third_party/WebKit/Source/core/paint/PaintLayerClipper.h - chromium/src - Git at Google

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
  *   Roland Mainz <roland.mainz@informatik.med.uni-giessen.de>
  *   Josh Soref <timeless@mac.com>
  *   Boris Zbarsky <bzbarsky@mit.edu>
  *
  * 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * 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
  * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
  * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
  * (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.
  */

 #ifndef PaintLayerClipper_h
 #define PaintLayerClipper_h

 #include "core/CoreExport.h"
 #include "core/layout/ClipRectsCache.h"
 #include "core/layout/ScrollEnums.h"

 #include "platform/graphics/paint/GeometryMapper.h"

 #include "wtf/Allocator.h"

 namespace blink {

 class PaintLayer;

 enum ShouldRespectOverflowClipType { IgnoreOverflowClip, RespectOverflowClip };

 class ClipRectsContext {
   STACK_ALLOCATED();

  public:
   ClipRectsContext(const PaintLayer* root,
                    ClipRectsCacheSlot slot,
                    OverlayScrollbarClipBehavior overlayScrollbarClipBehavior =
                        IgnoreOverlayScrollbarSize,
                    const LayoutSize& accumulation = LayoutSize())
       : rootLayer(root),
         overlayScrollbarClipBehavior(overlayScrollbarClipBehavior),
         m_cacheSlot(slot),
         subPixelAccumulation(accumulation),
         respectOverflowClip(slot == PaintingClipRectsIgnoringOverflowClip
                                 ? IgnoreOverflowClip
                                 : RespectOverflowClip),
         respectOverflowClipForViewport(
             slot == RootRelativeClipRectsIgnoringViewportClip
                 ? IgnoreOverflowClip
                 : RespectOverflowClip) {}

   void setIgnoreOverflowClip() {
     DCHECK(!usesCache() || m_cacheSlot == PaintingClipRects);
     DCHECK(respectOverflowClip == RespectOverflowClip);
     if (usesCache())
       m_cacheSlot = PaintingClipRectsIgnoringOverflowClip;
     respectOverflowClip = IgnoreOverflowClip;
   }

   bool usesCache() const { return m_cacheSlot != UncachedClipRects; }

   ClipRectsCacheSlot cacheSlot() const { return m_cacheSlot; }

   const PaintLayer* rootLayer;
   const OverlayScrollbarClipBehavior overlayScrollbarClipBehavior;

  private:
   friend class PaintLayerClipper;

   ClipRectsCacheSlot m_cacheSlot;
   LayoutSize subPixelAccumulation;
   ShouldRespectOverflowClipType respectOverflowClip;
   ShouldRespectOverflowClipType respectOverflowClipForViewport;
 };

 // PaintLayerClipper is responsible for computing and caching clip
 // rects.
 //
 // These clip rects have two types: background and foreground.
 //
 // The "background rect" for a PaintLayer is almost the same as its visual
 // rect in the space of some ancestor PaintLayer (specified by rootLayer on
 // ClipRectsContext).
 // The only differences are that:
 //   * The unclipped rect at the start is LayoutRect::infiniteIntRect,
 // rather than the local overflow bounds of the PaintLayer.
 //   * CSS clip, the extent of visualOverflowRect(), and SVG root viewport
 // clipping is applied.
 // Thus, for example if there are no clips then the background rect will be
 // infinite. Also, whether overflow clip of the ancestor should be applied is a
 // parameter.
 //
 // The "foreground rect" for a PaintLayer is its "background rect", intersected
 // with any clip applied by this PaintLayer to its children.

