printing/emf_win.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "printing/emf_win.h"
   6
   7 #include "base/files/file.h"
   8 #include "base/files/file_path.h"
   9 #include "base/logging.h"
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/win/scoped_gdi_object.h"
  12 #include "base/win/scoped_hdc.h"
  13 #include "base/win/scoped_select_object.h"
  14 #include "skia/ext/platform_device.h"
  15 #include "third_party/skia/include/core/SkBitmap.h"
  16 #include "ui/gfx/codec/jpeg_codec.h"
  17 #include "ui/gfx/codec/png_codec.h"
  18 #include "ui/gfx/gdi_util.h"
  19 #include "ui/gfx/geometry/rect.h"
  20 #include "ui/gfx/geometry/size.h"
  21
  22 namespace {
  23
  24 int CALLBACK IsAlphaBlendUsedEnumProc(HDC,
  25                                       HANDLETABLE*,
  26                                       const ENHMETARECORD *record,
  27                                       int,
  28                                       LPARAM data) {
  29   bool* result = reinterpret_cast<bool*>(data);
  30   if (!result)
  31     return 0;
  32   switch (record->iType) {
  33     case EMR_ALPHABLEND: {
  34       *result = true;
  35       return 0;
  36       break;
  37     }
  38   }
  39   return 1;
  40 }
  41
  42 int CALLBACK RasterizeAlphaBlendProc(HDC metafile_dc,
  43                                      HANDLETABLE* handle_table,
  44                                      const ENHMETARECORD *record,
  45                                      int num_objects,
  46                                      LPARAM data) {
  47     HDC bitmap_dc = *reinterpret_cast<HDC*>(data);
  48     // Play this command to the bitmap DC.
  49     ::PlayEnhMetaFileRecord(bitmap_dc, handle_table, record, num_objects);
  50     switch (record->iType) {
  51     case EMR_ALPHABLEND: {
  52       const EMRALPHABLEND* alpha_blend =
  53           reinterpret_cast<const EMRALPHABLEND*>(record);
  54       // Don't modify transformation here.
  55       // Old implementation did reset transformations for DC to identity matrix.
  56       // That was not correct and cause some bugs, like unexpected cropping.
  57       // EMRALPHABLEND is rendered into bitmap and metafile contexts with
  58       // current transformation. If we don't touch them here BitBlt will copy
  59       // same areas.
  60       ::BitBlt(metafile_dc,
  61                alpha_blend->xDest,
  62                alpha_blend->yDest,
  63                alpha_blend->cxDest,
  64                alpha_blend->cyDest,
  65                bitmap_dc,
  66                alpha_blend->xDest,
  67                alpha_blend->yDest,
  68                SRCCOPY);
  69       break;
  70     }
  71     case EMR_CREATEBRUSHINDIRECT:
  72     case EMR_CREATECOLORSPACE:
  73     case EMR_CREATECOLORSPACEW:
  74     case EMR_CREATEDIBPATTERNBRUSHPT:
  75     case EMR_CREATEMONOBRUSH:
  76     case EMR_CREATEPALETTE:
  77     case EMR_CREATEPEN:
  78     case EMR_DELETECOLORSPACE:
  79     case EMR_DELETEOBJECT:
  80     case EMR_EXTCREATEFONTINDIRECTW:
  81       // Play object creation command only once.
  82       break;
  83
  84     default:
  85       // Play this command to the metafile DC.
  86       ::PlayEnhMetaFileRecord(metafile_dc, handle_table, record, num_objects);
  87       break;
  88     }
  89     return 1;  // Continue enumeration
  90 }
  91
  92 // Bitmapt for rasterization.
