Notes for HTML i18n Guidelines Devt

- Setting directionality for an entire document in a bidirectional script

• Add dir="rtl" to the html tag.

  This will cause block elements and table columns to start on the right and flow from right to left. The Unicode bidirectional algorithm should automatically handle the inline text directionality. All block elements in the document will inherit this setting unless it is explicitly overridden.

  No dir attribute is needed for documents that have a base directionality of ltr, since this is the default.

  Note: in Internet Explorer adding the dir attribute to the html tag also moves the scroll bar to the left of the browser window.

• Enter all text in a single logical order, and leave it to the Unicode bidirectional algorithm to order the text as appropriate.

  Example: the Hebrew text that reads as follows

  The title says "פעילות הבינאום, W3C" in Hebrew.

  Would be typed into the editor and stored in the computer memory (though not necessarily displayed if your editor is bidi aware) as

  The title says "פעילות הבינאום, W3C" in Hebrew.

  Occasionally there may be situations where the Unicode bidirectional algorithm doesn't quite do what is required. Alternatively, you may want to assign a different directionality to a part of the page. In these cases you can apply additional markup to override the default ordering.

• If using an ISO encoding, choose iso-8859-8-i. (Alternatively use utf-8 or utf-16.)

  See explanation in the html4.01 spec.

• Other topics:
  • What if I want to change the directionality of a part of the page?
  • What if the Unicode algorithm doesn't order chunks of text the way I want?
  • What if I want to override the effects of the Unicode algorithm?
  • Shouldn't I use CSS styling for this?

- Changing the directional properties of a part of the text

• Add the dir attribute to an element that encompasses all the text.

  If the dir attribute is added to a block element, all subordinate elements inherit the directionality (unless of course their directionality is changed explicitly using a different value for dir). Elements and their contents will flow from the right of the displayed page towards the left.

  Example: The following lines of text show a right-to-left paragraph embedded in this left-to-right page.

  להוביל את הרשת למיצוי הפוטנציאל שלה…

  The code underlying this paragraph, ordered as per the characters in memory, is:

  <p dir="rtl">להוביל את הרשת למיצוי הפוטנציאל שלה… <img src="globe.gif" alt="globe"/></p>

  Note the effect of the dir attribute in placing the image to the left of the text.

  At a simple level the Unicode bidirectional algorithm takes care of the reordering of inline text, but where there is nesting of directionality the dir attribute needs to be used.

  Example: The following line of text is coded without any dir attributes. Note that the order of the two Hebrew words is correct, but the text 'W3C' should appear on the left hand side of the quotation.

  The title says "פעילות הבינאום, W3C" in Hebrew.

  To get the correct result we surround the text within the quote marks with a span element and set the dir attribute rtl as shown here (with all characters as ordered in memory).

  <p>The title says "<span dir="rtl">פעילות הבינאום, W3C</span>" in Hebrew.</p>

  The result when displayed is:

  The title says "פעילות הבינאום, W3C" in Hebrew.

• Use markup to achieve this effect rather than CSS styling or the Unicode control characters for bidi embedding.
  • Explain what the Unicode control characters are. The avoidance of control characters is recommended by Unicode and Markup Languages. The HTML spec also warns against mixing control codes and markup.
  • The CSS2 spec also advises against the use of CSS for implementing bidi in HTML4.01. In fact it goes as far as to say that conformant HTML processors do not have to support the CSS bidi functionality. Does this change for XHTML?
• Other topics:
  • What if the Unicode algorithm doesn't order chunks of text the way I want?
  • What if I want to override the effects of the Unicode algorithm?

- Overriding the Unicode bidirectional algorithm

• Use the bdo element to force the directionality of a sequence of inline characters.

  'bdo' stands for 'bidirectional override'. This inline element can be used to override the Unicode bidirectional algorithm if the dir attribute doesn't produce the desired result or if you want to produce a different result.

  Example: Illustrations of the characters as stored in memory in earlier examples are produced by simply applying a bdo tag to produce a left to right flow of characters regardless of the directionality of the characters involved. So the earlier example showing how text was stored in the computer's memory

  The title says "פעילות הבינאום, W3C" in Hebrew.

  can be produced using the following underlying code

  <p><bdo dir="ltr">The title says "פעילות הבינאום, W3C" in Hebrew.</bdo></p>

  Without the bdo tag, the Unicode bidirectional algorithm would have produced the following result

  The title says "פעילות הבינאום, W3C" in Hebrew.

• Use the special entities, &lrm; and &rlm; to force directionality of directionally neutral characters.

  These represent two special characters in Unicode that can be used after the neutral character whose directionality is ambiguous. Problems typically arise for punctuation that falls between characters in a bidirectional script and characters in a non-bidirectional script. The entities are Unicode characters that are strongly typed, so they help disambiguate the context for the Unicode bidirectional algorithm.

  Example: In the following sentence, despite the use of the dir attribute, the commas between the English text that are part of the Hebrew right to left flow have become confused. This is because they are surrounded by Latin text, and the Unicode bidirectional algorithm assumes that they are part of the Latin text flow that goes from left to right.

  פעילות הבינאום, W3C, W3C, W3C, פעילות הבינאום, W3C

  This can be easily remedied by adding a &rlm; entity immediately after the commas, as shown here

  פעילות הבינאום, W3C,‏ W3C,‏ W3C,‏ פעילות הבינאום, W3C

  The code that produced this result is

  <p dir="rtl">פעילות הבינאום, W3C,&rlm; W3C,&rlm; W3C,&rlm; פעילות הבינאום, W3C</p>

  Should we suggest the use of hex values, since XHTML is XML? Actually, I think XML ought to have meaningful entity names for these invisible formatting control characters - makes the code a lot easier to manage/understand.

- Declaring the language of a whole page

- Labelling text in a different language

- Specifying the language of a linked page

- Specifying language codes

- Creating an internationalised page header