Re: Rendering combining marks
Re: Rendering combining marks
- Subject: Re: Rendering combining marks
- From: George Nachman <email@hidden>
- Date: Mon, 3 Jan 2011 16:45:19 -0800
On Mon, Jan 3, 2011 at 1:47 PM, Wim Lewis <email@hidden> wrote:
>
> On 2 Jan 2011, at 1:23 PM, George Nachman wrote:
>> I'm using CGContextShowGlyphsWithAdvances to render fixed-width text
>> because it is very fast. If a glyph is missing, I use
>> CTFontCreateForString() to pick a better font, and that usually works.
>> I ran into a case that I just can't solve with this technique [...]
>
> Do you need layout+rendering to be fast, or just rendering? If the latter, for example if you're drawing a fixed string multiple times, you could use a higher level routine to do the layout (e.g. CTTypesetterCreateLine() or CTLineCreateWithAttributedString()) and then extract the glyphs, offsets, so on from the typeset line to draw with CGContextShowGlyphsWithAdvances().
>
> (Actually I'd be surprised if CGContextShowGlyphsWithAdvances() is much faster than CTLineDraw() --- I'd guess that simply caching the typeset line will get you most of the available speedup.)
It's rare that I have text that requires layout. 99% is plain old
ASCII. It's not fixed text but I don't mind having a slower code path
for more complex text.
I tried using CTLineCreateWithAttributedString() and then rendering it
with CTLineDraw() but it still fails to draw certain glyphs. For
example, U+23B7: RADICAL SYMBOL BOTTOM appears as a box (the missing
glyph symbol). It exists in the "Apple Symbols" font, but I guess it's
just using the font I requested. If I use -[NSAttributedString
drawInRect:], it can render the glyph, despite my specifying
AndaleMono as the font. I wish I could do all my text drawing with
-[NSAttributedString drawInRect:], but it is very slow. I tried using
that call for only "problem" characters and
CGContextShowGlyphsWithAdvances for "normal" characters, but I can't
get the baselines to line up correctly (the attributed string draws a
few pixels lower for some reason). If I could get the baselines to
match up, this would be an ideal solution.
Another smaller issue is that CTLineCreateWithAttributedString() +
CTLineDraw() doesn't perform layout as nicely as -[NSAttributedString
drawInRect:] in some edge cases. For instance, the sequence U+0061
U+20D1 (where the latter is COMBINING RIGHT HARPOON ABOVE) draws the
diacritic through the top of the letter, while -[NSAttributedString
drawInRect:] places it just above the letter.
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden