Modify PDF form fields in C++

Read and set text-field limits, change field appearance, delete a named field, and clear text in selected Form XObjects using Aspose.PDF for C++.

Read the first field text limit

The form must contain at least one field. Only the first field is inspected; outputFile is unused.

1. Open the input PDF as a Document.
2. Select index 0 from the form Fields array.
3. Cast the field to TextBoxField.
4. Print MaxLen when the cast succeeds.

#include <Aspose.PDF.Cpp/InteractiveFeatures/Forms/TextBoxField.h>

#include <Aspose.PDF.Cpp/Document.h>
#include <Aspose.PDF.Cpp/Page.h>

using namespace System;
using namespace Aspose::Pdf;
using namespace Aspose::Pdf::Forms;
using namespace Aspose::Pdf::Text;

void FormExamples::GetFieldLimit(String inputFile, String outputFile)
{
    auto document = MakeObject<Document>(inputFile);
    auto field = document->get_Form()->get_Fields()->idx_get(0);
    if (auto textBoxField = field.dynamic_pointer_cast<TextBoxField>())
    {
        std::cout << (String::Format(u"Limit: {0}", textBoxField->get_MaxLen())) << std::endl;
    }
}

Set a named field character limit

The input must contain the target field. This snippet retains the qualified base-class Save() call from the source.

1. Create FormEditor and bind the input PDF.
2. Call SetFieldLimit() for First Name with a limit of 15.
3. Save through the SaveableFacade base implementation.

#include <Aspose.PDF.Cpp/Facades/FormEditor.h>

using namespace System;

void FormExamples::SetFieldLimit(String inputFile, String outputFile)
{
    auto form = MakeObject<Aspose::Pdf::Facades::FormEditor>();
    form->BindPdf(inputFile);
    form->SetFieldLimit(String(u"First Name"), 15);
    form->Aspose::Pdf::Facades::SaveableFacade::Save(outputFile);
}

Change the first text field font

The form must have at least one field and Calibri must be available.

1. Open the input PDF as a Document.
2. Select form field index 0 and cast it to TextBoxField.
3. Create a DefaultAppearance using Calibri from FontRepository, size 10, and black text.
4. Assign the appearance when the cast succeeds.
5. Save the PDF with Save().

#include <Aspose.PDF.Cpp/Document.h>
#include <Aspose.PDF.Cpp/Text/FontRepository.h>
#include <Aspose.PDF.Cpp/Color.h>
#include <Aspose.PDF.Cpp/InteractiveFeatures/DefaultAppearance.h>
#include <Aspose.PDF.Cpp/InteractiveFeatures/Forms/TextBoxField.h>

using namespace System;
using namespace Aspose::Pdf;
using namespace Aspose::Pdf::Forms;
using namespace Aspose::Pdf::Annotations;
using namespace Aspose::Pdf::Text;

void FormExamples::SetFormFieldFont(String inputFile, String outputFile)
{
    auto document = MakeObject<Document>(inputFile);
    auto field = document->get_Form()->get_Fields()->idx_get(0);
    if (auto textBoxField = field.dynamic_pointer_cast<TextBoxField>())
    {
        textBoxField->set_DefaultAppearance(MakeObject<DefaultAppearance>(
            FontRepository::FindFont(String(u"Calibri")), 10, Color::get_Black()->ToRgb()));
    }

    document->Save(outputFile);
}

Delete a named AcroForm field

1. Open the input PDF as a Document.
2. Call Delete() on Aspose::Pdf::Forms::Form for the field named First Name.
3. Save the PDF with Save().

#include <Aspose.PDF.Cpp/Document.h>
#include <Aspose.PDF.Cpp/InteractiveFeatures/Forms/Form.h>

using namespace System;
using namespace Aspose::Pdf;
using namespace Aspose::Pdf::Forms;

void FormExamples::DeleteFormField(String inputFile, String outputFile)
{
    auto document = MakeObject<Document>(inputFile);
    document->get_Form()->Delete(String(u"First Name"));
    document->Save(outputFile);
}

Clear text in matching Typewriter XObjects

This modifies selected Form XObjects, not the values of all AcroForm fields.

1. Open the input PDF as a Document.
2. Enumerate XForm resources on page 1.
3. Select resources whose IT is Typewriter and Subtype is Form.
4. Visit each selected resource with TextFragmentAbsorber.
5. Set every detected fragment text to an empty string.
6. Save the PDF with Save().

#include <Aspose.PDF.Cpp/Document.h>
#include <Aspose.PDF.Cpp/Page.h>
#include <Aspose.PDF.Cpp/PageCollection.h>
#include <Aspose.PDF.Cpp/Resources.h>

#include <Aspose.PDF.Cpp/InteractiveFeatures/Forms/Form.h>
#include <Aspose.PDF.Cpp/InteractiveFeatures/Forms/FormType.h>
#include <Aspose.PDF.Cpp/Text/TextFragment.h>
#include <Aspose.PDF.Cpp/Text/TextFragmentAbsorber.h>
#include <Aspose.PDF.Cpp/Text/TextFragmentCollection.h>
#include <Aspose.PDF.Cpp/XForm.h>
#include <Aspose.PDF.Cpp/XFormCollection.h>

using namespace System;
using namespace Aspose::Pdf;
using namespace Aspose::Pdf::Forms;
using namespace Aspose::Pdf::Text;

void FormExamples::ClearTextInForm(String inputFile, String outputFile)
{
    auto document = MakeObject<Document>(inputFile);
    for (auto& form : document->get_Pages()->idx_get(1)->get_Resources()->get_Forms())
    {
        if (String(u"Typewriter") == form->get_IT() && String(u"Form") == form->get_Subtype())
        {
            auto absorber = MakeObject<TextFragmentAbsorber>();
            absorber->Visit(form);

            for (auto& fragment : absorber->get_TextFragments())
            {
                fragment->set_Text(String::Empty);
            }
        }
    }
    document->Save(outputFile);
}