ESC in MessageDlg
lazarus / 31-LCL

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Walmir · 2014-08-26 17:31

I have the following code in a BeforeDelete event of a TField:
Code: [Select]procedure TdmData.qryServBeforeDelete(DataSet:
TDataSet);
begin
  if Application.MessageBox('Do qyou want to delete this
service?','Confirme',
  MB_YESNO + MB_ICONQUESTION + MB_DEFBUTTON2) = IDNO then
    Abort;
end;
When the user hits the ESC key, the record is deleted...
Is there  a logic error in my code?
It was ported from Delphi without modifications.

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howardpc · 2014-08-26 18:18

Quote from: Walmir on August 26, 2014, 07:31:19 pmIs there  a logic
error in my code?

Yes, you miss the case that the returned value is IDCANCEL (pressing
Esc).
So change it to
Code: [Select]if Application.MessageBox(...) in [IDNO, IDCANCEL] then
  Abort;

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Bart · 2014-08-26 18:22

The native MessageDlg function on Vista+ return IDCANCEL when you
close the dialog using the escape key. And IDCANCEL <>IDNO, so the
record will be deleted.

Your Delphi might not use the native Vista+ dialogs (it depends on
Delphi version), and so it may return IDNO on Escape key (this is how
non-native (as in: we (LCL) draw the dialog ourselfs, using standard
form en buttons) MessageDlg works).

You shoud test for IDYES and then and only then delete the record (as
you should have doe in the first place IMHO).

Bart

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taazz · 2014-08-26 18:23

Quote from: howardpc on August 26, 2014, 08:18:21 pmQuote from: Walmir
on August 26, 2014, 07:31:19 pmIs there  a logic error in my code?

Yes, you miss the case that the returned value is IDCANCEL (pressing
Esc).
So change it to
Code: [Select]if Application.MessageBox(...) in [IDNO, IDCANCEL] then
  Abort;
or simple
Code: [Select]if Application.MessageBox(...) <> IDYES then
  Abort;