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298 Day 8
NOTE
NOTE
NOTE
The Default Property
The Default property is another key property of buttons. Windows has a standard
mechanism for dealing with dialog boxes. One of the features of this mechanism is as follows:
If a control other than a button has keyboard focus and the user presses the Enter key on the
keyboard, the dialog box will behave as if the user had clicked the default button. The default
button is the button that has the BS_DEFPUSHBUTTON style set (usually the OK button). This
feature has been the bane of programmers and the curse of data-entry personnel for years. The
Default property is used to set a button as the default button for a form. The default value
for this property is false. To make a button the default button, set its Default property to
true. If you don’t specifically set any button’s Default property to true, the form will not
close when the user presses the Enter key.
When the user closes the form by pressing the Enter key, the OnClick
handler of the default button (if one exists) will be called before the
form closes.
The Cancel Property
The Cancel property works with the Esc key in much the same way as the Default property
works with the Enter key. When the user presses the Esc key to close a form, the return value
from ShowModal() will be the ModalResult value of the button whose Cancel property is set
to true. If no button has its Cancel property set to true, mrCancel will be returned if the user
uses the Esc key to close the form (mrCancel is equal to 2; see Table 8.7).
Closing a form by clicking the system close box or by pressing Alt+F4
will result in mrCancel being returned from ShowModal() as you would
expect. Pressing the Esc key, however, will result in a return value of
the ModalResult property being set to whatever button has the Cancel
property set to true. The OnClick handler for the Cancel button will be
called before the form closes. No OnClick handler is called if the user
uses the system close box or Alt+F4 to close the form. Be sure to
anticipate the different ways users might use (or abuse) your forms.
You may have more than one button with a Default property set to
true. Likewise, you may have more than one button with the Cancel