Re: Why does this TextOut() sometimes hang up?

From:

"Peter Olcott" <NoSpam@SeeScreen.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 10 May 2007 23:29:12 -0500

Message-ID:

<qiS0i.55006$OT4.4268@newsfe19.lga>

That makes sense since it can't tell how CPU intensive a
task is until it runs that task, and no sense stopping and
re-scheduling a task if you don't know how long it will
execute. Scheduling to the CPU with the least current load
might be as good as automated load balancing can get on a
desktop.

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in
message news:njr743pejkrfocl5dqleuka7qmvr968igf@4ax.com...

Neither of them are this smart. They schedule the next
feasilbe thread on the first
available processor.
joe

On Thu, 10 May 2007 11:06:00 -0500, "Peter Olcott"
<NoSpam@SeeScreen.com> wrote:

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in
message news:9qa643hgj4houe8mjp6bid8cq6s4r428je@4ax.com...

Yes, in fact it *does* run the thread on any available
processor; this is the advantage of
muiltithreading.

Note that you get best performance if the number of
running threads is no greater than the
number of available CPUs (take a look at my Thread
Affinity Explorer to see how
performance can actually drop with massive numbers of
threads)
joe

Of course if the processor is spending most of its time
context switching it would not be getting much performance
on the tasks that it is switching. I wonder how
sophisticated the load balancing would be on XP or Vista?
Would these both be smart enough to place a very CPU
intensive process on its own processor?

On Wed, 9 May 2007 23:22:21 -0500, "Peter Olcott"
<NoSpam@SeeScreen.com> wrote:

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in
message
news:jbv443ljs188hnspe0ha1h71cv4gj0mc41@4ax.com...

Any time you put this kind of code in, it is screaming
"this should have been a thread!"
Such gross hacks were required in Win16, but they
should
be avoided in Win32.
joe

It just occurred to me that this sort of advice (about
multi-threading) has recently taken on much more
significance with multi-processor machines becoming the
norm. I would estimate that it would be pretty easy for
the
OS to allocate a thread to a separate processor, once
the
programmer has divided up the processing into separate
threads.

On Wed, 9 May 2007 17:46:18 -0500, "Peter Olcott"
<NoSpam@SeeScreen.com> wrote:

"Mark Salsbery"
<MarkSalsbery@discussions.microsoft.com>
wrote in message
news:03D471C4-281F-403A-A60B-A67459BF1AE9@microsoft.com...

I should have read the code more closely :)

Maybe you need to pump messages in the loop if it's
on
the
same thread as
the window's UI thread.

//An example message pump. Call periodically in
your
loop.
MSG msg;
while ( ::PeekMessage( &msg, NULL, 0, 0,
PM_NOREMOVE ) )
{
  if ( !AfxGetApp()->PumpMessage( ) )
  {
     break;
  }
}

I stuck the above code in a function called
PumpMessages()
and it solved my problem, thanks!

"Peter Olcott" wrote:

"Mark Salsbery"
<MarkSalsbery@discussions.microsoft.com>
wrote in message
news:E603B544-517C-4595-B222-BD6364F7792A@microsoft.com...

Are you painting over the top of your drawn text?

Besides the TextOut() in the loop you may need to
redraw
the same text in
response to WM_PAINT (OnPaint()) to make sure
it's
redrawn
when the window
is repainted as well as in the loop.

Mark

I am using the basic double buffering method that
paints
a
memory DC to the screen.

"Peter Olcott" wrote:

I tried to make the equivalent of a simple
ProgressBar
by
displaying a count in the window of the
outermost
one
of
several nested loops. This process is very CPU
intensive
so
I have to force screen updates. The count works
correctly
unless I move the window, and then the window is
no
longer
updated. What is causing this, and how can I fix
it?

// The TextOut() display code inside a very
tight
loop
    ClientArea.TextOut(0, 0, String,
strlen(String));
    MainWin->InvalidateRect(NULL);
    MainWin->UpdateWindow();

// Window member data
  CDC ClientArea; // virtual window device
context
  CBitmap m_bmp; // virtual window bitmap

// Window Constructor
MainWindow::MainWindow()
{
  ScreenWidth = GetSystemMetrics(SM_CXSCREEN);
  ScreenHeight = GetSystemMetrics(SM_CYSCREEN);
  Create(NULL, "SeeScreen the Screen
Recognizer",
WS_OVERLAPPEDWINDOW | WS_HSCROLL | WS_VSCROLL,
rectDefault,
NULL, "TextMenu");
  CClientDC DC(this);

  // Create bitmap for virtual window
  ClientArea.CreateCompatibleDC(&DC);
  m_bmp.CreateCompatibleBitmap(&DC, ScreenWidth,
ScreenHeight);
  ClientArea.SelectObject(&m_bmp);

  // use standard background
  MainBrush.CreateStockObject(WHITE_BRUSH);
  ClientArea.SelectObject(&MainBrush);

  // paint background of virtual window
  ClientArea.PatBlt(0, 0, ScreenWidth,
ScreenHeight,
PATCOPY);
}

// Update screen using contents of virtual
window.
afx_msg void MainWindow::OnPaint()
{
  CPaintDC DC(this);
  DC.BitBlt(0, 0, ScreenWidth, ScreenHeight,
&ClientArea,
0,
0, SRCCOPY);
}

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm