Use the font height as caret height instead of the line height

third_party/WebKit/Source/core/layout/LayoutText.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Andrew Wellington (proton@wiretapped.net)
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * 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
@@ skipping 714 matching lines @@
                                       int caretOffset,
                                       LayoutUnit* extraWidthToEndOfLine) {
   if (!inlineBox)
     return LayoutRect();
 
   ASSERT(inlineBox->isInlineTextBox());
   if (!inlineBox->isInlineTextBox())
     return LayoutRect();
 
   InlineTextBox* box = toInlineTextBox(inlineBox);
+  // Find an InlineBox before caret position, which is used to get caret height.
+  InlineBox* caretBox = box;
+  if (box->prevLeafChild() && caretOffset == 0)

[drott, 2016/12/14 16:42:22]

In https://bugs.chromium.org/p/chromium/issues/detail?id=588060#c12 Yosin
mentions 
"The actual font for calculating caret rectangle should be taken from a
character around caret in following order:
1. a character before caret; left for dir=LTR, right for dir=RTL"

So, I believe this needs to take RTL into account here, and it would be good to
have an additional test which covers and illustrates this font boundary size
change. 

+    caretBox = box->prevLeafChild();
 
-  int height = box->root().selectionHeight().toInt();
-  int top = box->root().selectionTop().toInt();
+  // Get caret height from a font of character.
+  const ComputedStyle* styleToUse =
+      caretBox->getLineLayoutItem().style(caretBox->isFirstLineStyle());
+  int height = styleToUse->font().primaryFont()->getFontMetrics().height();
+  int top = caretBox->logicalTop().toInt();
 
   // Go ahead and round left to snap it to the nearest pixel.
   LayoutUnit left = box->positionForOffset(caretOffset);
 
   // Distribute the caret's width to either side of the offset.
   LayoutUnit caretWidthLeftOfOffset = caretWidth() / 2;
   left -= caretWidthLeftOfOffset;
   LayoutUnit caretWidthRightOfOffset = caretWidth() - caretWidthLeftOfOffset;
 
   left = LayoutUnit(left.round());
@@ skipping 1227 matching lines @@
   LayoutRect rect = LayoutRect(
       IntRect(firstRunX(), firstRunY(), linesBox.width(), linesBox.height()));
   LayoutBlock* block = containingBlock();
   if (block && hasTextBoxes())
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 }  // namespace blink