If the <use> is hidden and the child of it is visible, should clip the non-resource

third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceClipper.cpp

 /*
  * Copyright (C) 2004, 2005, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2011 Dirk Schulze <krit@webkit.org>
  *
  * 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.
@@ skipping 68 matching lines @@
             continue;
         // Only shapes or paths are supported for direct clipping. We need to fallback to masking for texts.
         if (childLayoutObject->isSVGText()) {
             m_clipContentPath.clear();
             return false;
         }
         if (!childElement->isSVGGraphicsElement())
             continue;
 
         const ComputedStyle* style = childLayoutObject->style();
-        if (!style || style->display() == NONE || style->visibility() != VISIBLE)
+        if (!style || style->display() == NONE)

[fs, 2016/04/19 10:17:27]

I went looking through the various specs (CSS Masking [1], SVG 1.1 2ed [2]), and
they all said:

"If a child element is made invisible by display or visibility it does not
contribute to the clipping path."

So now I'm a little bit confused as to what the current state of affairs is
here... So I went digging and found [3] - and nothing changing that behavior
again. So I think the behavior should not change (except for <use> of course.)

(If you want to reference anything here, then [1] might be the most relevant -
more so than the <use> element reference.)

[1] https://drafts.fxtf.org/css-masking-1/#ClipPathElement
[2] https://www.w3.org/TR/SVG/masking.html#EstablishingANewClippingPath
[3] https://www.w3.org/2009/07/01-svg-minutes.html#item02

[hyunjunekim2, 2016/04/27 12:18:40]

So Just check child of <use> element whether visible or not.

             continue;
 
         // Current shape in clip-path gets clipped too. Fallback to masking.
         if (style->svgStyle().hasClipper()) {
             m_clipContentPath.clear();
             return false;
         }
 
         // First clip shape.
         if (m_clipContentPath.isEmpty()) {
@@ skipping 73 matching lines @@
 
     for (SVGElement* childElement = Traversal<SVGElement>::firstChild(*element()); childElement; childElement = Traversal<SVGElement>::nextSibling(*childElement)) {
         LayoutObject* layoutObject = childElement->layoutObject();
         if (!layoutObject)
             continue;
 
         const ComputedStyle* style = layoutObject->style();
         if (!style || style->display() == NONE || style->visibility() != VISIBLE)
             continue;
 
         bool isUseElement = isSVGUseElement(*childElement);

[fs, 2016/04/19 10:17:27]

You need to fix this code-path too. The easiest way to end up in this code-path
is likely to use a nested <clipPath>:

<clipPath id="nested">
...
</clipPath>
<clipPath id="clip" clip-path="url(#nested)">
...
</clipPath>

[hyunjunekim2, 2016/04/27 12:18:40]

Added a test and fixed it.

         if (isUseElement) {
             const SVGGraphicsElement* clippingElement = toSVGUseElement(*childElement).targetGraphicsElementForClipping();
             if (!clippingElement)
                 continue;
 
             layoutObject = clippingElement->layoutObject();
             if (!layoutObject)
                 continue;
         }
 
@@ skipping 20 matching lines @@
 void LayoutSVGResourceClipper::calculateClipContentPaintInvalidationRect()
 {
     // This is a rough heuristic to appraise the clip size and doesn't consider clip on clip.
     for (SVGElement* childElement = Traversal<SVGElement>::firstChild(*element()); childElement; childElement = Traversal<SVGElement>::nextSibling(*childElement)) {
         LayoutObject* layoutObject = childElement->layoutObject();
         if (!layoutObject)
             continue;
         if (!layoutObject->isSVGShape() && !layoutObject->isSVGText() && !isSVGUseElement(*childElement))
             continue;
         const ComputedStyle* style = layoutObject->style();
-        if (!style || style->display() == NONE || style->visibility() != VISIBLE)
+        if (!style || style->display() == NONE)

[fs, 2016/04/19 10:17:27]

Same comment here as in calculateClipContentPathIfNeeded().

[hyunjunekim2, 2016/04/27 12:18:40]

Done.

             continue;
+
+        if (isSVGUseElement(*childElement) && !toSVGUseElement(*childElement).isVisibleGraphicsElementForClipping())
+            continue;
+
         m_clipBoundaries.unite(layoutObject->localToSVGParentTransform().mapRect(layoutObject->paintInvalidationRectInLocalSVGCoordinates()));
     }
     m_clipBoundaries = toSVGClipPathElement(element())->calculateAnimatedLocalTransform().mapRect(m_clipBoundaries);
 }
 
 bool LayoutSVGResourceClipper::hitTestClipContent(const FloatRect& objectBoundingBox, const FloatPoint& nodeAtPoint)
 {
     FloatPoint point = nodeAtPoint;
     if (!SVGLayoutSupport::pointInClippingArea(this, point))
         return false;
@@ skipping 40 matching lines @@
         AffineTransform transform;
         transform.translate(objectBoundingBox.x(), objectBoundingBox.y());
         transform.scaleNonUniform(objectBoundingBox.width(), objectBoundingBox.height());
         return transform.mapRect(m_clipBoundaries);
     }
 
     return m_clipBoundaries;
 }
 
 } // namespace blink