SREC Recognition Functions
This section takes a brief look at some of SREC's exported recognition
functions, including
CreateCompatibleHRC,
ProcessHRC, and
CreatePenDataHRC. The code uses the macro
#define lpHRC ((LPHRCinternal) hrc)
to represent a far pointer to the
HRC object.
CreateCompatibleHRC
The
CreateCompatibleHRC function allocates an HRCinternal structure in the local heap, creates an
HPENDATA block for the pen data, and returns a far pointer to the structure. The LPTR argument forces
LocalAlloc to return a far pointer to the allocation instead of a memory handle. This
far pointer serves as SREC's
HRC handle.
Since the
HRC has no configurable elements, SREC ignores any template
HRC provided in the first parameter.
HRC WINAPI CreateCompatibleHRC( HRC hrcTemplate, HREC hrec )
{
HRC hrc;
hrc = (HRC) LocalAlloc( LPTR, sizeof( HRCinternal ) );
if (hrc)
{
lpHRC->hrec = hrec;
lpHRC->hpendata = CreatePenData( NULL, 0, PDTS_HIENGLISH, 0 );
if (lpHRC->hpendata)
return (hrc);
}
LocalFree( (HLOCAL) hrc ); // If error, free allocation
return NULL; // and return NULL
}
ProcessHRC
The most interesting feature of SREC's
ProcessHRC function is the way it sets a time limit for processing. If called with a
limit of PH_MIN or PH_DEFAULT,
ProcessHRC passes the address of a callback function to
SetTimer. When the specified time-out period elapses, the callback function receives
control and sets a global flag called vfOutOfTime.
A recognizer can use this technique to ensure that it does not overrun a
specified time limit. Its internal processing functions should check the vfOutOfTime flag regularly and, if it is set, terminate immediately. In this case,
ProcessHRC returns a value of HRCR_INCOMPLETE to tell the caller recognition has not yet
finished.
int WINAPI ProcessHRC( HRC hrc, DWORD dwTimeMax )
{
UINT idTimer, uTime;
int iRet;
- fOutOfTime = FALSE; // Initialize time-out flag
if (dwTimeMax != PH_MAX) // If time limit specified ...
{
uTime = (dwTimeMax == PH_MIN) ? 50 : 200;
idTimer = SetTimer( NULL, NULL, uTime, (TIMERPROC) TimerProc );
iRet = GetSYG( hrc ); // Quit if out of time
KillTimer( NULL, idTimer );
}
else
iRet = GetSYG( hrc ); // Don't quit until finished
return (iRet);
}
VOID CALLBACK TimerProc( HWND hwnd, UINT ms, UINT iId, DWORD dwTm )
{
}
CreatePenDataHRC
SREC keeps an
HPENDATA handle in its
HRC structure. Because the
AddPenInputHRC function has already stored pen input in the internal
HPENDATA block,
CreatePenDataHRC simply duplicates the block.
HPENDATA WINAPI CreatePenDataHRC( HRC hrc )
{
if (hrc)
return (DuplicatePenData( lpHRC->hpendata, 0 ));
else
return NULL;
}
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