Urdu Gap Analysis

W3C Group Draft Note

More details about this document
This version:
https://www.w3.org/TR/2024/DNOTE-arab-ur-gap-20240719/
Latest published version:
https://www.w3.org/TR/arab-ur-gap/
Latest editor's draft:
https://w3c.github.io/alreq/gap-analysis/arab-ur-gap.html
History:
https://www.w3.org/standards/history/arab-ur-gap/
Commit history
Editor:
(W3C)
Feedback:
GitHub w3c/alreq (pull requests, new issue, open issues)

Abstract

This document describes and prioritises gaps for the support of Urdu on the Web and in eBooks. In particular, it is concerned with text layout. It checks that needed features are supported in W3C specifications, in particular HTML and CSS and those relating to digital publications. It also checks whether the features have been implemented in browsers and ereaders. This is a preliminary analysis.

Status of This Document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

🚩
This document is retired and MUST NOT be used for further technical work.
See Arabic Script Gap Analysis instead.

🚩 Retired document. Do not use.

This document describes and prioritises gaps for the support of Urdu on the Web and in eBooks. In particular, it is concerned with text layout. It checks that needed features are supported in W3C specifications, in particular HTML and CSS and those relating to digital publications. It also checks whether the features have been implemented in browsers and ereaders. This document complements the document Urdu Layout Requirements, which describes the requirements for areas where gaps appear. It is linked to from the language matrix that tracks Web support for many languages.

This document is an individual contribution, and is not currently a work item in any group, however, you can contact the Internationalization Working Group for more information. We welcome contributions to this and/or other documents.

This document was published by the Internationalization Working Group as a Group Draft Note using the Note track.

Group Draft Notes are not endorsed by W3C nor its Members.

This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

The W3C Patent Policy does not carry any licensing requirements or commitments on this document.

This document is governed by the 03 November 2023 W3C Process Document.

1. Introduction

The W3C needs to make sure that the needs of scripts and languages around the world are built in to technologies such as HTML, CSS, SVG, etc. so that Web pages and eBooks can look and behave as people expect around the world.

This page documents difficulties people encounter when trying to use the Urdu language with the Arabic (Nastaliq) script on the Web.

Having identified an issue, it investigates the current status with regards to web specifications and implementations by user agents (browsers, e-readers, etc.), and attempts to prioritise the severity of the issue for web users.

A summary of this report and others can be found as part of the language matrix.

1.1 Work flow

This version of the document is a preliminary analysis

Gap analysis work usually starts with a preliminary analysis, conducted quickly by one or a small group of experts. Then a more detailed analysis is carried out, involving a wider range of experts. The detailed analysis may involve the development of tests, in order to illustrate issues and track results for browsers. The next phase is ongoing maintenance. It is expected that the resulting document will not be frozen: as gaps are fixed, this should be noted in the document. It is also possible that new gaps are noticed or arise, and they can be added to this document when that happens.

As the gap analysis develops, the requirements for features that are problematic should be described in the companion document, Urdu Layout Requirements. Links to the appropriate part of that document should be added to this document as the material is created. Note that the requirements document should not contain any technology-specific information: all of that belongs here.

1.2 Prioritization

This document not only describes gaps, it also attempts to prioritise them in terms of the impact on the local user. The prioritisation is indicated by colour.

Key:

It is important to note that these colours do not indicate to what extent a particular feature is broken. They indicate the impact of a broken or missing feature on the content author or end user.

Basic styling is the level that would be generally accepted as sufficient for most Web pages. Advanced level support would include additional features one might expect to include in ebooks or other advanced typographic formats. There may be features of a script or language that are not supported on the Web, but that are not generally regarded as necessary (usually archaic or obscure features). In this case, the feature can be described here, but the status should be marked as OK.

The decision as to what priority level is assigned to a described gap is down to the experts doing the gap analysis. It may not always be straightforward to decide. If a given section in this document refers to more than one feature that is broken, each with different impacts on Web users, the priority for the section should be the lowest denominator.

