Handle inheritable page attributes

Add getAttribute for handling inheritable page attributes, and fix
getPageImages and annotation flattening code to use it.

4 files changed, 46 insertions, 35 deletions

diff --git a/libqpdf/QPDFObjectHandle.cc b/libqpdf/QPDFObjectHandle.cc
index a0d45c86..b802a55c 100644
--- a/libqpdf/QPDFObjectHandle.cc
+++ b/libqpdf/QPDFObjectHandle.cc
@@ -18,6 +18,7 @@
 #include <qpdf/Pl_QPDFTokenizer.hh>
 #include <qpdf/BufferInputSource.hh>
 #include <qpdf/QPDFExc.hh>
+#include <qpdf/QPDFPageObjectHelper.hh>
 
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
@@ -1109,24 +1110,11 @@ QPDFObjectHandle::getGeneration() const
 std::map<std::string, QPDFObjectHandle>
 QPDFObjectHandle::getPageImages()
 {
-    // Note: this code doesn't handle inherited resources.  If this
-    // page dictionary doesn't have a /Resources key or has one whose
-    // value is null or an empty dictionary, you are supposed to walk
-    // up the page tree until you find a /Resources dictionary.  As of
-    // this writing, I don't have any test files that use inherited
-    // resources, and hand-generating one won't be a good test because
-    // any mistakes in my understanding would be present in both the
-    // code and the test file.
-
-    // NOTE: If support of inherited resources (see above comment) is
-    // implemented, edit comment in QPDFObjectHandle.hh for this
-    // function.  Also remove call to pushInheritedAttributesToPage
-    // from qpdf.cc when show_page_images is true.
-
     std::map<std::string, QPDFObjectHandle> result;
-    if (this->hasKey("/Resources"))
+    QPDFObjectHandle resources =
+        QPDFPageObjectHelper(*this).getAttribute("/Resources", false);
+    if (resources.isDictionary())
     {
-	QPDFObjectHandle resources = this->getKey("/Resources");
 	if (resources.hasKey("/XObject"))
 	{
 	    QPDFObjectHandle xobject = resources.getKey("/XObject");
diff --git a/libqpdf/QPDFPageDocumentHelper.cc b/libqpdf/QPDFPageDocumentHelper.cc
index fa50c471..3eec789b 100644
--- a/libqpdf/QPDFPageDocumentHelper.cc
+++ b/libqpdf/QPDFPageDocumentHelper.cc
@@ -79,20 +79,12 @@ QPDFPageDocumentHelper::flattenAnnotations(
             "document does not have updated appearance streams,"
             " so form fields will not be flattened");
     }
-    pushInheritedAttributesToPage();
     std::vector<QPDFPageObjectHelper> pages = getAllPages();
     for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
          iter != pages.end(); ++iter)
     {
         QPDFPageObjectHelper ph(*iter);
-        QPDFObjectHandle page_oh = ph.getObjectHandle();
-        if (page_oh.getKey("/Resources").isIndirect())
-        {
-            QTC::TC("qpdf", "QPDFPageDocumentHelper indirect resources");
-            page_oh.replaceKey("/Resources",
-                               page_oh.getKey("/Resources").shallowCopy());
-        }
-        QPDFObjectHandle resources = ph.getObjectHandle().getKey("/Resources");
+        QPDFObjectHandle resources = ph.getAttribute("/Resources", true);
         if (! resources.isDictionary())
         {
             // This should never happen and is not exercised in the
diff --git a/libqpdf/QPDFPageObjectHelper.cc b/libqpdf/QPDFPageObjectHelper.cc
index c5ede04f..4d58da32 100644
--- a/libqpdf/QPDFPageObjectHelper.cc
+++ b/libqpdf/QPDFPageObjectHelper.cc
@@ -15,6 +15,42 @@ QPDFPageObjectHelper::QPDFPageObjectHelper(QPDFObjectHandle oh) :
 {
 }
 
+QPDFObjectHandle
+QPDFPageObjectHelper::getAttribute(std::string const& name,
+                                   bool copy_if_shared)
+{
+    bool inheritable = ((name == "/MediaBox") || (name == "/CropBox") ||
+                        (name == "/Resources") || (name == "/Rotate"));
+
+    QPDFObjectHandle node = this->oh;
+    QPDFObjectHandle result(node.getKey(name));
+    std::set<QPDFObjGen> seen;
+    bool inherited = false;
+    while (inheritable && result.isNull() && node.hasKey("/Parent"))
+    {
+        seen.insert(node.getObjGen());
+        node = node.getKey("/Parent");
+        if (seen.count(node.getObjGen()))
+        {
+            break;
+        }
+        result = node.getKey(name);
+        if (! result.isNull())
+        {
+            QTC::TC("qpdf", "QPDFPageObjectHelper non-trivial inheritance");
+            inherited = true;
+        }
+    }
+    if (copy_if_shared && (inherited || result.isIndirect()))
+    {
+        QTC::TC("qpdf", "QPDFPageObjectHelper copy shared attribute");
+        result = result.shallowCopy();
+        this->oh.replaceKey(name, result);
+    }
+    return result;
+}
+
+
 std::map<std::string, QPDFObjectHandle>
 QPDFPageObjectHelper::getPageImages()
 {
@@ -159,12 +195,7 @@ QPDFPageObjectHelper::removeUnreferencedResources()
     std::vector<std::string> to_filter;
     to_filter.push_back("/Font");
     to_filter.push_back("/XObject");
-    QPDFObjectHandle resources = this->oh.getKey("/Resources");
-    if (resources.isDictionary())
-    {
-        resources = resources.shallowCopy();
-        this->oh.replaceKey("/Resources", resources);
-    }
+    QPDFObjectHandle resources = getAttribute("/Resources", true);
     for (std::vector<std::string>::iterator d_iter = to_filter.begin();
          d_iter != to_filter.end(); ++d_iter)
     {
diff --git a/libqpdf/QPDF_optimization.cc b/libqpdf/QPDF_optimization.cc
index 59a01ea3..f282e5f3 100644
--- a/libqpdf/QPDF_optimization.cc
+++ b/libqpdf/QPDF_optimization.cc
@@ -208,10 +208,10 @@ QPDF::pushInheritedAttributesToPageInternal2(
 
     if (type == "/Pages")
     {
-	// Make a list of inheritable keys.  Any key other than /Type,
-	// /Parent, Kids, or /Count is an inheritable attribute.  Push
-	// this object onto the stack of pages nodes that have values
-	// for this attribute.
+	// Make a list of inheritable keys. Only the keys /MediaBox,
+	// /CropBox, /Resources, and /Rotate are inheritable
+	// attributes. Push this object onto the stack of pages nodes
+	// that have values for this attribute.
 
 	std::set<std::string> inheritable_keys;
 	std::set<std::string> keys = cur_pages.getKeys();