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

.proc circle
        .include "circle.inc"
        ;; We use the algorithm jerkos method
        ;; https://schwarzers.com/algorithms/
        LDY Y_pos
        LDX X_pos
        ;; 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
        LSR
        LSR
        LSR
        STA t1
while_x_bigger_then_y:

        STY Y_pos
        STX X_pos
        STA temp
        jsr pixel_draw
        LDY Y_pos
        LDX X_pos
        LDA temp


        INY ; y++

        ;;t1 += y
        CLC
        LDA t1
        STY temp
        ADC temp
        STA t1
        ;; t2 = t1 -x
        SEC
        STX temp
        SBC temp

        ;; if t2 < 0 then skip to endif
        CMP #$00
        BMI endif
if:
        DEX; x--
        STA t1; t1 = t2
endif:
        ;; repeat if X > Y
        STX temp
        TYA
        CMP temp
        JMP while_x_bigger_then_y
        BEQ while_x_bigger_then_y
.endproc