* Fix popup location for tables
This commit introduces the `popupAbsCoords` option to the $button widget
and implements an absolut coordinate format.
Coordinates for popups are stored in the format `(x,y,w,h)`. These
coordinates are relative to the offset parent of the element that
defines the popup.
This commits adds a second format `@(x,y,w,h)`. Coordinates specified in
this format a relative to the pages root element.
The `popupAbsCoords` option of the $button widget enables the use of
this coordinates.
* Unify the declaration of the RegEx for parsing the popup-position
The regular expression was declared in three locations with the same
content. This commit supplies a new function `parseCoordinates` in
`popup.js`. This function returns the parsed coordinates and understands
the classic/absolute coordinates.
This function is used in `reveal.js` and `action-popup.js` to parse the
coordinates.
* Add documentation for coordinate systems
* Consolidate creating coordinate strings
The Popup object now contains a `buildCoordinates` method that can be
used to build coordinate strings. It takes an "enum" for the coordinate-
system to use. This makes everything easily extensible and prevents the
use of magic values.
* Add tests for `parseCoordinates` and `buildCoordinates`
* Add `tv-popup-abs-coords` to `collectDOMVariables`
This will make the absolute coordinates available for the
`DraggableWidget` and the `EventCatcherWidget`.
* Add documentation for the `tv-popup-abs-coords`
... to the `DraggableWidget` and the `EventCatcherWidget`.
These improvements rely on the new JSON operators to be useful. Those improvements were originally in #6522 but now there's an updated version in #6666. Managing things is simpler if I merge these changes now
