L_TwainQueryProperty

#include "lttwn.h"

L_LTTWN_API L_INT L_TwainQueryProperty (hSession, uCapability, ppltProperty, uStructSize)

HTWAINSESSION hSession;	handle to an existing TWAIN session
L_UINT uCapability;	capability constant
pLTWAINPROPERTYQUERY * ppltProperty;	pointer to a pointer to a structure
L_UINT uStructSize;	size, in bytes, of the structure pointed to by ppltProperty

Gets the available property values.

Parameter	Description
hSession	Handle to an existing TWAIN session. This handle is obtained by calling the L_TwainInitSession or L_TwainInitSession2 or L_TwainInitSession2 function.
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 L_TwainFreePropQueryStructure function.
uStructSize	Size, in bytes, of the structure pointed to by ppltProperty, for versioning. Use sizeof(TWAINPROPERTYQUERY).

Returns

SUCCESS	The function was successful.
! = SUCCESS	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.

Example

L_INT TwainQueryPropertyExample(L_INT16 uValue,HTWAINSESSION g_hSession) 
{ 
   L_INT nRet, nIndex; 
   pLTWAINPROPERTYQUERY pltQuery = NULL; 
   // Query capability possible values 
   nRet = L_TwainQueryProperty (g_hSession, 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)(INT_PTR)pltQuery->pltwOneValue->Item; 
         if (ptwFixVal->Whole == uValue) 
         { 
            L_TwainFreePropQueryStructure(&pltQuery); 
            return SUCCESS; 
         } 
      } 
      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) 
            { 
               L_TwainFreePropQueryStructure (&pltQuery); 
               return SUCCESS; 
            } 
         } 
      } 
      break; 
   } 
   L_TwainFreePropQueryStructure (&pltQuery); 
   return FAILURE; 
}

Help Version 19.0.2017.10.27

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Function References

Functions:	L_TwainStartCapsNeg, L_TwainEndCapsNeg, L_TwainGetProperties, L_TwainSetCapability, L_TwainGetCapability, L_TwainInitSession, L_TwainEndSession.
Topics:	Getting and Setting Capabilities
	TWAIN Functionality: Property Functions.