Converting xls file into PDF in via cpp - c++

Question

I'm working on Visual Studio 2019 community, and I'm writing an MFC application in cpp. I want to add a functionality to the dialog box - such that when pressing a button it converts an existing xls file into pdf file. I've tried using the extension Aspose.Cells.Cpp and Aspose.PDF.Cpp with this code, but I get a lot of errors in the code of the DLL itself. I've also tried installing libHARU from here, but I didn't manage to make it work.
I've tried looking for another way to convert xls to pdf in MFC application in cpp, or another environment for creating desktop applications (which has some basic functionalities such as adding a pressing button in MFC, so I won't have to write everything from scratch with Win32 API), but I didn't find anything. Perhaps someone can explain to me how to perform this conversion in cpp so that I can use it when writing an MFC app, or could refer me to some useful information about another way of creating the application which supports this type of conversions?

Answer 1

You said in your comments to me that you can assume the user has Excel installed on his machine. If so, then you can use Excel's automation object model to manipulate Excel. You could do stuff like #import the type library and stuff...maybe that would make prettier C++. My experience, however, with driving Office apps is to stick more with just raw dispatch pointers. I've had less go wrong that way. This probably needs some more error checking and stuff, but that's up to you.
... and a big caveat. This is for an interactive app...which I halfway assume since you are using the MFC topic. With a service, Microsoft does not recommend you drive their Office applications in this manner. I tested this on one .xlsx file and it worked. Assume it will work for .xls as well. For other formats, you might need to use different import functions.
void ConvertFile(LPCWSTR lpszFileIn, LPCWSTR lpszFileOut)
{
CComDispatchDriver excel;
if (SUCCEEDED(excel.CoCreateInstance(_T("Excel.Application"), NULL, CLSCTX_LOCAL_SERVER)))
{
_variant_t vWorkbooks;
if (SUCCEEDED(excel.GetPropertyByName(L"Workbooks", &vWorkbooks)))
{
CComDispatchDriver workbooks(vWorkbooks.pdispVal);
_variant_t vWorksheet;
if (SUCCEEDED(workbooks.Invoke1(L"Open", &_variant_t(lpszFileIn), &vWorksheet)))
{
CComDispatchDriver worksheet(vWorksheet.pdispVal);
UINT xlTypePdf = 0;
HRESULT hr = worksheet.Invoke2(L"ExportAsFixedFOrmat", &_variant_t(xlTypePdf), &_variant_t(lpszFileOut), NULL);
if (FAILED(hr))
{
_com_error err(hr);
AfxMessageBox(err.ErrorMessage());
}
}
}
excel.Invoke0(L"Quit", NULL);
}
}

Answer 2

I'll give a solution, but this one doesn't use c++, just command line and LibreOffice app:
Use command line Libre Office tool: --convert-to
--convert-to output_file_extension[:output_filter_name] [--outdir output_dir] files
Batch convert files. If --outdir is not specified, then current working directory is used as output_dir.
Eg. --convert-to pdf *.doc
--convert-to pdf:writer_pdf_Export --outdir /home/user *.doc
More details about how to use this command you'll find here: https://help.libreoffice.org/Common/Starting_the_Software_With_Parameters
Later edit: Here is a sample of how to implement the above solution in a C++/MFC code:
STARTUPINFO si = { 0 };
si.cb = sizeof(si);
PROCESS_INFORMATION pi = { 0 };
sCommand.Format(_T("C:\\WINDOWS\\System32\\cmd.exe /c
C:\\LibreOffice\\program\\swriter.exe --convert-to pdf -outdir
c:\\temp\\ c:\\temp\\MyFile.doc"));
::CreateProcess(0, sCommand, 0, 0, TRUE, CREATE_NO_WINDOW, 0, 0, &si, &pi);