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: Anders Lassen <email@hidden>
- Date: Tue, 23 Jun 2009 22:01:50 +0200
Hi,
I have learned a bit more since I started this investigation. So now I
know that I can use Core Text or ATSUI to get glyph metrics.
(see former email responses about this)
Anders Lassen
On Jun 23, 2009, at 8:39 PM, Scott Thompson wrote:
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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