Occasionally I come across:
"Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-GB" lang="en-GB"
dir="ltr">
......and so I have a question or two where the w3c specs seem (to me) to
be a little bit vague on:
(a) Is the dir="ltr" really necessary? I.e. Does it serve any real
purpose in this context.
E.g. If I am a viewer whose native browser is set up to read Hebrew or
Arabic would I be correct in assuming that, if reading an
English-language page without 'dir=ltr', the page would still be
presented correctly -- in the same way that a Hebrew or Arabic page
(without a 'dir') is correctly presented (rtl) in my English-language
based browser?
(b) If it is presented correctly without the 'dir' (as seems to be the
case), how does the browser determine the direction (I believe that
browsers are not meant to rely on the 'lang' attribute to determine
this?). Is it a function of the encoding being used?
Any explanation gratefully received ;-)
Thanks..
--
Jake (ja**@gododdin.demon.co.uk -- just a 'spam trap' mail address)
5  10599 
Jake wrote: <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-GB" lang="en-GB"
dir="ltr">
.....and so I have a question or two where the w3c specs seem (to me) to
be a little bit vague on:
There's a lot of vagueness in them, but what do you mean in this context?
(a) Is the dir="ltr" really necessary?
No. The default value for dir is "ltr", see
http://www.w3.org/TR/html4/struct/di...locklevel-bidi
(The DTD does not say this, because an element by default _inherits the
dir setting from its parent, so the default dir="ltr" really applies to
the root element only.)
Note that this does not depend on the language (declared or real); if
you have <html lang="ar">, you still have dir="ltr".
I.e. Does it serve any real purpose in this context.
Other than being explicit, no.
E.g. If I am a viewer whose native browser is set up to read Hebrew or
Arabic would I be correct in assuming that, if reading an
English-language page without 'dir=ltr', the page would still be
presented correctly
Yes.
-- in the same way that a Hebrew or Arabic page
(without a 'dir') is correctly presented (rtl) in my English-language
based browser?
A correctly written Hebrew or Arabic page is represented correctly on
any correctly behaving browser, if the browser has a capability of
rendering Hebrew or Arabic characters. (There's no requirement that a
browser be capable of rendering all the possible characters.)
The writing direction primarily depends on the inherent directionality
of characters, not on the dir attribute, which specifies the direction
for directionally neutral characters (roughly speaking - it also affects
the directionality of table columns, the default alignment, etc.).
(b) If it is presented correctly without the 'dir' (as seems to be the
case), how does the browser determine the direction (I believe that
browsers are not meant to rely on the 'lang' attribute to determine
this?).
They have been explicitly told _not_ to use the 'lang' attribute _at
all_ for that. The default is dir="rtl", and right-to-left characters
run right to left independently of this.
Is it a function of the encoding being used?
No. (Well, there's "visual Hebrew" encoding which really means
backwards-written Hebrew, but just stay away from it, mm'kay?)
On Thu, 1 Dec 2005, Jake wrote: Occasionally I come across:
dir="ltr">
(a) Is the dir="ltr" really necessary? I.e. Does it serve any real
purpose in this context.
No.
(b) If it is presented correctly without the 'dir' (as seems to be the
case), how does the browser determine the direction (I believe that
browsers are not meant to rely on the 'lang' attribute to determine
this?).
"dir=ltr" is the default value.
For "dir=rtl", read
http://ppewww.ph.gla.ac.uk/~flavell/...direction.html
and see the examples at
http://www.unics.uni-hannover.de/nht...onal-text.html
Is it a function of the encoding being used?
Only for "visual vs. logical Hebrew". But "visual Hebrew" is evil®
and should not be used anymore.
--
Evil® is a registered trademark of the President of the United States.
On Thu, 1 Dec 2005, Jake wrote: (a) Is the dir="ltr" really necessary? I.e. Does it serve any real
purpose in this context.
One thing to stress is that the dir= attribute is defined to have no
effect on characters which possess an inherent directionality: the
only way to influence those is with a <bdo...> element.
The purpose of the dir= attribute is to resolve ambiguities which
occur when mixing rtl and ltr scripts: characters which have neutral
directionality could get positioned inappropriately if left to the
browser's own rules. We found that liberal use of the dir= attribute
when mixing directionality was a good way to get the desired results,
avoiding browser anomalies and, in some cases, bugs.
(The unicode rules for automatically resolving directionality
ambiguities are rather complex!).
You've already been pointed to http://ppewww.ph.gla.ac.uk/~flavell/...direction.html
cheers
In message <Pi*******************************@ppepc56.ph.gla. ac.uk>,
Alan J. Flavell <fl*****@ph.gla.ac.uk> writes On Thu, 1 Dec 2005, Jake wrote:
(a) Is the dir="ltr" really necessary? I.e. Does it serve any real
purpose in this context.
One thing to stress is that the dir= attribute is defined to have no
effect on characters which possess an inherent directionality: the
only way to influence those is with a <bdo...> element.
The purpose of the dir= attribute is to resolve ambiguities which
occur when mixing rtl and ltr scripts: characters which have neutral
directionality could get positioned inappropriately if left to the
browser's own rules. We found that liberal use of the dir= attribute
when mixing directionality was a good way to get the desired results,
avoiding browser anomalies and, in some cases, bugs.
(The unicode rules for automatically resolving directionality
ambiguities are rather complex!).
You've already been pointed to
http://ppewww.ph.gla.ac.uk/~flavell/...direction.html
Indeed I have, and most instructional it was. My thanks to you, Jukka,
and Andreas for your comments.
I raised the question following comments by someone in another forum who
keeps insisting that it's necessary 'to avoid potential problems with
browsers in far-off foreign parts' -- or words to that effect ;-)
As my IE6 browser seems to have no problem rendering Hebrew and Arabic
correctly (rtl) even though the (X)HTML pages have no explicit
directionality, I suspected that the 'dir=ltr/rtl' wasn't going to have
any effect on page as a whole.
The explanations given in this thread makes things a little clearer.
cheers
Regards.
--
Jake (ja**@gododdin.demon.co.uk -- just a 'spam trap' mail address)
On Sat, 3 Dec 2005, Jake wrote: As my IE6 browser seems to have no problem rendering Hebrew and Arabic
correctly (rtl) even though the (X)HTML pages have no explicit
directionality,
Internet Explorer 6 does not implement the bidi algorithm http://www.unicode.org/reports/tr9/ - at least not completely.
If you observe differences between Mozilla and IE 6, you can be
sure that IE is wrong. You find such examples on Alan's and my
pages. Other browsers (Opera, Konqueror), however, are even worse.
It is therefore a good idea to mark _every_ piece of text with
the DIR attribute when you have Arabic or Hebrew text in your page.
--
Netscape 3.04 does everything I need, and it's utterly reliable.
Why should I switch? Peter T. Daniels in <news:sci.lang> This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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