Fix content generation to only generate dirty page objects.

BUG=pdfium:717
R=dsinclair@chromium.org,thestig@chromium.org

Change-Id: I7e0e6fd301d40f9b5341d40cf11167b7748af243
Reviewed-on: https://pdfium-review.googlesource.com/6071
Reviewed-by: dsinclair <dsinclair@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

2 files changed, 57 insertions, 12 deletions

diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
index 2cf10bd7cb..7abf7a4964 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
@@ -17,6 +17,7 @@
 #include "core/fpdfapi/page/cpdf_path.h"
 #include "core/fpdfapi/page/cpdf_pathobject.h"
 #include "core/fpdfapi/page/cpdf_textobject.h"
+#include "core/fpdfapi/parser/cpdf_array.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_document.h"
 #include "core/fpdfapi/parser/cpdf_name.h"
@@ -59,23 +60,49 @@ CPDF_PageContentGenerator::CPDF_PageContentGenerator(CPDF_Page* pPage)
 CPDF_PageContentGenerator::~CPDF_PageContentGenerator() {}
 
 void CPDF_PageContentGenerator::GenerateContent() {
+  CPDF_Document* pDoc = m_pDocument.Get();
   CFX_ByteTextBuf buf;
-  for (auto& pPageObj : m_pageObjects) {
-    if (CPDF_ImageObject* pImageObject = pPageObj->AsImage())
-      ProcessImage(&buf, pImageObject);
-    else if (CPDF_PathObject* pPathObj = pPageObj->AsPath())
-      ProcessPath(&buf, pPathObj);
-    else if (CPDF_TextObject* pTextObj = pPageObj->AsText())
-      ProcessText(&buf, pTextObj);
+  if (!m_pageObjects.empty()) {
+    if (!ProcessPageObjects(&buf))
+      return;
   }
   CPDF_Dictionary* pPageDict = m_pPage->m_pFormDict.Get();
   CPDF_Object* pContent =
-      pPageDict ? pPageDict->GetDirectObjectFor("Contents") : nullptr;
-  if (pContent)
-    pPageDict->RemoveFor("Contents");
-
-  CPDF_Stream* pStream = m_pDocument->NewIndirect<CPDF_Stream>();
+      pPageDict ? pPageDict->GetObjectFor("Contents") : nullptr;
+  CPDF_Stream* pStream = pDoc->NewIndirect<CPDF_Stream>();
   pStream->SetData(buf.GetBuffer(), buf.GetLength());
+  if (pContent) {
+    CPDF_Array* pArray = ToArray(pContent);
+    if (pArray) {
+      pArray->AddNew<CPDF_Reference>(pDoc, pStream->GetObjNum());
+      return;
+    }
+    CPDF_Reference* pReference = ToReference(pContent);
+    if (!pReference) {
+      pPageDict->SetNewFor<CPDF_Reference>("Contents", m_pDocument.Get(),
+                                           pStream->GetObjNum());
+      return;
+    }
+    CPDF_Object* pDirectObj = pReference->GetDirect();
+    if (!pDirectObj) {
+      pPageDict->SetNewFor<CPDF_Reference>("Contents", m_pDocument.Get(),
+                                           pStream->GetObjNum());
+      return;
+    }
+    CPDF_Array* pObjArray = pDirectObj->AsArray();
+    if (pObjArray) {
+      pObjArray->AddNew<CPDF_Reference>(pDoc, pStream->GetObjNum());
+      return;
+    }
+    if (pDirectObj->IsStream()) {
+      CPDF_Array* pContentArray = pDoc->NewIndirect<CPDF_Array>();
+      pContentArray->AddNew<CPDF_Reference>(pDoc, pDirectObj->GetObjNum());
+      pContentArray->AddNew<CPDF_Reference>(pDoc, pStream->GetObjNum());
+      pPageDict->SetNewFor<CPDF_Reference>("Contents", pDoc,
+                                           pContentArray->GetObjNum());
+      return;
+    }
+  }
   pPageDict->SetNewFor<CPDF_Reference>("Contents", m_pDocument.Get(),
                                        pStream->GetObjNum());
 }
@@ -107,6 +134,23 @@ CFX_ByteString CPDF_PageContentGenerator::RealizeResource(
   return name;
 }
 
+bool CPDF_PageContentGenerator::ProcessPageObjects(CFX_ByteTextBuf* buf) {
+  bool bDirty = false;
+  for (auto& pPageObj : m_pageObjects) {
+    if (!pPageObj->IsDirty())
+      continue;
+    bDirty = true;
+    if (CPDF_ImageObject* pImageObject = pPageObj->AsImage())
+      ProcessImage(buf, pImageObject);
+    else if (CPDF_PathObject* pPathObj = pPageObj->AsPath())
+      ProcessPath(buf, pPathObj);
+    else if (CPDF_TextObject* pTextObj = pPageObj->AsText())
+      ProcessText(buf, pTextObj);
+    pPageObj->SetDirty(false);
+  }
+  return bDirty;
+}
+
 void CPDF_PageContentGenerator::ProcessImage(CFX_ByteTextBuf* buf,
                                              CPDF_ImageObject* pImageObj) {
   if ((pImageObj->matrix().a == 0 && pImageObj->matrix().b == 0) ||
diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
index 6c54d3130e..302375d536 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
@@ -30,6 +30,7 @@ class CPDF_PageContentGenerator {
  private:
   friend class CPDF_PageContentGeneratorTest;
 
+  bool ProcessPageObjects(CFX_ByteTextBuf* buf);
   void ProcessPath(CFX_ByteTextBuf* buf, CPDF_PathObject* pPathObj);
   void ProcessImage(CFX_ByteTextBuf* buf, CPDF_ImageObject* pImageObj);
   void ProcessGraphics(CFX_ByteTextBuf* buf, CPDF_PageObject* pPageObj);