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Q89445: INFO: Causes for Failure of DC-Creation Functions

Article: Q89445
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): kb16bitonly kbSDKWin16
Last Modified: 16-JUN-1999

3.00 3.10
WINDOWS
kbprg

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

- Microsoft Windows Software Development Kit (SDK) 3.1 
-------------------------------------------------------------------------------

SUMMARY
=======

The DC-creation functions [CreateDC(), CreateIC(), and CreateCompatibleDC()] can
fail for several reasons. When one of these functions fails, it returns NULL.
This article discusses eight causes for DC-creation failure and provides a
resolution or explanation for each.

NOTE: Since the device driver would have already been loaded when
CreateCompatibleDC() is used, causes 1, 3, 5, 6, and 7 do not apply to it.

Causes for Failure
------------------

- Application runs out of file handles.

- Insufficient system resources.

- Insufficient global memory.

- Global atom tables are full.

- Not enough selectors are free.

- The DEVMODE structure passed in is not the right size.

- The logical device (device driver) or the physical device is not found.

- The function cannot initialize the created DC.

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

The order in which the causes are listed below does not provide any indication
of how often each cause occurs.

Cause 1: Application Runs Out of File Handles
---------------------------------------------

Resolution 1: Use the SetHandleCount() function to open more file handles. For
more information on the file limit, query in the Microsoft Knowledge Base on the
following words:

  limits and open and files


Explanation 1: The GDI requires a file handle to load the device driver and other
files from disk.

Cause 2: Insufficient System Resources
--------------------------------------

Resolution 2: Verify that system resources are not lost because an application
does not delete objects that it creates. If you are developing for Windows 3.1,
use the debugging version of Windows 3.1. For other information on tracking down
lost system resources, query in the Microsoft Knowledge Base on the following
words:

  lost and heapwalk and system and resources


The article "Careful Windows Resource Allocation and Cleanup Improves Application
Hygiene," in the September 1991 issue of the "Microsoft Systems Journal"
discusses this issue further.

Explanation 2: These functions use the GDI's heap. Unless each application frees
all the resources that it allocates, eventually Windows does not have enough
memory to support the creation of DCs.

Cause 3: Insufficient Global Memory
-----------------------------------

Resolution 3: Close some applications and try again.

Explanation 3: The driver must be loaded into global memory.

Cause 4: Global Atom Tables Are Full
------------------------------------

Resolution 4: Minimize the creation of global atoms. Try closing some
applications.

Explanation 4: The GDI uses global atoms during the DC-creation process.

Cause 5: Not Enough Selectors Are Free
--------------------------------------

Resolution 5: Minimize the use of GlobalAlloc(). Each GlobalAlloc()call uses one
of the limited selectors available to Windows (4096 in protected mode and 8192
in 386 enhanced mode). For more information, query in the Microsoft Knowledge
Base on the following words:

  handle and limits and protected and enhanced mode


Cause 6: The DEVMODE Structure Passed In Is Not the Right Size
--------------------------------------------------------------

Resolution 6: The size of the DEVMODE structure varies from printer to printer.
You can find the size of the DEVMODE structure for a particular printer by
calling ExtDeviceMode() with wMode equal to zero.

Cause 7: The Logical Device (Device

Driver) or the Physical Device Is Not Found
-------------------------------------------

Resolution 7: Check to see if you have the device driver and that the physical
device is connected and ready for use. You can check this by attempting to print
to that printer from other applications.

Cause 8: The Function Cannot Initialize the Created DC
------------------------------------------------------

Resolution 8: Restart Windows and try again.

Explanation 8: The objects used to initialize a DC are predefined. This problem
is likely to occur only when one of the applications in the system has corrupted
Windows' internal data.

REFERENCES
==========



Additional query words: 3.00 3.10 fails

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Keywords          : kb16bitonly kbSDKWin16 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbinfo

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

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