Hi Martin,
Many thanks for your reply (as always :) ). And d'oh, yes, the glyph/character
thing was an oversight - I'm usually very careful about this as I am aware they
can be very different, so thanks for picking me up on that. Also thanks for the
pointer to -ensureLayoutForCharacterRange: - that works perfectly. So my new
method looks like this:
- (void)forceInitialLayout
{
NSInteger charIndex = (20000 > [[self textStorage] length] ? [[self
textStorage] length] : 20000);
if (charIndex > 0)
{
if(floor(NSAppKitVersionNumber) >= NSAppKitVersionNumber10_5)
{
[layoutManagerensureLayoutForCharacterRange:NSMakeRange(0, charIndex)];
}
else
{
charIndex -= 1;
[layoutManagerlocationForGlyphAtIndex:[layoutManagerglyphIndexForCharacterAtIndex:charIndex]];
}
}
}
I think your explanation of the problem is most likely spot on, too - the text
container of the glyph is different after layout has finished. I do have
noncontiguous layout enabled, but the above seems to work nicely either way.
Thanks again!
All the best,
Keith
----- Original Message ----
From: Martin Wierschin <[email protected]>
To: Keith Blount <[email protected]>
Cc: Cocoa Developers <[email protected]>
Sent: Fri, March 12, 2010 10:52:07 PM
Subject: Re: Forcing text layout
Hello Keith!
> - (void)forceInitialLayout
> {
> NSInteger charIndex = (50000 > [[self textStorage] length] ? [[self
> textStorage] length] : 50000);
> if (charIndex > 0)
> {
> charIndex -= 1;
> [layoutManagerlocationForGlyphAtIndex:charIndex];
You shouldn't play loose which character/glyph indexes. I'm sure you know, but
the mapping between chars/glyphs is arbitrary and your method could
theoretically trigger an out-of-bounds exception. In practice it probably won't
because I believe the Cocoa typesetter always produces more glyphs than
characters (eg: inserting null glyphs as padding).
That point aside, I've also experienced issues with when forcing layout to a
specific character index. Notably that the the mapping from characters to
glyphs doesn't seem stable until layout is complete. I've seen
-[NSLayoutManager numberOfGlyphs] change before/after layout! Perhaps the
TextEdit code you quoted fails for that reason, eg: the mapping from the final
character index (the image attachment) to its corresponding glyph changes after
layout finishes.
My solution was to conditionally use -[NSLayoutManager
ensureLayoutForCharacterRange:] when running on Leopard or later. That punts
the problem entirely to Apple to solve. Another thing to check: do you have
discontinuous layout enabled? I never did, but perhaps that's a factor for you.
~Martin
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