  93 class RasterBitmap {
  94  public:
  95   explicit RasterBitmap(const gfx::Size& raster_size)
  96       : saved_object_(NULL) {
  97     context_.Set(::CreateCompatibleDC(NULL));
  98     if (!context_.IsValid()) {
  99       NOTREACHED() << "Bitmap DC creation failed";
 100       return;
 101     }
 102     ::SetGraphicsMode(context_.Get(), GM_ADVANCED);
 103     void* bits = NULL;
 104     gfx::Rect bitmap_rect(raster_size);
 105     gfx::CreateBitmapHeader(raster_size.width(), raster_size.height(),
 106                             &header_.bmiHeader);
 107     bitmap_.Set(::CreateDIBSection(context_.Get(), &header_, DIB_RGB_COLORS,
 108                                    &bits, NULL, 0));
 109     if (!bitmap_)
 110       NOTREACHED() << "Raster bitmap creation for printing failed";
 111
 112     saved_object_ = ::SelectObject(context_.Get(), bitmap_);
 113     RECT rect = bitmap_rect.ToRECT();
 114     ::FillRect(context_.Get(), &rect,
 115                static_cast<HBRUSH>(::GetStockObject(WHITE_BRUSH)));
 116
 117   }
 118
 119   ~RasterBitmap() {
 120     ::SelectObject(context_.Get(), saved_object_);
 121   }
 122
 123   HDC context() const {
 124     return context_.Get();
 125   }
 126
 127   base::win::ScopedCreateDC context_;
 128   BITMAPINFO header_;
 129   base::win::ScopedBitmap bitmap_;
 130   HGDIOBJ saved_object_;
 131
 132  private:
 133   DISALLOW_COPY_AND_ASSIGN(RasterBitmap);
 134 };
 135
 136
 137
 138 }  // namespace
 139
 140 namespace printing {
 141
 142 bool DIBFormatNativelySupported(HDC dc, uint32 escape, const BYTE* bits,
 143                                 int size) {
 144   BOOL supported = FALSE;
 145   if (ExtEscape(dc, QUERYESCSUPPORT, sizeof(escape),
 146                 reinterpret_cast<LPCSTR>(&escape), 0, 0) > 0) {
 147     ExtEscape(dc, escape, size, reinterpret_cast<LPCSTR>(bits),
 148               sizeof(supported), reinterpret_cast<LPSTR>(&supported));
 149   }
 150   return !!supported;
 151 }
 152
 153 Emf::Emf() : emf_(NULL), hdc_(NULL) {
 154 }
 155
 156 Emf::~Emf() {
 157   Close();
 158 }
 159
 160 void Emf::Close() {
 161   DCHECK(!hdc_);
 162   if (emf_)
 163     DeleteEnhMetaFile(emf_);
 164   emf_ = NULL;
 165 }
 166
 167 bool Emf::InitToFile(const base::FilePath& metafile_path) {
 168   DCHECK(!emf_ && !hdc_);
 169   hdc_ = CreateEnhMetaFile(NULL, metafile_path.value().c_str(), NULL, NULL);
 170   DCHECK(hdc_);
 171   return hdc_ != NULL;
 172 }
 173
 174 bool Emf::InitFromFile(const base::FilePath& metafile_path) {
 175   DCHECK(!emf_ && !hdc_);
 176   emf_ = GetEnhMetaFile(metafile_path.value().c_str());
 177   DCHECK(emf_);
 178   return emf_ != NULL;
 179 }
 180
 181 bool Emf::Init() {
 182   DCHECK(!emf_ && !hdc_);
 183   hdc_ = CreateEnhMetaFile(NULL, NULL, NULL, NULL);
 184   DCHECK(hdc_);
 185   return hdc_ != NULL;
 186 }
 187
 188 bool Emf::InitFromData(const void* src_buffer, uint32 src_buffer_size) {
 189   DCHECK(!emf_ && !hdc_);
 190   emf_ = SetEnhMetaFileBits(src_buffer_size,
 191                             reinterpret_cast<const BYTE*>(src_buffer));
 192   return emf_ != NULL;
 193 }
 194
 195 bool Emf::FinishDocument() {
 196   DCHECK(!emf_ && hdc_);
 197   emf_ = CloseEnhMetaFile(hdc_);
 198   DCHECK(emf_);
 199   hdc_ = NULL;
 200   return emf_ != NULL;
 201 }
 202
 203 bool Emf::Playback(HDC hdc, const RECT* rect) const {
 204   DCHECK(emf_ && !hdc_);
 205   RECT bounds;
 206   if (!rect) {
 207     // Get the natural bounds of the EMF buffer.
