HELP! How to do an immediate refresh.
Marc -- msd@cadcentre.co.uk
Friday, August 16, 1996
Environment: VC++ 4.0, Windows NT 3.51, SP 4
Hi,
I want to do an immediate refresh of the whole thread/application, such that
requests to create windows, change text, etc. are displayed on the screen
before I drop back into the MFC message loop(/pumper!).
I've tried RedrawWindow(NULL, NULL, RDW_INVALIDATE |
RDW_UPDATENOW |
RDW_ALLCHILDREN)
on each of my CFrameWnd derived objects, but this sends a WM_PAINT message
to all windows whether they need refreshing or not, which is slow and causes
the whole application to flicker. This technique also didn't allow me
to curtail paint messages for my graphics areas, as they were sent to my
OnPaint handler *after* I returned from RedrawWindow, so I couldn't
differentiate them from other, normal paint messages. I thought RDW_UPDATENOW
meant lots of little SendMessages would be sent and processed *before*
RedrawWindow returned, as opposed to the PostMessage alternative.
I also tried explicitly looking for WM_PAINT messages in the event queue
using ::PeekMessage, this would have done the trick, but for some reason
it's a feature of ::PeekMessage to view/retrieve all types of messages except,
you guessed it, WM_PAINT messages.
I hope someone can help me out.
Thanks,
Marc.
--
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Pradeep Tapadiya -- pradeep@nuview.com
Monday, August 19, 1996
[Mini-digest: 6 responses]
At 04:10 PM 8/16/96 +0100, you wrote:
>
>Environment: VC++ 4.0, Windows NT 3.51, SP 4
>
>Hi,
>
>I want to do an immediate refresh of the whole thread/application, such that
>requests to create windows, change text, etc. are displayed on the screen
>before I drop back into the MFC message loop(/pumper!).
>
>I've tried RedrawWindow(NULL, NULL, RDW_INVALIDATE |
> RDW_UPDATENOW |
> RDW_ALLCHILDREN)
>on each of my CFrameWnd derived objects, but this sends a WM_PAINT message
>to all windows whether they need refreshing or not, which is slow and causes
>the whole application to flicker. This technique also didn't allow me
>to curtail paint messages for my graphics areas, as they were sent to my
>OnPaint handler *after* I returned from RedrawWindow, so I couldn't
>differentiate them from other, normal paint messages. I thought RDW_UPDATENOW
>meant lots of little SendMessages would be sent and processed *before*
>RedrawWindow returned, as opposed to the PostMessage alternative.
>
>I also tried explicitly looking for WM_PAINT messages in the event queue
>using ::PeekMessage, this would have done the trick, but for some reason
>it's a feature of ::PeekMessage to view/retrieve all types of messages except,
>you guessed it, WM_PAINT messages.
>
>I hope someone can help me out.
>Thanks,
>Marc.
>
I am obviously missing something. Why can't you call UpdateAllViews for
all the docs that you have? Moreover, you can pass a "hint" parameter
in UpdateAllViews and specify what exactly do you want to be updated.
Pradeep
-----From: "Greg Tighe"
> Environment: VC++ 4.0, Windows NT 3.51, SP 4
>
> I want to do an immediate refresh of the whole thread/application, such that
> requests to create windows, change text, etc. are displayed on the screen
> before I drop back into the MFC message loop(/pumper!).
>
How about looping through all of your application's windows and
invoking the UpdateWindow() method for each? From the online help:
Updates the client area by sending a WM_PAINT message if the update
region is not empty. The UpdateWindow member function sends a WM_PAINT
message directly, bypassing the application queue. If the update
region is empty, WM_PAINT is not sent.
-Greg Tighe
Applied Intelligent Systems, Inc.
Ann Arbor, MI
gdt@aisinc.com
-----From: Marty Fried
Have you tried UpdateWindow()? That should only send a WM_PAINT if
the update region is not empty, ie if the window actually needs
updating.
WM_PAINT messages are generated by the system, and sent as needed.
Otherwise, the messages would clog the queue, and you would be
processing them much too often. I believe WM_TIMER messages also
work this way.
Marty Fried
-----From: bop@gandalf.se
Well, you say INVALIDATE ALLCHILDREN, and it does! All child
windows are repainted, because you said they were invalid.
Try invalidating ONLY the areas that NEED repainting (sounds logical,
doesn't it ?). In many cases you can then use pDC->RectVisible(...)
in the drawing function to determine if a particular part of your window
needs repainting.
> This technique also didn't allow me
> to curtail paint messages for my graphics areas, as they were sent to my
> OnPaint handler *after* I returned from RedrawWindow, so I couldn't
> differentiate them from other, normal paint messages. I thought RDW_UPDATENOW
> meant lots of little SendMessages would be sent and processed *before*
> RedrawWindow returned, as opposed to the PostMessage alternative.
>
> I also tried explicitly looking for WM_PAINT messages in the event queue
> using ::PeekMessage, this would have done the trick, but for some reason
> it's a feature of ::PeekMessage to view/retrieve all types of messages except,
> you guessed it, WM_PAINT messages.
WM_PAINT is special, because it is deliberately suppressed until all
other messages have been processed. If you think about it, it is smart to
NOT start painting until ALL messages potentially affecting the
window have been processed.
BTW, I think WM_PAINT isn't actually stored in the message
queue, but is an internal flag that a windows needs repainting.
This way you get only ONE paint message, and only after
other messages are processed.
Bo Persson
bop@gandalf.se
-----From: Mike Blaszczak
At 04:10 PM 8/16/96 +0100, you wrote:
>Environment: VC++ 4.0, Windows NT 3.51, SP 4
>I want to do an immediate refresh of the whole thread/application, such that
>requests to create windows, change text, etc. are displayed on the screen
>before I drop back into the MFC message loop(/pumper!).
You can't. Windows are refreshed via WM_PAINT messages which are only
sent when your message pump is running. That you want to do this suggests
that you have something very wrong with the design of your application.
>RedrawWindow() ... causes the whole application to flicker.
RedrawWindow() doesn't cause an application to flicker: improperly written
painting code does. When you paint, you should try to repaint as little
as possible. An application flickers when it erases everything and repaints
everything. You should either not erase and paint in-place or absolutely
minimize the area of painting you do.
>This technique also didn't allow me
>to curtail paint messages for my graphics areas, as they were sent to my
>OnPaint handler *after* I returned from RedrawWindow, so I couldn't
>differentiate them from other, normal paint messages.
You might try using ValidateRect(). You might also try LockWindowUpdate().
.B ekiM
http://www.nwlink.com/~mikeblas <--- trip report central
1995 Honda VFR750F (Serial number 00050!) 4 Corners 1996!
1987 Yamaha FZ700 (damaged) AMA, HRC, VFROC
These words are my own: I do not speak for Microsoft.
-----From: "Rommel Songco"
In handling a WM_PAINT message, why don't you check your internal data
structures to see if a window needs repainting. As you said, a WM_PAINT
message can be caused by either a normal invalid area in the window or a
call to RedrawWindow with entire windows invalidated. All your windows
receive the WM_PAINT message because you invalidated the entire client
areas of your windows by making hrgnUpdate and lprcUpdate NULL and using
the flag RDW_INVALIDATE.
Regards,
Rommel
rsongco@spectrasoft.com
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