Re: Calculating paragraph numbers
Re: Calculating paragraph numbers
- Subject: Re: Calculating paragraph numbers
- From: Douglas Davidson <email@hidden>
- Date: Thu, 29 Jan 2004 09:55:45 -0800
On Jan 28, 2004, at 11:00 PM, Mark Alldritt wrote:
I'm trying to figure out how I can calculate the paragraph number of
the
current selection in a text view. I've studied the code on
http://developer.apple.com/documentation/Cocoa/Conceptual/TextLayout/
Tasks/C
ountLines.html, but it suggests that I iterate over the entire text to
count
the lines. Is there some way to get this information directly?
Otherwise,
I can see this getting slower and slower as the length of text grows.
NSTextStorage, and its superclass NSMutableAttributedString, do not
maintain paragraph number information for the text they contain,
because the text system does not need this information. It often uses
the range of the paragraph surrounding a particular location, but has
no interest in numbering the paragraphs. Obviously you can determine
this information by iterating through the text, but as you say this
will be O(text length). The natural solution would be for you to cache
this information. You can determine when the text changes in several
ways; at the text view level, the text view's delegate is notified of
all user changes to the text. At the text storage level, it is
possible to keep track of all changes to the text.
Douglas Davidson
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