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wiasCreatePropContext function (wiamdef.h)

  • Artikel

The wiasCreatePropContext function allocates a property context to indicate which of an item's properties are being changed by the application.

Syntax

HRESULT wiasCreatePropContext(
                 ULONG                cPropSpec,
  [in]           PROPSPEC             *pPropSpec,
                 ULONG                cProps,
  [in, optional] PROPID               *pProps,
  [in]           WIA_PROPERTY_CONTEXT *pContext
);

Parameters

cPropSpec

Specifies the total number of PROPSPEC structures in the pPropSpec array.

[in] pPropSpec

Pointer to the first element of an array of PROPSPEC structures identifying which properties are changing.

cProps

Specifies the number of property identifiers stored in this context.

[in, optional] pProps

Pointer to the first element of an array of property identifiers that indicate the properties to put into this property context.

[in] pContext

Pointer to a WIA_PROPERTY_CONTEXT structure that contains a property context.

Return value

On success, the function returns S_OK. If the function fails, it returns a standard COM error or one of the WIA error codes.

Remarks

This function allocates a property context and fills in its values. This function is generally used in wiasValidateItemProperties where the properties written by the application are validated.

Entries in the property context are identifiers for properties that either have dependents, or are themselves dependent on other properties. A context is used to mark which properties are being changed. When the property context is no longer needed, it should be freed by a call to wiasFreePropContext.

The properties to which an application writes are specified by the pPropSpec array. The properties that were changed by the application, as well as any properties dependent on the changed properties, are specified by the pProps array. Only properties that have been changed by the application (and any dependent properties) can be specified in pProps.

For more information. see the PROPSPEC structure.

Drivers can specify additional properties when creating a property context with wiasCreatePropContext.

The following properties are always present in WIA_PROPERTY_CONTEXT:

  • WIA_IPA_DATATYPE

  • WIA_IPA_DEPTH

  • WIA_IPS_XRES

  • WIA_IPS_XPOS

  • WIA_IPS_XEXTENT

  • WIA_IPA_PIXELS_PER_LINE

  • WIA_IPS_YRES

  • WIA_IPS_YPOS

  • WIA_IPS_YEXTENT

  • WIA_IPA_NUMBER_OF_LINES

  • WIA_IPS_CUR_INTENT

  • WIA_IPA_TYMED

  • WIA_IPA_FORMAT

Requirements

Requirement Value
Target Platform Desktop
Header wiamdef.h (include Wiamdef.h)
Library Wiaservc.lib
DLL Wiaservc.dll

See also

WIA_PROPERTY_CONTEXT

wiasFreePropContext

wiasValidateItemProperties