 // Motivation for this class:
 //
 // The main reason for this cache is that we compute the clip rects during
 // a layout tree walk but need them during a paint tree walk (see example
 // below for some explanations).
 //
 // A lot of complexity in this class come from the difference in inheritance
 // between 'overflow' and 'clip':
 // * 'overflow' applies based on the containing blocks chain.
 //    (http://www.w3.org/TR/CSS2/visufx.html#propdef-overflow)
 // * 'clip' applies to all descendants.
 //    (http://www.w3.org/TR/CSS2/visufx.html#propdef-clip)
 //
 // Let's take an example:
 // <!DOCTYPE html>
 // <div id="container" style="position: absolute; height: 100px; width: 100px">
 //   <div id="inflow" style="height: 200px; width: 200px;
 //       background-color: purple"></div>
 //   <div id="fixed" style="height: 200px; width: 200px; position: fixed;
 //       background-color: orange"></div>
 // </div>
 //
 // The paint tree looks like:
 //               html
 //              /   |
 //             /    |
 //            /     |
 //      container  fixed
 //         |
 //         |
 //       inflow
 //
 // If we add "overflow: hidden" to #container, the overflow clip will apply to
 // #inflow but not to #fixed. That's because #fixed's containing block is above
 // #container and thus 'overflow' doesn't apply to it. During our tree walk,
 // #fixed is a child of #container, which is the reason why we keep 3 clip rects
 // depending on the 'position' of the elements.
 //
 // Now instead if we add "clip: rect(0px, 100px, 100px, 0px)" to #container,
 // the clip will apply to both #inflow and #fixed. That's because 'clip'
 // applies to any descendant, regardless of containing blocks. Note that
 // #container and #fixed are siblings in the paint tree but #container does
 // clip #fixed. This is the reason why we compute the painting clip rects during
 // a layout tree walk and cache them for painting.
 class CORE_EXPORT PaintLayerClipper {
   DISALLOW_NEW();

  public:
   explicit PaintLayerClipper(const PaintLayer&, bool useGeometryMapper);

   void clearClipRectsIncludingDescendants();
   void clearClipRectsIncludingDescendants(ClipRectsCacheSlot);

   // Returns the background clip rect of the layer in the local coordinate
   // space. Only looks for clips up to the given ancestor.
   LayoutRect localClipRect(const PaintLayer* ancestorLayer) const;

   // Computes the same thing as backgroundRect in calculateRects(), but skips
   // apllying CSS clip and the visualOverflowRect() of |m_layer|.
   ClipRect backgroundClipRect(const ClipRectsContext&) const;

   // This method figures out our layerBounds in coordinates relative to
   // |rootLayer|. It also computes our background and foreground clip rects
   // for painting/event handling. Pass offsetFromRoot if known.
   void calculateRects(const ClipRectsContext&,
                       const LayoutRect& paintDirtyRect,
                       LayoutRect& layerBounds,
                       ClipRect& backgroundRect,
                       ClipRect& foregroundRect,
                       const LayoutPoint* offsetFromRoot = 0) const;

   ClipRects& paintingClipRects(const PaintLayer* rootLayer,
                                ShouldRespectOverflowClipType,
                                const LayoutSize& subpixelAccumulation) const;

  private:
   ClipRects& getClipRects(const ClipRectsContext&) const;

   void calculateClipRects(const ClipRectsContext&, ClipRects&) const;
   ClipRects* clipRectsIfCached(const ClipRectsContext&) const;
   ClipRects& storeClipRectsInCache(const ClipRectsContext&,
                                    ClipRects* parentClipRects,
                                    const ClipRects&) const;

   void getOrCalculateClipRects(const ClipRectsContext&, ClipRects&) const;

   bool shouldClipOverflow(const ClipRectsContext&) const;
   bool shouldRespectOverflowClip(const ClipRectsContext&) const;

   ClipRect clipRectWithGeometryMapper(const ClipRectsContext&,
                                       bool isForeground) const;
   void mapLocalToRootWithGeometryMapper(const ClipRectsContext&,
                                         LayoutRect& localRect) const;
   void calculateRectsWithGeometryMapper(
       const ClipRectsContext&,
       const LayoutRect& paintDirtyRect,
       LayoutRect& layerBounds,
       ClipRect& backgroundRect,
       ClipRect& foregroundRect,
       const LayoutPoint* offsetFromRoot = 0) const;

   ClipRect applyOverflowClipToBackgroundRectWithGeometryMapper(
       const ClipRectsContext&,
       const ClipRect&) const;

   const PaintLayer& m_layer;
   std::unique_ptr<GeometryMapper> m_geometryMapper;
 };

