Delphi 7 - Changing font sub-property is not updating component - properties

Question

I'm having problems in design time with a StringGrid I've made. When a property called "Header" is changed, the Invalidate method works fine and the Grid is repainted in design-time. However, when a sub-property Font is added, the Grid does not update when Header's font is changed in desig-time. If I click on Grid or expand a cell after changing font, then it is updated.
Here is my code:
unit GridsEx;
interface
uses
Windows, SysUtils, Classes, Controls, Grids, Graphics, Dialogs;
const
CONST_CELL_PADDING = 4;
type
TStringGridEx = class;
THeader = class(TPersistent)
private
FGrid: TStringGridEx;
FColCount: Longint;
FColor: TColor;
FFont: TFont;
FHeight: Integer;
procedure SetColor(Value: TColor);
procedure SetColCount(Value: Longint);
procedure SetHeight(Value: Integer);
procedure SetFont(Value: TFont);
protected
public
constructor Create; overload;
constructor Create(const AGrid: TStringGridEx); overload;
destructor Destroy; override;
procedure Assign(Source: TPersistent); override;
published
property ColCount: Longint read FColCount write SetColCount;
property Color: TColor read FColor write SetColor;
property Font: TFont read FFont write SetFont;
property Height: Integer read FHeight write SetHeight;
end;
TStringGridEx = class(TStringGrid)
private
FHeader: THeader;
protected
procedure DrawCell(ACol, ARow: Integer; Rect: TRect; State: TGridDrawState); override;
property ColCount;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
procedure AfterConstruction; override;
published
property Header: THeader read FHeader write FHeader;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Additional', [TStringGridEx]);
end;
{ THeader }
constructor THeader.Create;
begin
FColor := clBtnFace;
FColCount := 3;
FFont := TFont.Create;
FFont.Name := 'Tahoma';
FFont.Size := 9;
FFont.Color := clNavy;
FHeight := 22;
end;
procedure THeader.Assign(Source: TPersistent);
begin
inherited;
end;
constructor THeader.Create(const AGrid: TStringGridEx);
begin
Self.Create;
FGrid := AGrid;
end;
procedure THeader.SetColCount(Value: Longint);
begin
if (Value <> FColCount) then
begin
if (Value < 1) then Value := 1;
FColCount := Value;
FGrid.ColCount := FColCount;
FGrid.Invalidate;
end;
end;
procedure THeader.SetColor(Value: TColor);
begin
if (Value <> FColor) then
begin
FColor := Value;
FGrid.Invalidate;
end;
end;
procedure THeader.SetHeight(Value: Integer);
begin
if (Value <> FHeight) then
begin
if (Value < 0) then Value := 0;
FHeight := Value;
FGrid.RowHeights[0] := FHeight;
FGrid.Invalidate;
end;
end;
destructor THeader.Destroy;
begin
FreeAndNil(FFont);
inherited;
end;
procedure THeader.SetFont(Value: TFont);
begin
FFont.Assign(Value);
FGrid.Invalidate;
end;
{ TStringGridEx }
procedure TStringGridEx.AfterConstruction;
begin
inherited;
FHeader := THeader.Create(Self);
ColCount := FHeader.ColCount;
RowHeights[0] := FHeader.Height;
end;
constructor TStringGridEx.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
DefaultDrawing := False;
DefaultRowHeight := 20;
//Ctl3D := False;
FixedCols := 0;
FixedRows := 1;
Cells[0, 0] := 'Serial';
Cells[1, 0] := 'Name';
Cells[0, 1] := '00001';
Cells[1, 1] := 'Lorem Ipsum';
end;
destructor TStringGridEx.Destroy;
begin
FreeAndNil(FHeader);
inherited;
end;
procedure TStringGridEx.DrawCell(ACol, ARow: Integer; Rect: TRect; State: TGridDrawState);
var
TextRect: TRect;
TextFormat: Cardinal;
begin
inherited;
Canvas.Brush.Style := bsSolid;
Canvas.Brush.Color := clWindow;
if (ARow = 0) then
begin
Canvas.Brush.Color := FHeader.Color;
Canvas.Font.Assign(FHeader.Font);
end;
Canvas.FillRect(Rect);
TextFormat := DT_SINGLELINE or DT_VCENTER or DT_LEFT or DT_END_ELLIPSIS;
TextRect := Rect;
TextRect.Left := TextRect.Left + (CONST_CELL_PADDING);
DrawText(Canvas.Handle, PAnsiChar(Cells[ACol, ARow]), Length(Cells[ACol, ARow]), TextRect, TextFormat);
end;
end.
English is not my language, so sorry for typos. Appreciate your help.

Answer 1

The grid doesn't update when you assign values to the Font's sub-properties because you are not assigning a TFont.OnChange event handler to invalidate the grid when any aspect of the Font changes.
