computeBounds
Computes the bounds for @widget in the coordinate space of @target.
FIXME: Explain what "bounds" are.
If the operation is successful, true is returned. If @widget has no bounds or the bounds cannot be expressed in @target's coordinate space (for example if both widgets are in different windows), false is returned and @bounds is set to the zero rectangle.
It is valid for @widget and @target to be the same widget.
Return
true if the bounds could be computed
Parameters
target
the GtkWidget
outBounds
the rectangle taking the bounds