Allow setting a form field's value

ChangeLog

@@ -1,5 +1,10 @@
 2018-06-21  Jay Berkenbilt  <ejb@ql.org>
 
+	* Added methods QPDFAcroFormDocumentHelper::setNeedAppearances and
+	added methods to QPDFFormFieldObjectHelper to set a field's value,
+	optionally updating the document to indicate that appearance
+	streams need to be regenerated.
+
 	* Added QPDFObject::newUnicodeString and QPDFObject::unparseBinary
 	to allow for more convenient creation of strings that are
 	explicitly encoded in UTF-16 BE. This is useful for creating

include/qpdf/QPDFAcroFormDocumentHelper.hh

@@ -135,6 +135,23 @@ class QPDFAcroFormDocumentHelper: public QPDFDocumentHelper
     QPDFFormFieldObjectHelper
     getFieldForAnnotation(QPDFAnnotationObjectHelper);
 
+    // Return the current value of /NeedAppearances. If
+    // /NeedAppearances is missing, return false as that is how PDF
+    // viewers are supposed to interpret it.
+    QPDF_DLL
+    bool getNeedAppearances();
+
+    // Indicate whether appearance streams must be regenerated. If you
+    // modify a field value, you should call setNeedAppearances(true)
+    // unless you also generate an appearance stream for the
+    // corresponding annotation at the same time. If you generate
+    // appearance streams for all fields, you can call
+    // setNeedAppearances(false). If you use
+    // QPDFFormFieldObjectHelper::setV, it will automatically call
+    // this method unless you tell it not to.
+    QPDF_DLL
+    void setNeedAppearances(bool);
+
   private:
     void analyze();
     void traverseField(QPDFObjectHandle field,

include/qpdf/QPDFFormFieldObjectHelper.hh

@@ -114,6 +114,29 @@ class QPDFFormFieldObjectHelper: public QPDFObjectHelper
     QPDF_DLL
     int getQuadding();
 
+    // Set an attribute to the given value
+    QPDF_DLL
+    void setFieldAttribute(std::string const& key, QPDFObjectHandle value);
+
+    // Set an attribute to the given value as a Unicode string (UTF-16
+    // BE encoded). The input string should be UTF-8 encoded.
+    QPDF_DLL
+    void setFieldAttribute(std::string const& key,
+                           std::string const& utf8_value);
+
+    // Set /V (field value) to the given value. Optionally set
+    // /NeedAppearances to true. You can explicitly tell this method
+    // not to set /NeedAppearances if you are going to explicitly
+    // generate an appearance stream yourself.
+    QPDF_DLL
+    void setV(QPDFObjectHandle value, bool need_appearances = true);
+
+    // Set /V (field value) to the given string value encoded as a
+    // Unicode string. The input value should be UTF-8 encoded. See
+    // comments above about /NeedAppearances.
+    QPDF_DLL
+    void setV(std::string const& utf8_value, bool need_appearances = true);
+
   private:
     class Members
     {

libqpdf/QPDFAcroFormDocumentHelper.cc

@@ -250,3 +250,38 @@ QPDFAcroFormDocumentHelper::traverseField(
             QPDFFormFieldObjectHelper(our_field);
     }
 }
+
+bool
+QPDFAcroFormDocumentHelper::getNeedAppearances()
+{
+    bool result = false;
+    QPDFObjectHandle acroform = this->qpdf.getRoot().getKey("/AcroForm");
+    if (acroform.isDictionary() &&
+        acroform.getKey("/NeedAppearances").isBool())
+    {
+        result = acroform.getKey("/NeedAppearances").getBoolValue();
+    }
+    return result;
+}
+
+void
+QPDFAcroFormDocumentHelper::setNeedAppearances(bool val)
+{
+    QPDFObjectHandle acroform = this->qpdf.getRoot().getKey("/AcroForm");
+    if (! acroform.isDictionary())
+    {
+        this->qpdf.getRoot().warnIfPossible(
+            "ignoring call to QPDFAcroFormDocumentHelper::setNeedAppearances"
+            " on a file that lacks an /AcroForm dictionary");
+        return;
+    }
+    if (val)
+    {
+        acroform.replaceKey("/NeedAppearances",
+                            QPDFObjectHandle::newBool(true));
+    }
+    else
+    {
+        acroform.removeKey("/NeedAppearances");
+    }
+}

libqpdf/QPDFFormFieldObjectHelper.cc

@@ -1,5 +1,6 @@
 #include <qpdf/QPDFFormFieldObjectHelper.hh>
 #include <qpdf/QTC.hh>
+#include <qpdf/QPDFAcroFormDocumentHelper.hh>
 
