[Lazarus] TSynEdit bug in destructor?

[Mattias Gaertner]

Bart <bartjunk64 at gmail.com> hat am 8. November 2011 um 17:49 geschrieben:

>[...]
> function TEditorPageControl.ClosePage(Index: Integer): Boolean;
> var
>   Cancel: Boolean;
>   Pg: TTabSheet;
>   Ed: TEditor;
> begin
>   Result := False;
>   if (Index > PageCount - 1) then Exit;
>   Pg := Pages[Index];  //<-- Pg owns the SynEdit
>   Cancel := False;
>   if Assigned(FOnBeforeCloseEditor) then FOnBeforeCloseEditor(Pg, Cancel);
>   if Not Cancel then
>   begin
>
>     //newly added code
>     Ed := EditorAtPage(Pg);  //<- returns the SynEdit in question
>     Application.ReleaseComponent(Ed);
>     Application.ProcessMessages; 
ProcessMessages only processes the next messages in the event queue.
You are still processing the current message. Processing means calling a
function and waiting for it to return. 
 
 

>     //end newly added code
>
>     Pg.PageControl := nil;
>     Pg.Free;
>     Result := True;
>     if PageCount = 0 then InternalEditorStatusChange(nil, scAll);
>   end;
>   Debugln('TEditorPageControl.ClosePage End.');
> end;
>
> This did not work, so I changed it into
>
> function TEditorPageControl.ClosePage(Index: Integer): Boolean;
> var
>   Cancel: Boolean;
>   Pg: TTabSheet;
>   Ed: TEditor;
> begin
>   Result := False;
>   if (Index > PageCount - 1) then Exit;
>   Pg := Pages[Index];  //<-- Pg owns the SynEdit
>   Cancel := False;
>   if Assigned(FOnBeforeCloseEditor) then FOnBeforeCloseEditor(Pg, Cancel);
>   if Not Cancel then
>   begin
>
>     Ed := EditorAtPage(Pg);  //<- returns the SynEdit in question
>     Application.ReleaseComponent(Ed);
>     Application.ProcessMessages;
>
>     Pg.PageControl := nil;
>     Application.ReleaseComponent(Pg);
>     Application.ProcessMessages;
>
>     Result := True;
>     if PageCount = 0 then InternalEditorStatusChange(nil, scAll);
>   end;
> end;
>
> I had to use Application.ReleaseComponent on both the SynEdit and the
> TabSheet in order to get it to work.
>
> Does this look OK?
>
>
> >> Feauture or bug?
> > By design. You should not free something that is in use.
>
> That depends on the meaning of "in use" ;-)
> I did not know it (the SynEdit) was actually doing something at all. 
See the call stack in View / Debug Windows / Call Stack. 
 
 

> This code worked perfectly in Delphi 3. 
The winapi works differently than other widgetsets. Other widgetsets work more
object oriented. The LCL was designed to work with various widgetsets. 
 
 

> It also works fine if the SynEdit is replaced by a Memo. 
 
Mattias
 
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