Find the ppi, area, and dimensions of a screen.

screen_details.lua

#!/usr/bin/env lua

--- returns the ppi from the resolution and diagonical inches of the screen.
-- @func ppi
-- @param inch is the diagonal inches of screen.
-- @param width is the width of native resolution.
-- @param height is the height of native resolution.
function ppi(inch, width, height)
    return math.sqrt(width^2 + height^2) / inch -- ppi = pixels/inch
end

--- returns the physical width and height of screen in inches.
-- @func ss
-- @param inch is the diagonal inches of screen.
-- @param width is the width of native resolution.
-- @param height is the height of native resolution.
function ss(inch, width, height)
    local ip = inch / math.sqrt(width^2 + height^2) -- ip = inches/pixels
    -- returns width and height in inches.
    return ip * width, ip * height
end

--- gets the area of the screen.
-- @func area
-- @param inch is the diagonal inches of screen.
-- @param width is the width of native resolution.
-- @param height is the height of native resolution.
function area(inch, width, height)
    local total = 1

    --[[ note: using ipairs{} to declare a constructed table from the
    return of the closure ss. This way save time and memory in run. ]]
    for _,v in ipairs{ss(inch, width, height)} do
        total = total * v
    end

    return total
end

--- initializer for parameter manipulation through closure constructor.
-- Uses the parameters by closure initialization.
-- @func area
-- @param inch is the diagonal inches of screen.
-- @param width is the width of native resolution.
-- @param height is the height of native resolution.
-- @param fn function that manipulates the parameters after closure declare.
dimensions = function(inch, width, height)
    width = width or 1920
    height = height or 1080

    return function(fn)
        return fn(inch, width, height)
    end
end