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What does cancel property of button do?

Posted on 2011-09-07
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Last Modified: 2012-05-12
What does cancel property of button do?
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Question by:Ashok
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10 Comments
 
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Expert Comment

by:mlmcc
ID: 36499853
If it is like the VB property, it allows you to cancel the action if you set it to TRUE

mlmcc
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Geert Gruwez earned 500 total points
ID: 36499902
this property is mostly used with modal forms

for the ok button, the property Default is set to True
for the cancel button, the property Cancel is set to True

This is allows someone using Enter or Esc (resp Ok button, Cancel button) to close the modal form

you get the modal result of a form (which button was pressed)
case Form.ShowModal of
  mrCancel: ShowMessage('Cancel was pressed');
  mrOk: ShowMessage('Ok was pressed');
else
  ShowMessage('Some other values');
end;
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Author Comment

by:Ashok
ID: 36499967
Esc key calls OnClick event handler of the button

Following are choices to pick the correct answer from
a) It automatically displays Cancel as the Button caption
b) It determines if the button's OnClick event handler is called when the Escape key <Esc> is pressed on the keyboard
c) It calls the parent forms' OnClose event
d) It causes popup menu to be displayed when the button is clicked which permits the user to select Cancel

d is incorrect answer.

In this test, it allows to select only one answer.  Are there more than 1 correct answer for above?

Thanks,
Ashok
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Expert Comment

by:HubbleFlubble
ID: 36499978
Please note that to give a ModalResult back from ShowModal on that form, you have to set the ModalResult property of the button to mrCancel.
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Assisted Solution

by:Geert Gruwez
Geert Gruwez earned 500 total points
ID: 36499983
it's b
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Expert Comment

by:Geert Gruwez
ID: 36499992
just check the delphi code for the keystroke:
procedure TCustomButton.CMDialogKey(var Message: TCMDialogKey);
begin
  with Message do
    if  (((CharCode = VK_RETURN) and FActive) or
      ((CharCode = VK_ESCAPE) and FCancel)) and
      (KeyDataToShiftState(Message.KeyData) = []) and CanFocus then
    begin
      Click;
      Result := 1;
    end else
      inherited;
end;

Open in new window

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Author Comment

by:Ashok
ID: 36499997
Geert_Gruwez,

I thought so.

What about a?
When we use Cancel property, does it by default also change Caption to "Cancel"?

This can be only verified if you have Delphi installed on your computer.

Thanks,
Ashok
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LVL 37

Assisted Solution

by:Geert Gruwez
Geert Gruwez earned 500 total points
ID: 36500001
no, this is a misdeception

this happens when you change the kind property to bkCancel of a TBitBtn
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Expert Comment

by:Geert Gruwez
ID: 36500004
verified ?
or from experience :)
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Author Comment

by:Ashok
ID: 36500017
I have not verified as I have Window 7 64 bit and no Delphi installed.

But from experience, as far as I remember.
I might be wrong.

Ashok
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