Re: Error during redisplay

[Kenichi Handa <handa@m17n.org>]

In article <E1JU9V5-0001nM-1x@fencepost.gnu.org>, Richard Stallman <rms@gnu.org> writes:

> to .emacs fixes the problem. Apparently, pure strings in
> mode-line-format don't like to be added auto-composed properties.

>     In auto-compose-chars, inhibit-read-only is bound to t while
>     the code add auto-composed property.  If it's still not
>     allowed, are there anyway to detect that the string is pure?

> There is something not clean about trying to modify a string in
> mode-line-format when a user turns on a feature that doesn't intend to
> change the mode line.  That seems like a flaw in the design of
> something.

The current design requires to add `composition' property to
a string to properly display the string if it contains, for
instance, some of Indic characters, and to add
`auto-composed' property to avoid the repeated generation of
`composition' property.

> The strings in mode-line-format are supposed to be set up correct when
> Emacs is dumped.  Should they have these properties, or not?  That is
> the first question.

If mode-line-format has not been modified, I think it
doesn't contain any characters that require composition
(except for the case that we support such ligatures as "Fi"
in the future).  One way is to check if the string contains
any such characters, and if not, avoid any composition
processing.  As the string tends to be short, doing that
check repeatedly will not be that inefficient.

> If they SHOULD have these properties, probably we should make sure they have
> these properties from the start, or from an early point in building Emacs.

That's impossible.  How to compose them depends on which
font to use.

---
Kenichi Handa
handa@ni.aist.go.jp