Expand description
Button widget.
+--------+
| frame |
+---+----+
| \----------\
+---+----+ +-----+-----+
| button | | (textbox) |
+--------+ +-----------+If a label string is provided, a Textbox label will be created as a sibling to
the Button element.
The push and release control functions target the frame node, and assume that
the first child is the button node.