Added StartPage and EndPage methods to the Emf class because the GDI StartPage and EndPage APIs do not work in a metafile DC. We write custom GDICOMMENT records to designate a StartPage and EndPage.

BUG=None
TEST=Unit-tests provided.

Review URL: http://codereview.chromium.org/2947006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52084 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 107 insertions, 0 deletions

diff --git a/printing/emf_win.cc b/printing/emf_win.cc
index d8e03af..e93acf2 100644
--- a/printing/emf_win.cc
+++ b/printing/emf_win.cc
@@ -14,6 +14,24 @@
 #include "gfx/rect.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
+namespace {
+const int kCustomGdiCommentSignature = 0xdeadbabe;
+struct PageBreakRecord {
+  int signature;
+  enum PageBreakType {
+    START_PAGE,
+    END_PAGE,
+  } type;
+  explicit PageBreakRecord(PageBreakType type_in)
+      : signature(kCustomGdiCommentSignature), type(type_in) {
+  }
+  bool IsValid() const {
+    return (signature == kCustomGdiCommentSignature) &&
+           (type >= START_PAGE) && (type <= END_PAGE);
+  }
+};
+}
+
 namespace printing {
 
 bool DIBFormatNativelySupported(HDC dc, uint32 escape, const BYTE* bits,
@@ -232,6 +250,8 @@ bool Emf::Record::SafePlayback(const XFORM* base_matrix) const {
   // device.
   // TODO(sanjeevr): We should also add JPEG/PNG support for SetSIBitsToDevice
   //
+  // We also process any custom EMR_GDICOMMENT records which are our
+  // placeholders for StartPage and EndPage.
   // Note: I should probably care about view ports and clipping, eventually.
   bool res;
   switch (record()->iType) {
@@ -343,6 +363,27 @@ bool Emf::Record::SafePlayback(const XFORM* base_matrix) const {
       // Ignore it.
       res = true;
       break;
+    case EMR_GDICOMMENT: {
+      const EMRGDICOMMENT* comment_record =
+          reinterpret_cast<const EMRGDICOMMENT*>(record());
+      if (comment_record->cbData == sizeof(PageBreakRecord)) {
+        const PageBreakRecord* page_break_record =
+            reinterpret_cast<const PageBreakRecord*>(comment_record->Data);
+        if (page_break_record && page_break_record->IsValid()) {
+          if (page_break_record->type == PageBreakRecord::START_PAGE) {
+            res = !!::StartPage(context_->hdc);
+          } else if (page_break_record->type == PageBreakRecord::END_PAGE) {
+            res = !!::EndPage(context_->hdc);
+          } else {
+            res = false;
+            NOTREACHED();
+          }
+        } else {
+          res = Play();
+        }
+      }
+      break;
+    }
     default: {
       res = Play();
       break;
@@ -351,6 +392,25 @@ bool Emf::Record::SafePlayback(const XFORM* base_matrix) const {
   return res;
 }
 
+bool Emf::StartPage() {
+  DCHECK(hdc_);
+  if (!hdc_)
+    return false;
+  PageBreakRecord record(PageBreakRecord::START_PAGE);
+  return !!GdiComment(hdc_, sizeof(record),
+                      reinterpret_cast<const BYTE *>(&record));
+}
+
+bool Emf::EndPage() {
+  DCHECK(hdc_);
+  if (!hdc_)
+    return false;
+  PageBreakRecord record(PageBreakRecord::END_PAGE);
+  return !!GdiComment(hdc_, sizeof(record),
+                      reinterpret_cast<const BYTE *>(&record));
+}
+
+
 Emf::Enumerator::Enumerator(const Emf& emf, HDC context, const RECT* rect) {
   context_.handle_table = NULL;
   context_.objects_count = 0;
diff --git a/printing/emf_win.h b/printing/emf_win.h
index 9f3dffe..9581d77 100644
--- a/printing/emf_win.h
+++ b/printing/emf_win.h
@@ -84,6 +84,12 @@ class Emf {
     return hdc_;
   }
 
+  // Inserts a custom GDICOMMENT records indicating StartPage/EndPage calls
+  // (since StartPage and EndPage do not work in a metafile DC). Only valid
+  // when hdc_ is non-NULL.
+  bool StartPage();
+  bool EndPage();
+
   // Saves the EMF data to a file as-is. It is recommended to use the .emf file
   // extension but it is not enforced. This function synchronously writes to the
   // file. For testing only.
diff --git a/printing/emf_win_unittest.cc b/printing/emf_win_unittest.cc
index fb85282..3b4c473 100644
--- a/printing/emf_win_unittest.cc
+++ b/printing/emf_win_unittest.cc
@@ -6,11 +6,13 @@
 
 // For quick access.
 #include <wingdi.h>
+#include <winspool.h>
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
+#include "base/scoped_handle_win.h"
 #include "printing/printing_context.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -113,3 +115,42 @@ TEST_F(EmfPrintingTest, Enumerate) {
   context.DocumentDone();
 }
 
+// Disabled if no "UnitTest printer" exists.
+TEST_F(EmfPrintingTest, PageBreak) {
+  ScopedHDC dc(CreateDC(L"WINSPOOL", L"UnitTest Printer", NULL, NULL));
+  if (!dc.Get())
+    return;
+  printing::Emf emf;
+  EXPECT_TRUE(emf.CreateDc(dc.Get(), NULL));
+  EXPECT_TRUE(emf.hdc() != NULL);
+  int pages = 3;
+  while (pages) {
+    EXPECT_TRUE(emf.StartPage());
+    ::Rectangle(emf.hdc(), 10, 10, 190, 190);
+    EXPECT_TRUE(emf.EndPage());
+    --pages;
+  }
+  EXPECT_TRUE(emf.CloseDc());
+  uint32 size = emf.GetDataSize();
+  std::vector<BYTE> data;
+  EXPECT_TRUE(emf.GetData(&data));
+  EXPECT_EQ(data.size(), size);
+  emf.CloseEmf();
+
+  // Playback the data.
+  DOCINFO di = {0};
+  di.cbSize = sizeof(DOCINFO);
+  di.lpszDocName = L"Test Job";
+  int job_id = ::StartDoc(dc.Get(), &di);
+  EXPECT_TRUE(emf.CreateFromData(&data.front(), size));
+  EXPECT_TRUE(emf.SafePlayback(dc.Get()));
+  ::EndDoc(dc.Get());
+  // Since presumably the printer is not real, let us just delete the job from
+  // the queue.
+  HANDLE printer = NULL;
+  if (::OpenPrinter(L"UnitTest Printer", &printer, NULL)) {
+    ::SetJob(printer, job_id, 0, NULL, JOB_CONTROL_DELETE);
+    ClosePrinter(printer);
+  }
+}
+