Consider the midpoint (or Bresenham) algorithm for rasterizing lines given below:

(1) Input (x₁, y₁​) and (x₂​, y​₂)

(2) y = y₁

(3) d = f(x₁​ + 1, y₁​ + ½) // f is the implicit form of a line

(4) for x = x​ 1​ to x​ 2

(5) do

(6) plot(x,y)

(7) if(d<0)

(8) then

(9) y = y + 1

(10) d = d + (y₁​ - y₂) + (x₂​ - x₁)

(11) else

(12) d = d + (y₁ - y₂)

(13) end

(14) end

Which statements are true?

P: For a line with slope m>1, we should change the outer loop in line (4) to be over y.

Q: Lines (10) and (12) update the decision variable d through an incremental evaluation of the line equation f.

R: The algorithm fails if d is ever 0.