[Lazarus] animated splash screen for lengthy operation, works with windows, doesn't with linux
Michael Van Canneyt
michael at freepascal.org
Mon Mar 27 16:50:45 CEST 2023
On Mon, 27 Mar 2023, Luca Olivetti via lazarus wrote:
> El 27/3/23 a les 16:13, Michael Van Canneyt via lazarus ha escrit:
>>
>>
>> On Mon, 27 Mar 2023, Luca Olivetti via lazarus wrote:
>>
>>> El 27/3/23 a les 11:59, Luca Olivetti via lazarus ha escrit:
>>>
>>>> [*] instead of opening the query I spawn a thread that opens it, wait
>>>> for it to finish while executing Application.ProcessMessages and
>>>> eventually reraise the exception that was generated inside the thread.
>>>
>>>
>>> Speaking of which, I encapsulated it in a procedure (TWaitForm is the
>>> spash screen, Aproc is a procedure of object, TExecInThread simply
>>> calls AProc in its execute method):
>>>
>>> procedure ExecWithSplash(AProc:TThreadProc);
>>> var wf:TWaitForm;
>>> ut:TExecInThread;
>>> begin
>>> Wf:=TWaitForm.Create(Application);
>>> WF.Show;
>>> ut:=TExecInThread.create(AProc);
>>> while not ut.Finished
>>> Application.ProcessMessages
>>> wf.free;
>>> if ut.FatalException<>nil then
>>> raise(ut.FatalException);
>>> ut.free;
>>
>> Ehm. In case of an exception, ut will never be freed ?
>
> That's what I said.
> I was looking for a way to free it *and* raise the exception in the
> context of the main thread.
> If I move the ut.free before the raise, the exception has already been
> freed and it's invalid, causing a sigsev, if I enclose it in a
> try..finally the exception handler will be called after the finally has
> freed the thread (and the exception, so it's the same problem).
Normally, I'd do
Raise Exception(ut.fatalexception.classtype).Create(ut.fatalexception.message);
Michael.
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