From: Aki Inoue <a...@apple.com>
Subject: Re: NSLayoutManager and best override point for temporary
attributes
To: "Keith Blount" <keithblo...@yahoo.com>
Cc: "Martin Wierschin" <mar...@nisus.com>, cocoa-dev@lists.apple.com
Date: Friday, October 2, 2009, 10:24 PM
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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