Windows GDI Printer error StartDocPrinter - c++

Question

Actually I am working with Qt printing and need to send the RAW command (ESCP command) to printer. After did some search and I found that I need to use the Windows API to do it.
Refer to this thread : win32-c-print-string-to-printer
I have created the code like below :
const QString pName = "EPSON LX-300+ /II";
LPBYTE lpData;
BOOL bStatus = FALSE;
HANDLE hPrinter = NULL;
DOC_INFO_1 DocInfo;
DWORD dwPrtJob = 0L;
DWORD dwBytesWritten = 0L;
LPTSTR printerName = new wchar_t[pName.length() + 1];
pName.toWCharArray(printerName);
printerName[pName.length()] = '\0';
QString so = "\x1b#Is it works?";
QByteArray ba = so.toUtf8();
lpData = (unsigned char*)(ba.data());
DWORD dwCount = ba.length();
qDebug() << so;
bStatus = OpenPrinter(printerName, &hPrinter, NULL);
if(bStatus) {
DocInfo.pDocName = (LPTSTR)_T("My Document");
DocInfo.pOutputFile = NULL;
DocInfo.pDatatype = (LPTSTR)_T("RAW");
dwPrtJob = StartDocPrinter (
hPrinter,
1,
(LPBYTE)&DocInfo);
qDebug() << GetLastError();
if (dwPrtJob > 0) {
qDebug() << "COMMAND";
// Send the data to the printer.
bStatus = WritePrinter (
hPrinter,
lpData,
dwCount,
&dwBytesWritten);
}
qDebug() << dwCount;
qDebug() << dwBytesWritten;
EndDocPrinter (hPrinter);
// Close the printer handle.
bStatus = ClosePrinter(hPrinter);
qDebug() << bStatus;
}
if (!bStatus || (dwCount != dwBytesWritten)) {
bStatus = FALSE;
} else {
bStatus = TRUE;
}
delete printerName;
And the code failed on StartDocPrinter, it returning 0 which mean failed. And using the GetLastError(), the function return 1804. And refer to this, the error is ERROR_INVALID_DATATYPE. I am not sure what error is it. And i try to use different DocInfo.pDatatype to "RAW", "TEXT", and "XPS_PASS", the result is the same.
Is there anything I can do how to fix it?

Answer 1

DOC_INFO_1 DocInfo;
DocInfo.pDocName = (LPTSTR)_T("My Document");
DocInfo.pOutputFile = NULL;
DocInfo.pDatatype = (LPTSTR)_T("RAW");
This casting boils down to
DocInfo.pDocName = (wchar_t*)L"My Document";
...
Where pDocName is declared as wchar_t* This is wrong and the cast simply hides the errors and warnings. Try to avoid Microsoft T macro altogether, these macros are outdated and useless. Use C++ char and wchar_t* instead. To declare UTF16 wide char string in Windows, use the L prefix. The correct usage is as follows:
DOC_INFO_1 DocInfo;
wchar_t docName[100], dataType[100];
wcscpy_s(docName, 100, L"Print Job");
wcscpy_s(dataType, 100, L"RAW");
DocInfo.pDocName = docName;
DocInfo.pOutputFile = NULL;
DocInfo.pDatatype = dataType;
Example:
const QString pName = "EPSON LX-300+ /II";
wchar_t printerName[100];
pName.toWCharArray(printerName);
pName[pName.length()] = '\0';
HANDLE hprinter;
if (OpenPrinter(printerName, &hprinter, NULL))
{
DOC_INFO_1 DocInfo;
wchar_t docName[100], dataType[100];
wcscpy_s(docName, 100, L"Print Job");
wcscpy_s(dataType, 100, L"RAW");
DocInfo.pDocName = docName;
DocInfo.pOutputFile = NULL;
DocInfo.pDatatype = dataType;
DWORD printJob = StartDocPrinter(hprinter, 1, (LPBYTE)&DocInfo);
if (printJob && StartPagePrinter(hprinter))
{
MessageBox(0, L"StartPagePrinter OKAY", 0, 0);
DWORD written = 0;
int buflen = 100;
char *buf = new char[buflen];
strcpy_s(buf, buflen, "123");
if (WritePrinter(hprinter, buf, 3, &written))
MessageBox(0, L"OKAY", 0, 0);
delete[]buf;
EndPagePrinter(hprinter);
EndDocPrinter(hprinter);
}
ClosePrinter(hprinter);
}