forground / background colours:
var FG: array of array of TColor; BG: array of array of TColor;
3. At the start of the program, we have to initialize the arrays. Code the OnCreate event handler of the form as follows:
procedure TForm1.FormCreate(Sender: TObject); var Col, Row: integer; begin // Set the sizes of the arrays SetLength(FG, Grid.ColCount, Grid.ColCount); SetLength(BG, Grid.ColCount, Grid.ColCount); // Initialize with default colors for Col := 0 to Grid.ColCount - 1 do begin for Row := 0 to Grid.RowCount - 1 do begin FG[Col, Row] := clBlack; BG[Col, Row] := clWhite; end; end; end;
3. Let Delphi write the template of an event handler: on the form, select the stringgrid component, and on the Events page of the Object Inspector, double click on the rectangle next to OnDrawCell.
4. Complete the event handler as follows:
procedure TForm1.GridDrawCell(Sender: TObject; ACol, ARow: Integer; Rect: TRect; State: TGridDrawState); var S: string; begin S := Grid.Cells[ACol, ARow]; // Fill rectangle with colour Grid.Canvas.Brush.Color := BG[ACol, ARow]; Grid.Canvas.FillRect(Rect); // Next, draw the text in the rectangle Grid.Canvas.Font.Color := FG[ACol, ARow]; Grid.Canvas.TextOut(Rect.Left + 2, Rect.Top + 2, S); end;
5. Let's write a quick routine for testing. When we click on a stringgrid cell, it should show the text "clicked" and set foreground/background colours randomly but with enough contrast.
procedure TForm1.GridClick(Sender: TObject); var Col, Row: integer; Colo1, Colo2, Colo3: byte; begin Col := Grid.Col; Row := Grid.Row; // Calculate contrasting random colours Colo1 := 200 + Random(56); Colo2 := 200 + Random(56); Colo3 := 100 + Random(156); BG[Col, Row] := RGB(Colo1, Colo2, Colo3); FG[Col, Row] := RGB(255 - Colo3, 255 - Colo1, 255 - Colo2); // Set the text to be displayed Grid.Cells[Col, Row] := 'clicked'; end;
Note that you can not directly change the colour of a cell, you can only tell the system that it should use such and such colours when next time it redraws the cell. In our example, it is the statement
Note also that if the stringgrid (or part of it) becomes visible again after it was hidden (e.g. obscured by another window), then GridDrawCell is called automatically for every cell that becomes visible.
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