Your SetFont() setter method does not get called when setting the Font's individual sub-properties. Only when setting the Font property itself. The OnChange event is fired for individual changes to the Font, so you need an event handler for it.
There are also several other bugs in your code:
you are defining 2 constructors for THeader when you only need 1 constructor.
you are not implementing THeader.Assign() to copy anything.
you are not defining a setter method for the TStringGridEx.Header property. You are taking ownership of the caller's input THeader object instead of copying property values from it, and leaking the previous THeader object that you were holding a pointer to.
you are handling your TStringGridEx initialization in AfterConstruction() instead of in the constructor, where it belongs.
Try this:
unit GridsEx;
interface
uses
Windows, SysUtils, Classes, Controls, Grids, Graphics, Dialogs;
const
CONST_CELL_PADDING = 4;
type
TStringGridEx = class;
THeader = class(TPersistent)
private
FGrid: TStringGridEx;
FColCount: Longint;
FColor: TColor;
FFont: TFont;
FHeight: Integer;
procedure FontChanged(Sender: TObject);
procedure SetColor(Value: TColor);
procedure SetColCount(Value: Longint);
procedure SetHeight(Value: Integer);
procedure SetFont(Value: TFont);
public
constructor Create(const AGrid: TStringGridEx);
destructor Destroy; override;
procedure Assign(Source: TPersistent); override;
published
property ColCount: Longint read FColCount write SetColCount;
property Color: TColor read FColor write SetColor;
property Font: TFont read FFont write SetFont;
property Height: Integer read FHeight write SetHeight;
end;
TStringGridEx = class(TStringGrid)
private
FHeader: THeader;
procedure SetHeader(AValue: THeader);
protected
procedure DrawCell(ACol, ARow: Integer; Rect: TRect; State: TGridDrawState); override;
property ColCount;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
property Header: THeader read FHeader write SetHeader;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Additional', [TStringGridEx]);
end;
{ THeader }
procedure THeader.Assign(Source: TPersistent);
var
H: THeader;
begin
if Source is THeader then
begin
H := THeader(Source);
ColCount := H.ColCount;
Color := H.Color;
Font := H.Font;
Height := H.Height;
end else
inherited;
end;
constructor THeader.Create(const AGrid: TStringGridEx);
begin
inherited Create;
FGrid := AGrid;
FColor := clBtnFace;
FColCount := 3;
FFont := TFont.Create;
FFont.Name := 'Tahoma';
FFont.Size := 9;
FFont.Color := clNavy;
FFont.OnChange := FontChanged;
FHeight := 22;
end;
destructor THeader.Destroy;
begin
FFont.Free;
inherited;
end;
procedure THeader.FontChanged(Sender: TObject);
begin
FGrid.Invalidate;
end;
procedure THeader.SetColCount(Value: Longint);
begin
if (Value < 1) then Value := 1;
if (Value <> FColCount) then
begin
FColCount := Value;
FGrid.ColCount := FColCount;
FGrid.Invalidate;
end;
end;
procedure THeader.SetColor(Value: TColor);
begin
if (Value <> FColor) then
begin
FColor := Value;
FGrid.Invalidate;
end;
end;
procedure THeader.SetHeight(Value: Integer);
begin
if (Value < 0) then Value := 0;
if (Value <> FHeight) then
begin
FHeight := Value;
FGrid.RowHeights[0] := FHeight;
FGrid.Invalidate;
end;
end;
procedure THeader.SetFont(Value: TFont);
begin
FFont.Assign(Value);
end;
{ TStringGridEx }
constructor TStringGridEx.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
FHeader := THeader.Create(Self);
DefaultDrawing := False;
DefaultRowHeight := 20;
//Ctl3D := False;
FixedCols := 0;
FixedRows := 1;
ColCount := FHeader.ColCount;
RowHeights[0] := FHeader.Height;
Cells[0, 0] := 'Serial';
Cells[1, 0] := 'Name';
Cells[0, 1] := '00001';
Cells[1, 1] := 'Lorem Ipsum';
end;
destructor TStringGridEx.Destroy;
begin
FHeader.Free;
inherited;
end;
procedure TStringGridEx.DrawCell(ACol, ARow: Integer; Rect: TRect; State: TGridDrawState);
var
TextRect: TRect;
TextFormat: Cardinal;
S: string;
begin
inherited;
Canvas.Brush.Style := bsSolid;
Canvas.Brush.Color := clWindow;
if (ARow = 0) then
begin
Canvas.Brush.Color := FHeader.Color;
Canvas.Font.Assign(FHeader.Font);
end;
Canvas.FillRect(Rect);
TextFormat := DT_SINGLELINE or DT_VCENTER or DT_LEFT or DT_END_ELLIPSIS;
TextRect := Rect;
TextRect.Left := TextRect.Left + (CONST_CELL_PADDING);
S := Cells[ACol, ARow];
DrawText(Canvas.Handle, PChar(S), Length(S), TextRect, TextFormat);
end;
procedure TStringGridEx.SetHeader(AValue: THeader);
begin
FHeader.Assign(AValue);
end;
end.
