Custom Common Controls Writing

FastReport contains a set of common controls, which can be placed on dialogue forms inside the report. They are as follows:

  TfrxLabelControl
  TfrxEditControl
  TfrxMemoControl
  TfrxButtonControl
  TfrxCheckBoxControl
  TfrxRadioButtonControl
  TfrxListBoxControl
  TfrxComboBoxControl
  TfrxDateEditControl
  TfrxImageControl
  TfrxBevelControl
  TfrxPanelControl
  TfrxGroupBoxControl
  TfrxBitBtnControl
  TfrxSpeedButtonControl
  TfrxMaskEditControl
  TfrxCheckListBoxControl

These control elements correspond to Delphi component palette standard controls. If standard functionality does not satisfy you, you can create your own common control and use it in your reports.

Basic class for all common controls is TfrxDialogControl class declared in frxClass file:

  TfrxDialogControl = class(TfrxReportComponent)
  protected
    procedure InitControl(AControl: TControl);
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    class function GetDescription: String; virtual;
    property Caption: String;
    property Color: TColor;
    property Control: TControl;
    property OnClick: TfrxNotifyEvent;
    property OnDblClick: TfrxNotifyEvent;
    property OnEnter: TfrxNotifyEvent;
    property OnExit: TfrxNotifyEvent;
    property OnKeyDown: TfrxKeyEvent;
    property OnKeyPress: TfrxKeyPressEvent;
    property OnKeyUp: TfrxKeyEvent;
    property OnMouseDown: TfrxMouseEvent;
    property OnMouseMove: TfrxMouseMoveEvent;
    property OnMouseUp: TfrxMouseEvent;
  published
    property Left;
    property Top;
    property Width;
    property Height;
    property Font;
    property ParentFont;
    property Enabled: Boolean;
    property Visible;
  end;

To create your own control element, you should inherit from this class and override at least the constructor and GetDescription methods. It will be necessary to create common control and initialize it via InitControl method in constructor. GetDescription method is to return common control description. As you can see from TfrxDialogControl class description, it already contains huge number of properties and methods in public section. You need to transfer any necessary properties/events into “published” section of your common control, and also to create new properties, which are typical for your element.

Common control registration and deleting is performed via frxObjects global object methods declared in frxDsgnIntf file:

frxObjects.RegisterObject(ClassRef: TfrxComponentClass; ButtonBmp: TBitmap);
frxObjects.Unregister(ClassRef: TfrxComponentClass);

During registration you should specify control class name and its picture. ButtonBmp size should be 16x16 pixels.

Let us examine the example of the common control, which has simplified functionality of the standard Delphi TBitBtn control, for example.

uses frxClass, frxDsgnIntf, Buttons;

type
  TfrxBitBtnControl = class(TfrxDialogControl)
  private
    FButton: TBitBtn;
    procedure SetKind(const Value: TBitBtnKind);
    function GetKind: TBitBtnKind;
  public
    constructor Create(AOwner: TComponent); override;
    class function GetDescription: String; override;
    property Button: TBitBtn read FButton;
  published
    { add new properties }
    property Kind: TBitBtnKind read GetKind write SetKind default bkCustom;
    { these properties are already declared in  parent class }
    property Caption;
    property OnClick;
    property OnEnter;
    property OnExit;
    property OnKeyDown;
    property OnKeyPress;
    property OnKeyUp;
    property OnMouseDown;
    property OnMouseMove;
    property OnMouseUp;
  end;

constructor TfrxBitBtnControl.Create(AOwner: TComponent);
begin
  { default constructor }
  inherited;
  { create  required common control }
  FButton := TBitBtn.Create(nil);
  FButton.Caption := 'BitBtn';
  { initialize it }
  InitControl(FButton);
  { it will have such size by default }
  Width := 75;
  Height := 25;
end;

class function TfrxBitBtnControl.GetDescription: String;
begin
  Result := 'BitBtn control';
end;

procedure TfrxBitBtnControl.SetKind(const Value: TBitBtnKind);
begin
  FButton.Kind := Value;
end;

function TfrxBitBtnControl.GetKind: TBitBtnKind;
begin
  Result := FButton.Kind;
end;

var
  Bmp: TBitmap;

initialization
  Bmp := TBitmap.Create;
  {Load picture from resource. Of course, you should beforehand place it there.}
  Bmp.LoadFromResourceName(hInstance, 'frxBitBtnControl');
  frxObjects.RegisterObject(TfrxBitBtnControl, Bmp);

finalization
  frxObjects.Unregister(TfrxBitBtnControl);
  Bmp.Free;

end.