Possible Causes of Dialog Box Creation Failure

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.1 and 3.0

SUMMARY

The dialog box creation routines (CreateDialog(), CreateDialogParam(), CreateDialogIndirect(), CreateDialogIndirectParam(), DialogBox(), DialogBoxParam(), DialogBoxIndirect(), and DialogBoxIndirectParam()) can fail for several reasons. When one of these functions fails, the dialog box is not displayed on the screen. Of the causes for dialog box creation failure, this article discusses nine, which are listed below, and provides a resolution or explanation:

1. Application runs out of file handles.

2. One or more text strings in a dialog resource starts with the character represented by the value 255 (0xFF).

3. Several small compiled resource (RES) files are combined using the MS-DOS command "COPY /b".

4. A dialog box with an edit control cannot be created when at least ten dialog boxes, each with one or more edit controls, are open simultaneously.

   NOTE: The above statement is not correct for Windows 3.1 because this is a problem relating to real mode and Windows 3.1 does not run in real mode.

5. The dialog resource is not included in the RC file.

6. Insufficient system resources.

7. In a dialog registered with a private dialog class, the dialog procedure does not return the value returned from DefDlgProc as its return value.

8. Wrong HINSTANCE value used.

9. A dialog box with an edit control or a combo box with an edit control must have a HEAPSIZE statement with a value > 0 in the .DEF file.

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 this procedure, query this Knowledge Base on the words:

   resources and SetHandleCount

Explanation 1

Windows requires a file handle to load a resource. Because each dialog box creation routine loads dialog resources, an application must have at least one file handle available for that purpose.

Cause 2

One or more text strings in a dialog resource start with the character represented by the value 255 (0xFF).

Resolution 2

For an explanation of two methods to work around this cause, query this Knowledge base on the words:

   string and resource and 255

Explanation 2

Windows uses the number 255 to indicate that a resource is represented by an ordinal value instead of by a string name. During the process of parsing the resource that contains one of these characters, Windows incorrectly skips the next two bytes and treats the new position in the resource as the next piece of data.

Cause 3

Several small compiled resource (RES) files are combined using the MS-DOS command "COPY /b".

Resolution 3

Use the #include directive to combine the files at the source level. If the Windows Resource Compiler cannot handle the large RC file, consider storing the resources in a resource-only DLL. For more information, query this knowledge base on the words:

   combined and res

Explanation 3

The Resource Compiler shipped with version 3.0 of the Windows Software Development Kit (SDK) has been enhanced to handle resource files much larger than its Windows 2.x counterpart. The format of the compiled resource files in Windows 3.0 does not support concatenation of RES files.

Cause 4

A dialog box with an edit control cannot be created when at least ten dialog boxes, each with one or more edit controls, are open simultaneously.

Resolution 4

Specify the DS_LOCALEDIT style in the dialog box template, or create the edit control explicitly with the CreateWindow() function.

Explanation 4

For more information, query this Knowledge Base on the words:

   dialog and GlobalAlloc and fails

Cause 5

The dialog resource is not included in the RC file.

Resolution 5

Use RCINCLUDE to include the dialog resource in the RC file.

Explanation 5

Include the DLG file created by the Dialog Editor into the RC file so the Resource Compiler can add the dialog resource to the executable file.

Cause 6

Insufficient system resources.

Resolution 6

Verify that system resources are not lost because an application does not delete objects that it creates. For more information, query this Knowledge Base on the words:

   lost and heapwalk

Explanation 6

Unless each application frees all the resources that it allocates, eventually Windows does not have enough memory to create the controls and/or the dialog box itself.

Cause 7

In a dialog registered with a private dialog class, the dialog procedure does not return the value returned from DefDlgProc() as its return value.

Resolution 7

Whenever the private-class dialog procedure passes an unprocessed message to DefDlgProc(), the dialog procedure must propagate the value returned by DefDlgProc().

Explanation 7

When a private-class dialog procedure passes an unprocessed message to DefDlgProc(), it must return the value returned from DefDlgProc(). This behavior differs from that of a default-class dialog procedure, which usually returns FALSE outside the message switch when it does not process a message. If a private-class dialog procedure is implemented in this way, and the procedure does not process the WM_NCCREATE message, it will return FALSE. The CreateWindow() function sends the WM_NCCREATE message to create the non- client area of the dialog window. CreateWindow() treats a response of FALSE from the dialog procedure as failure and returns a NULL handle to the application.

Cause 8

Wrong HINSTANCE value used.

Resolution 8

Specify the application's instance handle.

Explanation 8

The dialog box creation routine must specify the application's instance because the dialog template is stored in the application instance.

Cause 9

A dialog box with an edit control or a combo box with an edit control must have a HEAPSIZE statement with a value > 0 in the .DEF file.

Resolution 9

Set the value of HEAPSIZE to > 0 in your .DEF file.

Explanation 9

Windows allocates memory for edit controls out of your local heap. If you do not have a HEAPSIZE statement, it cannot create the edit control.