DOCERR: ControlData Structure Not Completely Documented

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SUMMARY

The ControlData structure documented on page 92 of the "Programmer's Reference, Volume 4: Resources" manual that comes with the Microsoft Windows version 3.1 Software Development Kit (SDK) is not complete. This structure is also not complete in the online Help file (under the heading "Dialog Box Resource").

The correct structure is:

struct ControlData {

    WORD  x;
    WORD  y;
    WORD  cx;
    WORD  cy;
    WORD  wID;
    DWORD lStyle;
    union
    {
        BYTE class;     /* if (class & 0x80) */
        char szClass[]; /* otherwise         */
    } ClassID;
    char szText[];
    BYTE cbCreateInfo;  /* added */
    char CreateInfo[];  /* added */

cbCreateInfo specifies the number of bytes of additional data that follows this item's description and precedes the next item's description (that is, it specifies the length of CreateInfo).

CreateInfo also specifies additional data that the CreateWindow function passes to the WM_CREATE handler of the control (through the lpCreateParams field of the CREATESTRUCT data structure). This field is zero length if cbCreateInfo is zero.

MORE INFORMATION

When you are using the Windows 3.1 SDK Dialog Editor and Resource Compiler to create dialog box templates that are bound to .EXE files, the cbCreateInfo field is initialized to 0. The only way for an application to use these fields is to create a dialog box template on the fly and call one of the following functions: CreateDialogIndirect, CreateDialogIndirectParam, DialogBoxIndirect, or DialogBoxIndirectParam.

Note that the Windows 3.1 Dialog Manager passes a pointer to the item following the cbCreateInfo field in the dialog template even if cbCreateInfo is 0. This means that controls that rely on the lpCreateParams field in the CREATESTRUCT being NULL when there is no extra creation information will NOT function properly when using a standard Windows dialog resource.