Fix omissions in text appearance generation

When generating appearance streams for variable text annotations,
properly handle the cases of there being no appearance dictionary, no
appearance stream, or an appearance stream with no BMC..EMC marker.

ChangeLog

@@ -1,5 +1,10 @@
 2019-01-20  Jay Berkenbilt  <ejb@ql.org>
 
+	* When generating appearance streams for variable text
+	annotations, properly handle the cases of there being no
+	appearance dictionary, no appearance stream, or an appearance
+	stream with no BMC..EMC marker.
+
 	* When flattening annotations, remove annotations from the file
 	that don't have appearance streams. These were previously being
 	preserved, but since they are invisible, there is no reason to

libqpdf/QPDFFormFieldObjectHelper.cc

@@ -506,6 +506,7 @@ class ValueSetter: public QPDFObjectHandle::TokenFilter
     {
     }
     virtual void handleToken(QPDFTokenizer::Token const&);
+    virtual void handleEOF();
     void writeAppearance();
 
   private:
@@ -515,6 +516,7 @@ class ValueSetter: public QPDFObjectHandle::TokenFilter
     double tf;
     QPDFObjectHandle::Rectangle bbox;
     enum { st_top, st_bmc, st_emc, st_end } state;
+    bool replaced;
 };
 
 ValueSetter::ValueSetter(std::string const& DA, std::string const& V,
@@ -525,7 +527,8 @@ ValueSetter::ValueSetter(std::string const& DA, std::string const& V,
     opt(opt),
     tf(tf),
     bbox(bbox),
-    state(st_top)
+    state(st_top),
+    replaced(false)
 {
 }
 
@@ -575,8 +578,22 @@ ValueSetter::handleToken(QPDFTokenizer::Token const& token)
     }
 }
 
-void ValueSetter::writeAppearance()
+void
+ValueSetter::handleEOF()
 {
+    if (! this->replaced)
+    {
+        QTC::TC("qpdf", "QPDFFormFieldObjectHelper replaced BMC at EOF");
+        write("/Tx BMC\n");
+        writeAppearance();
+    }
+}
+
+void
+ValueSetter::writeAppearance()
+{
+    this->replaced = true;
+
     // This code does not take quadding into consideration because
     // doing so requires font metric information, which we don't
     // have in many cases.
@@ -768,6 +785,29 @@ QPDFFormFieldObjectHelper::generateTextAppearance(
     QPDFAnnotationObjectHelper& aoh)
 {
     QPDFObjectHandle AS = aoh.getAppearanceStream("/N");
+    if (AS.isNull())
+    {
+        QTC::TC("qpdf", "QPDFFormFieldObjectHelper create AS from scratch");
+        QPDFObjectHandle::Rectangle rect = aoh.getRect();
+        QPDFObjectHandle::Rectangle bbox(
+            0, 0, rect.urx - rect.llx, rect.ury - rect.lly);
+        QPDFObjectHandle dict = QPDFObjectHandle::parse(
+            "<< /Resources << /ProcSet [ /PDF /Text ] >>"
+            " /Type /XObject /Subtype /Form >>");
+        dict.replaceKey("/BBox", QPDFObjectHandle::newFromRectangle(bbox));
+        AS = QPDFObjectHandle::newStream(
+            this->oh.getOwningQPDF(), "/Tx BMC\nEMC\n");
+        AS.replaceDict(dict);
+        QPDFObjectHandle AP = aoh.getAppearanceDictionary();
+        if (AP.isNull())
+        {
+            QTC::TC("qpdf", "QPDFFormFieldObjectHelper create AP from scratch");
+            aoh.getObjectHandle().replaceKey(
+                "/AP", QPDFObjectHandle::newDictionary());
+            AP = aoh.getAppearanceDictionary();
+        }
+        AP.replaceKey("/N", AS);
+    }
     if (! AS.isStream())
     {
         aoh.getObjectHandle().warnIfPossible(

qpdf/qpdf.testcov

@@ -422,3 +422,6 @@ qpdf bytes fallback warning 0
 qpdf invalid utf-8 in auto 0
 qpdf input password hex-bytes 0
 QPDFPageDocumentHelper ignore annotation with no appearance 0
+QPDFFormFieldObjectHelper create AS from scratch 0
+QPDFFormFieldObjectHelper create AP from scratch 0
+QPDFFormFieldObjectHelper replaced BMC at EOF 0

qpdf/qtest/qpdf.test

@@ -261,18 +261,29 @@ $td->runtest("compare files",
 show_ntests();
 # ----------
 $td->notify("--- Appearance Streams ---");
-$n_tests += 4;
+$n_tests += 8;
 
-$td->runtest("generate appearances and flatten",
-             {$td->COMMAND =>
-                  "qpdf --qdf --no-original-object-ids --static-id" .
-                  " --generate-appearances --flatten-annotations=all" .
-                  " need-appearances.pdf a.pdf"},
-             {$td->STRING => "", $td->EXIT_STATUS => 0},
-             $td->NORMALIZE_NEWLINES);
-$td->runtest("compare files",
-             {$td->FILE => "a.pdf"},
-             {$td->FILE => "appearances-a.pdf"});
+foreach my $f ('need-appearances',
+               'need-appearances-more',
+               'need-appearances-more2')
+{
+    $td->runtest("generate appearances and flatten ($f)",
+                 {$td->COMMAND =>
+                      "qpdf --qdf --no-original-object-ids --static-id" .
+                      " --generate-appearances --flatten-annotations=all" .
+                      " $f.pdf a.pdf"},
+                 {$td->STRING => "", $td->EXIT_STATUS => 0},
+                 $td->NORMALIZE_NEWLINES);
+    my $exp = 'appearances-a';
+    if ($f =~ m/appearances(-.*)$/)
+    {
+        $exp .= $1;
+    }
+    $exp .= '.pdf';
+    $td->runtest("compare files",
+                 {$td->FILE => "a.pdf"},
+                 {$td->FILE => $exp});
+}
 
 $td->runtest("more choices",
              {$td->COMMAND =>