Mention appearances in pdf-set-form-values example

ChangeLog

@@ -1,5 +1,9 @@
 2020-02-22  Jay Berkenbilt  <ejb@ql.org>
 
+	* Update pdf-set-form-values.cc to use and mention
+	generateAppearance, which hadn't been added when the example was
+	originally created.
+
 	* Detect, warn, and correct the case of /Pages in the document
 	catalog incorrectly pointing to a page or intermediate node
 	instead of the root of the pages tree. Fixes #398.

examples/pdf-set-form-values.cc

@@ -73,23 +73,23 @@ int main(int argc, char* argv[])
                  annot_iter != annotations.end(); ++annot_iter)
             {
                 // For each annotation, find its associated field. If
-                // it's a text field, set its value. This will
-                // automatically update the document to indicate that
-                // appearance streams need to be regenerated. At the
-                // time of this writing, qpdf doesn't have any helper
-                // code to assist with appearance stream generation,
-                // though there's nothing that prevents it from being
-                // possible.
+                // it's a text field, set its value.
                 QPDFFormFieldObjectHelper ffh =
                     afdh.getFieldForAnnotation(*annot_iter);
                 if (ffh.getFieldType() == "/Tx")
                 {
-                    // Set the value. This will automatically set
-                    // /NeedAppearances to true. If you don't want to
-                    // do that, pass false as the second argument. For
-                    // details see comments in
-                    // QPDFFormFieldObjectHelper.hh.
-                    ffh.setV(value);
+                    // Set the value. Passing false as the second
+                    // value prevents qpdf from setting
+                    // /NeedAppearances to true (but will not turn it
+                    // off if it's already on), so we call
+                    // generateAppearance after setting the value. You
+                    // may or may not want to do this depending on
+                    // whether the appearance streams generated by
+                    // qpdf are good enough for your purposes. For
+                    // additional details, please see comments in
+                    // QPDFFormFieldObjectHelper.hh for this method.
+                    ffh.setV(value, false);
+                    ffh.generateAppearance(*annot_iter);
                 }
             }
         }