Locating Properties

To bind an object handle (::HOBJ) to a certain feature offered by the device at runtime the C interface offers several functions that can be used to do that. Let's assume an application wants to access a 64 bit integer property that is called Width and is located somewhere in the devices feature tree. In this case, we want to bind the property of the base setting. The code to bind the device feature to a C interface object would look more or less like this:

//-----------------------------------------------------------------------------
// This function will try to obtain the handle to a certain driver feature list
HOBJ getDriverList( HDRV hDrv, const char* pName, const char* pAddListName, TDMR_ListType type )
//-----------------------------------------------------------------------------
{
  TPROPHANDLING_ERROR objResult;
  TDMR_ERROR dmrResult;
  HOBJ hObj = INVALID_ID;
  HLIST baseList;
 
  // try to locate the base list for these property
  if( ( dmrResult = DMR_FindList( hDrv, pAddListName, type, 0, &baseList ) ) == DMR_NO_ERROR )
  {
    // try to locate the property
    if( ( objResult = OBJ_GetHandleEx( baseList, pName, &hObj, smIgnoreProperties | smIgnoreMethods, 0 ) ) != PROPHANDLING_NO_ERROR )
    {
      printf( "OBJ_GetHandle for %s failed: %d Handle: %d. This list might not be supported by this device\n", pName, objResult, hObj );
    }
  }
  else
  {
    printf( "DMR_FindList failed: %d. Lists of type %d are not available for this device\n", dmrResult, type );
  }
  return hObj;
}
 
//-----------------------------------------------------------------------------
HOBJ getSettingProp( HDRV hDrv, const char* pSettingName, const char* pPropName )
//-----------------------------------------------------------------------------
{
  return getDriverProperty( hDrv, pPropName, pSettingName, dmltSetting );
}
 
//-----------------------------------------------------------------------------
void myFun()
//-----------------------------------------------------------------------------
{
  HDRV hDrv = getTheDriverHandleFromSomewhere();
  HOBJ hProp = getSettingProp( hDrv, "Base", "Width" );
  int64_type maxVal = 0;
  // now the property is ready to use when available:
  if( hProp != INVALID_ID )
  {
    OBJ_GetI64( hProp, &maxVal, 0 );
    OBJ_SetI64( hProp, maxVal / 2 ); // set the width to half of its maximum value
  }
  else
  {
    // oops... The feature is not offered by this device
  }
}