A better fix for scaling issue.

chrome/renderer/print_web_view_helper_win.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 "chrome/renderer/print_web_view_helper.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/process_util.h"
 #include "base/win/scoped_gdi_object.h"
 #include "base/win/scoped_hdc.h"
 #include "base/win/scoped_select_object.h"
 #include "chrome/common/print_messages.h"
-#include "printing/custom_scaling.h"
 #include "printing/metafile.h"
 #include "printing/metafile_impl.h"
 #include "printing/metafile_skia_wrapper.h"
 #include "printing/page_size_margins.h"
 #include "printing/units.h"
 #include "skia/ext/vector_canvas.h"
 #include "skia/ext/platform_device.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
 #include "ui/gfx/gdi_util.h"
@@ skipping 85 matching lines @@
 
   // Calculate the dpi adjustment.
   // Browser will render context using desired_dpi, so we need to calculate
   // adjustment factor to play content on the printer DC later during the
   // actual printing.
   double actual_shrink = static_cast<float>(params.params.desired_dpi /
                                             params.params.dpi);
   gfx::Size page_size_in_dpi;
   gfx::Rect content_area_in_dpi;
 
-  // If we are printing PDF, it may not fit into metafile using 72dpi.
-  // (Metafile is based on screen resolution here.)
-  // (See http://code.google.com/p/chromium-os/issues/detail?id=16088)
-  // If PDF plugin encounter this issue it will save custom scale in TLS,
-  // so we can apply the same scaling factor here.
-  // If will do so ONLY if default scaling does not work.
-  // TODO(gene): We should revisit this solution for the next versions.

[vandebo (ex-Chrome), 2012/05/08 18:25:01]

It might be good to leave this TODO.  Making the scale factor explicit in the
flow might be generally beneficial.

[gene, 2012/05/08 18:34:52]

Done.
Moved next to the code where we retrieve scale factor.

-  // Two possible solutions:
-  // We can create metafile of the right size (or resizable)
-  // https://code.google.com/p/chromium/issues/detail?id=126037
-  // or
-  // We should return scale factor all the way from the plugin:
-  //   webkit::ppapi::PluginInstance::PrintPDFOutput - scale calculated here
-  //   webkit::ppapi::PluginInstance::PrintPageHelper
-  //   webkit::ppapi::PluginInstance::PrintPage
-  //   webkit::ppapi::WebPluginImpl::printPage
-  //   WebKit::WebPluginContainerImpl::printPage
-  //   WebKit::ChromePluginPrintContext::spoolPage - always return 1.0 scale
-  //   WebKit::WebFrameImpl::printPage
-  //   PrintWebViewHelper::RenderPage
-  //   PrintWebViewHelper::PrintPageInternal
-
-  printing::ClearCustomPrintingPageScale();
-
   // Render page for printing.
   metafile.reset(RenderPage(params.params, page_number, frame, false,
                             metafile.get(), &actual_shrink, &page_size_in_dpi,
                             &content_area_in_dpi));
 
-  double custom_scale;
-  if (printing::GetCustomPrintingPageScale(&custom_scale)) {
-    actual_shrink = custom_scale;
-    printing::ClearCustomPrintingPageScale();
-  }
-
   // Close the device context to retrieve the compiled metafile.
   if (!metafile->FinishDocument())
     NOTREACHED();
 
   // Get the size of the compiled metafile.
   uint32 buf_size = metafile->GetDataSize();
   DCHECK_GT(buf_size, 128u);
 
   PrintHostMsg_DidPrintPage_Params page_params;
   page_params.data_size = buf_size;
@@ skipping 113 matching lines @@
     PrintHeaderAndFooter(canvas.get(), page_number + 1,
                          print_preview_context_.total_page_count(),
                          css_scale_factor * webkit_page_shrink_factor,
                          page_layout_in_points,
                          *header_footer_info_);
   }
 
   if (*actual_shrink <= 0 || webkit_scale_factor <= 0) {
     NOTREACHED() << "Printing page " << page_number << " failed.";
   } else {
-    // Update the dpi adjustment with the "page |actual_shrink|" calculated in
-    // webkit.
-    *actual_shrink /= (webkit_scale_factor * css_scale_factor);
+    // While rendering certain plugins (PDF) to metafile, we might need to
+    // set custom scale factor. Update |actual_shrink| with custom scale
+    // if it is set on canvas.
+    if (!printing::MetafileSkiaWrapper::GetCustomScaleOnCanvas(*canvas,
+        actual_shrink)) {

[vandebo (ex-Chrome), 2012/05/08 18:25:01]

nit: argument alignment

[gene, 2012/05/08 18:34:52]

Moved both on the next line. Aligning |actual_shrink| with *canvas pushed to 81
char line :(.

+      // Update the dpi adjustment with the "page |actual_shrink|" calculated in
+      // webkit.
+      *actual_shrink /= (webkit_scale_factor * css_scale_factor);
+    }
   }
 
   bool result = metafile->FinishPage();
   DCHECK(result);
 
   if (!params.supports_alpha_blend) {
     // PreviewMetafile (PDF) supports alpha blend, so we only hit this case
     // for NativeMetafile.
     DCHECK(!is_preview);
     skia::PlatformDevice* platform_device = skia::GetPlatformDevice(device);
@@ skipping 72 matching lines @@
     shared_buf.Unmap();
     return false;
   }
   shared_buf.GiveToProcess(base::GetCurrentProcessHandle(), shared_mem_handle);
   shared_buf.Unmap();
 
   Send(new PrintHostMsg_DuplicateSection(routing_id(), *shared_mem_handle,
                                          shared_mem_handle));
   return true;
 }