Q36324: HOWTO: Perform Background Processing Without Using Timers

Article: Q36324
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.0,3.1
Operating System(s): 
Keyword(s): kbSDKPlatform kbGrpDSUser kbWndw kbWndwMsg kbFAQ kbwin16sdkfaq kb16bitonly
Last Modified: 18-JUL-2001

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
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SUMMARY
=======

A Windows-based application that performs a long, background task, such as
repaginating a word processing document, can be designed in a number of
different ways.

A polling task can be accomplished by setting a timer to fire at the desired
interval. Many non-polling tasks can be performed in pieces. Although Windows
does not have a method to schedule processing based on overall system load, an
application can wait until there are no other messages to be processed by that
application before proceeding. This article discusses the code required to
implement this method.

NOTE: This polling method is unnecessary for native Win32 applications.

MORE INFORMATION
================

It is important that each piece of the task be relatively small. This allows
Windows to devote processing time to other applications running in the system.
Similarly, once the task is complete, it is important that the application
signal that it is idle. This allows Windows to optimize its performance and to
prolong battery life on portable computers.

The following code skeleton demonstrates how this might be implemented:

     WinMain
     {
     do application initialization

     fBackgroundToDo = TRUE;
     fRunning = TRUE;

     while (fBackgroundToDo && fRunning)
          {
          if (fBackgroundToDo)
               {
               if ((PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
                    {
                    if (msg.message == WM_QUIT)
                         {
                         fRunning = FALSE;
                         break;
                         }

                    TranslateMessage(&msg);
                    DispatchMessage(&msg);
                    }
               else
                    fBackgroundToDo = DoABitOfBackground();
               }
          else if ((fRunning = GetMessage(&msg, NULL, NULL, NULL)) != 0)
               {
               TranslateMessage(&msg);
               DispatchMessage(&msg);

               fBackgroundToDo = IsThereBackgroundToDo();
               }
          }
     }

For additional information on this topic, query on the following words in this
Knowledge Base:

  SpawnAndWait


Additional query words:

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Keywords          : kbSDKPlatform kbGrpDSUser kbWndw kbWndwMsg kbFAQ kbwin16sdkfaq kb16bitonly 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : WINDOWS:3.0,3.1
Issue type        : kbhowto

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