The MathML <maction> element provides a possibility to bind actions to (sub-) expressions.
The action itself is specified by the actiontype attribute, which accepts several values. To specify which child elements are addressed by the action, you can make use of the selection attribute.
The action which specifies what happens for this element. Possible values are:
statusline: If there is a click on the expression or the reader moves the pointer over it, the message is sent to the browser's status line. The syntax is: <maction actiontype="statusline"> expressionmessage </maction>.
toggle: When there is a click on the subexpression, the rendering alternates the display of selected subexpressions. Therefore each click increments the selection value.
The syntax is: <maction actiontype="toggle" selection="positive-integer" > expression1expression2expressionN </maction>.
tooltip: When the pointer moves over the expression, a tooltip box with a message is displayed near the expression.
The syntax is: <maction actiontype="tooltip"> expressionmessage </maction>.
With Gecko 15.0 (Firefox 15.0 / Thunderbird 15.0 / SeaMonkey 2.12) the selection attribute is only taken into account with the actiontype "toggle".
Starting with Gecko 16.0 (Firefox 16.0 / Thunderbird 16.0 / SeaMonkey 2.13) the selection attribute is also taken into account when an unknown actiontype is specified. If an actiontype is not specified (is empty) or when the selection attribute is invalid, the markup will throw an MathML error (invalid-markup).