Accessibility Extension

MathJax offers accessibility support via its own built-in extension that provides a choice of support options as well as a high degree of personalization. The extension can be activated either via the context menu, which itself is fully accessible, or by default using configuration options. Similarly its various features and options are best selected via the MathJax Menu or programmatically using the accessibility options. We discuss the different features of the accessibility tool at the hand of the context menu, roughly in the order in which they appear.

Most features of the Accessibility extensions are based on technology provided by the Speech Rule Engine. For some more details and information please also see there.

MathJax’s supports the widest selection of browsers, operating systems, and assistive technologies as they only require the use of well-supported web standards such as WAI-ARIA, in particular labels and live regions.

Interactive Exploration

The main feature is an interactive exploration mode that allows a reader to traverse and explore sub-expressions step-by-step. The explorer is activated in the context menu by checking the Activate item in the Accessibility sub-menu.

Once a math expression is focused, the explorer can be started by pressing the Enter key. The cursor keys then allow traversal of the expression.

During traversal, focused sub-expressions are highlighted and optionally magnified. In addition, an aural rendering is pushed to a screen reader, if one is available, and a tactile rendering can be read on a Braille display, if one is connected.

Speech & Braille Support

Both aural and tactile rendering can be controlled via the options in the Speech sub-menu. Speech Output and Braille Output, respectively, control whether or not speech or Braille output is generated. If speech is generated, it is by default also displayed in Speech Subtitles, which can be switched off and hidden. Braille on the other hand is by default hidden but can be displayed by switching on the Braille Subtitles.

Speech is generally generated with respect to the currently chosen locale (if it is available). In addition, there are a number of different rule sets that can be chosen for translating math to text, where each can have a number of different preferences for how a particular expression is spoken. By default, MathJax uses the MathSpeak rule set in Verbose mode; however, the menu allows this to be changed to either the ClearSpeak or ChromeVox. Each rule set has several different preference settings; three in the case of MathSpeak, for example, which primarily influence the length of produced text. ClearSpeak on the other hand has a large number of preferences that allow very fine-tuned control over how different types of expressions are spoken. The MathJax menu allows a smart choice of preferences by only displaying the preferences that are currently relevant for the sub-expression that is currently explored. The Select Preferences option opens a selection box for all possible ClearSpeak preference choices.

Some rule-set and preference settings can also be controlled by keyboard commands. This allows the user to have the same expression read in different variants without having to leave the exploration mode. The > key switches rule sets between MathSpeak and ClearSpeak if both are available for the current locale. The < key cycles preferences for the currently active rule set. For ClearSpeak rules, preference cycling depends on the type of the currently explored sub-expression, similar to smart selection of menu entries.

The speech language can be adjusted in the Language sub-menu in the Speech options. MathJax currently only supports speech in English, French, German, and Spanish. The only available Braille output is Nemeth. We are hoping to add more in the future.

In addition to voicing expressions, the explorer allows for queries on sub-expression, such as getting positional information with respect to the context, as well as summaries of the sub-expression currently explored.

Abstraction

In addition to textual summaries of expressions, MathJax offers the possibility to abstract certain sub-expressions so that the entire sub-expression is visually replaced by a placeholder symbol and interactive traversal treats it as a single element. This allows the reader to abstract away details and to better observe the overall structure of a formula.

Abstraction can be triggered either via mouse click on a collapsible expression or via pressing the Enter key during keyboard exploration. Expressions that can be abstracted can also be discovered using some of the highlighting features.

Highlight

During interactive exploration, the sub-expression that is explorered is automatically highlighted, by default with a blue background color. The highlighting can be customized by changing Background or Foreground colors in in the Highlight sub-menu of the MathJax contextual menu. In addition, the opacity of both Background and Foreground can be adjusted by two slider bars underneath the respective sub-menus.

The Highlight sub-menu also provides a choice of highlighters for marking collapsible sub-expressions: The Flame highlighter permanently colors collapsible sub-expressions while successively darkening the background for nested collapsible expressions. The Hover highlighter colors each collapsible sub-expression only when hovering over it with the mouse pointer.

A final highlighting feature is Tree Coloring, in which expressions are visually distinguished by giving neighbouring symbols different, ideally contrasting foreground colors.

Magnification

During exploration, the accessibility extension can optionally magnify the sub-expression that is currently explored. The zoomed version of the expression is overlaid on the original one when traversing the formula. For keyboard exploration, this can be switched on in the Magnification sub-menu by selecting the Keyboard option.

A similar effect can be achieved by exploring an expression with the mouse. When using the Mouse option in the Magnification sub-menu, the sub-expression over which the mouse pointer hovers is zoomed.

The zoom factor of the magnification can also be adjusted. The values available in the context menu are 200%, 300%, 400%, and 500%.

Semantic Info

The Semantic Info sub-menu contains a number of options that allow the reader to see the semantic classifications MathJax applies to a particular sub-expression, by hovering over it with the mouse pointer. The choices here are

  • Type is an immutable property of an expression that is independent of its particular position in a formula. Note, however that types can change depending on the subject area of a document.

  • Role is dependent on the context of a sub-expression in the overall expression.

  • Prefix is information pertaining to the position of a sub-expression. Examples are 'exponent', 'radicand', etc. These would also be spoken during interactive exploration.

For more details on all of these concepts, see also the documentation of the Speech Rule Engine.