A cell can be scored as OK if the feature in question is specified in an appropriate specification, and is supported by user agents. A specification that is in CR or later and has two implementations in 'major' browsers will count. This means that the feature may not be supported in all browsers yet. (At some point in the future we may try to distinguish, visually, whether support is available in a specification but still pending in major browsers or applications.)

2. Text direction

See also General page layout & progression for features such as column layout, page turning direction, etc. that are affected by text direction.

2.1 Vertical text

Are the script requirements for vertically oriented text met? What about if you mix vertical text with scripts that are normally only horizontal? Do you need a switch to use different characters in vertical vs. horizontal text? Does the browser support short runs of horizontal text in vertical lines (tate-chu-yoko in Japanese) as expected? Is the orientation of characters and the directional ordering of characters supported as needed?

#242 CSS Writing-modes sideways values not implemented

Languages: arb pes ug ur ks 2

This issue is applicable to most languages.

Vertical text may occur for special effects (the spine of a book, table column headings, etc). Typographically, it is simply horizontal text that is rotated. There is no way to do this effectively until browsers support the new CSS properties.

For more details, see this GitHub issue, which is being used to track this gap. Please add any discussion there, and not to this issue.

2.2 Bidirectional text

If this script runs right-to-left, are there any issues when handling that? Is bidirectional text adequately supported? What about numbers and expressions? Do the Unicode bidi controls and HTML markup provide the support needed? Is isolation of directional runs problematic?

3. Glyph shaping & positioning

3.1 Fonts & font styles

Do the standard fallback fonts used in browsers (eg. serif, sans-serif, cursive, etc.) match expectations? Are special font or OpenType features needed for this script that are not available?

#279 Wrong glyph digit shapes for extended arabic-indic digits

Languages: arb pes ur 2

This issue is applicable to Persian, Urdu and Sindhi. Persian, Urdu and Sindhi use extended-arabic-indic codepoints for digits in list counter styles. However, languages that use these code points tend to prefer specific glyph shapes for certain numbers, as shown here. More:

The GAP
An intelligent opentype font may be able to detect the language of the text and substitute appropriate glyphs if it is used for the content, but here we are looking at the default behaviour of the browser, with no fonts explicitly assigned to the text. Blink displays Persian digit glyphs in all three cases. Webkit renders the correct glyphs for Persian and Urdu, but not for Sindhi. Gecko renders Persian glyph shapes throughout, even though it uses different fonts for Persian vs. Urdu/Sindhi.
Priority
While this is clearly not right, more user feedback is needed if we are to determine that this causes readability issues. Therefore labelling this, for now, as Advanced.
Tests & results
Interactive test, The browser uses appropriate digit glyph shapes for Persian, Urdu, and Sindhi by default.
Action taken
GeckoBlinkWebkit
Outcomes
tbd

#276 Font fallback should allow selection of a Nastaliq font

Languages: arb pes ur ks 1

This issue is applicable to Urdu, Kashmiri, and other Arabic script orthographies.

Languages such as Urdu and Kashmiri are written in a nastaliq style of Arabic, and authors will typically want any font fallback to select another nastaliq font, rather than a naskh or other font.

More:

The GAP
Currently there is no way to tell the browser to fall back to a nastaliq font, rather than a naskh or other font.

Neither Gecko, Blink, nor Webkit support this. Before they can, CSS needs to provide a way for authors to indicate that a nastaliq generic font should be used.

Priority
This is a high priority for languages such as Urdu and Kashmiri, where nastaliq fonts are the norm, and incorrect substitutions may cause readability and cultural issues. It is also a useful feature for other languages, such as Persian or Kurdish, where nastaliq styles may be used for certain types of text.

Tests & results
Interactive test, font-family:generic(nastaliq) will apply a nastaliq font in Urdu

Action taken
Discussion document: Generic font families

CSS discussion threads:

Bug reports: GeckoBlinkWebkit

Outcomes
The CSS Fonts 4 spec now defines a generic(ident) syntax which will be used for newly-introduced, and especially for script-specific, generics.

generic(nastaliq) has been added as one of the generic family names.

