Re: Rendering combining marks
Re: Rendering combining marks
- Subject: Re: Rendering combining marks
- From: George Nachman <email@hidden>
- Date: Tue, 4 Jan 2011 22:17:00 -0800
That's exactly what I needed, thanks!
On Mon, Jan 3, 2011 at 8:34 PM, Aki Inoue <email@hidden> wrote:
> -drawInRect: variant is designed for matching the field editor layout.
>
> -drawWithRect: variant is the base and should be used over the other two.
>
> Aki Inoue
>
>
> On 2011/01/03, at 16:45, George Nachman <email@hidden> wrote:
>
>> 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.
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