May be set to one of normal, active, or
disabled. In a dialog box, one button may be designated
the
“default” button (meaning, roughly, “the one that
gets invoked when the user presses <Enter>”).
active indicates that this is currently the default button;
normal means that it may become the default button, and
disabled means that it is not defaultable. The default is
normal.
Depending on the theme, the default button may be displayed with
an extra highlight ring, or with a different border color.
If greater than zero, specifies how much space, in character
widths, to allocate for the text label. If less than zero,
specifies a minimum width. If zero or unspecified, the natural
width of the text label is used. Note that some themes may specify
a non-zero -width in the style.