Pascal Super Library/Pascal Super Library (CW International)(1997).bin/BORL_TIP/TI1000/TI1721.ASC

Text File | 1993-10-21 | 8KB | 331 lines

  PRODUCT  :  Borland Pascal                        NUMBER  :  1721
  VERSION  :  All
       OS  :  DOS
     DATE  :  October 21, 1993                         PAGE  :  1/5

    TITLE  :  Does a Turbo Vision control have the input focus?




  The following program demonstrates how to detect if a control
  in a Turbo Vision dialog has received the focus. The key is the
  cmReceivedFocus message, which gets sent to the owner of a
  control whenever that control is about to receive the focus.
  Here is sample code showing how to respond to the message:

  procedure TTrainDialog.HandleEvent(var Event: TEvent);
  begin
    if (Event.What = EvBroadCast)
    and (Event.InfoPtr = MyInputLine)
    and (Event.Command = cmReceivedFocus) then begin
      MessageBox('Got cmReceivedFocus Message, nil, mfOkCancel);
    end;
    TDialog.HandleEvent(Event);
  end;

  The above code sample assumes that an inputline has been inserted
  into a dialog. Whenever the user TABs to the input line, then
  the cmReceivedFocus message is sent to the control's owner. Note
  that its not sent to the control itself, but to the control's
  owner! Note also that this is a broadcast message. Of course
  its not enough just to pick up on broadcast cmReceivedFocus
  messages. You also have to detect which control has just
  received the focus. To do this, you can use the InfoPtr field
  of the incoming TEVENT record. This field will contain a
  pointer to the control that is about to receive the focus. The
  example code here literally compares the pointer to a second
  copy of a pointer to that control. If they are equal, then
  you know that you have the right control. Of course, the above
  code assumes that you have explicitly saved and declared a
  pointer to the inputline, as shown in the included example
  program.
      Now that you understand how cmReceivedFocus messages
  work, you might be interested in seeing another way of handling
  the same problem. This is to override the SetState function which
  actually generates cmReceivedFocus messages. In the program
  shown below, the following code fragment will enable and
  disable the state of a command on the statusline, depending
  on whether or not the control has the focus.

  procedure TMyButton.SetState(AState: Word; Enable: Boolean);
  begin
    inherited SetState(AState, Enable);













  PRODUCT  :  Borland Pascal                        NUMBER  :  1721
  VERSION  :  All
       OS  :  DOS
     DATE  :  October 21, 1993                         PAGE  :  2/5

    TITLE  :  Does a Turbo Vision control have the input focus?




    if (AState = sfFocused) and (Enable = False) then
      DisableCommands([cmFoo]);
    if (AState = sfFocused) and (Enable = True) then
      EnableCommands([cmFoo]);
  end;

  The key to the above code is that it checks for sfFocused
  messages to find out whether the control is receiving or
  losing the focus.
         When running the following program, watch the status
  line to see which control has the focus.
  }

  program DlgFocus;
  uses
    App, Dialogs, Drivers, Menus, MsgBox, Validate, Views, Objects;

  const
    cmDialogBox = 101;
    cmTest      = 102;
    cmButton    = 103;
    cmInput      = 104;
    InputLength = 128;
    TheMessage = 'The Input line just received focus.' + #13#10 +
                 'Chose OK to set Ok in the Inputline' + #13#10 +
                 'Chose Cancel to set Cancel in the InputLine';

  type
    PMyButton = ^TMyButton;
    TMyButton = Object(TButton)
      procedure SetState(AState: Word; Enable: Boolean); virtual;
    end;

    PTrainDialog = ^TTrainDialog;
    TTrainDialog = Object(TDialog)
        MyInputLine: PInputLine;
      constructor Init(Bounds: TRect; ATitle: String);
      procedure HandleEvent(var Event: TEvent); virtual;
    end;

    TMyApp = Object(TApplication)
      constructor Init;
      procedure InitStatusLine; virtual;













  PRODUCT  :  Borland Pascal                        NUMBER  :  1721
  VERSION  :  All
       OS  :  DOS
     DATE  :  October 21, 1993                         PAGE  :  3/5