 208     bounds = GetPageBounds(1).ToRECT();
 209     rect = &bounds;
 210   }
 211   return PlayEnhMetaFile(hdc, emf_, rect) != 0;
 212 }
 213
 214 bool Emf::SafePlayback(HDC context) const {
 215   DCHECK(emf_ && !hdc_);
 216   XFORM base_matrix;
 217   if (!GetWorldTransform(context, &base_matrix)) {
 218     NOTREACHED();
 219     return false;
 220   }
 221   Emf::EnumerationContext playback_context;
 222   playback_context.base_matrix = &base_matrix;
 223   gfx::Rect bound = GetPageBounds(1);
 224   RECT rect = bound.ToRECT();
 225   return bound.IsEmpty() ||
 226          EnumEnhMetaFile(context,
 227                          emf_,
 228                          &Emf::SafePlaybackProc,
 229                          reinterpret_cast<void*>(&playback_context),
 230                          &rect) != 0;
 231 }
 232
 233 gfx::Rect Emf::GetPageBounds(unsigned int page_number) const {
 234   DCHECK(emf_ && !hdc_);
 235   DCHECK_EQ(1U, page_number);
 236   ENHMETAHEADER header;
 237   if (GetEnhMetaFileHeader(emf_, sizeof(header), &header) != sizeof(header)) {
 238     NOTREACHED();
 239     return gfx::Rect();
 240   }
 241   // Add 1 to right and bottom because it's inclusive rectangle.
 242   // See ENHMETAHEADER.
 243   return gfx::Rect(header.rclBounds.left,
 244                    header.rclBounds.top,
 245                    header.rclBounds.right - header.rclBounds.left + 1,
 246                    header.rclBounds.bottom - header.rclBounds.top + 1);
 247 }
 248
 249 unsigned int Emf::GetPageCount() const {
 250   return 1;
 251 }
 252
 253 HDC Emf::context() const {
 254   return hdc_;
 255 }
 256
 257 uint32 Emf::GetDataSize() const {
 258   DCHECK(emf_ && !hdc_);
 259   return GetEnhMetaFileBits(emf_, 0, NULL);
 260 }
 261
 262 bool Emf::GetData(void* buffer, uint32 size) const {
 263   DCHECK(emf_ && !hdc_);
 264   DCHECK(buffer && size);
 265   uint32 size2 =
 266       GetEnhMetaFileBits(emf_, size, reinterpret_cast<BYTE*>(buffer));
 267   DCHECK(size2 == size);
 268   return size2 == size && size2 != 0;
 269 }
 270
 271 int CALLBACK Emf::SafePlaybackProc(HDC hdc,
 272                                    HANDLETABLE* handle_table,
 273                                    const ENHMETARECORD* record,
 274                                    int objects_count,
 275                                    LPARAM param) {
 276   Emf::EnumerationContext* context =
 277       reinterpret_cast<Emf::EnumerationContext*>(param);
 278   context->handle_table = handle_table;
 279   context->objects_count = objects_count;
 280   context->hdc = hdc;
 281   Record record_instance(record);
 282   bool success = record_instance.SafePlayback(context);
 283   DCHECK(success);
 284   return 1;
 285 }
 286
 287 Emf::EnumerationContext::EnumerationContext() {
 288   memset(this, 0, sizeof(*this));
 289 }
 290
 291 Emf::Record::Record(const ENHMETARECORD* record)
 292     : record_(record) {
 293   DCHECK(record_);
 294 }
 295
 296 bool Emf::Record::Play(Emf::EnumerationContext* context) const {
 297   return 0 != PlayEnhMetaFileRecord(context->hdc,
 298                                     context->handle_table,
 299                                     record_,
 300                                     context->objects_count);
 301 }
 302
 303 bool Emf::Record::SafePlayback(Emf::EnumerationContext* context) const {
 304   // For EMF field description, see [MS-EMF] Enhanced Metafile Format
 305   // Specification.
 306   //
 307   // This is the second major EMF breakage I get; the first one being
 308   // SetDCBrushColor/SetDCPenColor/DC_PEN/DC_BRUSH being silently ignored.
 309   //
 310   // This function is the guts of the fix for bug 1186598. Some printer drivers
 311   // somehow choke on certain EMF records, but calling the corresponding
 312   // function directly on the printer HDC is fine. Still, playing the EMF record
 313   // fails. Go figure.
 314   //
 315   // The main issue is that SetLayout is totally unsupported on these printers
 316   // (HP 4500/4700). I used to call SetLayout and I stopped. I found out this is
 317   // not sufficient because GDI32!PlayEnhMetaFile internally calls SetLayout(!)
