add code comments and compiler flag for circle draw.

wip-hugo/routines/circle/circle.inc

@@ -2,6 +2,7 @@
 .include "../pixel/pixel.inc"
 ;; public args
         radius = ARGVEC + 2
+        ;; and others from pixel.inc
 ;; private args
         t1    = $E0
         t2    = $E1

wip-hugo/routines/circle/circle.s

@@ -1,5 +1,6 @@
 ;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
 
+
 ;;We have named the parts of the circle as such.
 ;;               |
 ;;      qbb (7)  |      qab (8)
@@ -12,12 +13,18 @@
 ;;               |
 ;;               v Y
 
-;; The q stands for quarter, whe have 4 quarter, and each quarter is split into 2
+;; The q stands for quarter, whe have 4 quarter, and each quarter is split into 2 (a and b)
+;; We use jerko's method https://schwarzers.com/algorithms/
+;;
+;; There exist 4 uniqe half-quarter-pairs such that they share the same byte_to_paint
+; and another 4 uniqe ... such that they shair the same Y value.
+;; The Y value is the mod 8 rest of the position of the byte to paint.
+;; We paint one pixel in each half quarter area for each loop.
+
+.proc circle; user-procedure :clobbers (A X Y) :clobbers-arguments 3
 
-.proc circle
 .include "circle.inc"
-
+        ;; Because loop is so big, We need to save positions in pointer
-        ;; Because loop is so big, We need to save position in pointer
         LDA #<while_x_bigger_then_y
         STA jmp_location_pointer
         LDA #>while_x_bigger_then_y
@@ -42,6 +49,7 @@
         STA t1
 
 draw_upper_px_in_circle:
+        ;; move uppwards
         SEC
         LDA Y_pos
         STA temp_
@@ -49,6 +57,8 @@ draw_upper_px_in_circle:
         STA Y_pos
 
         JSR  pixel_draw
+
+        ;; initial pixel for 2 half-quarter arias
         LDA btp_mem_pos
         STA btp_mem_pos_qbb
         STA btp_mem_pos_qab
@@ -57,11 +67,13 @@ draw_upper_px_in_circle:
         STA btp_mem_pos_qab + 1
 
 
+        ;; initial Y value for one half-quarter aria
         STY Y_qbb
 
+        ;; reset changes we have made to circle Y_pos
         LDA temp_
         STA Y_pos
-draw_left_px_in_circle:
+draw_left_px_in_circle: ;similar as above
         SEC
         LDA X_pos
         STA temp_
@@ -82,7 +94,7 @@ draw_left_px_in_circle:
 
         LDA temp_
         STA X_pos
-draw_lower_px_in_circle:
+draw_lower_px_in_circle: ;similar as above
         CLC
         LDA Y_pos
         STA temp_
@@ -107,15 +119,12 @@ draw_lower_px_in_circle:
 
         LDA temp_
         STA Y_pos
-draw_right_px_in_circle:
+draw_right_px_in_circle:; similar as above
         CLC
         LDA X_pos
         ADC radius
         STA X_pos
-        ;; We only draw the first pixel using absolute position.
-        ;; After that we use relative position.
         JSR pixel_draw
-        ;; This sets byte_to_paint, btp_mem_pos and Y
 
         LDA btp_mem_pos
         STA btp_mem_pos_qda
@@ -124,13 +133,15 @@ draw_right_px_in_circle:
 
         STY Y_qda
         STY Y_qaa
-        LDX #$08
-while_x_bigger_then_y: ; X=8 always expected
 
+
+        LDX #$08 ; X=8 always expected inside the loop
+while_x_bigger_then_y:
+draw_pixels.
 draw_qaa:
         LDY Y_qaa
-        LDA byte_to_paint ;A byte containing a single 1. Coresponds to X position in the chunk.
+        LDA byte_to_paint ;A byte containing a single 1. Coresponds to 2^rest(X_pos/8)
-        ORA (btp_mem_pos), Y
+        ORA (btp_mem_pos), Y; Y = rest(Y_pos/8)
         STA (btp_mem_pos), Y
 draw_qba:
         LDA byte_to_paint_qca
@@ -165,6 +176,8 @@ draw_qab:
         STA (btp_mem_pos_qab), Y
 
 
+;; Y_rel and X_rel is the X and Y in the eye of the algorithm. Thsese are calculated seperatly from the pixel cordinates,
+;; but are modified at the same time. This is becsuse the pixel cordinate system is complex (see pixel draw)
 
 change_Y:
         INC Y_rel ; y++
@@ -203,8 +216,6 @@ qcb_x:
         BCC qcb_x_end
 qcb_x_overflow:
         INC byte_to_paint_qcb
-        ;LDA #$01
-        ;STA byte_to_paint_qcb
         Sub_16 btp_mem_pos_qcb, btp_mem_pos_qcb + 1, #$08, #$00,!
         Sub_16 btp_mem_pos_qbb, btp_mem_pos_qbb + 1, #$08, #$00,!
 qcb_x_end:
@@ -231,8 +242,6 @@ qaa_x:
         ASL byte_to_paint
         BCC qaa_x_end
 qaa_x_overflow:
-
-
         Sub_16 btp_mem_pos, btp_mem_pos + 1, #$08, #$00, ! ;+8
         Sub_16 btp_mem_pos_qda, btp_mem_pos_qda + 1, #$08, #$00, ! ;+8
         ;; Restores byte to paint