{*******************************************************}
{                                                       }
{         Delphi VCL Extensions (RX)                    }
{                                                       }
{         Copyright (c) 1998 Master-Bank                }
{                                                       }
{*******************************************************}

unit MrgMngr;

{$I RX.INC}

interface

uses Classes, Controls, Forms, VCLUtils;

type
  TFormRequestEvent = procedure(Sender: TObject; CurrentForm: TCustomForm;
    var NewForm: TCustomForm) of object;
  TFormReorderEvent = procedure(Sender: TObject;
    Activated, Deactivated: TCustomForm) of object;
  TFormHistory = class;
  TFormHistoryCommand = (hcNone, hcAdd, hcBack, hcForward, hcGoto);

{ TMergeManager }

  TMergeManager = class(TComponent)
  private
    FMergeFrame: TWinControl;
    FFormHistory: TFormHistory;
    FHistoryCommand: TFormHistoryCommand;
    FOnGetBackForm: TFormRequestEvent;
    FOnGetForwardForm: TFormRequestEvent;
    FOnChange: TNotifyEvent;
    FOnReorder: TFormReorderEvent;
    function IsForm: Boolean;
    function NotIsForm: Boolean;
    procedure ReadForm(Reader: TReader);
    procedure WriteForm(Writer: TWriter);
    procedure SetMergeFrame(Value: TWinControl);
    function GetActiveForm: TCustomForm;
    procedure SetActiveForm(Value: TCustomForm);
  protected
    procedure DefineProperties(Filer: TFiler); override;
    function GetBackForm: TCustomForm; virtual;
    function GetForwardForm: TCustomForm; virtual;
    procedure Notification(AComponent: TComponent;
      Operation: TOperation); override;
    procedure DoChange; dynamic;
    procedure DoReorder(Deactivated: TCustomForm); dynamic;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    procedure Merge(AForm: TCustomForm; Show: Boolean);
    function GotoForm(AForm: TCustomForm): Boolean;
    function GotoFormClass(AFormClass: TFormClass): Boolean;
    procedure GoBack;
    procedure GoForward;
    procedure GotoHistoryIndex(HistoryIndex: Integer);
    property FormHistory: TFormHistory read FFormHistory;
    property ActiveForm: TCustomForm read GetActiveForm write SetActiveForm;
    property HistoryCommand: TFormHistoryCommand read FHistoryCommand
      write FHistoryCommand;
  published
    property MergeFrame: TWinControl read FMergeFrame write SetMergeFrame
      stored NotIsForm;
    property OnGetBackForm: TFormRequestEvent read FOnGetBackForm
      write FOnGetBackForm;
    property OnGetForwardForm: TFormRequestEvent read FOnGetForwardForm
      write FOnGetForwardForm;
    property OnChange: TNotifyEvent read FOnChange write FOnChange;
    property OnReorder: TFormReorderEvent read FOnReorder write FOnReorder;
  end;

{ TFormHistory }

  TFormHistory = class(TList)
  private
    FCurrent: Integer;
    FHistoryCapacity: Integer;
    procedure SetCurrent(Value: Integer);
    procedure SetHistoryCapacity(Value: Integer);
    function GetForm(Index: Integer): TCustomForm;
  public
    constructor Create;
    destructor Destroy; override;
    procedure AddForm(AForm: TCustomForm);
    procedure DeleteHistoryItem(Index: Integer);
    function RemoveItem(Item: TComponent): Boolean;
    procedure ResetHistory;
    property Current: Integer read FCurrent write SetCurrent;
    property HistoryCapacity: Integer read FHistoryCapacity
      write SetHistoryCapacity;
    property Forms[Index: Integer]: TCustomForm read GetForm;
  end;

implementation

{ TMergeManager }

constructor TMergeManager.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FFormHistory := TFormHistory.Create;
  FHistoryCommand := hcAdd;
end;

destructor TMergeManager.Destroy;
begin
  FFormHistory.Free;
  inherited Destroy;
end;

function TMergeManager.NotIsForm: Boolean;
begin
  Result := (MergeFrame <> nil) and not (MergeFrame is TCustomForm);
end;

function TMergeManager.IsForm: Boolean;
begin
  Result := (MergeFrame <> nil) and ((MergeFrame = Owner) and
    (Owner is TCustomForm));
end;

procedure TMergeManager.ReadForm(Reader: TReader);
begin
  if Reader.ReadBoolean then
    if Owner is TCustomForm then MergeFrame := TWinControl(Owner);
end;

procedure TMergeManager.WriteForm(Writer: TWriter);
begin
  Writer.WriteBoolean(IsForm);
end;

procedure TMergeManager.DefineProperties(Filer: TFiler);
{$IFDEF WIN32}
  function DoWrite: Boolean;
  begin
    if Assigned(Filer.Ancestor) then
      Result := IsForm <> TMergeManager(Filer.Ancestor).IsForm
    else Result := IsForm;
  end;
{$ENDIF}
begin
  inherited DefineProperties(Filer);
  Filer.DefineProperty('IsForm', ReadForm, WriteForm,
    {$IFDEF WIN32} DoWrite {$ELSE} IsForm {$ENDIF});
end;

procedure TMergeManager.SetMergeFrame(Value: TWinControl);
begin
  if FMergeFrame <> Value then begin
    FMergeFrame := Value;
{$IFDEF WIN32}
    if Value <> nil then Value.FreeNotification(Self);
{$ENDIF}
    FFormHistory.ResetHistory;
  end;
end;

function TMergeManager.GetActiveForm: TCustomForm;
var
  I: Integer;
begin
  if (MergeFrame <> nil) and (MergeFrame.ControlCount > 0) then begin
    for I := MergeFrame.ControlCount - 1 downto 0 do begin
      if MergeFrame.Controls[I] is TCustomForm then begin
        Result := TCustomForm(MergeFrame.Controls[I]);
        Exit;
      end;
    end;
  end;
  Result := nil;
end;

