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* Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
* Portions are Copyright (C) 1998 Netscape Communications Corporation.
* Other contributors:
* Robert O'Callahan <>
* David Baron <>
* Christian Biesinger <>
* Randall Jesup <>
* Roland Mainz <>
* Josh Soref <>
* Boris Zbarsky <>
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 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
* Lesser General Public License for more details.
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
* Alternatively, the contents of this file may be used under the terms
* of either the Mozilla Public License Version 1.1, found at
* (the "MPL") or the GNU General Public
* License Version 2.0, found at
* (the "GPL"), in which case the provisions of the MPL or the GPL are
* applicable instead of those above. If you wish to allow use of your
* version of this file only under the terms of one of those two
* licenses (the MPL or the GPL) and not to allow others to use your
* version of this file under the LGPL, indicate your decision by
* deletingthe provisions above and replace them with the notice and
* other provisions required by the MPL or the GPL, as the case may be.
* If you do not delete the provisions above, a recipient may use your
* version of this file under any of the LGPL, the MPL or the GPL.
#include "config.h"
#include "core/rendering/RenderLayerClipper.h"
#include "core/frame/Settings.h"
#include "core/rendering/RenderLayer.h"
#include "core/rendering/RenderView.h"
namespace blink {
static void adjustClipRectsForChildren(const RenderObject& renderer, ClipRects& clipRects)
EPosition position =>position();
// A fixed object is essentially the root of its containing block hierarchy, so when
// we encounter such an object, we reset our clip rects to the fixedClipRect.
if (position == FixedPosition) {
} else if (position == RelativePosition) {
} else if (position == AbsolutePosition) {
static void applyClipRects(const ClipRectsContext& context, RenderObject& renderer, LayoutPoint offset, ClipRects& clipRects)
ASSERT(renderer.hasOverflowClip() || renderer.hasClip());
RenderView* view = renderer.view();
if (clipRects.fixed() && context.rootLayer->renderer() == view)
offset -= view->frameView()->scrollOffsetForFixedPosition();
if (renderer.hasOverflowClip()) {
ClipRect newOverflowClip = toRenderBox(renderer).overflowClipRect(offset, context.scrollbarRelevancy);
clipRects.setOverflowClipRect(intersection(newOverflowClip, clipRects.overflowClipRect()));
if (renderer.isPositioned())
clipRects.setPosClipRect(intersection(newOverflowClip, clipRects.posClipRect()));
if (renderer.hasClip()) {
LayoutRect newClip = toRenderBox(renderer).clipRect(offset);
clipRects.setPosClipRect(intersection(newClip, clipRects.posClipRect()));
clipRects.setOverflowClipRect(intersection(newClip, clipRects.overflowClipRect()));
clipRects.setFixedClipRect(intersection(newClip, clipRects.fixedClipRect()));
RenderLayerClipper::RenderLayerClipper(RenderLayerModelObject& renderer)
: m_renderer(renderer)
ClipRects* RenderLayerClipper::clipRectsIfCached(const ClipRectsContext& context) const
if (!m_cache)
return 0;
ClipRectsCache::Entry& entry = m_cache->get(context.cacheSlot);
// FIXME: We used to ASSERT that we always got a consistent root layer.
// We should add a test that has an inconsistent root. See
// for an example.
if (context.rootLayer != entry.root)
return 0;
ASSERT(entry.scrollbarRelevancy == context.scrollbarRelevancy);
// This code is useful to check cached clip rects, but is too expensive to leave enabled in debug builds by default.
ClipRectsContext tempContext(context);
tempContext.cacheSlot = UncachedClipRects;
ClipRects clipRects;
calculateClipRects(tempContext, clipRects);
ASSERT(clipRects == *entry.clipRects);
return entry.clipRects.get();
ClipRects* RenderLayerClipper::storeClipRectsInCache(const ClipRectsContext& context, ClipRects* parentClipRects, const ClipRects& clipRects) const
ClipRectsCache::Entry& entry = cache().get(context.cacheSlot);
entry.root = context.rootLayer;
entry.scrollbarRelevancy = context.scrollbarRelevancy;
if (parentClipRects) {
// If our clip rects match the clip rects of our parent, we share storage.
if (clipRects == *parentClipRects) {
entry.clipRects = parentClipRects;
return parentClipRects;
entry.clipRects = ClipRects::create(clipRects);
return entry.clipRects.get();
ClipRects* RenderLayerClipper::getClipRects(const ClipRectsContext& context) const
if (ClipRects* result = clipRectsIfCached(context))
return result;
// Note that it's important that we call getClipRects on our parent
// before we call calculateClipRects so that calculateClipRects will hit
// the cache.
