Re: Problem: how to get glyph descent and ascent
Re: Problem: how to get glyph descent and ascent
- Subject: Re: Problem: how to get glyph descent and ascent
- From: Scott Thompson <email@hidden>
- Date: Tue, 23 Jun 2009 13:39:18 -0500
On Jun 23, 2009, at 1:02 PM, Anders Lassen wrote:
The font descent is the maximum descent for all characters in that
font, so it will not help me to position the character correct
Unfortunately the documentation on the text system in Mac OS X can be
very difficult to navigate (as you have no doubt learned). There is
documentation on QuickDraw, ATSUI, Core Text, the Cocoa System etc...
etc... some of it's legacy, some of it's deprecated, and it's really
hard to know what you should use.
I would recommend looking at the Cocoa Text system (if you are a Cocoa
app) then drop down to the Core Text level if that is not sufficient.
I would use ATSUI as a last resort.
Speaking in very broad terms, the text systems on the OS are much
happier if you start out at the character level and let them manage
the conversion from characters to glyphs. You can then get at the
glyph information, but the information you can learn about any
particular glyph is usually given in the context of an entire line of
text that has been arranged for you. To learn about an individual
glyph you would have to either arrange for it to be put into it's own
style run, or you would have to dig around in the font tables yourself
(a practice I would recommend avoiding if at all possible).
You started out asking about glyphs and now are talking about
characters. What information are you starting with in your
application? Do you have a set of characters that represents some sub-
expression of your formula, or are you starting out with a set of
glyph ids?
Scott
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