Need the dimensions of "character frame"

[Pierre Clouthier]

I am looking for someone who knows how to determine the coordinates of the exact rectangle that touches top and bottom of a string of characters, which I call "character frame".

The character frame is not to be confused with the character cell, which includes room for upper-case characters, diacritics and descenders. The character cell will often be greater than the character frame, and is not suitable for what I'm looking for.

The dimensions of the rectangle will be returned in points.

Can anyone help with this?

Thanks,

[Pierre Clouthier]

As shown in the diagram above, the font ascender, caps height and X-height are too coarse for determining the character frame.

- The lower case 'L' and 'i' are higher than the caps height.
- In some fonts, some lower-case letters will protrude beyond the X-height.
- A single period '.' will be lower then the X-height.
- How does one ascertain there is a descender? Checking for "gjpqy" doesn't catch the thousands of foreign characters with descenders.
- How do you catch upper-case letters with diacritics, which are as high as the ascender? There are too many foreign characters for enumeration to be practical.