Scroll-bar element widgets

<element id="range">
  <scrollbar>horizontal</scrollbar>
  <config>
    <minimum_size>range_width</minimum_size>
    <range>100</range>
    <page_size>25</page_size>
    <increment>10</increment>
  </config>
  <appearance>range-appearance</appearance>
</element>

<!-- -->
<dim id="range_width">100</dim>

<appearance id="range-appearance" type="scrollbar">

    <!-- -->

</appearance>

Specifying an element with a scrollbar creates a new theme widget which is an x::w::scrollbar widget. scrollbar's value is either horizontal or vertical, and this is equivalent to invoking the factory's create_horizontal_scrollbar() or create_vertical_scrollbar() method.

An optional config value initializes the x::w::scrollbar_config parameter, as follows:

minimum_size

Sets the x::w::scrollbar_config's minimum_size. The value of the minimum_size element is an id of a dim.

range, page_size, increment, and value

These elements set x::w::scrollbar_config's corresponding values.

An optional appearance element sets the optional appearance object parameter to create_horizontal_scrollbar() or create_vertical_scrollbar().