procedure TMergeManager.SetActiveForm(Value: TCustomForm);
begin
  GotoForm(Value);
end;

function TMergeManager.GetBackForm: TCustomForm;
begin
  if FormHistory.Current < 1 then
    Result := nil
  else
    Result := FormHistory.Forms[FormHistory.Current - 1];
  if Assigned(FOnGetBackForm) then FOnGetBackForm(Self, ActiveForm, Result);
end;

function TMergeManager.GetForwardForm: TCustomForm;
begin
  if FormHistory.Current >= FormHistory.Count - 1 then
    Result := nil
  else
    Result := FormHistory.Forms[FormHistory.Current + 1];
  if Assigned(FOnGetForwardForm) then FOnGetForwardForm(Self, ActiveForm, Result);
end;

procedure TMergeManager.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited Notification(AComponent, Operation);
  if Operation = opRemove then begin
    if AComponent = MergeFrame then MergeFrame := nil;
    if FormHistory.RemoveItem(AComponent) then DoChange;
  end;
end;

procedure TMergeManager.DoChange;
begin
  if Assigned(FOnChange) then FOnChange(Self);
end;

procedure TMergeManager.DoReorder(Deactivated: TCustomForm);
begin
  if Assigned(FOnReorder) then FOnReorder(Self, ActiveForm, Deactivated);
end;

procedure TMergeManager.Merge(AForm: TCustomForm; Show: Boolean);
begin
  MergeForm(MergeFrame, TForm(AForm), alClient, Show);
  GotoForm(AForm);
end;

function TMergeManager.GotoForm(AForm: TCustomForm): Boolean;
var
  I: Integer;
  OldActiveForm: TCustomForm;
begin
  Result := False;
  OldActiveForm := ActiveForm;
  if MergeFrame = nil then Exit;
  for I := 0 to MergeFrame.ControlCount - 1 do begin
    if MergeFrame.Controls[I] = AForm then begin
      AForm.BringToFront;
      case HistoryCommand of
        hcNone: ;
        hcAdd: FormHistory.AddForm(AForm);
        hcBack: FormHistory.Current := FormHistory.Current - 1;
        hcForward: FormHistory.Current := FormHistory.Current + 1;
        hcGoto: ;
      end;
      HistoryCommand := hcAdd;
      DoReorder(OldActiveForm);
      DoChange;
      Result := True;
      Exit;
    end;
  end;
end;

function TMergeManager.GotoFormClass(AFormClass: TFormClass): Boolean;
var
  I: Integer;
begin
  Result := False;
  if MergeFrame = nil then Exit;
  for I := 0 to MergeFrame.ControlCount - 1 do begin
    if MergeFrame.Controls[I] is AFormClass then begin
      Result := GotoForm(MergeFrame.Controls[I] as TCustomForm);     
      Exit;
    end;
  end;
end;

procedure TMergeManager.GoBack;
begin
  HistoryCommand := hcBack;
  GotoForm(GetBackForm);
end;

procedure TMergeManager.GoForward;
begin
  HistoryCommand := hcForward;
  GotoForm(GetForwardForm);
end;

procedure TMergeManager.GotoHistoryIndex(HistoryIndex: Integer);
var
  SaveCurrent: Integer;
begin
  SaveCurrent := FormHistory.Current;
  FormHistory.Current := HistoryIndex;
  try
    HistoryCommand := hcGoto;
    GotoForm(FormHistory.Forms[HistoryIndex]);
  finally
    if ActiveForm <> FormHistory.Forms[HistoryIndex] then
      FormHistory.Current := SaveCurrent;
  end;
end;

{ TFormHistory }

constructor TFormHistory.Create;
begin
  inherited Create;
  FCurrent := -1;
  FHistoryCapacity := 10;
end;

destructor TFormHistory.Destroy;
begin
  inherited Destroy;
end;

procedure TFormHistory.SetCurrent(Value: Integer);
begin
  if Value < 0 then Value := -1;
  if Value > Count - 1 then Value := Count - 1;
  if FCurrent <> Value then begin
    FCurrent := Value;
  end;
end;

procedure TFormHistory.SetHistoryCapacity(Value: Integer);
var
  I: Integer;
begin
  if Value < FHistoryCapacity then begin
    for I := 0 to Count - Value do begin
      RemoveItem(Forms[0]);
    end;
  end;
  FHistoryCapacity := Value;
end;

function TFormHistory.GetForm(Index: Integer): TCustomForm;
begin
  Result := TCustomForm(Items[Index]);
end;

procedure TFormHistory.AddForm(AForm: TCustomForm);
var
  I: Integer;
begin
  for I := Count - 1 downto Current + 1 do begin
    DeleteHistoryItem(I);
  end;
  for I := 0 to Count - HistoryCapacity do begin
    DeleteHistoryItem(0);
  end;
  if Count < HistoryCapacity then begin
    Add(AForm);
  end;
  Current := Count - 1;
end;

procedure TFormHistory.DeleteHistoryItem(Index: Integer);
begin
  if (Index >= 0) and (Index < Count) then begin
    Delete(Index);
    if Current > Count - 1 then Current := Count - 1;
  end;
end;

function TFormHistory.RemoveItem(Item: TComponent): Boolean;
var
  I: Integer;
begin
  Result := False;
  for I := Count - 1 downto 0 do begin
    if Items[I] = Item then begin
      DeleteHistoryItem(I);
      Result := True;
    end;
  end;
end;

procedure TFormHistory.ResetHistory;
begin
  Clear;
  Current := -1;
end;

end.