 }  // namespace blink

 #endif  // LayerClipper_h
	/*
	* Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
	* Copyright (C) 2013 Intel Corporation. All rights reserved.
	*
	* Portions are Copyright (C) 1998 Netscape Communications Corporation.
	*
	* Other contributors:
	* Robert O'Callahan <roc+@cs.cmu.edu>
	* David Baron <dbaron@fas.harvard.edu>
	* Christian Biesinger <cbiesinger@web.de>
	* Randall Jesup <rjesup@wgate.com>
	* Roland Mainz <roland.mainz@informatik.med.uni-giessen.de>
	* Josh Soref <timeless@mac.com>
	* Boris Zbarsky <bzbarsky@mit.edu>
	*
	* 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
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* 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
	* http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
	* License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
	* (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.
	*/

	#ifndef PaintLayerClipper_h
	#define PaintLayerClipper_h

	#include "core/CoreExport.h"
	#include "core/layout/ClipRectsCache.h"
	#include "core/layout/ScrollEnums.h"

	#include "platform/graphics/paint/GeometryMapper.h"

	#include "wtf/Allocator.h"

	namespace blink {

	class PaintLayer;

	enum ShouldRespectOverflowClipType { IgnoreOverflowClip, RespectOverflowClip };

	class ClipRectsContext {
	STACK_ALLOCATED();

	public:
	ClipRectsContext(const PaintLayer* root,
	ClipRectsCacheSlot slot,
	OverlayScrollbarClipBehavior overlayScrollbarClipBehavior =
	IgnoreOverlayScrollbarSize,
	const LayoutSize& accumulation = LayoutSize())
	: rootLayer(root),
	overlayScrollbarClipBehavior(overlayScrollbarClipBehavior),
	m_cacheSlot(slot),
	subPixelAccumulation(accumulation),
	respectOverflowClip(slot == PaintingClipRectsIgnoringOverflowClip
	? IgnoreOverflowClip
	: RespectOverflowClip),
	respectOverflowClipForViewport(
	slot == RootRelativeClipRectsIgnoringViewportClip
	? IgnoreOverflowClip
	: RespectOverflowClip) {}

	void setIgnoreOverflowClip() {
	DCHECK(!usesCache() \|\| m_cacheSlot == PaintingClipRects);
	DCHECK(respectOverflowClip == RespectOverflowClip);
	if (usesCache())
	m_cacheSlot = PaintingClipRectsIgnoringOverflowClip;
	respectOverflowClip = IgnoreOverflowClip;
	}

	bool usesCache() const { return m_cacheSlot != UncachedClipRects; }

	ClipRectsCacheSlot cacheSlot() const { return m_cacheSlot; }

	const PaintLayer* rootLayer;
	const OverlayScrollbarClipBehavior overlayScrollbarClipBehavior;

	private:
	friend class PaintLayerClipper;

	ClipRectsCacheSlot m_cacheSlot;
	LayoutSize subPixelAccumulation;
	ShouldRespectOverflowClipType respectOverflowClip;
	ShouldRespectOverflowClipType respectOverflowClipForViewport;
	};

	// PaintLayerClipper is responsible for computing and caching clip
	// rects.
	//
	// These clip rects have two types: background and foreground.
	//
	// The "background rect" for a PaintLayer is almost the same as its visual
	// rect in the space of some ancestor PaintLayer (specified by rootLayer on
	// ClipRectsContext).
	// The only differences are that:
	// * The unclipped rect at the start is LayoutRect::infiniteIntRect,
	// rather than the local overflow bounds of the PaintLayer.
	// * CSS clip, the extent of visualOverflowRect(), and SVG root viewport
	// clipping is applied.
	// Thus, for example if there are no clips then the background rect will be
	// infinite. Also, whether overflow clip of the ancestor should be applied is a
	// parameter.
	//
	// The "foreground rect" for a PaintLayer is its "background rect", intersected
	// with any clip applied by this PaintLayer to its children.

