The user can display the drop down menu by pressing
any mouse button while the pointer is on the value area or by pressing Enter when
the widget has keyboard focus.
Size and Contents
The depth is calculated to contain one line, in `font,
or, if the title is shown and its font is larger,
`titlefont.
The width is affected by:
the longest of the choices, as displayed in `font, plus the
raised rectangle and an area around it (to be precise, the longest of the choices that
can fit in the screen),
the attributes affecting overall width listed in the "Size, position, etc. on screen or
in parent" page, and
user resizing of the width, if `resizeable is 1.
The current choice is shown and, to its right, a raised rectangle which has no function.
Color
The color of the value area, the background, is `bg,
whose default is `grey (more precisely, the value of
s.GREY).