86 lines
2 KiB
ArmAsm
86 lines
2 KiB
ArmAsm
;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
|
|
|
|
;drawing line from 2 cordinates
|
|
;;# (X_end, Y_end) #
|
|
;;# * #
|
|
;;# * #
|
|
;;# * #
|
|
;;# (X_pos, Y_pos) #
|
|
;;NOTE THAT Y_pos >) Y_end, X_pos <= X_end. Min 45deg!
|
|
|
|
.proc line_up_inv
|
|
;; Look at line_down for referense
|
|
.include "line.inc"; Defines memory positions, ex X_pos
|
|
|
|
LDA #$00
|
|
STA V + 1
|
|
STA dx_2 + 1
|
|
|
|
SEC
|
|
LDA dy
|
|
SBC dx
|
|
Mult_16 A, V + 1
|
|
STA V
|
|
|
|
Mult_16 dx_2, dx_2 + 1
|
|
|
|
;; D = dx_2 - dy. (signed 16-bit)
|
|
SEC
|
|
LDA dx_2
|
|
SBC dy
|
|
STA D
|
|
LDA dx_2 + 1
|
|
SBC #$00
|
|
STA D + 1
|
|
|
|
;; because C flag is wrong value we let dy_2 be 1 to small
|
|
Sub_16 dy_2, dy_2 +1, #$01,#$00
|
|
|
|
selfmod:
|
|
LDA dx_2
|
|
STA case_2 + 1
|
|
LDA dx_2 + 1
|
|
STA case_2 + 7
|
|
LDA V
|
|
STA case_1 + 3
|
|
LDA V + 1
|
|
STA case_1 + 9
|
|
end_selfmod:
|
|
JSR pixel_calc ;;only used first pixel. after this relative position is abused
|
|
STA byte_to_paint
|
|
INY
|
|
Sub_16 btp_mem_pos, btp_mem_pos + 1, #$00, #$00,!
|
|
CLC
|
|
LDX dy
|
|
for_y:
|
|
LDA byte_to_paint
|
|
ORA (btp_mem_pos), Y
|
|
STA (btp_mem_pos), Y
|
|
decrement_y_pos:
|
|
DEY
|
|
BNE decrement_y_pos_end
|
|
move_8px_up:
|
|
LDY #$08
|
|
Sub_16 btp_mem_pos, btp_mem_pos + 1,#$3F , #$01,!
|
|
decrement_y_pos_end:
|
|
DEX
|
|
BEQ end
|
|
LDA D + 1
|
|
BMI case_2
|
|
case_1:
|
|
Sub_16 D, D + 1, #V, #V + 1,!
|
|
increment_pixel_x:
|
|
LSR byte_to_paint
|
|
BCC for_y
|
|
move_8px_left:
|
|
ROR byte_to_paint
|
|
;; C = 1 or 0
|
|
Add_16 btp_mem_pos, btp_mem_pos + 1, #$08, #$00
|
|
JMP for_y
|
|
case_2:
|
|
Add_16 D, D + 1, #dx_2, #dx_2 + 1,!
|
|
CLC
|
|
JMP for_y
|
|
end:
|
|
RTS
|
|
.endproc
|