Accessibility

Section 1.2 Accessibility

PreFigure prioritizes the creation of accessible mathematical diagrams. In particular, authors can easily include annotations that control how a reader can navigate a diagram using a screen reader.

Diagram Exploration Keyboard Controls

Key	Action
Enter, A	Activate keyboard driven exploration
B	Activate menu driven exploration
Escape	Leave exploration mode
Cursor down	Explore next lower level
Cursor up	Explore next upper level
Cursor right	Explore next element on level
Cursor left	Explore previous element on level
X	Toggle expert mode
W	Extra details if available
Space	Repeat speech
M	Activate step magnification
Comma	Activate direct magnification
N	Deactivate magnification
Z	Toggle subtitles
C	Cycle contrast settings
T	Monochrome colours
L	Toggle language (if available)
K	Kill current sound
Y	Stop sound output
O	Start and stop sonification
P	Repeat sonification output

Figure 1.2.1. An annotated version of Figure 1.1.1

A reader may explore Figure 1.2.1 using a screen reader by first sending the focus to the diagram by either clicking in the diagram or pressing the tab key sufficiently many times. The arrow keys are then used to explore the diagram in more detail. For instance, the Down and Up arrow keys produce more or less detail while the Left and Right arrow keys focus on components at the same level. When the focus is on the graph, pressing "O" will play a sonification of the graph. The annotations are read using the diagcess library created by Volker Sorge

www.birmingham.ac.uk/staff/profiles/computer-science/academic-staff/sorge-volker

The modifications to the PreFigure source needed to produce the annotations are shown in Listing 1.2.2.

<diagram dimensions="(300, 300)" margins="5">
  <definition> a=1 </definition>
  <definition> f(x) = exp(x/3)*cos(x) </definition>
  <coordinates bbox="[-4,-4,4,4]">
    <grid-axes xlabel="x" ylabel="y"/>
    <graph at="graph" function='f' />
    <tangent-line at="tangent" function="f" point="a"/>
    <point at="point" p="(a, f(a))">
      <m>(a,f(a))</m>
    </point>
  </coordinates>

  <annotations>
    <annotation ref="figure"
                text="The graph of a function and its tangent line at the point a equals 1">
      <annotation ref="graph-tangent" text="The graph and its tangent line">
        <annotation ref="graph" text="The graph of the function f" sonify="yes"/>
        <annotation ref="point" text="The point a comma f of a"/>
        <annotation ref="tangent" text="The tangent line to the graph of f at the point"/>
      </annotation>
    </annotation>
  </annotations>

</diagram>

Listing 1.2.2. The PreFigure source for the annotated diagram

Notice that important graphical components are given an @at attribute, which serves as a handle to be used by the annotations. The <annotations> element contains a tree of <annotations> whose structure specifies how the screen reader will respond to arrow presses. An <annotation> element contains a reference to the handle of a graphical component, which specifies how the components are highlighted.

Furthermore, as seen in Figure 1.2.3 authors can create, from the same XML source, tactile versions of diagrams, including braille labels, suitable for embossing and including in a braille document.

Figure 1.2.3. A tactile version produced from the XML source in Listing 1.1.2.

Indeed, the difficulty in creating tactile diagrams that emboss well was one of the original motivations of the PreFigure project.

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