TMemo.OnEnter Event

Occurs when a control receives the input focus.

Pascal

property OnEnter: TNotifyEvent;

C++

__property TNotifyEvent OnEnter;

Description

Use the OnEnter event handler to cause any special processing to occur when a control becomes active.

The OnEnter event does not occur when switching between forms or between another application and the application that includes the control.

When switching between controls in separate container controls such as the TPanel and the TGroupBox controls, an OnEnter event occurs for the container before the OnEnter event of the contained control.

Similarly, an OnExit event of the container occurs after the OnExit event of the control in a container when focus moves to another control outside the container.

For example, consider a form with an OK button and a group box that contains three radio buttons, where focus is currently on the OK button. When the user clicks one of the radio buttons, an OnExit event of the button occurs, followed by an OnEnter event on the group box, and finally an OnEnter event on the radio button that was clicked. If the user then clicks on the OK button, an OnExit event for the radio button occurs followed by an OnExit event for the group box, and then the button's OnEnter event occurs.

C++ Examples:

Copy Code

/*
This example takes an edit control, a button, and a rich
edit control on a form.  When the user presses the button, a
Font dialog appears.  When the user clicks the Apply (not OK)
button in the Font dialog, the currently selected font is
applied to the active control. Clicking the button sets the
ActiveControl to the button.  That is why we need to save
the ActiveControl in a shared OnEnter procedure.  In the rich
edit, only the text selected converts.
*/
TWinControl *myActiveControl;

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  FontDialog1->Options << fdApplyButton;
  FontDialog1->Execute();
}

void __fastcall TForm1::FontDialog1Apply(TObject *Sender, HWND Wnd)
{
  if (myActiveControl->ClassNameIs("TEdit"))
   (dynamic_cast<TEdit *>(myActiveControl))->Font->Assign(FontDialog1->Font);
  else if (myActiveControl->ClassNameIs("TRichEdit"))
    (dynamic_cast<TRichEdit *>(myActiveControl))->SelAttributes->Assign(FontDialog1->Font);
  else
    MessageBeep(0);
}

void __fastcall TForm1::Edit1Enter(TObject *Sender)
{
  myActiveControl = ActiveControl;
}

Copy Code

/*
This example uses an edit box and a memo control on a form.
When either the edit box or the memo is the active control,
it is colored yellow. When the active control becomes 
inactive, the color of the control returns to the Windows
system color for a window.  These event handlers could also
be shared.
*/
void __fastcall TForm1::Edit1Enter(TObject *Sender)
{
  Edit1->Color = clYellow;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Edit1Exit(TObject *Sender)
{
  Edit1->Color = clWindow;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Memo1Enter(TObject *Sender)
{
  Memo1->Color = clYellow;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Memo1Exit(TObject *Sender)
{
  Memo1->Color = clWindow;
}

Delphi Examples:

Copy Code

{
This example takes an edit control, a button, and a rich
edit control on a form.  When the user presses the button, a
Font dialog appears.  When the user clicks the Apply (not OK)
button in the Font dialog, the currently selected font is
applied to the active control. Clicking the button sets the
ActiveControl to the button.  That is why we need to save
the ActiveControl in a shared OnEnter procedure.  In the rich
edit, only the text selected converts.
} 
procedure TForm1.Button1Click(Sender: TObject);
begin
   FontDialog1.Options := FontDialog1.Options + [fdApplyButton];
   FontDialog1.Execute;
end;

procedure TForm1.Edit1Enter(Sender: TObject);
begin
  myActiveControl := ActiveControl;
end;

procedure TForm1.FontDialog1Apply(Sender: TObject; Wnd: HWND);
begin
  if myActiveControl is TEdit then
    with myActiveControl as TEdit do
       Font.Assign(TFontDialog(Sender).Font)
  else if myActiveControl is TRichEdit then
    with myActiveControl as TRichEdit do
      SelAttributes.Assign(TFontDialog(Sender).Font)
  else
    Beep;
end;

Copy Code

{
This example uses an edit box and a memo control on a form.
When either the edit box or the memo is the active control,
it is colored yellow. When the active control becomes 
inactive, the color of the control returns to the Windows
system color for a window.  These event handlers could also
be shared.
} 
procedure TForm1.Edit1Enter(Sender: TObject);
begin
  Edit1.Color := clYellow;
end;

procedure TForm1.Edit1Exit(Sender: TObject);
begin
  Edit1.Color := clWindow;
end;

procedure TForm1.Memo1Enter(Sender: TObject);
begin
  Memo1.Color := clYellow;
end;

procedure TForm1.Memo1Exit(Sender: TObject);
begin
  Memo1.Color := clWindow;
end;