[CSSRegions] Not possible to clear the selection when mixing content from different FlowThreads

Source/core/rendering/RenderView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 687 matching lines @@
 void RenderView::setMaximalOutlineSize(int o)
 {
     if (o != m_maximalOutlineSize) {
         m_maximalOutlineSize = o;
 
         // maximalOutlineSize affects compositing layer dimensions.
         compositor()->setCompositingLayersNeedRebuild();    // FIXME: this really just needs to be a geometry update.
     }
 }
 
+// When exploring the RenderTree looking for the nodes involved in the Selection, sometimes it's
+// required to change the traversing direction because the "start" position is below the "end" one.
+static inline RenderObject* getNextOrPrevRenderObjectBasedOnDirection(const RenderObject* o, const RenderObject* stop, bool& continueExploring, bool& exploringBackwards)
+{
+    RenderObject* next;
+    if (exploringBackwards) {
+        next = o->previousInPreOrder();
+        continueExploring = next && !(next)->isRenderView();
+    } else {
+        next = o->nextInPreOrder();
+        continueExploring = next && next != stop;
+        exploringBackwards = !next && (next != stop);
+        if (exploringBackwards) {
+            next = stop->previousInPreOrder();
+            continueExploring = next && !next->isRenderView();
+        }
+    }
+
+    return next;
+}
+
 void RenderView::setSelection(RenderObject* start, int startPos, RenderObject* end, int endPos, SelectionRepaintMode blockRepaintMode)
 {
     // Make sure both our start and end objects are defined.
     // Check www.msnbc.com and try clicking around to find the case where this happened.
     if ((start && !end) || (end && !start))
         return;
 
     // Just return if the selection hasn't changed.
     if (m_selectionStart == start && m_selectionStartPos == startPos &&
         m_selectionEnd == end && m_selectionEndPos == endPos)
         return;
 
-    if ((start && end) && (start->flowThreadContainingBlock() != end->flowThreadContainingBlock()))
-        return;
-
     // Record the old selected objects.  These will be used later
     // when we compare against the new selected objects.
     int oldStartPos = m_selectionStartPos;
     int oldEndPos = m_selectionEndPos;
 
     // Objects each have a single selection rect to examine.
     typedef HashMap<RenderObject*, OwnPtr<RenderSelectionInfo> > SelectedObjectMap;
     SelectedObjectMap oldSelectedObjects;
     SelectedObjectMap newSelectedObjects;
 
     // Blocks contain selected objects and fill gaps between them, either on the left, right, or in between lines and blocks.
     // In order to get the repaint rect right, we have to examine left, middle, and right rects individually, since otherwise
     // the union of those rects might remain the same even when changes have occurred.
     typedef HashMap<RenderBlock*, OwnPtr<RenderBlockSelectionInfo> > SelectedBlockMap;
     SelectedBlockMap oldSelectedBlocks;
     SelectedBlockMap newSelectedBlocks;
 
     RenderObject* os = m_selectionStart;
     RenderObject* stop = rendererAfterPosition(m_selectionEnd, m_selectionEndPos);
-    while (os && os != stop) {
+    bool exploringBackwards = false;
+    bool continueExploring = os && (os != stop);
+    while (continueExploring) {
         if ((os->canBeSelectionLeaf() || os == m_selectionStart || os == m_selectionEnd) && os->selectionState() != SelectionNone) {
             // Blocks are responsible for painting line gaps and margin gaps.  They must be examined as well.
             oldSelectedObjects.set(os, adoptPtr(new RenderSelectionInfo(os, true)));
             if (blockRepaintMode == RepaintNewXOROld) {
                 RenderBlock* cb = os->containingBlock();
                 while (cb && !cb->isRenderView()) {
                     OwnPtr<RenderBlockSelectionInfo>& blockInfo = oldSelectedBlocks.add(cb, nullptr).iterator->value;
                     if (blockInfo)
                         break;
                     blockInfo = adoptPtr(new RenderBlockSelectionInfo(cb));
                     cb = cb->containingBlock();
                 }
             }
         }
 
-        os = os->nextInPreOrder();
+        os = getNextOrPrevRenderObjectBasedOnDirection(os, stop, continueExploring, exploringBackwards);
     }
 
     // Now clear the selection.
     SelectedObjectMap::iterator oldObjectsEnd = oldSelectedObjects.end();
     for (SelectedObjectMap::iterator i = oldSelectedObjects.begin(); i != oldObjectsEnd; ++i)
         i->key->setSelectionStateIfNeeded(SelectionNone);
 
     // set selection start and end
     m_selectionStart = start;
     m_selectionStartPos = startPos;
@@ skipping 18 matching lines @@
             o->setSelectionStateIfNeeded(SelectionInside);
         o = o->nextInPreOrder();
     }
 
     if (blockRepaintMode != RepaintNothing)
         layer()->clearBlockSelectionGapsBounds();
 
     // Now that the selection state has been updated for the new objects, walk them again and
     // put them in the new objects list.
     o = start;
-    while (o && o != stop) {
+    exploringBackwards = false;
+    continueExploring = o && (o != stop);
+    while (continueExploring) {
         if ((o->canBeSelectionLeaf() || o == start || o == end) && o->selectionState() != SelectionNone) {
             newSelectedObjects.set(o, adoptPtr(new RenderSelectionInfo(o, true)));
             RenderBlock* cb = o->containingBlock();
             while (cb && !cb->isRenderView()) {
                 OwnPtr<RenderBlockSelectionInfo>& blockInfo = newSelectedBlocks.add(cb, nullptr).iterator->value;
                 if (blockInfo)
                     break;
                 blockInfo = adoptPtr(new RenderBlockSelectionInfo(cb));
                 cb = cb->containingBlock();
             }
         }
 
-        o = o->nextInPreOrder();
+        o = getNextOrPrevRenderObjectBasedOnDirection(o, stop, continueExploring, exploringBackwards);
     }
 
     if (!m_frameView || blockRepaintMode == RepaintNothing)
         return;
 
     m_frameView->beginDeferredRepaints();
 
     // Have any of the old selected objects changed compared to the new selection?
     for (SelectedObjectMap::iterator i = oldSelectedObjects.begin(); i != oldObjectsEnd; ++i) {
         RenderObject* obj = i->key;
@@ skipping 369 matching lines @@
 #endif
 
     if (layoutState)
         layoutState->m_isPaginated = m_fragmenting;
 
     if (m_flowThreadState != RenderObject::NotInsideFlowThread)
         m_root->setFlowThreadStateIncludingDescendants(m_flowThreadState);
 }
 
 } // namespace WebCore