PRB: Screen Saver Applications Cannot Be Debugged Properly
ID: Q123871
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The information in this article applies to:
-
Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 4.0, 5.0, 6.0
on the following platforms: x86
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Windows 2000, version 1.0
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:
- Try debugging your application without using the Always-on-Top feature.
Add the feature when the application is ready to be released.
- 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:
- Build the program with debug information.
- Set a breakpoint on line 73 of FRACTAL.C.
- 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.
- 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.
Additional query words:
9.00 Always Top HWND_TOP hung frozen not responding
Keywords : kbDebug kbide kbWinOS2000 kbVC kbVC200 kbVC210 kbVC400 kbVC500 kbVC600 kbx86
Version : winnt:2.0,2.1,4.0,5.0,6.0; :1.0
Platform : winnt
Issue type : kbprb