;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-

.proc circle
        .include "circle.inc"
        ;; We use the algorithm jerkos method
        ;; https://schwarzers.com/algorithms/


        ;; X_pos = X_pos + r (hack, should fix later ( xpos == ypos is not always true))
        CLC
        LDA X_pos
        ADC radius
        STA X_pos

        ;; t1 = radius >> 4
        LDA radius
        LSR A
        LSR A
        LSR A
        LSR A
        STA t1
while_x_bigger_then_y:

        jsr pixel_draw

        INC Y_pos ; y++

        ;;t1 += y
        CLC
        LDA t1
        ADC Y_pos
        STA t1
        ;; t2 = t1 - x
        SEC
        LDA t2
        SBC X_pos
        STA t2
        ;; if t2 < 0 then skip to endif
        CMP #$00
        BMI endif
if:
        DEC X_pos ; x--
        LDA t2
        STA t1    ; t1 = t2
endif:
        ;; repeat if X > Y
        LDA X_pos
        CMP Y_pos

        BNE while_x_bigger_then_y
        RTS
.endproc