

Glyph Metrics - jcr
http://www.freetype.org/freetype2/docs/glyphs/glyphs-3.html

======
jcr
The folks at freetype.org have gotten "advance measure" (also known as simply
"advance") correct -- It depends on the horizontal or vertical layout
orientation. Unfortunately, it seems the mozilla folks _may_ have implemented
the CSS3 'ch' unit incorrectly:

[http://www.w3.org/TR/css3-values/#ch-
unit](http://www.w3.org/TR/css3-values/#ch-unit)

    
    
      ch unit
        Equal to the used advance measure of the "0" (ZERO, U+0030)
        glyph found in the font used to render it.
    

[https://developer.mozilla.org/en-
US/docs/Web/CSS/length](https://developer.mozilla.org/en-
US/docs/Web/CSS/length)

    
    
      ch
        This unit represents the width, or more precisely the advance
        measure, of the glyph '0' (zero, the Unicode character U+0030)
        in the element's font.
    

If you change the layout orientation of text from horizontal to vertical, the
"advance measure" will change. If the "advance measure" remains constant
between the two, then vertically orientation would result in characters
(glyphs) overwriting each other.

The above is just the mozilla docs so I really need to check the mozilla
source code to make sure.