 318   // Damn.
 319   //
 320   // So I resorted to manually parse the EMF records and play them one by one.
 321   // The issue with this method compared to using PlayEnhMetaFile to play back
 322   // an EMF buffer is that the later silently fixes the matrix to take in
 323   // account the matrix currently loaded at the time of the call.
 324   // The matrix magic is done transparently when using PlayEnhMetaFile but since
 325   // I'm processing one field at a time, I need to do the fixup myself. Note
 326   // that PlayEnhMetaFileRecord doesn't fix the matrix correctly even when
 327   // called inside an EnumEnhMetaFile loop. Go figure (bis).
 328   //
 329   // So when I see a EMR_SETWORLDTRANSFORM and EMR_MODIFYWORLDTRANSFORM, I need
 330   // to fix the matrix according to the matrix previously loaded before playing
 331   // back the buffer. Otherwise, the previously loaded matrix would be ignored
 332   // and the EMF buffer would always be played back at its native resolution.
 333   // Duh.
 334   //
 335   // I also use this opportunity to skip over eventual EMR_SETLAYOUT record that
 336   // could remain.
 337   //
 338   // Another tweak we make is for JPEGs/PNGs in calls to StretchDIBits.
 339   // (Our Pepper plugin code uses a JPEG). If the printer does not support
 340   // JPEGs/PNGs natively we decompress the JPEG/PNG and then set it to the
 341   // device.
 342   // TODO(sanjeevr): We should also add JPEG/PNG support for SetSIBitsToDevice
 343   //
 344   // We also process any custom EMR_GDICOMMENT records which are our
 345   // placeholders for StartPage and EndPage.
 346   // Note: I should probably care about view ports and clipping, eventually.
 347   bool res = false;
 348   const XFORM* base_matrix = context->base_matrix;
 349   switch (record()->iType) {
 350     case EMR_STRETCHDIBITS: {
 351       const EMRSTRETCHDIBITS * sdib_record =
 352           reinterpret_cast<const EMRSTRETCHDIBITS*>(record());
 353       const BYTE* record_start = reinterpret_cast<const BYTE *>(record());
 354       const BITMAPINFOHEADER *bmih =
 355           reinterpret_cast<const BITMAPINFOHEADER *>(record_start +
 356                                                      sdib_record->offBmiSrc);
 357       const BYTE* bits = record_start + sdib_record->offBitsSrc;
 358       bool play_normally = true;
 359       res = false;
 360       HDC hdc = context->hdc;
 361       scoped_ptr<SkBitmap> bitmap;
 362       if (bmih->biCompression == BI_JPEG) {
 363         if (!DIBFormatNativelySupported(hdc, CHECKJPEGFORMAT, bits,
 364                                         bmih->biSizeImage)) {
 365           play_normally = false;
 366           bitmap.reset(gfx::JPEGCodec::Decode(bits, bmih->biSizeImage));
 367         }
 368       } else if (bmih->biCompression == BI_PNG) {
 369         if (!DIBFormatNativelySupported(hdc, CHECKPNGFORMAT, bits,
 370                                         bmih->biSizeImage)) {
 371           play_normally = false;
 372           bitmap.reset(new SkBitmap());
 373           gfx::PNGCodec::Decode(bits, bmih->biSizeImage, bitmap.get());
 374         }
 375       }
 376       if (!play_normally) {
 377         DCHECK(bitmap.get());
 378         if (bitmap.get()) {
 379           SkAutoLockPixels lock(*bitmap.get());
 380           DCHECK_EQ(bitmap->colorType(), kN32_SkColorType);
 381           const uint32_t* pixels =
 382               static_cast<const uint32_t*>(bitmap->getPixels());
 383           if (pixels == NULL) {
 384             NOTREACHED();
 385             return false;
 386           }
 387           BITMAPINFOHEADER bmi = {0};
 388           gfx::CreateBitmapHeader(bitmap->width(), bitmap->height(), &bmi);
 389           res = (0 != StretchDIBits(hdc, sdib_record->xDest, sdib_record->yDest,
