Chart Interactions

A dump of Alan's gist notes for the moment.

* Data entry panel
  * Hover or focus over a legend row highlights the corresponding chart and legend elements
  * Labels
    * Must have content; will default to placeholder content (Section 1, Section 2, etc) if content is completely cleared
    * Begin with placeholder content (Section 1, Section 2, etc)
    * Editing a row's label updates the corresponding Legend labeling, but only if a Value has already been entered
  * Values
    * Validates that any entered Value is a number (integer or float) and is greater than or equal to 0
      * Display a warning and does not update chart preview if entry is invalid
    * Filling in a valid value and moving focus off the entry box updates the chart and legend (adding or updating)
    * Clearing a value and moving focus off the entry box updates the chart and legend to remove the corresponding chart and legend elements
  * Reset All
    * This button resets all Label and Value entry boxes to the default state, but does not reset the chart Title and Description
* Chart preview panel
* When focus moves to the chart preview panel, a screen reader user should hear an overall description of the current chart
  * Individual chart elements are not focusable, but corresponding Legend elements are focusable and navigtable via the arrow keys 
  * Title and Description 
    * Begin with placeholder content
    * Inline edited
    * No undo
 * Legend
   * Focus over a legend row highlights the corresponding chart and data entry elements
   * Label, value and percentage should be read by screen reader for each row (accessible data table)
   * Total should be focusable as well
   * Navigation via arrow keys
 * Chart
   * Hover or focus over a chart element (pie slice) highlights the corresponding legend and data entry elements