ugrr... Fixing printing scaling again.

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 82 matching lines @@
   skia::InitializeDC(metafile->context());
 
   int page_number = params.page_number;
 
   // 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);
-  if (print_for_preview_) {
-    // While printing from the preview, we are using PDF to print.
-    // It creates a temp metafile based on screen DC. The standard scale factor
-    // may not fit an entire content of the PDF to the metafile. It will cause
-    // output to be cutoff.
-    // (See http://code.google.com/p/chromium-os/issues/detail?id=16088 and
-    // related Chrome bugs)
-    // In such case we need to calculate the same scale ratio PDF plugin will
-    // calculate during printing.
-    // TODO(gene): Revisit current implementation and address comments below.
-    // (http://code.google.com/p/chromium/issues/detail?id=123408)
-    // Ideally, we should return this parameter from the plugin to avoid code
-    // duplication. However, currently the call stack involves WebKit and at
-    // some point shrink factor was cutoff and always returns 1.0.
-    //   webkit::ppapi::PluginInstance::PrintPDFOutput - ratio 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
-    //
-    // Another solution is to build in scaling factor into metafile itself
-    // (for example, GDI comments), and make metafile playback to take care of
-    // scaling automatically.
-    actual_shrink = gfx::CalculatePageScale(
-        metafile->context(),
-        params.params.content_size.width(),
-        params.params.content_size.height());
-  }
-
   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.

[Albert Bodenhamer, 2012/05/02 23:49:18]

In my dream world we can just create a DC that matches the capabilities of the
page and avoid the need to do funky things with scaling factors and viewports.

Perhaps create a bug for the TODO to serve as a place for discussion?

+  // Ideal way would be to 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 208 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;
 }