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

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

Index: third_party/WebKit/Source/core/layout/LayoutText.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutText.cpp b/third_party/WebKit/Source/core/layout/LayoutText.cpp
index d6cc72e451eedaad34ef2b71ad43a2af188884a5..796646bafef56944887896421c951f0f3f56ce9f 100644
--- a/third_party/WebKit/Source/core/layout/LayoutText.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutText.cpp
@@ -733,8 +733,8 @@ LayoutRect LayoutText::localCaretRect(InlineBox* inlineBox,
 
   InlineTextBox* box = toInlineTextBox(inlineBox);
 
-  int height = box->root().selectionHeight().toInt();
-  int top = box->root().selectionTop().toInt();
+  int height = style()->font().primaryFont()->getFontMetrics().height();

[yosin_UTC9, 2016/11/30 01:44:02]

Could you use font ascendant and descendant instead of height?

top = baseline - font_ascendant;
bottom = baseline + font_descendant;

BTW, I'm not sure we should use actual font instead of computed font.
The font used by |inlineBox| can be different of |style()->font()| due by
missing glyph, e.g. kanji character with "font-family: Arial".

I found following code fragment in InlineTextBoxPainter:

  const ComputedStyle& styleToUse =
      m_inlineTextBox.getLineLayoutItem().styleRef(
          m_inlineTextBox.isFirstLineStyle());

Note: ::first-letter characters and rest of characters are placed into different
InlineTextBox.

I'm not an expert of this area, drott@ will provide more information.

[joone, 2016/12/02 01:24:43]

But, we need the height value and can get it easily by just calling the height
method of FontMetrics: the height value is calculated by ascent() + descent().
I used the above code to get the computed font.

[yosin_UTC9, 2016/12/02 01:42:35]

This function returns rectangle rather than height. Caret rectangle should be:

line top

  +
  |
  |
  |
 -+- baseline
  |

line bottom


This patch returns:


line top

  +
  |
  |
  |
  |
  +- line bottom

+  int top = box->root().selectionBottom().toInt() - height;
 
   // Go ahead and round left to snap it to the nearest pixel.
   LayoutUnit left = box->positionForOffset(caretOffset);