Browsers are not yet supporting that.

3.2 Context-based shaping and positioning

Does the script in question require additional user control features to support alterations to the position or shape of glyphs, for example adjusting the distance between the base text and diacritics, or changing the glyphs used in a systematic way? Do you need to be able to compose/decompose conjuncts, or show characters that are otherwise hidden, etc?

3.3 Letterform slopes, weights, & italics

This covers ways of modifying the glyphs, such as for italicisation, bolding, oblique, etc. Do italic fonts lean in the right direction? Is synthesised italicisation problematic? Are there other problems relating to bolding or italicisation - perhaps relating to generalised assumptions of applicability?

3.4 Cursive text

If this script is cursive (eg. Arabic, N’Ko, Syriac, etc), are there problems or needed features related to the handling of cursive text? Do cursive links break if parts of a word are marked up or styled? Do Unicode joiner and non-joiner characters behave as expected?

#222 Inline elements/styling break cursive shaping

Languages: arb pes ug ur ks 2

This issue is applicable to text in all cursive scripts.

When elements surround part of a cursive run of text, and apply styling, the results often break the cursive joins. (See the results of trying to colour individual letters in the illustration below – as expected above, unsuccessful below.)

Screenshot 2021-01-22 at 15 19 49

shaping-2

Specs: After some discussion, the CSS spec requires the following (see CSS Text: Shaping Across Element Boundaries):

  1. Markup alone around part of a joined up sequence must not disturb the joining behaviour.
  2. Styling that doesn't affect the characters, such as text-decoration, must not break the joins.
  3. Styling that does affect the shape of the characters should not break the joins, however the result is not well defined for complex glyph arrangements such as ligatures where the markup occurs between characters that make up the ligature.
  4. Non-zero margins, padding, and borders, will break the join, as will isolation boundaries.

Tests & results: Interactive test, A span with a colour change for one letter in an Arabic word doesn't break the joining behaviour

  • Gecko: ✅ *Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Firefox/102.0*
  • Blink: ✅ *Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36*
  • Webkit: ❌ *Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.5 Safari/605.1.15*
I18n test suite, Cursive joining
  • Gecko: ✅❌ *Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Firefox/102.0*
  • Blink: ✅ ❌ *Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36*
  • Webkit: ❌ *Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.5 Safari/605.1.15*
Webkit breaks cursive joining as soon as markup appears around a character, and so obviously fails for any type of styling application, too.

Gecko and Blink keep joins for styling that doesn't affect the shape of the characters (eg. text-decoration), and keeps it for colour changes, however Firefox fails for changes in font-weight, font-style, and font-size, as well as for markup such as em and b tags.

(Gecko and Blink also only pass some of the tests for non-zero margin/padding/border and bdi isolation. Which expect the cursive joins to be broken.)

Browser bug reports: GeckoBlinkWebkit

Priority: It would be useful to decide on the potential impact of the failures described here, so as to prioritise the issue. Is the inability to surround/style parts of a word a significant issue? It may be problematic when defining a term (using dfn) if the term is only part of the run of letters between spaces, eg. after the definite article.

#221 Text opacity shows glyph overlap

Languages: arb pes ug ur ks 2

This issue is likely to apply to all cursive script text.

When opacity is applied to text, Gecko and Blink produce dark patches where the cursive glyphs overlap, but Webkit and Legacy Edge don't. See the test.

text-opacity

For more details, see this GitHub issue, which is being used to track this gap.

#220 Text stroke cuts joining glyphs apart

Languages: arb pes ug ur ks 2

This issue is likely to apply to all cursive script text, but also to other scripts that have joins between letters.

When text stroke effects are applied to cursive text, they should not interrupt the cursive flow.

The GAP
Unfortunately, that's not the case for current implementations. Overlaps where the glyphs join produce double breaks in the cursive flow.