 390                                     sdib_record->cxDest,
 391                                     sdib_record->cyDest, sdib_record->xSrc,
 392                                     sdib_record->ySrc,
 393                                     sdib_record->cxSrc, sdib_record->cySrc,
 394                                     pixels,
 395                                     reinterpret_cast<const BITMAPINFO *>(&bmi),
 396                                     sdib_record->iUsageSrc,
 397                                     sdib_record->dwRop));
 398         }
 399       } else {
 400         res = Play(context);
 401       }
 402       break;
 403     }
 404     case EMR_SETWORLDTRANSFORM: {
 405       DCHECK_EQ(record()->nSize, sizeof(DWORD) * 2 + sizeof(XFORM));
 406       const XFORM* xform = reinterpret_cast<const XFORM*>(record()->dParm);
 407       HDC hdc = context->hdc;
 408       if (base_matrix) {
 409         res = 0 != SetWorldTransform(hdc, base_matrix) &&
 410                    ModifyWorldTransform(hdc, xform, MWT_LEFTMULTIPLY);
 411       } else {
 412         res = 0 != SetWorldTransform(hdc, xform);
 413       }
 414       break;
 415     }
 416     case EMR_MODIFYWORLDTRANSFORM: {
 417       DCHECK_EQ(record()->nSize,
 418                 sizeof(DWORD) * 2 + sizeof(XFORM) + sizeof(DWORD));
 419       const XFORM* xform = reinterpret_cast<const XFORM*>(record()->dParm);
 420       const DWORD* option = reinterpret_cast<const DWORD*>(xform + 1);
 421       HDC hdc = context->hdc;
 422       switch (*option) {
 423         case MWT_IDENTITY:
 424           if (base_matrix) {
 425             res = 0 != SetWorldTransform(hdc, base_matrix);
 426           } else {
 427             res = 0 != ModifyWorldTransform(hdc, xform, MWT_IDENTITY);
 428           }
 429           break;
 430         case MWT_LEFTMULTIPLY:
 431         case MWT_RIGHTMULTIPLY:
 432           res = 0 != ModifyWorldTransform(hdc, xform, *option);
 433           break;
 434         case 4:  // MWT_SET
 435           if (base_matrix) {
 436             res = 0 != SetWorldTransform(hdc, base_matrix) &&
 437                        ModifyWorldTransform(hdc, xform, MWT_LEFTMULTIPLY);
 438           } else {
 439             res = 0 != SetWorldTransform(hdc, xform);
 440           }
 441           break;
 442         default:
 443           res = false;
 444           break;
 445       }
 446       break;
 447     }
 448     case EMR_SETLAYOUT:
 449       // Ignore it.
 450       res = true;
 451       break;
 452     default: {
 453       res = Play(context);
 454       break;
 455     }
 456   }
 457   return res;
 458 }
 459
 460 bool Emf::StartPage(const gfx::Size& /*page_size*/,
 461                     const gfx::Rect& /*content_area*/,
 462                     const float& /*scale_factor*/) {
 463   return true;
 464 }
 465
 466 bool Emf::FinishPage() {
 467   return true;
 468 }
 469
 470 Emf::Enumerator::Enumerator(const Emf& emf, HDC context, const RECT* rect) {
 471   items_.clear();
 472   if (!EnumEnhMetaFile(context,
 473                        emf.emf(),
 474                        &Emf::Enumerator::EnhMetaFileProc,
 475                        reinterpret_cast<void*>(this),
 476                        rect)) {
 477     NOTREACHED();
 478     items_.clear();
 479   }
 480   DCHECK_EQ(context_.hdc, context);
 481 }
 482
 483 Emf::Enumerator::~Enumerator() {
 484 }
 485
 486 Emf::Enumerator::const_iterator Emf::Enumerator::begin() const {
 487   return items_.begin();
 488 }
 489
 490 Emf::Enumerator::const_iterator Emf::Enumerator::end() const {
 491   return items_.end();
 492 }
 493
 494 int CALLBACK Emf::Enumerator::EnhMetaFileProc(HDC hdc,
 495                                               HANDLETABLE* handle_table,
