love-luigi/luigi/widget/sash.lua

return function (self)

    self:onEnter(function (event)
        local axis = self.parent.flow
        if axis == 'x' then
            self.cursor = 'sizewe'
        else
            self.cursor = 'sizens'
        end
    end)

    self:onPressDrag(function (event)
        local axis = self.parent.flow
        if axis == 'x' then
            dimension = 'width'
        else
            axis = 'y'
            dimension = 'height'
        end
        local prevSibling = self:getPreviousSibling()
        local nextSibling = self:getNextSibling()
        local prevSize = prevSibling and prevSibling[dimension]
        local nextSize = nextSibling and nextSibling[dimension]

        if prevSize then
            prevSibling:setDimension(dimension,
                event[axis] - prevSibling:calculatePosition(axis))
        end
        if nextSize then
            nextSibling:setDimension(dimension,
                nextSibling:calculatePosition(axis) +
                nextSibling:calculateDimension(dimension) - event[axis])
        end

    end)

end