Print with the correct physical dimensions when specified

third_party/WebKit/Source/core/page/PrintContext.cpp

 /*
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2007 Apple Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "core/page/PrintContext.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutView.h"
 #include "platform/graphics/GraphicsContext.h"
 
 namespace blink {
 
-// By imaging to a width a little wider than the available pixels,
-// thin pages will be scaled down a little, matching the way they
-// print in IE and Camino. This lets them use fewer sheets than they
-// would otherwise, which is presumably why other browsers do this.
+// By shrinking to a width of 75% (1.333f) we will render the correct physical
+// dimensions in paged media (i.e. cm, pt,). The shrinkage used
+// to be 80% (1.25f) to match other browsers - they have since moved on.
 // Wide pages will be scaled down more than this.
-const float printingMinimumShrinkFactor = 1.25f;
+const float printingMinimumShrinkFactor = 1.333f;
 
 // This number determines how small we are willing to reduce the page content
 // in order to accommodate the widest line. If the page would have to be
 // reduced smaller to make the widest line fit, we just clip instead (this
-// behavior matches MacIE and Mozilla, at least)
+// behavior matches MacIE and Mozilla, at least).
+// TODO(rhogan): Decide if this quirk is still required.
 const float printingMaximumShrinkFactor = 2;
 
 PrintContext::PrintContext(LocalFrame* frame)
     : m_frame(frame)
     , m_isPrinting(false)
     , m_linkedDestinationsValid(false)
 {
 }
 
 PrintContext::~PrintContext()
@@ skipping 41 matching lines @@
 void PrintContext::computePageRectsWithPageSizeInternal(const FloatSize& pageSizeInPixels)
 {
     if (!m_frame->document() || !m_frame->view() || !m_frame->document()->layoutView())
         return;
 
     LayoutView* view = m_frame->document()->layoutView();
 
     IntRect docRect = view->documentRect();
 
     int pageWidth = pageSizeInPixels.width();
-    int pageHeight = pageSizeInPixels.height();
+    // We scaled with floating point arithmetic and need to ensure results like 13329.99
+    // are treated as 13330 so that we don't mistakenly assign an extra page for the
+    // stray pixel.
+    int pageHeight = pageSizeInPixels.height() + LayoutUnit::epsilon();
 
     bool isHorizontal = view->style()->isHorizontalWritingMode();
 
     int docLogicalHeight = isHorizontal ? docRect.height() : docRect.width();
     int pageLogicalHeight = isHorizontal ? pageHeight : pageWidth;
     int pageLogicalWidth = isHorizontal ? pageWidth : pageHeight;
 
     int inlineDirectionStart;
     int inlineDirectionEnd;
     int blockDirectionStart;
@@ skipping 201 matching lines @@
 
 DEFINE_TRACE(PrintContext)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_frame);
     visitor->trace(m_linkedDestinations);
 #endif
 }
 
 } // namespace blink