This example shows the typical result for Arabic.

text-stroke

The set of modern languages using cursive scripts includes those that use the following scripts: Arabic, Syriac, Mongolian, Mandaic, N'Ko, Adlam, Hanifi Rohingya. It also affects text in archaic scripts, including Phags Pa, Manichaean, Psalter Pahlavi, Sogdian, Old Uyghur, Chorasmian.

However, this also affects scripts such as Devanagari (Hindi, Marathi, etc), Gurmukhi (Punjabi), Bengali, Gondi, Modi, Newa, etc. This example is Hindi:

Screenshot 2022-02-08 at 17 12 09

In Gecko, Blink, and Webkit the stroke around the text interrupts the cursive flow.

The property text-stroke is not yet in CSS, but has been implemented in major browsers under the name -webkit-text-stroke.

-webkit-text-stroke is currently specified in WhatWG's Compatibility spec.

Priority:
Marking as advanced because this is a decorative feature.

Tests
Interactive test, Text stroke applied to Arabic text doesn't cut joining glyphs apart
i18n test suite, Text stroke

Action taken
Issue, Standardize text-stroke Open.

Outcomes
tbd

3.5 Case & other character transforms

Does your script need special text transforms that are not supported? Does your script convert letters to uppercase, capitalised and lowercase alternatives according to your typographic needs? Do you need to to convert between half-width and full-width presentation forms?

4. Typographic units

4.1 Characters & encoding

Are there any character repertoire issues preventing use of this script on the Web? Do variation selectors need attention? Are there any other encoding-related issues?

4.2 Grapheme/word segmentation & selection

This is about how text is divided into graphemes, words, sentences, etc., and behaviour associated with that. Do Unicode grapheme clusters appropriately segment character units for your script? When you double- or triple-click on the text, is the expected range of characters highlighted? When you move through the text with the cursor, or backspace, etc. do you see the expected behaviour? (Some of the answers to these questions may be picker up in other sections, such as line-breaking, or initial-letter styling.)

5. Punctuation & inline features

5.1 Phrase & section boundaries

Are there specific problems related to punctuation or the interaction of the text with punctuation (for example separation of punctuation from previous text, but allowing no line break between)? Are there issues related to handling of abbreviation, ellipsis, or iteration? Are there problems related to bracketing information or demarcating things such as proper nouns, etc?

5.2 Quotations & citations

Are there any issues when dealing with quotations marks, especially when nested? Should block quotes be indented or handled specially?

5.3 Emphasis & highlighting

How are emphasis and highlighting achieved? If lines or marks are drawn alongside, over or through the text, do they need to be a special distance from the text itself? Is it important to skip characters when underlining, etc? How do things change for vertically set text?

5.4 Abbreviation, ellipsis, and repetition

What characters or other methods are used to indicate abbreviation, ellipsis & repetition?

5.5 Inline notes & annotations

The ruby spec currently specifies an initial subset of requirements for fine-tuning the typography of phonetic and semantic annotations of East Asian text, including furigana, pinyin and zhuyin fuhao systems. Is is adequate for what it sets out to do? What other controls will be needed in the future? What about other types of inline annotation, such as warichu? (For referent-type notes such as footnotes, see below.)

5.6 Text decoration & other inline features

This is about ways of marking text (see also specific sections dedicated to quotations and inline notes/annotations). Is it possible to express emphasis or highlight content as expected? Bold, italic and under-/over-lines are not always appropriate, and some scripts have their own unique ways of doing things, that are not in the Western tradition at all. Text delimiters mark certain items or sections off from the main text, such as book names in Chinese, quotations, head markers in Tibetan, etc, and often involve the use of punctuation. Is there any behaviour that isn't well supported, such as overlines for numeric digits in Syriac? Are there issues about the positioning or use of underlines? Some aspects related to the drawing of lines alongside or through text involve local typographic considerations. Do underlines need to be broken in special ways for this script? Do you need support for additional line shapes or widths? Does the distance or position of the lines relative to the text need to vary in ways that are not achievable? Are lines correctly drawn relative to vertical text?