That being said, you can remove the FColCount and FHeight members from THeader since they are delegated to TStringGridEx anyway, so just let TStringGridEx take care of them for you, you don't need to duplicate the work unnecessarily:
unit GridsEx;
interface
uses
Windows, SysUtils, Classes, Controls, Grids, Graphics, Dialogs;
const
CONST_CELL_PADDING = 4;
type
TStringGridEx = class;
THeader = class(TPersistent)
private
FGrid: TStringGridEx;
FColor: TColor;
FFont: TFont;
procedure FontChanged(Sender: TObject);
function GetColCount: Longint;
function GetHeight: Integer;
procedure SetColor(Value: TColor);
procedure SetColCount(Value: Longint);
procedure SetHeight(Value: Integer);
procedure SetFont(Value: TFont);
public
constructor Create(const AGrid: TStringGridEx);
destructor Destroy; override;
procedure Assign(Source: TPersistent); override;
published
property ColCount: Longint read GetColCount write SetColCount;
property Color: TColor read FColor write SetColor;
property Font: TFont read FFont write SetFont;
property Height: Integer read GetHeight write SetHeight;
end;
TStringGridEx = class(TStringGrid)
private
FHeader: THeader;
procedure SetHeader(AValue: THeader);
protected
procedure DrawCell(ACol, ARow: Integer; Rect: TRect; State: TGridDrawState); override;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
published
property ColCount default 3;
property Header: THeader read FHeader write SetHeader;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('Additional', [TStringGridEx]);
end;
{ THeader }
procedure THeader.Assign(Source: TPersistent);
var
H: THeader;
begin
if Source is THeader then
begin
H := THeader(Source);
ColCount := H.ColCount;
Color := H.Color;
Font := H.Font;
Height := H.Height;
end else
inherited;
end;
constructor THeader.Create(const AGrid: TStringGridEx);
begin
inherited Create;
FGrid := AGrid;
FColor := clBtnFace;
FFont := TFont.Create;
FFont.Name := 'Tahoma';
FFont.Size := 9;
FFont.Color := clNavy;
FFont.OnChange := FontChanged;
end;
destructor THeader.Destroy;
begin
FFont.Free;
inherited;
end;
procedure THeader.FontChanged(Sender: TObject);
begin
FGrid.Invalidate;
end;
function THeader.GetColCount: Longint;
begin
Result := FGrid.ColCount;
end;
function THeader.GetHeight: Integer;
begin
Result := FGrid.RowHeights[0];
end;
procedure THeader.SetColCount(Value: Longint);
begin
FGrid.ColCount := Value;
end;
procedure THeader.SetColor(Value: TColor);
begin
if (Value <> FColor) then
begin
FColor := Value;
FGrid.Invalidate;
end;
end;
procedure THeader.SetHeight(Value: Integer);
begin
FGrid.RowHeights[0] := Value;
end;
procedure THeader.SetFont(Value: TFont);
begin
FFont.Assign(Value);
end;
{ TStringGridEx }
constructor TStringGridEx.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
FHeader := THeader.Create(Self);
DefaultDrawing := False;
DefaultRowHeight := 20;
//Ctl3D := False;
FixedCols := 0;
FixedRows := 1;
ColCount := 3;
RowHeights[0] := 22;
Cells[0, 0] := 'Serial';
Cells[1, 0] := 'Name';
Cells[0, 1] := '00001';
Cells[1, 1] := 'Lorem Ipsum';
end;
destructor TStringGridEx.Destroy;
begin
FHeader.Free;
inherited;
end;
procedure TStringGridEx.DrawCell(ACol, ARow: Integer; Rect: TRect; State: TGridDrawState);
var
TextRect: TRect;
TextFormat: Cardinal;
S: string;
begin
inherited;
Canvas.Brush.Style := bsSolid;
Canvas.Brush.Color := clWindow;
if (ARow = 0) then
begin
Canvas.Brush.Color := FHeader.Color;
Canvas.Font.Assign(FHeader.Font);
end;
Canvas.FillRect(Rect);
TextFormat := DT_SINGLELINE or DT_VCENTER or DT_LEFT or DT_END_ELLIPSIS;
TextRect := Rect;
TextRect.Left := TextRect.Left + (CONST_CELL_PADDING);
S := Cells[ACol, ARow];
DrawText(Canvas.Handle, PChar(S), Length(S), TextRect, TextFormat);
end;
procedure TStringGridEx.SetHeader(AValue: THeader);
begin
FHeader.Assign(AValue);
end;
end.