... a single-line views::Label will correctly do this (as will RenderTextMac which is "always" single line). But RTHB's "native" multiline support will always align text to the top of the Label.

Chrome Version       : 58.0.3029.19
OS Version: OS X 10.12.3

What steps will reproduce the problem?
1. Use Label::SetLineHeight()

What is the expected result?

Expect text to be vertically cenetred


What happens instead of that?

Aligns vertically to the top (except when single line).



There is a TODO..

  // TODO(ckocagil): Add vertical alignment and line spacing support instead.
  int min_line_height() const { return min_line_height_; }
  void SetMinLineHeight(int line_height);


But it's not really documented what the default vertical alignment should be.

To fix, I think we can look to HarfBuzzLineBreaker. It has a |min_baseline| argument, which currently always takes Font::GetHeight(). If we instead pass DetermineBaselineCenteringText(line_height(), font_list()) (from render_text.cc), then we get centred vertical alignment.

DetermineBaselineCenteringText() is currently used to centre a single line in the display rectangle.

This suggests that callers of RenderText currently assume text is centred vertically. That is, creating text with a larger bounding box than it needs will centre text vertically -- if a caller assuming that behaviour is also using SetLineHeight(), then the text would no longer be properly centred with the current behaviour.


Said another way, I don't think currently we have a use-case for vertical alignment that isn't centred. So rather than making it adjsutable, I think we can just always centre.


Started -> https://codereview.chromium.org/2767163003