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| 1 /* | 1 /* |
| 2 * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved. | 2 * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved. |
| 3 * Copyright (C) 2013 Intel Corporation. All rights reserved. | 3 * Copyright (C) 2013 Intel Corporation. All rights reserved. |
| 4 * | 4 * |
| 5 * Portions are Copyright (C) 1998 Netscape Communications Corporation. | 5 * Portions are Copyright (C) 1998 Netscape Communications Corporation. |
| 6 * | 6 * |
| 7 * Other contributors: | 7 * Other contributors: |
| 8 * Robert O'Callahan <roc+@cs.cmu.edu> | 8 * Robert O'Callahan <roc+@cs.cmu.edu> |
| 9 * David Baron <dbaron@fas.harvard.edu> | 9 * David Baron <dbaron@fas.harvard.edu> |
| 10 * Christian Biesinger <cbiesinger@web.de> | 10 * Christian Biesinger <cbiesinger@web.de> |
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| 100 | 100 |
| 101 private: | 101 private: |
| 102 friend class DeprecatedPaintLayerClipper; | 102 friend class DeprecatedPaintLayerClipper; |
| 103 | 103 |
| 104 ClipRectsCacheSlot m_cacheSlot; | 104 ClipRectsCacheSlot m_cacheSlot; |
| 105 LayoutSize subPixelAccumulation; | 105 LayoutSize subPixelAccumulation; |
| 106 ShouldRespectOverflowClip respectOverflowClip; | 106 ShouldRespectOverflowClip respectOverflowClip; |
| 107 ShouldRespectOverflowClip respectOverflowClipForViewport; | 107 ShouldRespectOverflowClip respectOverflowClipForViewport; |
| 108 }; | 108 }; |
| 109 | 109 |
| 110 // DeprecatedPaintLayerClipper is responsible for computing and caching clip |
| 111 // rects. |
| 112 // |
| 113 // The main reason for this cache is that we compute the clip rects during |
| 114 // a layout tree walk but need them during a paint tree walk (see example |
| 115 // below for some explanations). |
| 116 // |
| 117 // A lot of complexity in this class come from the difference in inheritance |
| 118 // between 'overflow' and 'clip': |
| 119 // * 'overflow' applies based on the containing blocks chain. |
| 120 // (http://www.w3.org/TR/CSS2/visufx.html#propdef-overflow) |
| 121 // * 'clip' applies to all descendants. |
| 122 // (http://www.w3.org/TR/CSS2/visufx.html#propdef-clip) |
| 123 // |
| 124 // Let's take an example: |
| 125 // <!DOCTYPE html> |
| 126 // <div id="container" style="position: absolute; height: 100px; width: 100px"> |
| 127 // <div id="inflow" style="height: 200px; width: 200px; |
| 128 // background-color: purple"></div> |
| 129 // <div id="fixed" style="height: 200px; width: 200px; position: fixed; |
| 130 // background-color: orange"></div> |
| 131 // </div> |
| 132 // |
| 133 // The paint tree looks like: |
| 134 // html |
| 135 // / | |
| 136 // / | |
| 137 // / | |
| 138 // container fixed |
| 139 // | |
| 140 // | |
| 141 // inflow |
| 142 // |
| 143 // If we add "overflow: hidden" to #container, the overflow clip will apply to |
| 144 // #inflow but not to #fixed. That's because #fixed's containing block is above |
| 145 // #container and thus 'overflow' doesn't apply to it. During our tree walk, |
| 146 // #fixed is a child of #container, which is the reason why we keep 3 clip rects |
| 147 // depending on the 'position' of the elements. |
| 148 // |
| 149 // Now instead if we add "clip: rect(0px, 100px, 100px, 0px)" to #container, |
| 150 // the clip will apply to both #inflow and #fixed. That's because 'clip' |
| 151 // applies to any descendant, regardless of containing blocks. Note that |
| 152 // #container and #fixed are siblings in the paint tree but #container does |
| 153 // clip #fixed. This is the reason why we compute the painting clip rects during |
| 154 // a layout tree walk and cache them for painting. |
| 155 // |
| 156 // This class is NOT DEPRECATED, DeprecatedPaintLayer is and we match its |
| 157 // naming. |
| 110 class DeprecatedPaintLayerClipper { | 158 class DeprecatedPaintLayerClipper { |
| 111 DISALLOW_ALLOCATION(); | 159 DISALLOW_ALLOCATION(); |
| 112 WTF_MAKE_NONCOPYABLE(DeprecatedPaintLayerClipper); | 160 WTF_MAKE_NONCOPYABLE(DeprecatedPaintLayerClipper); |
| 113 public: | 161 public: |
| 114 explicit DeprecatedPaintLayerClipper(LayoutBoxModelObject&); | 162 explicit DeprecatedPaintLayerClipper(LayoutBoxModelObject&); |
| 115 | 163 |
| 116 void clearClipRectsIncludingDescendants(); | 164 void clearClipRectsIncludingDescendants(); |
| 117 void clearClipRectsIncludingDescendants(ClipRectsCacheSlot); | 165 void clearClipRectsIncludingDescendants(ClipRectsCacheSlot); |
| 118 | 166 |
| 119 LayoutRect childrenClipRect() const; // Returns the foreground clip rect of
the layer in the document's coordinate space. | 167 LayoutRect childrenClipRect() const; // Returns the foreground clip rect of
the layer in the document's coordinate space. |
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| 154 bool shouldRespectOverflowClip(const ClipRectsContext&) const; | 202 bool shouldRespectOverflowClip(const ClipRectsContext&) const; |
| 155 | 203 |
| 156 // FIXME: Could this be a LayoutBox? | 204 // FIXME: Could this be a LayoutBox? |
| 157 LayoutBoxModelObject& m_layoutObject; | 205 LayoutBoxModelObject& m_layoutObject; |
| 158 mutable OwnPtr<ClipRectsCache> m_cache; | 206 mutable OwnPtr<ClipRectsCache> m_cache; |
| 159 }; | 207 }; |
| 160 | 208 |
| 161 } // namespace blink | 209 } // namespace blink |
| 162 | 210 |
| 163 #endif // LayerClipper_h | 211 #endif // LayerClipper_h |
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Chromium Code Reviews
Issue 1327483003:
Add documentation to 2 DeprecatedPaintLayer objects (Closed)
Base URL: svn://svn.chromium.org/blink/trunk