Display fixed position objects on every page of paged media.

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintLayerPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/layout/ClipPathOperation.h"
 #include "core/layout/LayoutBlock.h"
@@ skipping 436 matching lines @@
 
     ClipRect ancestorBackgroundClipRect;
     if (parentLayer) {
         // Calculate the clip rectangle that the ancestors establish.
         ClipRectsContext clipRectsContext(paintingInfo.rootLayer, (paintFlags & PaintLayerUncachedClipRects) ? UncachedClipRects : PaintingClipRects, IgnoreOverlayScrollbarSize);
         if (shouldRespectOverflowClip(paintFlags, m_paintLayer.layoutObject()) == IgnoreOverflowClip)
             clipRectsContext.setIgnoreOverflowClip();
         ancestorBackgroundClipRect = m_paintLayer.clipper().backgroundClipRect(clipRectsContext);
     }
 
+    LayoutObject* object = m_paintLayer.layoutObject();
+    LayoutView* view = object->view();
+    bool isFixedPosObjectInPagedMedia = object->style()->position() == FixedPosition && object->container() == view && view->pageLogicalHeight();
     PaintLayer* paginationLayer = m_paintLayer.enclosingPaginationLayer();
     PaintLayerFragments fragments;
-    if (paginationLayer) {
+    if (isFixedPosObjectInPagedMedia) {
+        // "For paged media, boxes with fixed positions are repeated on every page."
+        // - https://www.w3.org/TR/2011/REC-CSS2-20110607/visuren.html#fixed-positioning
+        ASSERT(view->firstChild() && view->firstChild()->isLayoutBlock());
+        int pages = toLayoutBlock(view->firstChild())->logicalHeight() / view->pageLogicalHeight();
+        LayoutPoint paginationOffset;
+        for (int i = 0; i <= pages; i++) {
+            PaintLayerFragment fragment;
+            fragment.backgroundRect = paintingInfo.paintDirtyRect;
+            fragment.paginationOffset = paginationOffset;
+            fragments.append(fragment);
+            paginationOffset += LayoutPoint(0, view->pageLogicalHeight());
+        }
+    } else if (paginationLayer) {
         // FIXME: This is a mess. Look closely at this code and the code in Layer and fix any
         // issues in it & refactor to make it obvious from code structure what it does and that it's
         // correct.
         ClipRectsCacheSlot cacheSlot = (paintFlags & PaintLayerUncachedClipRects) ? UncachedClipRects : PaintingClipRects;
         ShouldRespectOverflowClipType respectOverflowClip = shouldRespectOverflowClip(paintFlags, m_paintLayer.layoutObject());
         // Calculate the transformed bounding box in the current coordinate space, to figure out
         // which fragmentainers (e.g. columns) we need to visit.
         LayoutRect transformedExtent = PaintLayer::transparencyClipBox(&m_paintLayer, paginationLayer, PaintLayer::PaintingTransparencyClipBox, PaintLayer::RootOfTransparencyClipBox, paintingInfo.subPixelAccumulation, paintingInfo.getGlobalPaintFlags());
         // FIXME: we don't check if paginationLayer is within paintingInfo.rootLayer here.
         paginationLayer->collectFragments(fragments, paintingInfo.rootLayer, paintingInfo.paintDirtyRect, cacheSlot, IgnoreOverlayScrollbarSize, respectOverflowClip, 0, paintingInfo.subPixelAccumulation, &transformedExtent);
@@ skipping 297 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     PaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize());
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink