Switch annotation flattening to use the form xobjects

Instead of directly putting the contents of the annotation appearance
streams into the page's content stream, add commands to render the
form xobjects directly. This is a more robust way to do it than the
original solution as it works properly with patterns and avoids
problems with resource name clashes between the pages and the form
xobjects.

2 files changed, 45 insertions, 39 deletions

diff --git a/include/qpdf/QPDFAnnotationObjectHelper.hh b/include/qpdf/QPDFAnnotationObjectHelper.hh
index 76ff0eac..47242499 100644
--- a/include/qpdf/QPDFAnnotationObjectHelper.hh
+++ b/include/qpdf/QPDFAnnotationObjectHelper.hh
@@ -72,23 +72,14 @@ class QPDFAnnotationObjectHelper: public QPDFObjectHelper
     QPDFObjectHandle getAppearanceStream(std::string const& which,
                                          std::string const& state = "");
 
-    // Return a matrix that transforms from the annotation's
-    // appearance stream's coordinates to the page's coordinates. This
-    // method also honors the annotation's NoRotate flag if set. The
-    // matrix is returned as a string representing the six floating
-    // point numbers to be passed to a cm operator. Returns the empty
-    // string if it is unable to compute the matrix for any reason.
-    // The value "rotate" should be set to the page's /Rotate value or
-    // 0 if none.
-    QPDF_DLL
-    std::string getAnnotationAppearanceMatrix(int rotate);
-
     // Generate text suitable for addition to the containing page's
-    // content stream that replaces this annotation's appearance
-    // stream. The value "rotate" should be set to the page's /Rotate
-    // value or 0 if none.
+    // content stream that draws this annotation's appearance stream
+    // as a form XObject. The value "name" is the resource name that
+    // will be used to refer to the form xobject. The value "rotate"
+    // should be set to the page's /Rotate value or 0 if none.
     QPDF_DLL
-    std::string getPageContentForAppearance(int rotate);
+    std::string getPageContentForAppearance(
+        std::string const& name, int rotate);
 
   private:
     class Members
diff --git a/include/qpdf/QPDFObjectHandle.hh b/include/qpdf/QPDFObjectHandle.hh
index 030ee11c..a878574b 100644
--- a/include/qpdf/QPDFObjectHandle.hh
+++ b/include/qpdf/QPDFObjectHandle.hh
@@ -559,27 +559,46 @@ class QPDFObjectHandle
     QPDF_DLL
     bool isOrHasName(std::string const&);
 
-    // Merge dictionaries with the following behavior, where "object"
-    // refers to the object whose method is invoked, and "other"
-    // refers to the argument:
-    // * If either object or other is not a dictionary, do nothing
-    // * Otherwise
-    //   * For each key in other
-    //     * If key is absent in object, insert it
-    //     * If key is present in object
-    //       * If both values are dictionaries, merge the dictionary from
-    //         other into the one from object
-    //       * If both values are arrays, append scalar elements from
-    //         other's that are not present in object's onto object's,
-    //         and ignore non-scalar elements in other's
-    //       * Otherwise ignore
+    // Merge resource dictionaries. Assumes resource dictionaries have
+    // the property that the collection of keys of all first-level
+    // dictionary members contains no duplicates. This method does
+    // nothing if both this object and the other object are not
+    // dictionaries. Otherwise, it has following behavior, where
+    // "object" refers to the object whose method is invoked, and
+    // "other" refers to the argument:
+    //
+    // * For each key in "other" whose value is an array:
+    //   * If "object" does not have that entry, shallow copy it.
+    //   * Otherwise, if "object" has an array in the same place,
+    //     append to that array any objects in "other"'s array that
+    //     are not already present.
+    // * For each key in "other" whose value is a dictionary:
+    //   * If "object" does not have that entry, shallow copy it.
+    //   * Otherwise, for each key in the subdictionary:
+    //     * If key is not present in "object"'s entry, shallow copy it.
+    //     * Otherwise, ignore. Conflicts are not detected.
+    //
     // The primary purpose of this method is to facilitate merging of
-    // resource dictionaries. Conflicts are ignored. If needed, a
-    // future version of qpdf may provide some mechanism for conflict
-    // resolution, such as providing a handler that is invoked with
-    // the path to the conflict.
-    QPDF_DLL
-    void mergeDictionary(QPDFObjectHandle other);
+    // resource dictionaries that are supposed to have the same scope
+    // as each other. For example, this can be used to merge a form
+    // XObject's /Resources dictionary with a form field's /DR.
+    // Conflicts are not detected. If, in the future, there should be
+    // a need to detect conflicts, this method could detect them and
+    // return a mapping from old to new names. This mapping could be
+    // used for filtering the stream. This would be necessary, for
+    // example, to merge a form XObject's resources with a page's
+    // resources with the intention of concatenating the content
+    // streams.
+    QPDF_DLL
+    void mergeResources(QPDFObjectHandle other);
+
+    // Get all resource names from a resourcey dictionary. If this
+    // object is a dctionary, this method returns a set of all the
+    // keys in all top-level subdictionaries. For resources
+    // dictionaries, this is the collection of names that may be
+    // referenced in the content stream.
+    QPDF_DLL
+    std::set<std::string> getResourceNames();
 
     // Return the QPDF object that owns an indirect object.  Returns
     // null for a direct object.
@@ -992,10 +1011,6 @@ class QPDFObjectHandle
         ParserCallbacks* callbacks);
     std::vector<QPDFObjectHandle> arrayOrStreamToStreamArray(
         std::string const& description, std::string& all_description);
-    void mergeDictionaryInternal(
-        QPDFObjectHandle other,
-        std::set<QPDFObjGen>& visiting,
-        int depth);
     static void warn(QPDF*, QPDFExc const&);
 
     class Members