Re: Custom text via Core Text in a layer.

FROM : Aki Inoue
DATE : Mon Nov 26 19:04:16 2007

John,

The code attached below is setting up sufficient environment for Cocoa 
drawing.

You should be able to just use NSStringDrawing methods like -
[NSAttributedString drawWithRect:options:].

Aki

On 2007/11/19, at 14:29, John Clayton wrote:

> Well,
>
> I'm definately not writing my own text system.  All I want to be 
> able to do is stick some NSAttributedText into a bounded area, on a 
> layer. Assuming CATextLayer isn't what I wanted, what would be the 
> approach to adapting the code below to use the Cocoa based APi's to 
> draw into that area? Is it actually easier?
>
> <side track / background info / reality hiatus>
> FYI: the original reason that I moved away from CATextLayer, was 
> that I wanted to provide a 'duration' value for the layer - and 
> doing that in conjunction with the way that I am rendering content 
> (CARenderer) wasn't working.
>
> So I decided that I needed more control.  I've since then moved 
> entirely away from touching the beginTime/duration properties of 
> layers at all, and have changed my custom rendering component to use 
> two newly created properties (projectBeginTime and projectDuration) 
> that define exactly the same thing, but are not influenced 
> indirectly by the Core Animation rendering engine (i.e. 
> CACurrentMediaTime + background modifications to the presentation 
> layer).
>
> Its actually more involved that that - but I thought I'd provide a 
> wee bit of a sense of the tangle I'm getting myself in :-)
>
> Incidentally, I can (and am) using a CATextLayer derived instance 
> for textual rendering in my project, which now works OK [so long as 
> I don't mess with duration] - my question is driven more out of 
> curiosity and learning desire.
> </side track / background info / reality hiatus>
>
> E.g.  this is what I've got now (which draws not-quite-the-same as 
> the standard CATextLayer).  The only reason I decided to use core-
> text was because there were about a handful of lines in there to get 
> my text rendered into a CGContextRef.  If Cocoa has a better way of 
> achieving the same thing (i.e. attributed strings, onto a 
> CGContextRef, for use by a CALayer) - then I'm all ears.
>
> // code begins...
> - (void) drawInContext:(CGContextRef)context
> {
>     // core-text, here we come
>     [NSGraphicsContext saveGraphicsState];
>     [NSGraphicsContext setCurrentContext:[NSGraphicsContext 
> graphicsContextWithGraphicsPort:context flipped:NO]];
>
>     CGContextSetTextMatrix(context, CGAffineTransformIdentity);
>     
>     CGMutablePathRef path = CGPathCreateMutable();
>     if(path)
>     {
>         CGPathAddRect(path, NULL, self.bounds);
>         
>         CTFramesetterRef framesetter = 
> CTFramesetterCreateWithAttributedString(
>             (CFAttributedStringRef)_string
>         );
>         
>         // Create the frame and draw it into the graphics context
>         CTFrameRef frame = CTFramesetterCreateFrame(framesetter,
>                                                     CFRangeMake(0, 0), path, NULL);
>         
>         if(frame)
>             CTFrameDraw(frame, context);
>         
>         if(framesetter)
>             CFRelease(framesetter);
>         
>         if(frame)
>             CFRelease(frame);
>     }
>     
>     if(path)
>         CFRelease(path);
>     
>     [NSGraphicsContext restoreGraphicsState];
> }
> // code ends...
>
> thanks for making it this far..
>
> On 19/11/2007, at 8:03 PM, Aki Inoue wrote:
>

>>> Bad assumption??

>> Yes 8-).
>>
>> CoreText is designed to be the base text layout engine for out 
>> platform.
>> And it's based on somewhat different graphics model from the Cocoa 
>> Text System.
>>
>> CT is mostly relying on the CG graphics state for specifying 
>> rendering attributes whereas the Text System is taking more markup 
>> attribute kind of approach.
>> So, even though some of the text attributes are toll-free bridged, 
>> text attributes recognized by CF is subset of the Text System and 
>> possibly stay that way.
>>
>> In other words, if you need to use all text attributes supported by 
>> the Text System, you should stay with the Text System.
>>
>> You should have to go down to CT for very limited reasons (i.e. 
>> writing your own text engine).
>>
>> Aki
>>
>> On 2007/11/19, at 10:46, John Clayton wrote:
>>

>>> I'm not - I just created a .rtf file in TextEdit, made some things 
>>> bold, some thing yellow, gave the whole text a background shadow - 
>>> and expected that this would then show up in core-text rendered 
>>> graphics as well.
>>>
>>> Bad assumption??
>>>
>>>
>>>
>>> On 19/11/2007, at 6:46 PM, j o a r wrote:
>>>

>>>>
>>>> On Nov 19, 2007, at 9:39 AM, John Clayton wrote:
>>>>

>>>>> I'm using the following code to draw an attributed string into a 
>>>>> layer (my own CATextLayer), but the text *always* draws black - 
>>>>> is there something simple that I'm doing wrong? I am of course 
>>>>> assuming that the colour into in the attributed string would 
>>>>> determine how that content is being drawn.

>>>>
>>>>
>>>> Quick off-list question:
>>>>
>>>> How certain are you that your attributes are set up correctly? 
>>>> Have you verified in some non-CT layer context that they do the 
>>>> right thing?
>>>>
>>>> j o a r
>>>>
>>>>

>>>
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>>

>