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Re: Progress of text system
From: |
Alexander Malmberg |
Subject: |
Re: Progress of text system |
Date: |
Mon, 24 Feb 2003 00:55:16 +0100 |
Richard Frith-Macdonald wrote:
[snip]
> However, from Alexanders description, the current layout contravenes
> the standard usage of classes/class clusters ...
> NSLayoutManager should be the abstract class providing the general
> implementation, and GSLayoutManager (or perhaps a more meaningful name
> like GSWesternLayoutManager) ought to be the subclass providing the
> specialised/optimised implementation. When NSLayoutManager is
> instantiated, it would provide a concrete instance of GSLayoutManager
> to actually do the work. This is the way the naming conventions for
> class clusters normally work, and doing things the other way round
> might confuse programmers. However, this is just a matter of the
> naming conventions for the classes and does not effect the real
> structure.
The naming is a bit unfortunate, but it's necessary for OPENSTEP
compatibility, and it's a fairly small price to pay for that. If
NSLayoutManager was the non-layout-specific version, subclasses of
NSLayoutManager would not work as on OS, and there would be no way of
creating plain GSLayoutManager instances.
> So NSLayout manager would provide the capabilities of storing layout
> runs and glyph storage etc, wheras the concrete subclass would provide
> the optimised generation algorithms. Indeed, if the concrete
> subclasses provided no ivars of their own, it would be possible for
> them to mutate at runtime depending on the
> languages used ... so when NSLayoutManager is instantiated it could
> create a GSWesternLayoutManager, but storage of chinese text might
> make it mutate into a slower but more general GSChineseLayoutManager
> for instance.
So far, there is nothing that would prevent mutating between
NSLayoutManager and other (hypothetical) text-view-supporting layout
managers.
[mail #2]
Richard Frith-Macdonald wrote:
> PS.
> Please note ... criticism of your changes to the text system are not
> meant to be unappreciative ... if it sounds like I'm saying that you've
> failed to address some of the issues (mainly the character<=>glyph
> relationships) that is not to imply that that I don't understand/like
> the improvements you have made. After all, Fred, Nicola and I have all
> failed to do anything much about this in the last year .... this stuff
> is not simple/easy!
True, the text system is a big and complicated thing, and it took a lot
of time to work through all the parts and see all the issues. I do feel,
however, that the structure to handle everything is in place, so
although there are things left to implement, I now know where to place
them and how they're supposed to fit in. :-)
(Or why they don't fit in; the text system isn't meant to handle
everything, and there are trade-offs involved.)
- Alexander Malmberg
- Progress of text system, Fred Kiefer, 2003/02/16
- Re: Progress of text system, Alexander Malmberg, 2003/02/16
- Re: Progress of text system, Alexander Malmberg, 2003/02/17
- Re: Progress of text system, Richard Frith-Macdonald, 2003/02/23
- Re: Progress of text system, Alexander Malmberg, 2003/02/23
- Re: Progress of text system, Fred Kiefer, 2003/02/24