I'm going to answer some of Peter's points, leaving aside the interesting digressions into Java subclassing etc. that have developed later in the discussion.
Thank you, Asmus. If people want to discuss normalisation and string handling in Java, they are welcome to do so, but they should use a different subject heading and not my (copyrighted :-) ) text.
At 04:19 AM 10/15/03 -0700, Peter Kirk wrote:
I note the following text from section 5.13, p.127, of the Unicode standard v.4:
Canonical equivalence must be taken into account in rendering multiple accents, so that any two canonically equivalent sequences display as the same.
This statement goes to the core of Unicode. If it is followed, it guarantees that normalizing a string does not change its appearance (and therefore it remains the 'same' string as far as the user is concerned.)
...
The guidelines are concerned with the average case: displaying the characters as *text*.
[The use of the word 'must' in a guideline is always awkward, since that word has such a strong meaning in the normative part of the standard.]
So, are you saying that for normal display of characters as text these guidelines must be followed?
Rendering systems should handle any of the canonically equivalent orders of combining
marks. This is not a performance issue: The amount of time necessary to reorder combining
marks is insignificant compared to the time necessary to carry out other work required
for rendering.
The interesting digressions on string libraries aside, the statement made here is in the context of the tasks needed for rendering. If you take a rendering library and add a normalization pass on the front of it, you'll be hard-pressed to notice a difference in performance, especially for any complex scripts.
So we conclude: "rendering any string as if it was normalized" is *not* a performance issue.
Thank you. This is the clarification I was looking for, and confirms my own suspicions. But are there any other views on this? I have heard them from implementers of rendering systems. But I have wondered if this is because of their reluctance to do the extra work required to conform to this requirement.
-- Peter Kirk [EMAIL PROTECTED] (personal) [EMAIL PROTECTED] (work) http://www.qaya.org/