 QPDFFormFieldObjectHelper::Members::~Members()
 {
@@ -188,3 +189,44 @@ QPDFFormFieldObjectHelper::getQuadding()
     }
     return result;
 }
+
+void
+QPDFFormFieldObjectHelper::setFieldAttribute(
+    std::string const& key, QPDFObjectHandle value)
+{
+    this->oh.replaceKey(key, value);
+}
+
+void
+QPDFFormFieldObjectHelper::setFieldAttribute(
+    std::string const& key, std::string const& utf8_value)
+{
+    this->oh.replaceKey(key, QPDFObjectHandle::newUnicodeString(utf8_value));
+}
+
+void
+QPDFFormFieldObjectHelper::setV(
+    QPDFObjectHandle value, bool need_appearances)
+{
+    setFieldAttribute("/V", value);
+    if (need_appearances)
+    {
+        QPDF* qpdf = this->oh.getOwningQPDF();
+        if (! qpdf)
+        {
+            throw std::logic_error(
+                "QPDFFormFieldObjectHelper::setV called with"
+                " need_appearances = true on an object that is"
+                " not associated with an owning QPDF");
+        }
+        QPDFAcroFormDocumentHelper(*qpdf).setNeedAppearances(true);
+    }
+}
+
+void
+QPDFFormFieldObjectHelper::setV(
+    std::string const& utf8_value, bool need_appearances)
+{
+    setV(QPDFObjectHandle::newUnicodeString(utf8_value),
+         need_appearances);
+}

qpdf/qtest/qpdf.test

@@ -115,7 +115,7 @@ my @form_tests = (
     'form-errors',
     );
 
-$n_tests += scalar(@form_tests);
+$n_tests += scalar(@form_tests) + 2;
 
 # Many of the form*.pdf files were created by converting the
 # LibreOffice document storage/form.odt to PDF and then manually
@@ -132,6 +132,15 @@ foreach my $f (@form_tests)
                  $td->NORMALIZE_NEWLINES);
 }
 
+$td->runtest("fill fields",
+             {$td->COMMAND => "test_driver 44 form-no-need-appearances.pdf"},
+             {$td->FILE => "form-no-need-appearances.out",
+                  $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+$td->runtest("compare files",
+             {$td->FILE => "a.pdf"},
+             {$td->FILE => "form-no-need-appearances-filled.pdf"});
+
 show_ntests();
 # ----------
 $td->notify("--- Stream Replacement Tests ---");

qpdf/qtest/qpdf/form-no-need-appearances.out

@@ -0,0 +1,3 @@
+Set field value: Text Box 1 -> 3.14 ÷ 0
+Set field value: Text Box 2 -> 3.14 ÷ 0
+test 44 done

qpdf/test_driver.cc

@@ -1584,6 +1584,34 @@ void runtest(int n, char const* filename1, char const* arg2)
             }
         }
     }
+    else if (n == 44)
+    {
+        // Set form fields.
+        QPDFAcroFormDocumentHelper afdh(pdf);
+        std::vector<QPDFFormFieldObjectHelper> fields = afdh.getFormFields();
+        for (std::vector<QPDFFormFieldObjectHelper>::iterator iter =
+                 fields.begin();
+             iter != fields.end(); ++iter)
+        {
+            QPDFFormFieldObjectHelper& field(*iter);
+            QPDFObjectHandle ft = field.getInheritableFieldValue("/FT");
+            if (ft.isName() && (ft.getName() == "/Tx"))
+            {
+                // \xc3\xb7 is utf-8 for U+00F7 (divided by)
+                field.setV("3.14 \xc3\xb7 0");
+                std::cout << "Set field value: "
+                          << field.getFullyQualifiedName()
+                          << " -> "
+                          << field.getValueAsString()
+                          << std::endl;
+            }
+        }
+        QPDFWriter w(pdf, "a.pdf");
+	w.setQDFMode(true);
+        w.setStaticID(true);
+        w.setSuppressOriginalObjectIDs(true);
+        w.write();
+    }
     else
     {
 	throw std::runtime_error(std::string("invalid test ") +