Re: Possible Pango 1.4 ideas

[Damon Chaplin <damon karuna uklinux net>]

On Mon, 2003-01-20 at 02:59, Havoc Pennington wrote: 
> On Sun, Jan 19, 2003 at 09:35:42PM -0500, Owen Taylor wrote: 
> > It looks like most of these items (except for Kerning) involve
> > PangoLayout. I think one of the most basic things that will have
> > to be dealt with is how to implement them and not turn PangoLayout
> > from barely-maintainable to unmaintainable.
> 
> Performance and memory usage also seems like an issue to me. We're
> already sort of suboptimal here.

I don't intend my layout code to be the default - most apps will
continue to use the basic PangoLayout code. Only those apps that want
more sophisticated text layout would switch on my code. (I don't want to
affect the reliability of current apps.) 

Fortunately the TeX algorithm is very nice, and fast. If it succeeds in
the first pass (without hyphenating), which it usually does if given a
decent layout width, it is only about 10% slower than the current code.
It does use quite a bit of memory temporarily while it does the layout,
but I haven't optimized that yet. 


> You and Owen have probably looked at it more, but as someone who used
> to spent a lot of time with Quark and Pagemaker, those apps certainly
> seemed to have substantially more complex text handling than
> PangoLayout does right now; even AbiWord does, doesn't it? I'm kind of
> skeptical that PangoLayout can handle their needs without becoming
> noticeably higher-overhead and much harder to maintain (if only in
> terms of sheer additional code size).
>
> But then, I realize that maintaining PangoSuperDuperLayout alongside
> PangoLayout isn't really attractive either.

I don't think Quark has that many more features. (My feature-list
basically came from reading a book on Quark.) Besides, if we don't put
it in Pango, then every app that wants decent text layout has to do it
themselves, which is too hard for developers really. 


> Another thing I'd throw in: it doesn't seem easy to get a reasonable
> API for a page layout or word processor app without having at least
> one such app constantly trying to use the API and iterating things
> based on that experience... how many Pango API changes/extensions did
> we make for GtkTextView? I remember quite a few. And compared to these
> complex apps GtkTextView is cake.

I don't think this will be a problem, but we'll see. 
(My long-term goal is to write a DTP app, so I can try it all out then.)
Damon