Advanced Windows Form message priority / threading.

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: Brian Keating EI9FXB (csharp)
Date: 11/29/04 

Date: Mon, 29 Nov 2004 08:43:08 -0800

Hello again,
I've already placed a few posts on this topic.
This time i've a simple application that exhibits my problem,
I've placed sample solution 8k on my website should anyone be interested in
having a look. http://briankeating.net/transfer/test.zip

To recap the problem I expected (and found).
I've a main GUI thead (main form), this GUI thread has an UpdateTextBox
function that appends a string in a textbox and It also has a button that
stops my worker thread(s) form calling Invoke on main thead.

private void UpdateTextBox(string strText)
{
System.Diagnostics.Debug.Assert(InvokeRequired != true, "Invoke was
                                   required", "calling begin invoke not on
the gui thread");
richTextBox1.Focus();
richTextBox1.AppendText(strText);
}

When my form loads I start two worker threads and these threads just loop
around and call Invoke on my main Form with a string to display.

private void ThreadEntryPoint()
{
while (!bStop)
{
string str = "Thread Id: " + GetHashCode() + ",\t" + nCount.ToString() + "
This is a passing string\r\n";

Invoke(new UpdateTextboxDelegate(UpdateTextBox), new object[] {str});
Interlocked.Increment(ref nCount);
//Thread.Sleep(1000); //slow sending
Thread.Sleep(10); //fast sending
} //end while
                        
MessageBox.Show(Thread.CurrentThread.ToString() + " thread closing");
}

Now if my worker threads are slow sending i.e. I call Thread.Sleep(1000);
i.e. wait a seond between each invoke call on the gui thread, then I have no
problem I can click my button and the event handler is called

private void button1_Click(object sender, System.EventArgs e)
{
    bStop = true;
}

However if my two threads are sending fast (only waiting 10 miliseconds)
then my GUI thread is so busy processing these update events that if i click
the stop button nothing happens.

... Hope that kinda clears things up about a GUI thread becoming unresponsive.

So what are my options?
I'm thinking that Inovke is basically like SendMessage so maybe somehow i
can replace the windows message loop to do the following, (basically
prioritised message queue)
loop
   peek all windows messages and process them, (get/dispatch)
   then peek for one of my Inoke calls (get/dispatch)
endloop

Now people that have helped me already may be asking what has as this to do
with windows running in different threads, well the reason I want to do this
is, say for example i have 2 windows in my application, one window is busy
receiving messages from a worker thread (so this is gonna become
unresponsive), i wouldn't like all other windows to become unresponsive too),
switching between windows will require my busy thread to handle some window
messages (loose focus maybe etc) so a prioritised message queue will allow
this, hey maybe this is enough I'll keep at it and see what happens.

But I gues this post comes down to one question,
Is there anyway I can plug into a windows forms message queue and check for
pending invoke calls as described above?

Thanks for any help
Brian.

p.s.
This is only a sample test app, so it's not perfect for many a reason,
I realise the two worker threads calling Invoke is pretty much the same as
One worker thread calling invoke.
clicking close on the forms gets executed straight away for some reason
(maybe it's handled differently?)
Clicking close will throw an exception cause i havn't stopped the worker
thread(s) from sending.

Relevant Pages

  • RE: Advanced Windows Form message priority / threading.
    ... If i want my Invoke calls in my message queue I prob have to use events? ... > I've a main GUI thead, this GUI thread has an UpdateTextBox ... > can replace the windows message loop to do the following, ... > I realise the two worker threads calling Invoke is pretty much the same as ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: .InvokeRequired always resulting in true
    ... the main GUI thread (called from the worker threads) but somehow... ... I presume they are in different windows? ... I presume you know that you need to do all this work on your GUI thread, ... ISynchronizeInvoke (every control does) and pass a delegate to its ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: Advanced Windows Form message priority / threading.
    ... updates if necessary. ... sending hundreds of Invoke or BeginInvoke messages ... > When my form loads I start two worker threads and these threads just loop> around and call Invoke on my main Form with a string to display. ... > I'm thinking that Inovke is basically like SendMessage so maybe somehow i> can replace the windows message loop to do the following, ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: CoBOL moved to OO
    ... of a list of file names' by using the Windows GUI and the keyboard alone ... > Alternatively write the collection elements to your text file with a Callback (see ... > invoke FileNames2 "new" returning os-Filenames ...
    (comp.lang.cobol)
  • Re: OnIdle() alternatives
    ... My impression is that the dragging appears to enter a subloop where the filters (the ... be prevented from being processed by mouse/menu/modal windows events? ... And is it possible to pass a message from a sub worker thread which has ... It may be that you are trying to signal to the GUI thread using CEvents. ...
    (microsoft.public.vc.mfc)