"How to get the width of a symbol ? "

I don't know the answer to the question you ask because, in part, I don't
know exactly what measurement you want when you refer to "font size" above
or "width of a symbol".

Please allow me to outline some basic concepts. I hope to at least answer
some aspect of your question. I am doing this rather informally.
Typographers would be horrified, I am sure.

Each character, in data abstraction, is referred to as a glyph. This
relationship, character as to glyph is similar to the relationship as
between number as to numeral. Each glyph is imagined to be positioned inside
a box, a "bounding" box, to be precise. All glyphs in a font are considered
to be inside such a box of the same size. This idea goes back to the days of
movable metal type. Then, the "bounding box" had a visible reality. It was
the size of the rectangular, working end of the metal used to impress the
paper.

Each glyph is positioned inside this box. Because of differences in shape,
not all characters hit the sides of the box. Indeed, in some instances,
parts of glyphs might extend beyond in digital type. For the most part, all
glyphs are conceived-of to be the same size as seen by the eye, all upper
case the same size and all lower case the same size. To achieve this ideal,
characters are actually different sizes within the box.

So, it is not trivial to determine the exact dimensions of any particular
glyph. The data to do so is in the font file but it is not available
explicitly. In principal, code could be written to do it.

To print text, the rasteriser (whether the Windows rasteriser alone or with
involvement of Adobe Type Manager or files therefrom [Windows XP]) uses the
TrueType file to get applicable data to print; however, leaving aside
whether it calculates character dimensions, it does not output any
dimensions that are externally accessible. So, you can't get the dimensions
even by running a trial page image. A programmer might be able to write code
to hook into the system to do this but that is by no means trivial either.

To complicate matters further, there is hinting and kerning. Both influence
the spacing between characters as printed. Hinting, less so since the
difference is typically a pixel or two (to refer to measurements on a
screen). Kerning shifts the printing position and can cause bounding boxes
to overlap. Indeed, in Word, you can alter the printing position on a
character-by-character basis over quite a wide range.

Hope this is useful.

I have done some reading on the topic but am far from being an expert.
Anyone offering corrections or additions would be welcome.

Tom Ferguson
MSMVP-DTS

 The "Bold" and "Italic" of a particular font don't have a influence on the
height, but have a tiny infulence on the width. For example, there are 80
ASCII characters in a line. When all characters are set "Bold", there number
of characters in a line has changed to 79 characters, and another character
hased moved to the next line. So I konw the width of character must have
changed when set "Bold", "Italic" and "superscript".
 Except that, I have an other question: "How to get the width of a symbol ?
" I konw the width of a symbol is connected to the symbol font, and the
width is not solely connected the size. For example, a symbol size is set to
12 points, the actual width may be much smaller.