TEdit and TMemo strange behaviour (bug ?)
lazarus / 8-Other

----------------------------------------------------------------------
Bart · 2006-05-05 10:08

Hi,

When you plave a TMemo or a TEdit on a form at designtime,  clear the
text, and then just run the program, one would not expect that the
TEdit or the TMemo gets modified, would you?

Take the following example:

On a new from drop
TEdit
 - Name = 'Edit1'
 - Clear the text
TMemo
 - Name = Memo1
 - Clear the Lines
TMemo
 - Name = Debugger
 - Clear the Lines

Now Set the OnChange event of Edit1 and Memo1 to TForm1.Memo1Changed

Add this codeCode: [Select]procedure TForm1.FormCreate(Sender:
TObject);
begin
  debugger.lines.add('FormCreate');
  if edit1.Modified then debugger.Lines.Add('  --> Edit1 is Modified')
else debugger.Lines.Add('  --> Edit1 is NOT Modified');
  if memo1.Modified then debugger.Lines.Add('  --> Memo1 is Modified')
else debugger.Lines.Add('  --> Memo1 is NOT Modified');
end;

procedure TForm1.FormShow(Sender: TObject);
begin
  debugger.lines.add('FormShow');
  if edit1.Modified then debugger.Lines.Add('  --> Edit1 is Modified')
else debugger.Lines.Add('  --> Edit1 is NOT Modified');
  if memo1.Modified then debugger.Lines.Add('  --> Memo1 is Modified')
else debugger.Lines.Add('  --> Memo1 is NOT Modified');
end;

procedure TForm1.Memo1Change(Sender: TObject);
begin
  debugger.lines.add(Format('-- Memo1Change is fired: Sender =
%s',[(Sender as TComponent).Name]))
end;

Run the program and watch the output in the Debugger memo:

On Lazarus 0.9.12/win32 it outputs:
Code: [Select]FormCreate
  --> Edit1 is NOT Modified
  --> Memo1 is NOT Modified
-- Memo1Change is fired: Sender = Edit1
FormShow
  --> Edit1 is Modified
  --> Memo1 is NOT Modified

On Lazarus 0.9.13/Linux (Suse 10.0) it outputs
Code: [Select]FormCreate
  --> Edit1 is NOT Modified
  --> Memo1 is NOT Modified
-- Memo1Change is fired: Sender = Memo1
-- Memo1Change is fired: Sender = Memo1
FormShow
  --> Edit1 is NOT Modified
  --> Memo1 is Modified

The same code in Delphi (3 Pro) outputs
Code: [Select]FormCreate
  --> Edit1 is NOT Modified
  --> Memo1 is NOT Modified
FormShow
  --> Edit1 is NOT Modified
  --> Memo1 is NOT Modified

So, somewhere between the OnCreate and OnShow of the form in win32 the
Edit's OnChange is called and in Linux the Memo's OnChange is called
even twice.

I would expect the behaviour I see in Delphi.
And even if this is by design, I would expect it to be the same in
Windows and Linux.

When you run an editor application of some sort and it even claims
that your empty editor at startup is modified, that does not sound OK
to me.

Can anyone reproduce this behaviour in more recent versions.
Does it behave different under win32 than under Linux, MacOS ...

If anyone can confirm this, I think I should file a bugreport.

Bart