DOCUMENT:Q123871  13-JUN-2002  [visualc]
TITLE   :PRB: Screen Saver Applications Cannot Be Debugged Properly
PRODUCT :Microsoft C Compiler
PROD/VER::2.0,2.1,2000,4.0,5.0,6.0
OPER/SYS:
KEYWORDS:kbDebug kbide kbOSWin2000 kbVC kbVC200 kbVC210 kbVC400 kbVC500 kbVC600 kbHWx86

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 4.0, 5.0, 6.0, used with:
    - the hardware: Intel x86 
 - Microsoft Windows 2000 Professional 
 - Microsoft Windows 2000 Server 
 - Microsoft Windows 2000 Advanced Server 
 - Microsoft Visual C++.NET (2002) 
-------------------------------------------------------------------------------

SYMPTOMS
========

You may run into problems when debugging screen saver type applications in the
Visual C++ development environment. For example, when attempting to debug the
SCRNSAVE application included with Visual C++ version 2.0, the program starts
correctly, but then may fail to return control and the focus to the debugger.

CAUSE
=====

This is expected behavior. Screen savers don't use the same desktop as normal
applications. When a breakpoint in the screen saver is encountered, the
operating system doesn't switch desktops. Thus, there may be no screen in which
to display the Visual C++ user interface and the breakpoint is essentially
ignored.

RESOLUTION
==========

There are two possible workarounds to this problem:

1. Try debugging your application without using the Always-on-Top feature. Add
   the feature when the application is ready to be released.

2. Use remote debugging. For more information on remote debugging, see the
   "Debugging Remote Applications" section in the "Using The Debugger" chapter
   of the "Visual C++ User's Guide," or search for "remote debugging," in the
   Visual C++ Books Online.

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

Steps to Reproduce Behavior
---------------------------

Using the Visual C++ version 2.0 SCRNSAVE sample in the
\MSVC20\SAMPLES\WIN32\SCRNSAVE directory on the distribution CD, do the
following:

1. Build the program with debug information.

2. Set a breakpoint on line 73 of FRACTAL.C.

3. Set /S as an option for FRACTAL.EXE. To do this, select Settings from the
   Project menu. Then select the Debug sheet from the Settings dialog. Type "/S"
   (without the quotation marks) on the Program Arguments line.

4. Run the program by pressing the F5 key. The screen should turn black and
   appear to hang. Bring up the Task List by pressing CTRL+ESC. Then quit Visual
   C++ to regain control of the system.

NOTE: The SCRNSAVE sample included with Visual C++ version 4.0 is entirely
different from that of Visual C++ version 2.0; it demonstrates Control Panel
utility library routines for managing "cpArrow" window class/spinner controls
used in applet dialog boxes.

NOTE: No screen saver sample is provided in Visual C++ .NET.

Additional query words: 9.00 Always Top HWND_TOP hung frozen not responding

======================================================================
Keywords          : kbDebug kbide kbOSWin2000 kbVC kbVC200 kbVC210 kbVC400 kbVC500 kbVC600 kbHWx86 
Technology        : kbVCsearch kbAudDeveloper kbVC32bitSearch
Version           : :2.0,2.1,2000,4.0,5.0,6.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2002.