ClipRects* parentClipRects = 0;
if (context.rootLayer != m_renderer.layer() && m_renderer.layer()->parent())
parentClipRects = m_renderer.layer()->parent()->clipper().getClipRects(context);
ClipRects clipRects;
calculateClipRects(context, clipRects);
return storeClipRectsInCache(context, parentClipRects, clipRects);
void RenderLayerClipper::clearClipRectsIncludingDescendants()
m_cache = nullptr;
for (RenderLayer* layer = m_renderer.layer()->firstChild(); layer; layer = layer->nextSibling())
void RenderLayerClipper::clearClipRectsIncludingDescendants(ClipRectsCacheSlot cacheSlot)
if (m_cache)
for (RenderLayer* layer = m_renderer.layer()->firstChild(); layer; layer = layer->nextSibling())
LayoutRect RenderLayerClipper::childrenClipRect() const
// FIXME: border-radius not accounted for.
// FIXME: Regions not accounted for.
RenderLayer* clippingRootLayer = clippingRootForPainting();
LayoutRect layerBounds;
ClipRect backgroundRect, foregroundRect, outlineRect;
// Need to use uncached clip rects, because the value of 'dontClipToOverflow' may be different from the painting path (<rdar://problem/11844909>).
ClipRectsContext context(clippingRootLayer, UncachedClipRects);
calculateRects(context, m_renderer.view()->unscaledDocumentRect(), layerBounds, backgroundRect, foregroundRect, outlineRect);
return clippingRootLayer->renderer()->localToAbsoluteQuad(FloatQuad(foregroundRect.rect())).enclosingBoundingBox();
LayoutRect RenderLayerClipper::localClipRect() const
// FIXME: border-radius not accounted for.
RenderLayer* clippingRootLayer = clippingRootForPainting();
LayoutRect layerBounds;
ClipRect backgroundRect, foregroundRect, outlineRect;
ClipRectsContext context(clippingRootLayer, PaintingClipRects);
calculateRects(context, PaintInfo::infiniteRect(), layerBounds, backgroundRect, foregroundRect, outlineRect);
LayoutRect clipRect = backgroundRect.rect();
if (clipRect == PaintInfo::infiniteRect())
return clipRect;
LayoutPoint clippingRootOffset;
m_renderer.layer()->convertToLayerCoords(clippingRootLayer, clippingRootOffset);
return clipRect;
void RenderLayerClipper::calculateRects(const ClipRectsContext& context, const LayoutRect& paintDirtyRect, LayoutRect& layerBounds,
ClipRect& backgroundRect, ClipRect& foregroundRect, ClipRect& outlineRect, const LayoutPoint* offsetFromRoot) const
bool isClippingRoot = m_renderer.layer() == context.rootLayer;
if (!isClippingRoot && m_renderer.layer()->parent()) {
backgroundRect = backgroundClipRect(context);
} else {
backgroundRect = paintDirtyRect;
foregroundRect = backgroundRect;
outlineRect = backgroundRect;
LayoutPoint offset;
if (offsetFromRoot)
offset = *offsetFromRoot;
m_renderer.layer()->convertToLayerCoords(context.rootLayer, offset);
layerBounds = LayoutRect(offset, m_renderer.layer()->size());
// Update the clip rects that will be passed to child layers.
if (m_renderer.hasOverflowClip()) {
// This layer establishes a clip of some kind.
if (!isClippingRoot || context.respectOverflowClip == RespectOverflowClip) {
foregroundRect.intersect(toRenderBox(m_renderer).overflowClipRect(offset, context.scrollbarRelevancy));
if (>hasBorderRadius())
// If we establish an overflow clip at all, then go ahead and make sure our background
// rect is intersected with our layer's bounds including our visual overflow,
// since any visual overflow like box-shadow or border-outset is not clipped by overflow:auto/hidden.
if (toRenderBox(m_renderer).hasVisualOverflow()) {
// FIXME: Perhaps we should be propagating the borderbox as the clip rect for children, even though
// we may need to inflate our clip specifically for shadows or outsets.
// FIXME: Does not do the right thing with CSS regions yet, since we don't yet factor in the
// individual region boxes as overflow.
