SkPDF Metafile: fix recording canvas scaling

printing/pdf_metafile_skia.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "printing/pdf_metafile_skia.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/files/file_util.h"
 #include "base/metrics/histogram.h"
 #include "base/numerics/safe_conversions.h"
@@ skipping 18 matching lines @@
 #endif
 
 #if defined(OS_POSIX)
 #include "base/file_descriptor_posix.h"
 #endif
 
 namespace {
 // This struct represents all the data we need to draw and redraw this
 // page into a SkDocument.
 struct Page {
-  Page(const SkSize& page_size, const SkRect& content_area)
+  Page(const SkSize& page_size, const SkRect& content_area, float scale)
       : page_size_(page_size),
         content_area_(content_area),
+        scale_factor_(scale),
         content_(/*NULL*/) {}
   SkSize page_size_;
   SkRect content_area_;
+  float scale_factor_;
   skia::RefPtr<SkPicture> content_;
 };
 }  // namespace
 
 static bool WriteAssetToBuffer(const SkStreamAsset* asset,
                                void* buffer,
                                size_t size) {
   // Calling duplicate() keeps original asset state unchanged.
   scoped_ptr<SkStreamAsset> assetCopy(asset->duplicate());
   size_t length = assetCopy->getLength();
@@ skipping 30 matching lines @@
   return true;
 }
 
 bool PdfMetafileSkia::StartPage(const gfx::Size& page_size,
                                 const gfx::Rect& content_area,
                                 const float& scale_factor) {
   if (data_->recorder_.getRecordingCanvas())
     this->FinishPage();
   DCHECK(!data_->recorder_.getRecordingCanvas());
   SkSize sk_page_size = gfx::SizeFToSkSize(gfx::SizeF(page_size));
-  data_->pages_.push_back(Page(sk_page_size, gfx::RectToSkRect(content_area)));
-
-  SkCanvas* recordingCanvas = data_->recorder_.beginRecording(
-      sk_page_size.width(), sk_page_size.height(), NULL, 0);
-  // recordingCanvas is owned by the data_->recorder_.  No ref() necessary.
-  if (!recordingCanvas)
-    return false;
-  recordingCanvas->scale(scale_factor, scale_factor);
-  return true;
+  data_->pages_.push_back(
+      Page(sk_page_size, gfx::RectToSkRect(content_area), scale_factor));
+  DCHECK_GT(scale_factor, 0.0f);

[Vitaly Buka (NO REVIEWS), 2015/04/03 20:51:39]

DCHECK is unnecessary 
crash on divided by 0 is obviuos

+  // We scale the recording canvas's size so that
+  // canvas->getTotalMatrix() returns a value that ignores the scale
+  // factor.  We store the scale factor and re-apply it to the PDF
+  // Canvas later.  http://crbug.com/469656
+  // Recording canvas is owned by the data_->recorder_.  No ref() necessary.
+  return !!data_->recorder_.beginRecording(sk_page_size.width() / scale_factor,
+                                           sk_page_size.height() / scale_factor,
+                                           NULL, 0);
 }
 
 skia::PlatformCanvas* PdfMetafileSkia::GetVectorCanvasForNewPage(
     const gfx::Size& page_size,
     const gfx::Rect& content_area,
     const float& scale_factor) {
   if (!StartPage(page_size, content_area, scale_factor))
     return nullptr;
   return data_->recorder_.getRecordingCanvas();
 }
@@ skipping 14 matching lines @@
 
   if (data_->recorder_.getRecordingCanvas())
     this->FinishPage();
 
   SkDynamicMemoryWStream pdf_stream;
   skia::RefPtr<SkDocument> pdf_doc =
       skia::AdoptRef(SkDocument::CreatePDF(&pdf_stream));
   for (const auto& page : data_->pages_) {
     SkCanvas* canvas = pdf_doc->beginPage(
         page.page_size_.width(), page.page_size_.height(), &page.content_area_);
+    // No need to save/restore, since this canvas is not reused after endPage()
+    canvas->scale(page.scale_factor_, page.scale_factor_);
     canvas->drawPicture(page.content_.get());
     pdf_doc->endPage();
   }
   if (!pdf_doc->close())
     return false;
 
   data_->pdf_data_.reset(pdf_stream.detachAsStream());
   return true;
 }
 
@@ skipping 124 matching lines @@
 
   metafile->data_->pages_.push_back(page);
 
   if (!metafile->FinishDocument())  // Generate PDF.
     metafile.reset();
 
   return metafile.Pass();
 }
 
 }  // namespace printing