Re: speed of testtext, directionality

[Karl Koehler <koehler or uni-bonn de>]

On 10 Jul 2000, Owen Taylor wrote:

> > #2: Strange behaviour of the arabic shaper when appending text to the end 
> > ot the line in left-to-right mode:
> > Actually, in this case, no shaping is done, and the characters do not 
> > appear ( Or only unshaped, if you have iso10646-1 encoded fonts ).
> > In this case, even though several arabic letters may have been typed,
> > any shaper's PangoAnalysis reveals that we are in a left-to-right run
> > of characters : analysis->level % 2 == 0 ! 
[ ... Ø]
> Hmmm - I can't seem to reproduce this. If I create an empty
> buffer in texttext, in LTR mode, and start typing in arabic
> characters, they are shaped as I would expect.

Actually, for me this is a sure  way to have them not shaped. 
My configuration:
  fribidi-0.1.12, and glib, pango, gtk+ from cvs ( yesterday;
  yes, I finally found an acceptable work-around for the firewall ! ),
  libc 2.1.3 .

I can't check on any other system, because I am currently not able to
build glib on AIX ( automake failes, telling me the following:
  configure.in: 66: required file `./config.h.in' not found 
).

> The cause of the two reshapes is:
> 
>  1) A reshape because the paragraph is invalidated when we move
>     the cursor position. While the PangoLayout structure 
>     doesn't actually change, we don't keep detailed information
>     about what changed in the paragraph - we just say "something
>     changed".
> 
>     This could probably be avoided with some more complexity - 
>     but a justification for not doing is that reshaping has
>     to be fast enough to handle reflowing pages and pages
>     of text. If we achieve that goal, we should be able to
>     handle a few extra reshapes without it hurting much.
Well, the auto-repeat can be made faster than I can type.
So while additional shaping during typing does not hurt,
it is noticeable when just running the cursor around.

> 
>  2) Another reshape when we display because of an optization 
>     gone astray.  [ ... ]
>     The appended patch does this and seems to help some.
It sure does ! Thank You, and keep up the good work,


		Karl