Don't let rounding prematurely influence document size when printing

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1973 matching lines @@
 {
     updateDistribution();
     return ensureStyleResolver().styleForPage(pageIndex);
 }
 
 bool Document::isPageBoxVisible(int pageIndex)
 {
     return styleForPage(pageIndex)->visibility() != HIDDEN; // display property doesn't apply to @page.
 }
 
-void Document::pageSizeAndMarginsInPixels(int pageIndex, IntSize& pageSize, int& marginTop, int& marginRight, int& marginBottom, int& marginLeft)
+void Document::pageSizeAndMarginsInPixels(int pageIndex, FloatSize& pageSize, int& marginTop, int& marginRight, int& marginBottom, int& marginLeft)
 {
     RefPtr<ComputedStyle> style = styleForPage(pageIndex);
 
-    int width = pageSize.width();
-    int height = pageSize.height();
+    float width = pageSize.width();

[eae, 2016/07/12 22:26:39]

This does not look right. Pages are always in full pixels. Even if that hadn't
been the case we should not use floats for sizes in layout. That's what
LayoutUnit is for.

[rhogan, 2016/07/13 18:27:13]

The main user of this API is print_web_view_helper.cc, and it does need to
consume the un-snapped value so that it can scale it without losing accuracy.
Maybe I should rename the method to pageSizeAndMarginsInSubpixels?

[eae, 2016/07/13 20:42:26]

In that case we need to use either LayoutUnits or doubles. Floats are not
precise enough.

+    float height = pageSize.height();
     switch (style->getPageSizeType()) {
     case PAGE_SIZE_AUTO:
         break;
     case PAGE_SIZE_AUTO_LANDSCAPE:
         if (width < height)
             std::swap(width, height);
         break;
     case PAGE_SIZE_AUTO_PORTRAIT:
         if (width > height)
             std::swap(width, height);
         break;
     case PAGE_SIZE_RESOLVED: {
         FloatSize size = style->pageSize();
         width = size.width();
         height = size.height();
         break;
     }
     default:
         ASSERT_NOT_REACHED();
     }
-    pageSize = IntSize(width, height);
+    pageSize = FloatSize(width, height);
 
     // The percentage is calculated with respect to the width even for margin top and bottom.
     // http://www.w3.org/TR/CSS2/box.html#margin-properties
     marginTop = style->marginTop().isAuto() ? marginTop : intValueForLength(style->marginTop(), width);
     marginRight = style->marginRight().isAuto() ? marginRight : intValueForLength(style->marginRight(), width);
     marginBottom = style->marginBottom().isAuto() ? marginBottom : intValueForLength(style->marginBottom(), width);
     marginLeft = style->marginLeft().isAuto() ? marginLeft : intValueForLength(style->marginLeft(), width);
 }
 
 void Document::setIsViewSource(bool isViewSource)
@@ skipping 3999 matching lines @@
 }
 
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().getString().utf8().data());
 }
 #endif