LayoutRect layerBoundsWithVisualOverflow = toRenderBox(m_renderer).visualOverflowRect();
toRenderBox(m_renderer).flipForWritingMode(layerBoundsWithVisualOverflow); // Layers are in physical coordinates, so the overflow has to be flipped.
if (!isClippingRoot || context.respectOverflowClip == RespectOverflowClip)
} else {
LayoutRect bounds = toRenderBox(m_renderer).borderBoxRect();
if (!isClippingRoot || context.respectOverflowClip == RespectOverflowClip)
// CSS clip (different than clipping due to overflow) can clip to any box, even if it falls outside of the border box.
if (m_renderer.hasClip()) {
// Clip applies to *us* as well, so go ahead and update the damageRect.
LayoutRect newPosClip = toRenderBox(m_renderer).clipRect(offset);
void RenderLayerClipper::calculateClipRects(const ClipRectsContext& context, ClipRects& clipRects) const
bool rootLayerScrolls = m_renderer.document().settings() && m_renderer.document().settings()->rootLayerScrolls();
if (!m_renderer.layer()->parent() && !rootLayerScrolls) {
// The root layer's clip rect is always infinite.
bool isClippingRoot = m_renderer.layer() == context.rootLayer;
// For transformed layers, the root layer was shifted to be us, so there is no need to
// examine the parent. We want to cache clip rects with us as the root.
RenderLayer* parentLayer = !isClippingRoot ? m_renderer.layer()->parent() : 0;
// Ensure that our parent's clip has been calculated so that we can examine the values.
if (parentLayer) {
// FIXME: Why don't we just call getClipRects here?
if (context.usesCache() && parentLayer->clipper().cachedClipRects(context)) {
clipRects = *parentLayer->clipper().cachedClipRects(context);
} else {
parentLayer->clipper().calculateClipRects(context, clipRects);
} else {
adjustClipRectsForChildren(m_renderer, clipRects);
// FIXME: This logic looks wrong. We'll apply overflow clip rects even if we were told to IgnoreOverflowClip if m_renderer.hasClip().
if ((m_renderer.hasOverflowClip() && (context.respectOverflowClip == RespectOverflowClip || !isClippingRoot)) || m_renderer.hasClip()) {
// This offset cannot use convertToLayerCoords, because sometimes our rootLayer may be across
// some transformed layer boundary, for example, in the RenderLayerCompositor overlapMap, where
// clipRects are needed in view space.
applyClipRects(context, m_renderer, roundedLayoutPoint(m_renderer.localToContainerPoint(FloatPoint(), context.rootLayer->renderer())), clipRects);
static ClipRect backgroundClipRectForPosition(const ClipRects& parentRects, EPosition position)
if (position == FixedPosition)
return parentRects.fixedClipRect();
if (position == AbsolutePosition)
return parentRects.posClipRect();
return parentRects.overflowClipRect();
ClipRect RenderLayerClipper::backgroundClipRect(const ClipRectsContext& context) const
ClipRects parentClipRects;
if (m_renderer.layer() == context.rootLayer)
m_renderer.layer()->parent()->clipper().getOrCalculateClipRects(context, parentClipRects);
ClipRect result = backgroundClipRectForPosition(parentClipRects,>position());
// Note: infinite clipRects should not be scrolled here, otherwise they will accidentally no longer be considered infinite.
if (parentClipRects.fixed() && context.rootLayer->renderer() == m_renderer.view() && result != PaintInfo::infiniteRect())
return result;
void RenderLayerClipper::getOrCalculateClipRects(const ClipRectsContext& context, ClipRects& clipRects) const
if (context.usesCache())
clipRects = *getClipRects(context);
calculateClipRects(context, clipRects);
RenderLayer* RenderLayerClipper::clippingRootForPainting() const
const RenderLayer* current = m_renderer.layer();
// FIXME: getting rid of current->hasCompositedLayerMapping() here breaks the
// compositing/backing/no-backing-for-clip.html layout test, because there is a
// "composited but paints into ancestor" layer involved. However, it doesn't make sense that
// that check would be appropriate here but not inside the while loop below.
if (current->isPaintInvalidationContainer() || current->hasCompositedLayerMapping())
return const_cast<RenderLayer*>(current);
while (current) {
if (current->isRootLayer())
return const_cast<RenderLayer*>(current);
current = current->compositingContainer();
if (current->transform() || current->isPaintInvalidationContainer())
return const_cast<RenderLayer*>(current);
return 0;
} // namespace blink