appWnd. I suppose I could only send a message when canWnd enqueues a
message in an empty queue. This would require syncroization between canWnd
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
See below...
On Wed, 30 Jul 2008 12:48:22 -0700, "Nick Schultz" <nick.schultz@flir.com>
wrote:
OK, I see what you are saying. I know I'm not exactly using your wrapper
the way it was intended:
I have a canThread and appThread that extends CWinThread and canWnd and
appWnd that extends CWnd.
a canThread is created imediately at start up, which then creates a
canWnd
which is responsible to responding to CANLIB's incoming packet
notifications.
When a client connects to the backend, it then creates an appThread which
then creates a appWnd. AppWnd receives messages from canWnd, applies
filters to the packets, and then sends them off to the client via
WM_COPYDATA.
I use your MsgWrapper just for packet communication. in canWnd I use
MsgWrapper::Post to send packets to appWnd. in canThread::onIdle() I then
MsgWrapper::Forward() those messages.
****
You would not use PostMessage from a thread after dequeuing in the
thread's OnIdle; it
makes no sense to put this in canThread::OnIdle because that only tells
you that the
secondary thread has nothing to do, and that would be an error. The whole
point of this
is that it appears in the main GUI thread and prevents it from becoming
saturated. In the
scenario you have created, you completely defeat the purpose of my IOCP
code by simply
doing unlimited posting to the main GUI thread, which is the whole point
of the code I
wrote: that does not and cannot work correctly. You MUST put this handler
in the main GUI
thread's OnIdle handler for it to make any sense at all. That's what I
discuss in my
article, and that's how my example code works.
****
By using this method, I noticed that I have been dropping packets, and I
traced it the MsgWrapper::Forward() function where PostMessage was failing
and the message got deleted.
****
When used correctly (which is not what you have done), it is impossible to
get message
queue saturation. Therefore, it is impossible to lose messages.
****
does each thread or window have its own message queue?
****
Each thread has its own message queue. My solution is for the main GUI
thread. This code
must be executed in the thread instance whose saturation you are trying to
prevent, and
therefore it must PostMessage to windows in that same thread. By
cross-posting, you have
essentially added a lot of code to end up with the original problem,
message queue
saturation, because you are keeping the secondary thread queue from
saturating and
cross-thread post to a thread that guarantees that you will then saturate
its queue. The
point here is that you use my queue as if it were the PostMessage
operation to the thread
you want to post to. The dequeue code (OnIdle) MUST execute in the
context of the thread
that you are trying to avoid saturating, not in some other random thread.
joe
****
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:78e1945i2vevabj41942vfp7jtddsf6eus@4ax.com...
See below...
On Wed, 30 Jul 2008 10:45:13 -0700, "Nick Schultz"
<nick.schultz@flir.com>
wrote:
"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:6e8194ppbtindjgboinq4lngvb754tn7ne@4ax.com...
See below...
On Wed, 30 Jul 2008 09:25:16 -0700, "Nick Schultz"
<nick.schultz@flir.com>
wrote:
Well I am using Mr. Newcomer's Completion I/O MsgWrapper to send
messages
between threads, however in large data bursts, the message pump gets
saturated and messages don't post.
****
That's simply not true. The whole point of the IOCP technique is so
that
messages do NOT
get lost!
*****
What happens when PostMessage returns false?
BOOL PostMessage(
HWND hWnd,
UINT Msg,
WPARAM wParam,
LPARAM lParam
);
Return Value
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero.
your code deletes the message regardless of the return value
****
This is based on the premise that there is no message queue saturation,
and since I am
only dequeing 10-20 messages at a time, I cannot possibly get message
queue saturation.
Note that I know the message queue is empty because I'm in the OnIdle
handler.
****
BOOL MsgWrapper::Forward()
{
BOOL result = wnd->PostMessage(msg, wParam, lParam));
delete this;
return result;
}
so if the message queue is filled, messages are dropped.
****
But, since it is obvious that it cannot possibly be filled (remember, we
are in the OnIdle
handler, which means that the message queue is empty!) there is no need
to
check! Since I
do not do PostMessage except via the IOCP queue, there is no possibility
the queue could
be saturated!
joe
****
I see what you are saying about not closing the window until it has
processed all of its messages and will look into that.
Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm
Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm