From b4bcf69210719810ca563b9f8c0179719e80d212 Mon Sep 17 00:00:00 2001
From: Henrique Nakashima <hnakashima@chromium.org>
Date: Wed, 11 Jul 2018 21:19:22 +0000
Subject: Write marked content operators when generating a stream.

The marked content operators are BMC, BDC and EMC. In the case of
BDC, it is preceded by a direct dict or a property name.

Bug: pdfium:1118
Change-Id: I3ee736ff7be3e7d7dde55ef581af3444a325e887
Reviewed-on: https://pdfium-review.googlesource.com/37470
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
---
 core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp | 71 +++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

(limited to 'core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp')

diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
index 88f14b2ce4..f6a941d200 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
@@ -13,7 +13,9 @@
 #include <utility>
 
 #include "core/fpdfapi/edit/cpdf_pagecontentmanager.h"
+#include "core/fpdfapi/edit/cpdf_stringarchivestream.h"
 #include "core/fpdfapi/font/cpdf_font.h"
+#include "core/fpdfapi/page/cpdf_contentmark.h"
 #include "core/fpdfapi/page/cpdf_docpagedata.h"
 #include "core/fpdfapi/page/cpdf_image.h"
 #include "core/fpdfapi/page/cpdf_imageobject.h"
@@ -94,6 +96,9 @@ CPDF_PageContentGenerator::GenerateModifiedStreams() {
   // Start regenerating dirty streams.
   std::map<int32_t, std::unique_ptr<std::ostringstream>> streams;
   std::set<int32_t> empty_streams;
+  std::unique_ptr<const CPDF_ContentMark> empty_content_mark =
+      pdfium::MakeUnique<CPDF_ContentMark>();
+  std::map<int32_t, const CPDF_ContentMark*> current_content_mark;
 
   for (int32_t dirty_stream : all_dirty_streams) {
     std::unique_ptr<std::ostringstream> buf =
@@ -108,6 +113,7 @@ CPDF_PageContentGenerator::GenerateModifiedStreams() {
 
     streams[dirty_stream] = std::move(buf);
     empty_streams.insert(dirty_stream);
+    current_content_mark[dirty_stream] = empty_content_mark.get();
   }
 
   // Process the page objects, write into each dirty stream.
@@ -119,6 +125,8 @@ CPDF_PageContentGenerator::GenerateModifiedStreams() {
 
     std::ostringstream* buf = it->second.get();
     empty_streams.erase(stream_index);
+    current_content_mark[stream_index] = ProcessContentMarks(
+        buf, pPageObj.Get(), current_content_mark[stream_index]);
     ProcessPageObject(buf, pPageObj.Get());
   }
 
@@ -129,6 +137,8 @@ CPDF_PageContentGenerator::GenerateModifiedStreams() {
       // Clear to show that this stream needs to be deleted.
       buf->str("");
     } else {
+      FinishMarks(buf, current_content_mark[dirty_stream]);
+
       // Return graphics to original state
       *buf << "Q\n";
     }
@@ -201,13 +211,19 @@ ByteString CPDF_PageContentGenerator::RealizeResource(
 
 bool CPDF_PageContentGenerator::ProcessPageObjects(std::ostringstream* buf) {
   bool bDirty = false;
+  std::unique_ptr<const CPDF_ContentMark> empty_content_mark =
+      pdfium::MakeUnique<CPDF_ContentMark>();
+  const CPDF_ContentMark* content_mark = empty_content_mark.get();
+
   for (auto& pPageObj : m_pageObjects) {
     if (m_pObjHolder->IsPage() && !pPageObj->IsDirty())
       continue;
 
     bDirty = true;
+    content_mark = ProcessContentMarks(buf, pPageObj.Get(), content_mark);
     ProcessPageObject(buf, pPageObj.Get());
   }
+  FinishMarks(buf, content_mark);
   return bDirty;
 }
 
@@ -219,6 +235,61 @@ void CPDF_PageContentGenerator::UpdateStreamlessPageObjects(
   }
 }
 
+const CPDF_ContentMark* CPDF_PageContentGenerator::ProcessContentMarks(
+    std::ostringstream* buf,
+    const CPDF_PageObject* pPageObj,
+    const CPDF_ContentMark* pPrev) {
+  const CPDF_ContentMark* pNext = &pPageObj->m_ContentMark;
+
+  size_t first_different = pPrev->FindFirstDifference(pNext);
+
+  // Close all marks that are in prev but not in next.
+  // Technically we should iterate backwards to close from the top to the
+  // bottom, but since the EMC operators do not identify which mark they are
+  // closing, it does not matter.
+  for (size_t i = first_different; i < pPrev->CountItems(); ++i)
+    *buf << "EMC\n";
+
+  // Open all marks that are in next but not in prev.
+  for (size_t i = first_different; i < pNext->CountItems(); ++i) {
+    const CPDF_ContentMarkItem* item = pNext->GetItem(i);
+
+    // Write mark tag.
+    *buf << "/" << item->GetName() << " ";
+
+    // If there are no parameters, write a BMC (begin marked content) operator.
+    if (item->GetParamType() == CPDF_ContentMarkItem::None) {
+      *buf << "BMC\n";
+      continue;
+    }
+
+    // If there are parameters, write properties, direct or indirect.
+    if (item->GetParamType() == CPDF_ContentMarkItem::DirectDict) {
+      CPDF_StringArchiveStream archive_stream(buf);
+      item->GetParam()->WriteTo(&archive_stream);
+      *buf << " ";
+    } else {
+      ASSERT(item->GetParamType() == CPDF_ContentMarkItem::PropertiesDict);
+      *buf << "/" << item->GetPropertyName() << " ";
+    }
+
+    // Write BDC (begin dictionary content) operator.
+    *buf << "BDC\n";
+  }
+
+  return pNext;
+}
+
+void CPDF_PageContentGenerator::FinishMarks(
+    std::ostringstream* buf,
+    const CPDF_ContentMark* pContentMark) {
+  // Technically we should iterate backwards to close from the top to the
+  // bottom, but since the EMC operators do not identify which mark they are
+  // closing, it does not matter.
+  for (size_t i = 0; i < pContentMark->CountItems(); ++i)
+    *buf << "EMC\n";
+}
+
 void CPDF_PageContentGenerator::ProcessPageObject(std::ostringstream* buf,
                                                   CPDF_PageObject* pPageObj) {
   if (CPDF_ImageObject* pImageObject = pPageObj->AsImage())
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