"""
```julia
legend_pos_from_angle(theta, xmin, xcenter, xmax, ymin, ycenter, ymax, inout)
```

Return `(x,y)` at an angle `theta` degrees from
`(xcenter,ycenter)` on a rectangle defined by (`xmin`,
`xmax`, `ymin`, `ymax`).
"""
function legend_pos_from_angle(theta, xmin, xcenter, xmax, ymin, ycenter, ymax)
    (s,c) = sincosd(theta)
    x = c < 0 ? (xmin-xcenter)/c : (xmax-xcenter)/c
    y = s < 0 ? (ymin-ycenter)/s : (ymax-ycenter)/s
    A = min(x,y)
    return (xcenter + A*c, ycenter + A*s)
end


"""
Split continuous range `[-1,1]` evenly into an integer `[1,2,3]`
"""
function legend_anchor_index(x)
    x<-1//3 && return 1
    x<1//3 && return 2
    return 3
end

"""
Turn legend argument into a (theta, :inner) or (theta, :outer) tuple.
For backends where legend position is given in normal coordinates (0,0) -- (1,1),
so :topleft exactly corresponds to (45, :inner) etc.

If `leg` is a (::Real,::Real) tuple, keep it as is.
"""
legend_angle(leg::Real) = (leg,:inner)
legend_angle(leg::Tuple{S,T}) where {S<:Real,T<:Real} = leg
legend_angle(leg::Tuple{S,Symbol}) where S<:Real = leg
legend_angle(leg::Symbol) = get(
                                (
                                 topleft            =   (135,:inner),
                                 top                =   (90, :inner),
                                 topright           =   (45, :inner),
                                 left               =   (180,:inner),
                                 right              =   (0,  :inner),
                                 bottomleft         =   (225,:inner),
                                 bottom             =   (270,:inner),
                                 bottomright        =   (315,:inner),
                                 outertopleft       =   (135,:outer),
                                 outertop           =   (90, :outer),
                                 outertopright      =   (45, :outer),
                                 outerleft          =   (180,:outer),
                                 outerright         =   (0,  :outer),
                                 outerbottomleft    =   (225,:outer),
                                 outerbottom        =   (270,:outer),
                                 outerbottomright   =   (315,:outer),
                                ),
                                leg,
                                (45, :inner)
                               )