LTwain::QueryProperty

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#include "ltwrappr.h"

virtual L_INT LTwain::QueryProperty (uCapability, ppltProperty, uStructSize)

L_UINT uCapability;	/* capability constant */
pLTWAINPROPERTYQUERY * ppltProperty;	/* pointer to a pointer to a structure */
L_UINT uStructSize;	/* size of the LTWAINPROPERTY structure, in bytes */

Gets the available property values.

Parameter	Description
uCapability	This is a capability constant defined by the TWAIN 1.9 specification. For example if the user wants the value(s) for the transfer count, the uCapability will be ICAP_XFERCOUNT.
ppltProperty	Pointer to a pointer to a LTWAINPROPERTYQUERY structure to be updated with the property values.
	The structure will be internally allocated if the function is successful.
	The structure should be freed by calling LTwain::FreePropQueryStructure function
uStructSize	Size of the LTWAINPROPERTYQUERY structure, in bytes, for versioning. Use sizeof(LTWAINPROPERTYQUERY).

Returns

SUCCESS	The function was successful.
<1	An error occurred. Refer to Return Codes.

Comments

Getting these values can help in determining what values a certain TWAIN source supports for a certain capability or property.

Required DLLs and Libraries

LTTWN

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

See Also

Functions:	LTwain::GetProperties, LTwain::SetCapability, LTwain::GetCapability, LTwain::InitSession, LTwain::EndSession.
Topics:	Getting and Setting Capabilities
	TWAIN Functionality: Property Functions.

Example

L_INT LTwain__QueryPropertyExample(L_INT16 uValue, CMyTwain *MyClass)
{
   L_INT                nRet, nIndex; 
   pLTWAINPROPERTYQUERY pltQuery = NULL; 
   // Query capability possible values
   nRet = MyClass->QueryProperty (ICAP_XRESOLUTION, &pltQuery , sizeof(LTWAINPROPERTYQUERY)); 
   if (nRet != SUCCESS) 
      return nRet; 
   // Check for the available values of the file transfer property
   switch (pltQuery->uType) 
   {
   case TWON_ONEVALUE: 
      if (pltQuery->pltwOneValue->ItemType == TWTY_FIX32)
      {
         pTW_FIX32 ptwFixVal = (pTW_FIX32)&(pltQuery->pltwOneValue->Item);
         if (ptwFixVal->Whole == uValue)
         {
            nRet = MyClass->FreePropQueryStructure(&pltQuery); 
            if(nRet != SUCCESS)
               return nRet;
         }
      }
      break;
   case TWON_ENUMERATION: 
      if (pltQuery->pltwEnumeration->ItemType == TWTY_FIX32) 
      {
         pTW_FIX32 ptwFixVal;
         for (nIndex = 0; nIndex < (L_INT)pltQuery->pltwEnumeration->NumItems; nIndex ++)
         {
            ptwFixVal = (pTW_FIX32)(pltQuery->pltwEnumeration->ItemList[nIndex]);
            if (ptwFixVal->Whole == uValue)
            {
               nRet = MyClass->FreePropQueryStructure (&pltQuery); 
               if(nRet != SUCCESS)
                  return nRet;
            }
         }
      }
      break; 
   }
   nRet = MyClass->FreePropQueryStructure (&pltQuery); 
   return nRet;
}