Using PoDoFo to fill a acroform

// dennis.jenkins.75 .at. gmail.com

// http://www.mail-archive.com/[email protected]/msg00963.html
// https://podofo.svn.sourceforge.net/svnroot/podofo/podofo/trunk/test/FormTest/FormTest.cpp
// http://www.adobe.com/devnet/acrobat/pdfs/PDF32000_2008.pdf

#include <iostream>
#include <podofo/podofo.h>

#define CP() do { std::cerr << "CheckPoint, line " << __LINE__ << "\n"; } while (0)

using namespace PoDoFo;

static bool verbose = false;

static const char   *GetFieldTypeName (EPdfField eType)
{
    switch (eType)
    {
        case ePdfField_PushButton: return "pushbutton";
        case ePdfField_CheckBox: return "checkbox";
        case ePdfField_RadioButton: return "radiobutton";
        case ePdfField_TextField: return "textfield";
        case ePdfField_ComboBox: return "combobox";
        case ePdfField_ListBox: return "listbox";
        case ePdfField_Signature: return "signature";
        case ePdfField_Unknown: return "unknown";
        default: return "??";
    }

    return NULL;
}

static void DumpPdfForm (const char *filename)
{
    PdfMemDocument      doc (filename);
    PdfPage         *pPage = NULL;

    for (int iPage = 0; iPage < doc.GetPageCount(); ++iPage)
    {
        pPage = doc.GetPage (iPage);

        std::cout << filename << ":  page: " << iPage + 1 << "  fields: " << pPage->GetNumFields() << "\n";

        for (int iField = 0; iField < pPage->GetNumFields(); ++iField)
        {
            PdfField    field = pPage->GetField (iField);

            if (verbose)
            {
                std::cout <<
                    "  field: " << iField + 1 <<
                    ", name: " << field.GetFieldName().GetString() <<
                    ", type: " << GetFieldTypeName (field.GetType()) <<
                    "\n";
            }
        }
    }
}

void    ListAnnotations (const char *filename, int nPage)
{
    PdfMemDocument doc (filename);
    PdfPage *pPage = doc.GetPage (nPage);

    printf ("index   GetType()  HasKey('FT')\n");

    int nAnnots = pPage->GetNumAnnots();
    for (int i = 0; i < nAnnots; i++) {
        const PdfAnnotation* pAnnot = const_cast<PdfPage*>(pPage)->GetAnnotation (i);

        bool b = pAnnot->GetObject()->GetDictionary().HasKey (PdfName ("FT"));

        printf ("%5d          %2d          %1d\n", i, pAnnot->GetType(), b);
    }
}

// See section 12.7.3.3 (page 434) of ISO-32000-1:2008.
// Need to construct an appearance stream for each form field,
// or configure document to generated one dynamically.

// See section 12.7.4.3 (page 444) of ISO-32000-1:2008.
// Shows a correct "Appearance Stream" for a text field.

// We can always directly hack the dictionary:
//    PdfAnnotation::GetObject()->GetDictionary()

static void HackPdfFormDocument (PdfDocument &doc)
{
// http://www.mail-archive.com/[email protected]/msg01155.html
// Stolen from PdfAcroForm::Init()
//  doc.GetAcroForm()->Init (PdfAcroForm::ePdfAcroFormDefaultAppearance_BlackText12pt);

    PdfObject *pObj = doc.GetAcroForm()->GetObject();

    pObj->GetDictionary().AddKey (PdfName ("NeedAppearances"), PdfVariant (true));

    if (!pObj->GetDictionary().HasKey("DA"))
    {
        PdfFont     *pFont = doc.CreateFont ("Arial");
        PdfObject   *pResource = NULL;
        PdfObject   *pFontDict = NULL;

// Create "DR" key.
        if (!pObj->GetDictionary().HasKey (PdfName ("DR")))
        {
            pObj->GetDictionary().AddKey (PdfName ("DR"), PdfDictionary());
        }
        pResource = pObj->GetDictionary().GetKey( PdfName("DR") );

        if (!pResource->GetDictionary().HasKey( PdfName ("Font")))
        {
            pResource->GetDictionary().AddKey (PdfName ("Font"), PdfDictionary());
        }
        pFontDict = pResource->GetDictionary().GetKey( PdfName("Font") );

        pFontDict->GetDictionary().AddKey( pFont->GetIdentifier(), pFont->GetObject()->Reference() );

// Create "DA" key.
        std::ostringstream oss;
        PdfLocaleImbue (oss);
        oss << "0 0 0 rg /" << pFont->GetIdentifier().GetName() << " 12 Tf";
        pObj->GetDictionary().AddKey( PdfName("DA"), PdfString( oss.str() ) );
    }
}

static void HackPdfForm (const char *in_fn, const char *out_fn)
{
    PdfMemDocument      doc (in_fn);
    PdfPage         *pPage = NULL;
//  PdfFont         *pFont = doc.CreateFont ("Arial");

    HackPdfFormDocument (doc);

    for (int iPage = 0; iPage < doc.GetPageCount(); ++iPage)
    {
        pPage = doc.GetPage (iPage);

        if (verbose)
        {
            std::cout << "  page: " << iPage + 1 << "  fields: " << pPage->GetNumFields() << "\n";
        }

        for (int iField = 0; iField < pPage->GetNumFields(); ++iField)
        {
            PdfField    field = pPage->GetField (iField);

            if (verbose)
            {
                std::cout <<
                    "  field: " << iField + 1 <<
                    ", name: " << field.GetFieldName().GetString() <<
                    ", type: " << GetFieldTypeName (field.GetType()) <<
                    "\n";
            }

            if (field.GetType() == ePdfField_TextField)
            {
                char tmp[32];
                snprintf (tmp, sizeof(tmp), "%d", iField);

                auto *tf = reinterpret_cast<PdfTextField*>(&field);
                tf->SetText (tmp);
                tf->SetBackgroundColor (1.0, 0.0, 0.0);
            } else if (field.GetType() == ePdfField_CheckBox) {
                auto *cb = reinterpret_cast<PdfCheckBox*>(&field);
                cb->SetChecked (true);
//              cb->SetAppearanceChecked ();
            }
        }
    }

    doc.Write (out_fn);
}


int main (int argc, char *argv[])
{
    try
    {
        PdfError::EnableDebug (false);

        if (argc == 2)
        {
            DumpPdfForm (argv[1]);
//          ListAnnotations (argv[1], 0);
        }
        else if (argc == 3)
        {
            HackPdfForm (argv[1], argv[2]);
        }
        else
        {
            std::cerr << "Usage:\n";
            std::cerr << "  " << argv[0] << " src.pdf\n";
            std::cerr << "  " << argv[0] << " src.pdf dest.pdf\n";
            return -1;
        }
    }

    catch (const PdfError &err)
    {
        err.PrintErrorMsg();
        return err.GetError();
    }

    return 0;
}