- From: David Lemon <typenerd@slip.net>
- Date: Thu, 2 Dec 1999 08:38:35 -0800
- To: <www-font@w3.org>
At 11:24 AM -0800 12/1/99, Nick Nussbaum wrote: > As long as you're explaining things so lucidly; Thanks ;-) > In Adobe fonts are accented Upper Case characters > always within the Em Square vertical constraints? > Do Pi/Symbol fonts always fall with in the em square vertical limits? Definitely not, in either case (pun allowed). Accented lowercase characters (think of l with acute) may go even higher than accented capitals. And the glyphs which extend farthest to the left, right and bottom in the Adobe library are all nonalphabetic symbols of various sorts (oh no - another typographic pun). There is no requirement that the font bounding box (the rectangle which would precisely enclose all the glyphs in the font if they were superimposed in their proper positions) have any relationship to the em square. The Type 1 specification states that no glyph should extend more than 2000 units in any direction from the origin (the 0,0 coordinate in the context of a 1000-unit em square), theoretically limiting bounding boxes to four times the height and width of the em - but although it's not recommended, I know of glyphs that go farther in width or depth (not height yet). Environments which need to be concerned with glyph extent (e.g. for clipping purposes) should check font bounding boxes, followed by glyph bounding boxes if necessary. But for optical and typographic purposes, nominal ascent and descent are useful for glyph placement, and should not be tied to bounding box height, depth or width. - David Lemon
Received on Thursday, 2 December 1999 11:40:25 UTC