rickj
commented
9 months ago Here is what we do (user selection on specifics):
EPUB Text Finder This section describes the algorithm that the TTS engine uses to find the text to read, and how it breaks it up into paragraphs. (In the code they’re called “Utterances” - terminology borrowed from Apple’s speech APIs.)
The contents of the following tags are always ignored regardless of the filter settings: script, noscript, style, object, noframes
The following list of tags are considered to be paragraph separators: br, hr, tr, td, p, blockquote, title, ul, ol, li, table, pre, div, h1, h2, h3, h4, h5, h6, article, section, figcaption, figure, dl, dt, dd, aside, address, header, nav, footer, hgroup, caption
In addition to locating the text, filtering types can be added to each utterance. The application can filter on any of these flags (for example, exclude figures and altText). Some of these filters are very simple and are applied to certain tags (for example, figures). Alt text is more complex, as the alt text utterances are extracted from a variety of tags and attributes. The accessibility text for math is similarly complex - we attempt to extract the accessibility description of the math and read that if possible (tagged with the math filter).
The ‘altText’ Filter This filter reads (or excludes) image alt text. Alt text is extracted from:
- The alt attribute of an img element.
- The aria-label attribute of any element where role == “img”.
The ‘figure’ Filter A paragraph has the figure filter if it is contained in an element where any one of these is true:
- The element is figure
- The epub:type attribute is figure
The ‘table’ Filter A paragraph has the figure filter if it is contained in an element where any one of these is true:
- The element is table
- The epub:type attribute is table
The ‘citation’ Filter A paragraph has the citation filter if it is contained in an element where the epub:type is one of the following:
- endnote
- endnotes
- footnote
- footnotes
- bibliography
The ‘uriLink’ Filter The purpose of this filter is to edit out links where the text of the link is the linked URL. (As opposed to links where the text of the link is just text - these we always still want read; it’s just a part of the text with a link applied.)
To detect this, we look for a elements, and extract both the element’s text and the href attribute.
- If the href begins with “mailto:” (then it is an email link). Compare the rest of the href (removing “mailto:”) with the text - if they match, apply the uriLink filter.
- If the href begins with “http:” or “https:” then:
- Trim the string “text” - remove all leading and trailing whitespace.
- See if the resulting string has at least one internal period and no internal whitespace. If so, then it looks URL-ish. See if this string is a substring of href. If it is, then apply the uriLink filter.
The ‘math’ Filter Math is one of the trickiest filters, because we extract the accessibility description from several different places. In place of the math element, we include the accessibility description and apply the “math” filter to it, so it can be excluded or included.
- If the element name is math and it contains an attribute named altText (the MathML standard attribute for math alt text), then the utterance returned is the altText value and it is marked with the math filter.
- If the element name is img and it has a a role element where role == “math” and the img contains an alt attribute, then the utterance returned is the alt attribute value, and it is marked with the math filter.
- If the element name is NOT img and it has a role element where role == “math” and the element contains an aria-label attribute, then the utterance returned is the aria-label value, and it is marked with the math filter.
- (Note: This is specific to our mathjax preprocessor code, when using chtml output): If the element is a span or div and its class contains “mjx-chtml”, then look for an aria-label on the parent of the element. The utterance returned is the aria-label value, and it is marked with the math filter.
- (Note: This is specific to our mathjax preprocessor code, when using svg output): If the element is a span or div and its class contains “vst-math-wrapper” - we look for a child of the element with the svg tag and look for the svg’s aria-label attribute. The utterance returned is the aria-label value, and it is marked with the math filter.
PDF Filtering PDF has similar logic to the above when the PDF is a tagged PDF. Paragraph separators are described by the standard set of block-level PDF tags. The tags that define the PDF filters are described as follows:
The PDF ‘altText’ Filter This filter detects if the pdf object is an image that has alt text defined. If so the utterance is the alt text.
The PDF ‘figure' Filter This filter detects if an utterance is contained in the Figure tag.
The PDF ‘table’ Filter This filter detects if an utterance is contained in the Table tag.
The PDF ‘caption’ Filter This filter detects if an utterance is contained in the Caption tag.
The PDF ‘math’ Filter This filter detects if an utterance is contained in the Formula tag.
The PDF ‘citation’ Filter This filter detects if an utterance is contained in the Note or FENote tag.
wareid
GeorgeKerscher
sueneu
clapierre
mattgarrish
HadrienGardeur
dalerrogers
Description
When using the ReadAloud function in a Reading System, or when a screen reader is being used, text citations in the text can be disruptive to reading comprehension. The same disruption occurs if a footnote is read where it occurs. The concept of skipability and escapeability has been discussed using SMIL and media overlays, but when using ReadAloud or with a screen reader has not yet been addressed.
This feature request originated in the EPUB Reading Systems accessibility testing, but it is not accessibility specific. We are requesting that the Publishing Community Group take up this issue. It relates to best practices for markup and having the feature in Reading Systems and with screen readers.