	// Motivation for this class:
	//
	// The main reason for this cache is that we compute the clip rects during
	// a layout tree walk but need them during a paint tree walk (see example
	// below for some explanations).
	//
	// A lot of complexity in this class come from the difference in inheritance
	// between 'overflow' and 'clip':
	// * 'overflow' applies based on the containing blocks chain.
	// (http://www.w3.org/TR/CSS2/visufx.html#propdef-overflow)
	// * 'clip' applies to all descendants.
	// (http://www.w3.org/TR/CSS2/visufx.html#propdef-clip)
	//
	// Let's take an example:
	// <!DOCTYPE html>
	// <div id="container" style="position: absolute; height: 100px; width: 100px">
	// <div id="inflow" style="height: 200px; width: 200px;
	// background-color: purple"></div>
	// <div id="fixed" style="height: 200px; width: 200px; position: fixed;
	// background-color: orange"></div>
	// </div>
	//
	// The paint tree looks like:
	// html
	// / \|
	// / \|
	// / \|
	// container fixed
	// \|
	// \|
	// inflow
	//
	// If we add "overflow: hidden" to #container, the overflow clip will apply to
	// #inflow but not to #fixed. That's because #fixed's containing block is above
	// #container and thus 'overflow' doesn't apply to it. During our tree walk,
	// #fixed is a child of #container, which is the reason why we keep 3 clip rects
	// depending on the 'position' of the elements.
	//
	// Now instead if we add "clip: rect(0px, 100px, 100px, 0px)" to #container,
	// the clip will apply to both #inflow and #fixed. That's because 'clip'
	// applies to any descendant, regardless of containing blocks. Note that
	// #container and #fixed are siblings in the paint tree but #container does
	// clip #fixed. This is the reason why we compute the painting clip rects during
	// a layout tree walk and cache them for painting.
	class CORE_EXPORT PaintLayerClipper {
	DISALLOW_NEW();

	public:
	explicit PaintLayerClipper(const PaintLayer&, bool useGeometryMapper);

	void clearClipRectsIncludingDescendants();
	void clearClipRectsIncludingDescendants(ClipRectsCacheSlot);

	// Returns the background clip rect of the layer in the local coordinate
	// space. Only looks for clips up to the given ancestor.
	LayoutRect localClipRect(const PaintLayer* ancestorLayer) const;

	// Computes the same thing as backgroundRect in calculateRects(), but skips
	// apllying CSS clip and the visualOverflowRect() of \|m_layer\|.
	ClipRect backgroundClipRect(const ClipRectsContext&) const;

	// This method figures out our layerBounds in coordinates relative to
	// \|rootLayer\|. It also computes our background and foreground clip rects
	// for painting/event handling. Pass offsetFromRoot if known.
	void calculateRects(const ClipRectsContext&,
	const LayoutRect& paintDirtyRect,
	LayoutRect& layerBounds,
	ClipRect& backgroundRect,
	ClipRect& foregroundRect,
	const LayoutPoint* offsetFromRoot = 0) const;

	ClipRects& paintingClipRects(const PaintLayer* rootLayer,
	ShouldRespectOverflowClipType,
	const LayoutSize& subpixelAccumulation) const;

	private:
	ClipRects& getClipRects(const ClipRectsContext&) const;

	void calculateClipRects(const ClipRectsContext&, ClipRects&) const;
	ClipRects* clipRectsIfCached(const ClipRectsContext&) const;
	ClipRects& storeClipRectsInCache(const ClipRectsContext&,
	ClipRects* parentClipRects,
	const ClipRects&) const;

	void getOrCalculateClipRects(const ClipRectsContext&, ClipRects&) const;

	bool shouldClipOverflow(const ClipRectsContext&) const;
	bool shouldRespectOverflowClip(const ClipRectsContext&) const;

	ClipRect clipRectWithGeometryMapper(const ClipRectsContext&,
	bool isForeground) const;
	void mapLocalToRootWithGeometryMapper(const ClipRectsContext&,
	LayoutRect& localRect) const;
	void calculateRectsWithGeometryMapper(
	const ClipRectsContext&,
	const LayoutRect& paintDirtyRect,
	LayoutRect& layerBounds,
	ClipRect& backgroundRect,
	ClipRect& foregroundRect,
	const LayoutPoint* offsetFromRoot = 0) const;

	ClipRect applyOverflowClipToBackgroundRectWithGeometryMapper(
	const ClipRectsContext&,
	const ClipRect&) const;

	const PaintLayer& m_layer;
	std::unique_ptr<GeometryMapper> m_geometryMapper;
	};

	} // namespace blink

	#endif // LayerClipper_h