DTWAIN_CallDSMProc

The DTWAIN_CallDSMProc allows an application to call the TWAIN Data Source Manager (DSM) directly

#include <twain.h>

LONG DTWAIN_CallDSMProc (

Parameters

AppID

The DTWAIN_IDENTITY for the application

SourceId

The DTWAIN_IDENTITY for the Data Source

lDG

Data Group of Twain Triplet

lDAT

Data of TWAIN Triplet

lMSG

 Message of Twain Triplet

pData                                

  Extra data required by Twain Triplet

Return Values

The TWAIN return code.  Consult the TWAIN 1.8 specification for return codes when the DSM is called.

Comments

The DTWAIN_CallDSMProc is a low-level DTWAIN function that allows an application to call the TWAIN Data Source Manager (DSM) directly.  When an application calls the DSM, the application must specify the TW_IDENTITY of the application and the source, a TWAIN triplet, and extra data.  The application and Source ID can be obtained by calling DTWAIN_GetTwainAppID and DTWAIN_GetSourceID, respectively.

The Twain triplet is divided into three arguments.  The triplet consists of a DG, DAT, and MSG value all denoted by the lDG, lDAT, and lMSG parameters, respectively.

The pData parameter represents a pointer to extra data that the triplet needs to perform the Twain function. This value depends on the DG, DAT, and MSG parameters.  Consult the Twain specification to see what value is placed here.

All ID, triplet, and extra info is described in the current TWAIN 1.8 documentation, available at http://www.twain.org.  For example, to set the gray scale response curves of a Data Source, the following call can be executed:

#include <dtwain.h>

#include <twain.h> /* Needed for TW_GRAYRESPONSE definition and DG_IMAGE,

DAT_GRAYRESPONSE, and MSG_SET.*/

TW_GRAYRESPONSE G;

DTWAIN_SOURCE Source;

/*...*/

DTWAIN_SysInitialize();

DTWAIN_StartTwainSession(NULL,NULL);

Source = DTWAIN_SelectSource( );

/*...*/

LONG RetVal = DTWAIN_CallDSMProc(DTWAIN_GetTwainAppID(),

                                DTWAIN_GetSourceID(Source),

                                DG_IMAGE,

                                DAT_GRAYRESPONSE,

                                MSG_SET,

                                &G);

Note that you need to include TWAIN.H for the definitions described above.  Note that you still need to use the DTWAIN_SysIntialize functions before using this function.

The DTWAIN_CallDSMProc should be used by experienced C or C++  TWAIN programmers who need to call the TWAIN DSM directly.  If you have little to no experience with calling functions directly to the TWAIN DSM, call this function at your own risk.  If a call to the DSM results in a change of TWAIN states, DTWAIN does not know internally that the state has changed.  Please be aware of this when calling DTWAIN_CallDSMProc.

TWAIN State Transitions

Depends on arguments to DTWAIN_CallDSMProc

Prerequisite Function Call(s)

DTWAIN_SysInitialize

DTWAIN_GetTwainAppID  (if AppID is not NULL)

DTWAIN_GetSourceID   (if SourceID is not NULL)

See Also

Low-Level DTWAIN functions