5.7 Data formats & numbers

If the script has its own set of number digits, are there any issues in how they are used? Does the script or language use special format patterns that are problematic (eg. 12,34,000 in India)? What about date/time formats and selection - and are non-Gregorian calendars needed? Do percent signs and other symbols associated with number work correctly, and do numbers need special decorations, (like in Ethiopic or Syriac)? How about the management of personal names, addresses, etc. in web pages: are there issues?

6. Line and paragraph layout

6.1 Line breaking & hyphenation

Does the browser capture the rules about the way text in your script wraps when it hits the end of a line? Does line-breaking wrap whole 'words' at a time, or characters, or something else (such as syllables in Tibetan and Javanese)? What characters should not appear at the end or start of a line, and what should be done to prevent that?

6.2 Text alignment & justification

When text in a paragraph needs to have flush lines down both sides, does it follow the rules for your script? Does the script need assistance to conform to a grid pattern? Does your script allow punctuation to hang outside the text box at the start or end of a line? Where adjustments are need to make a line flush, how is that done? Do you shrink/stretch space between words and/or letters? Are word baselines stretched, as in Arabic? What about paragraph indents, or the need for logical alignment keywords, such as start/end, rather than left/right?

6.3 Text spacing

Some scripts create emphasis or other effects by spacing out the words, letters or syllables in a word. Are there requirements for this script/language that are unsupported? (For justification related spacing, see below.)

6.4 Baselines, line-height, etc

Does the browser support requirements for baseline alignment between mixed scripts and in general?

6.5 Lists, counters, etc.

The CSS Counter Styles specification describes a limited set of simple and complex styles for counters to be used in list numbering, chapter heading numbering, etc.The rules plus more counter styles (totalling around 120 for over 30 scripts) are listed in the document Ready-made Counter Styles. Do these cover your needs? Are the details correct? Are there other aspects related to counters and lists that need to be addressed?

6.6 Styling initials

Does the browser or ereader correctly handle special styling of the initial letter of a line or paragraph, such as for drop caps or similar? How about the size relationship between the large letter and the lines alongide? where does the large letter anchor relative to the lines alongside? is it normal to include initial quote marks in the large letter? is the large letter really a syllable? etc. Are all of these things working as expected?

7. Page & book layout

7.1 General page layout & progression

How are the main text area and ancilliary areas positioned and defined? Are there any special requirements here, such as dimensions in characters for the Japanese kihon hanmen? The book cover for scripts that are read right-to-left scripts is on the right of the spine, rather than the left. Is that provided for? When content can flow vertically and to the left or right, how do you specify the location of objects, text, etc. relative to the flow? For example, keywords 'left' and 'right' are likely to need to be reversed for pages written in English and page written in Arabic. Do tables and grid layouts work as expected? How do columns work in vertical text? Can you mix block of vertical and horizontal text correctly? Does text scroll in the expected direction? Other topics that belong here include any local requirements for things such as printer marks, tables of contents and indexes.

7.2 Grids & tables

Does the script have special requirements for character grids or tables?

7.3 Footnotes, endnotes, etc.

Does your script have special requirements for footnotes, endnotes or other necessary annotations of this kind in the way needed for your culture? (There is a section above for purely inline annotations, such as ruby or warichu. This section is more about annotation systems that separate the reference marks and the content of the notes.)

7.4 Page headers, footers, etc.

Are there special conventions for page numbering, or the way that running headers and the like are handled?

7.5 Forms & user interaction

Are vertical form controls well supported? In right-to-left scripts, is it possible to set the base direction for a form field? Is the scroll bar on the correct side? etc.

8. Other

8.1 Culture-specific features

Sometimes a script or language does things that are not common outside of its sphere of influence. This is a loose bag of additional items that weren't previously mentioned. This section may also be relevant for observations related to locale formats (such as number, date, currency, format support).

8.2 What else?

There are many other CSS modules which may need review for script-specific requirements, not to mention the SVG, HTML, Speech, MathML and other specifications. What else is likely to cause problems for worldwide deployment of the Web, and what requirements need to be addressed to make the Web function well locally?

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