Keith,
If your custom attributes modifies just the graphics state (don't
affect the layout), you can override -[NSLayoutManager
showPackedGlyphs:length:glyphRange:atPoint:font:color:printingAdjustment
:].
The method is the bottleneck for calling CG APIs. You can query the
text attribute using glyphRange.location and see if there is one of
your custom attributes.
You should be able to customize alpha, color, blending mode,
compositing mode, clipping, etc.
Aki
On 2009/10/02, at 7:04, Keith Blount wrote:
Hi,
Looking at this again, would NSLayoutManager's
-textStorage:edited:range:changeInLength:invalidatedRange:
method be a good candidate for overriding to add temporary
attributes? The text storage calls this whenever it's edited and
provides it with the new range of characters. So it seems that I
could add any temporary attributes to the range that gets passed in
here, checking that changeInLength > 0.
Or, what if in the -addAttribute:..., -setAttributes:... and
removeAttribute:... methods of my NSTextStorage, I called through to
all of the text storage's layout managers to ask them to add the
temporary attribute if necessary, after -
edited:range:changeInLength: gets called?
Many thanks again!
All the best,
Keith
--- On Thu, 10/1/09, Martin Wierschin <mar...@nisus.com> wrote:
From: Martin Wierschin <mar...@nisus.com>
Subject: Re: NSLayoutManager and best override point for temporary
attributes
To: "Keith Blount" <keithblo...@yahoo.com>
Cc: cocoa-dev@lists.apple.com
Date: Thursday, October 1, 2009, 1:50 AM
Hi Keith,
I have certain custom text attributes that are used in
my NSTextStorage to which I would like to add temporary
attributes via the NSLayoutManager.
What version of OSX are you testing under? Under Leopard
there's a bug in -[NSLayoutManager
temporaryAttribute:atCharacterIndex:longestEffectiveRange:inRange:]
that calculates effective ranges that are too short. For
specific test cases this caused big inefficiencies in the
text system. I believe this bug is fixed in Snow Leopard.
more recently I have taken to overriding
NSLayoutManager's
-temporaryAttributesAtCharacterIndex:effectiveRange:
If this is too slow, then I'd look to using some kind of
cache for your calculations. But really, NSLayoutManager's
temporary attributes are already a cache; one likely to be
specifically designed for high performance index/run access.
I think your original idea of setting temporary attributes
whenever text changes would be the most efficient.
Perhaps you're recalculating too much, too often? I don't
know the access patterns for temporary attributes, but I
would guess they are only queried when associated text is
displayed on screen. If that's the case, you could fix them
up lazily, eg: whenever text changes just note down that the
attributes are dirty in that range. Your temporary attribute
methods in your NSLayoutManager subclass can then ensure
that temporary attributes are not dirty before they are
returned.
If none of that is efficient enough, you could rig up a
NSTextStorage subclass that has two sets of attributes: one
set for private use and another derived set which only the
layout system sees.
Hopefully some of that helps,
~Martin
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