Simplify computation of text selection top/bottom.

third_party/WebKit/Source/core/layout/line/RootInlineBox.cpp

 /*
  * Copyright (C) 2003, 2006, 2008 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 371 matching lines @@
   for (InlineBox* box = lastLeafChild(); box; box = box->prevLeafChild()) {
     if (box->getSelectionState() != SelectionNone)
       return box;
   }
 
   return nullptr;
 }
 
 LayoutUnit RootInlineBox::selectionTop() const {
   LayoutUnit selectionTop = m_lineTop;
-
   if (m_hasAnnotationsBefore)
     selectionTop -= !getLineLayoutItem().style()->isFlippedLinesWritingMode()
                         ? computeOverAnnotationAdjustment(m_lineTop)
                         : computeUnderAnnotationAdjustment(m_lineTop);
 
   if (getLineLayoutItem().style()->isFlippedLinesWritingMode() ||
       !prevRootBox())
     return selectionTop;
 
-  LayoutUnit prevBottom = prevRootBox()->selectionBottom();
-  if (prevBottom < selectionTop && block().containsFloats()) {
-    // This line has actually been moved further down, probably from a large

[pdr., 2016/12/01 21:54:48]

I traced this code back 12 years and found it was added for selection gaps,
which we have removed:
https://trac.webkit.org/changeset/7766/trunk/WebCore/khtml/rendering/render_l...

[eae, 2016/12/02 10:12:30]

Nice detective work there pdr!

-    // line-height, but possibly because the line was forced to clear floats.
-    // If so, let's check the offsets, and only be willing to use the previous
-    // line's bottom if the offsets are greater on both sides.
-    LayoutUnit prevLeft =
-        block().logicalLeftOffsetForLine(prevBottom, DoNotIndentText);
-    LayoutUnit prevRight =
-        block().logicalRightOffsetForLine(prevBottom, DoNotIndentText);
-    LayoutUnit newLeft =
-        block().logicalLeftOffsetForLine(selectionTop, DoNotIndentText);
-    LayoutUnit newRight =
-        block().logicalRightOffsetForLine(selectionTop, DoNotIndentText);
-    if (prevLeft > newLeft || prevRight < newRight)
-      return selectionTop;
-  }
-
-  return prevBottom;
+  return std::min(selectionTop, prevRootBox()->selectionBottom());
 }
 
 LayoutUnit RootInlineBox::selectionBottom() const {
   LayoutUnit selectionBottom = getLineLayoutItem().document().inNoQuirksMode()
                                    ? m_selectionBottom
                                    : m_lineBottom;
 
   if (m_hasAnnotationsAfter)
     selectionBottom += !getLineLayoutItem().style()->isFlippedLinesWritingMode()
                            ? computeUnderAnnotationAdjustment(m_lineBottom)
                            : computeOverAnnotationAdjustment(m_lineBottom);
 
   if (!getLineLayoutItem().style()->isFlippedLinesWritingMode() ||
       !nextRootBox())
     return selectionBottom;
 
-  LayoutUnit nextTop = nextRootBox()->selectionTop();
-  if (nextTop > selectionBottom && block().containsFloats()) {
-    // The next line has actually been moved further over, probably from a large
-    // line-height, but possibly because the line was forced to clear floats.
-    // If so, let's check the offsets, and only be willing to use the next
-    // line's top if the offsets are greater on both sides.
-    LayoutUnit nextLeft =
-        block().logicalLeftOffsetForLine(nextTop, DoNotIndentText);
-    LayoutUnit nextRight =
-        block().logicalRightOffsetForLine(nextTop, DoNotIndentText);
-    LayoutUnit newLeft =
-        block().logicalLeftOffsetForLine(selectionBottom, DoNotIndentText);
-    LayoutUnit newRight =
-        block().logicalRightOffsetForLine(selectionBottom, DoNotIndentText);
-    if (nextLeft > newLeft || nextRight < newRight)
-      return selectionBottom;
-  }
-
-  return nextTop;
+  return std::max(selectionBottom, nextRootBox()->selectionTop());
 }
 
 LayoutUnit RootInlineBox::blockDirectionPointInLine() const {
   return !block().style()->isFlippedBlocksWritingMode()
              ? std::max(lineTop(), selectionTop())
              : std::min(lineBottom(), selectionBottom());
 }
 
 LineLayoutBlockFlow RootInlineBox::block() const {
   return LineLayoutBlockFlow(getLineLayoutItem());
@@ skipping 352 matching lines @@
   }
   endBox = nullptr;
   return nullptr;
 }
 
 const char* RootInlineBox::boxName() const {
   return "RootInlineBox";
 }
 
 }  // namespace blink