Re: Widths in tables

Bert Bos (
Mon, 24 Apr 95 14:46:22 EDT

Dave Ragget writes:

|> | ch /* characters */
|> What are "characters" in a proportional-space environment?
|> In general terms, Jon's inference -- that "ch" is an inappropriate
|> length measure -- is quite correct. And not only for the reason
|> he states:
|I am assuming that when authors choose to use ch that they are aware
|of the perils involved - it makes perfect sense when the table is
|in a single fixed pitch font.
|The use of ems is problematic in this case as an em isn't the same
|as the width of a character for a fixed pitch font. My understanding
|is that the em is equal to the point size which is related to the
|height of the font - not its width.

That is not the way I heard it. em is a unit of width, not of height
(ex and others are for height). It is a measure associated with a font
by the designer and it is traditionally about the width of an M (hence
the name). An en is exaclty half an em.

In most fonts (and in fixed width fonts by definition), an en is about
the width of a digit, so in practice ch can be interpreted to be
exactly the same as en (or 0.5 em).


                          Bert Bos                      Alfa-informatica
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