    TITLE  :  Does a Turbo Vision control have the input focus?




      procedure HandleEvent(var Event: TEvent); virtual;
      procedure DialogBox;
    end;

  procedure TMyButton.SetState(AState: Word; Enable: Boolean);
  begin
    inherited SetState(AState, Enable);
    if (AState = sfFocused) and (Enable = False) then
      DisableCommands([cmButton]);
    if (AState = sfFocused) and (Enable = True) then
      EnableCommands([cmButton]);
  end;

  constructor TTrainDialog.Init(Bounds: TRect; ATitle: String);
  var
    R: TRect;
    Control: PView;
    S: String;
  begin
    TDialog.Init(Bounds, ATitle);
    R.Assign(2, 2, 37, 4);
    Insert(New(PMyButton, Init(R, 'Test', cmTest, bfNormal)));
    R.Assign(3, 5, 37, 6);
    MyInputLine := New(PInputLine, Init(R, InputLength));
    Insert(MyInputLine);
    R.Assign(2, 4, 24, 5);
    Insert(New(PLabel, Init(R, 'Delivery instructions',
       MyInputLine)));
    R.Assign(2, 7, 37, 9);
    Insert(New(PButton, Init(R, 'O~k~', cmOk, bfDefault)));

    S := '32';
    SetData(S);
  end;

  procedure TTrainDialog.HandleEvent(var Event: TEvent);
  var
    Result: Word;
    S: String;
  begin
    if (Event.What = EvBroadCast) and
       (Event.InfoPtr = MyInputLine) then
      case Event.Command of













  PRODUCT  :  Borland Pascal                        NUMBER  :  1721
  VERSION  :  All
       OS  :  DOS
     DATE  :  October 21, 1993                         PAGE  :  4/5

    TITLE  :  Does a Turbo Vision control have the input focus?




        cmReceivedFocus: EnableCommands([cmInput]);
        cmReleasedFocus: DisableCommands([cmInput]);
      end;
    TDialog.HandleEvent(Event);
  end;

  constructor TMyApp.Init;
  begin
    inherited Init;
    DisableCommands([cmInput,cmButton]);
  end;

  procedure TMyApp.HandleEvent(var Event: TEvent);
  begin
    TApplication.HandleEvent(Event);
    if Event.What = EvCommand then begin
      case Event.Command of
        cmDialogBox: DialogBox;
      else
        Exit;
      end;
      ClearEvent(Event);
    end;
  end;

  procedure TMyApp.InitStatusLine;
  var R: TRect;
  begin
    GetExtent(R);
    R.A.Y := R.B.Y - 1;
    StatusLine := New(PStatusLine, Init(R,
      NewStatusDef(0, $FFFF,
        NewStatusKey('', kbF10, cmMenu,
        NewStatusKey('~Alt-X~ Exit', kbAltX, cmQuit,
        NewStatusKey('~Alt-D~ Dialog', kbAltD, cmDialogBox,
        NewStatusKey('~Alt-F4~ Button Focused?',
                 kbAltF4, cmButton,
        NewStatusKey('~Alt-F5~ InputLine Focused?',
                 kbAltF5, cmInput,
        nil))))),
      nil)
    ));
  end;













  PRODUCT  :  Borland Pascal                        NUMBER  :  1721
  VERSION  :  All
       OS  :  DOS
     DATE  :  October 21, 1993                         PAGE  :  5/5

    TITLE  :  Does a Turbo Vision control have the input focus?




  procedure TMyApp.DialogBox;
  var
    R: TRect;
    D: PDialog;
  begin
    R.Assign(20,5,60,15);
    D := New(PTrainDialog, Init(R, 'Hit Tab, watch statusline'));
    if ValidView(D) <> Nil then DeskTop^.ExecView(D);
    Dispose(D, Done);
  end;

  var
    A: TMyApp;
  begin
    A.Init;
    A.Run;
    A.Done;
  end.


  DISCLAIMER: You have the right to use this technical information
  subject to the terms of the No-Nonsense License Statement that
  you received with the Borland product to which this information
  pertains.