Clean up transform methods in GraphicsContext.

Source/core/rendering/RenderBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 456 matching lines @@
             context->clipRoundedRect(RoundedRect(topCorner, topCornerRadii));
 
             IntRect bottomCorner(clipRect.rect().x(), rect.y(), rect.maxX() - clipRect.rect().x(), clipRect.rect().maxY() - rect.y());
             RoundedRect::Radii bottomCornerRadii;
             bottomCornerRadii.setBottomLeft(clipRect.radii().bottomLeft());
             context->clipRoundedRect(RoundedRect(bottomCorner, bottomCornerRadii));
         }
     }
 }
 
+// FIXME: See crbug.com/382491. The use of getCTM in this context is incorrect because the matrix returned does not
+// include scales applied at raster time, such as the device zoom.
 static LayoutRect shrinkRectByOnePixel(GraphicsContext* context, const LayoutRect& rect)
 {
     LayoutRect shrunkRect = rect;
     AffineTransform transform = context->getCTM();
     shrunkRect.inflateX(-static_cast<LayoutUnit>(ceil(1 / transform.xScale())));
     shrunkRect.inflateY(-static_cast<LayoutUnit>(ceil(1 / transform.yScale())));
     return shrunkRect;
 }
 
 LayoutRect RenderBoxModelObject::borderInnerRectAdjustedForBleedAvoidance(GraphicsContext* context, const LayoutRect& rect, BackgroundBleedAvoidance bleedAvoidance) const
@@ skipping 2060 matching lines @@
                     // of the box itself, which is always pixel-aligned.
                     IntRect rectToClipOut = border.rect();
 
                     // If the box is opaque, it is unnecessary to clip it out. However, doing so saves time
                     // when painting the shadow. On the other hand, it introduces subpixel gaps along the
                     // edges if they are not pixel-aligned. Those are avoided by insetting the clipping path
                     // by one pixel.
                     if (hasOpaqueBackground) {
                         // FIXME: The function to decide on the policy based on the transform should be a named function.
                         // FIXME: It's not clear if this check is right. What about integral scale factors?
+                        // FIXME: See crbug.com/382491. The use of getCTM may also be wrong because it does not include
+                        // device zoom applied at raster time.
                         AffineTransform transform = context->getCTM();
                         if (transform.a() != 1 || (transform.d() != 1 && transform.d() != -1) || transform.b() || transform.c())
                             rectToClipOut.inflate(-1);
                     }
 
                     if (!rectToClipOut.isEmpty()) {
                         context->clipOut(rectToClipOut);
                     }
                 }
             }
@@ skipping 159 matching lines @@
 
     LayoutUnit y = paddingTop() + borderTop();
 
     return currentStyle->isHorizontalWritingMode() ? LayoutRect(x, y, caretWidth, height) : LayoutRect(y, x, height, caretWidth);
 }
 
 bool RenderBoxModelObject::shouldAntialiasLines(GraphicsContext* context)
 {
     // FIXME: We may want to not antialias when scaled by an integral value,
     // and we may want to antialias when translated by a non-integral value.
+    // FIXME: See crbug.com/382491. getCTM does not include scale factors applied at raster time, such
+    // as device zoom.
     return !context->getCTM().isIdentityOrTranslationOrFlipped();
 }
 
 void RenderBoxModelObject::mapAbsoluteToLocalPoint(MapCoordinatesFlags mode, TransformState& transformState) const
 {
     // We don't expect to be called during layout.
     ASSERT(!view() || !view()->layoutStateEnabled());
 
     RenderObject* o = container();
     if (!o)
@@ skipping 90 matching lines @@
     ASSERT(!beforeChild || toBoxModelObject == beforeChild->parent());
     for (RenderObject* child = startChild; child && child != endChild; ) {
         // Save our next sibling as moveChildTo will clear it.
         RenderObject* nextSibling = child->nextSibling();
         moveChildTo(toBoxModelObject, child, beforeChild, fullRemoveInsert);
         child = nextSibling;
     }
 }
 
 } // namespace WebCore