 496                                               const ENHMETARECORD* record,
 497                                               int objects_count,
 498                                               LPARAM param) {
 499   Enumerator& emf = *reinterpret_cast<Enumerator*>(param);
 500   if (!emf.context_.handle_table) {
 501     DCHECK(!emf.context_.handle_table);
 502     DCHECK(!emf.context_.objects_count);
 503     emf.context_.handle_table = handle_table;
 504     emf.context_.objects_count = objects_count;
 505     emf.context_.hdc = hdc;
 506   } else {
 507     DCHECK_EQ(emf.context_.handle_table, handle_table);
 508     DCHECK_EQ(emf.context_.objects_count, objects_count);
 509     DCHECK_EQ(emf.context_.hdc, hdc);
 510   }
 511   emf.items_.push_back(Record(record));
 512   return 1;
 513 }
 514
 515 bool Emf::IsAlphaBlendUsed() const {
 516   bool result = false;
 517   ::EnumEnhMetaFile(NULL,
 518                     emf(),
 519                     &IsAlphaBlendUsedEnumProc,
 520                     &result,
 521                     NULL);
 522   return result;
 523 }
 524
 525 scoped_ptr<Emf> Emf::RasterizeMetafile(int raster_area_in_pixels) const {
 526   gfx::Rect page_bounds = GetPageBounds(1);
 527   gfx::Size page_size(page_bounds.size());
 528   if (page_size.GetArea() <= 0) {
 529     NOTREACHED() << "Metafile is empty";
 530     page_bounds = gfx::Rect(1, 1);
 531   }
 532
 533   float scale = sqrt(float(raster_area_in_pixels) / page_size.GetArea());
 534   page_size.set_width(std::max<int>(1, page_size.width() * scale));
 535   page_size.set_height(std::max<int>(1, page_size.height() * scale));
 536
 537
 538   RasterBitmap bitmap(page_size);
 539
 540   gfx::Rect bitmap_rect(page_size);
 541   RECT rect = bitmap_rect.ToRECT();
 542   Playback(bitmap.context(), &rect);
 543
 544   scoped_ptr<Emf> result(new Emf);
 545   result->Init();
 546   HDC hdc = result->context();
 547   DCHECK(hdc);
 548   skia::InitializeDC(hdc);
 549
 550   // Params are ignored.
 551   result->StartPage(page_bounds.size(), page_bounds, 1);
 552
 553   ::ModifyWorldTransform(hdc, NULL, MWT_IDENTITY);
 554   XFORM xform = {
 555     float(page_bounds.width()) / bitmap_rect.width(), 0,
 556     0, float(page_bounds.height()) / bitmap_rect.height(),
 557     static_cast<float>(page_bounds.x()),
 558     static_cast<float>(page_bounds.y()),
 559   };
 560   ::SetWorldTransform(hdc, &xform);
 561   ::BitBlt(hdc, 0, 0, bitmap_rect.width(), bitmap_rect.height(),
 562            bitmap.context(), bitmap_rect.x(), bitmap_rect.y(), SRCCOPY);
 563
 564   result->FinishPage();
 565   result->FinishDocument();
 566
 567   return result.Pass();
 568 }
 569
 570 scoped_ptr<Emf> Emf::RasterizeAlphaBlend() const {
 571   gfx::Rect page_bounds = GetPageBounds(1);
 572   if (page_bounds.size().GetArea() <= 0) {
 573     NOTREACHED() << "Metafile is empty";
 574     page_bounds = gfx::Rect(1, 1);
 575   }
 576
 577   RasterBitmap bitmap(page_bounds.size());
 578
 579   // Map metafile page_bounds.x(), page_bounds.y() to bitmap 0, 0.
 580   XFORM xform = {1,
 581                  0,
 582                  0,
 583                  1,
 584                  static_cast<float>(-page_bounds.x()),
 585                  static_cast<float>(-page_bounds.y())};
 586   ::SetWorldTransform(bitmap.context(), &xform);
 587
 588   scoped_ptr<Emf> result(new Emf);
 589   result->Init();
 590   HDC hdc = result->context();
 591   DCHECK(hdc);
 592   skia::InitializeDC(hdc);
 593
 594   HDC bitmap_dc = bitmap.context();
 595   RECT rect = page_bounds.ToRECT();
 596   ::EnumEnhMetaFile(hdc, emf(), &RasterizeAlphaBlendProc, &bitmap_dc, &rect);
 597
 598   result->FinishDocument();
 599
 600   return result.Pass();
 601 }
 602
 603
 604 }  // namespace printing