Sets the reading direction. This direction controls the primary direction
for widgets containing text, and also the direction in which the children
of the container are packed. The ability to set the direction is present
in order so that correct localization into languages with right-to-left
reading directions can be done. Generally, applications will let the
default reading direction present, except for containers where the
containers are arranged in an order that is explicitly visual rather than
logical (such as buttons for text justification).