[RESOLVED] How to UseWaitCursor correctly

[Eri523]

How progress information is sent to the main thread?

Like that:

System::Void Form1::DoCountWorker(FileStream ^fsInfile,BackgroundWorker ^bw,DoWorkEventArgs ^e)
{
  BinaryReader brInfile(fsInfile);
  const int nBufferSize=512;
  array<Byte> ^abBuffer;
  int nPercent=0,nLastPercent=-1;

  do {
    abBuffer=brInfile.ReadBytes(nBufferSize);
    for (int i=0;i<abBuffer->Length;++i)
      ++aulCounts[abBuffer[i]];
    if ((nPercent=(100*fsInfile->Position)/fsInfile->Length)!=nLastPercent) {
      bw->ReportProgress(nPercent);
      nLastPercent=nPercent;
    }
  } while (!bw->CancellationPending && abBuffer->Length==nBufferSize);
  brInfile.Close();
  if (bw->CancellationPending) e->Cancel=true;
}

System::Void Form1::bwDoCount_ProgressChanged(System::Object^  sender, System::ComponentModel::ProgressChangedEventArgs^  e)
{
  progress->Text=String::Format("Processing file... {0}&#37;",e->ProgressPercentage);
  progress->progressBar1->Value=e->ProgressPercentage;
}

Where progress is the progress dialog form object.

By debugging I found out that the bwDoCount_ProgressChanged() event handler runs in the context of the GUI thread, so IMO inter-thread communication is done internally by BackgroundWorker.

But the progress display doesn't cause the deadlock anyway, the problem was only exposed when I clicked the Cancel button. Cancellation is handled by this simple event handler in the progress dialog's form class:

System::Void Progress::bnCancel_Click(System::Object^  sender, System::EventArgs^  e)
{
  bwParentWorker->CancelAsync();
}

Where bwParentWorker is a tracking handle to the BackgroundWorker object that gets passed (i.e. assigned) from the main form object to the progress dialog's form object.

Closing the progress dialog in case I did not click the cancel button is donne by the completion handler (and works):

System::Void Form1::bwDoCount_RunWorkerCompleted(System::Object^  sender, System::ComponentModel::RunWorkerCompletedEventArgs^  e)
{
  if (e->Error) MessageBox::Show(this,e->Error->Message,"Error during file processing",MessageBoxButtons::OK,MessageBoxIcon::Error);
  bCountCancelled=e->Cancelled;
  if (progress->Visible) progress->Close();  // Progress dialog is still open: close it
  Cursor->Current=csrSaved;  // This has just been added in response to Arjay's latest post
  ewhWorkerReallyFinished->Set();
}

But, as described above, this handler doesn't even get called when I click Cancel.