Draw a sight line, a circular scanner or a filled oval without building a renderer first. These are five callable assembly routines over the existing pixel/span interface. You choose the bitmap, own the memory and call only the pieces your game needs.
Include it and make a call
BP needs 48 zero-page bytes; the caller uses &40. G is 160 ordinary RAM bytes at &0400. Copy the 256-entry bitmap_lo and bitmap_hi scanline tables and define PIXEL_WIDTH=320, PIXEL_HEIGHT=256. The tables cost 512 bytes. The bitmap begins at &5800; neighbouring byte columns are eight addresses apart. The caller owns the 6845, video ULA and palette.
Define GEO_WIDTH and GEO_HEIGHT as 320 and 256. Set GEO_PEN_MAX to 255 (pen ignored). Include the geometry 6502.inc and the backend exactly once, as shown at the bottom of the complete caller. Reserve 160 bytes at G plus 48 at BP, separately from code, stack, tables and display. Scratch needs no initialisation; public inputs do.
After the caller’s video setup, this is an ordinary direct call. Your game does not need the verification mailbox that follows it.
Outline an ellipse centred at (80,70), radii (48,24)
demo.asm, excerpt
; A normal game call: an outlined ellipse. Setup and mailbox are separate.
lda #$50
sta G+0
lda #$00
sta G+0+1
lda #$46
sta G+2
lda #$00
sta G+2+1
lda #$30
sta G+4
lda #$00
sta G+4+1
lda #$18
sta G+6
lda #$00
sta G+6+1
lda #$00
sta G+12
lda #$00
sta G+12+1
lda #$00
sta G+14
lda #$00
sta G+14+1
lda #$40
sta G+16
lda #$01
sta G+16+1
lda #$00
sta G+18
lda #$01
sta G+18+1
lda #0
sta G+8
lda #0
sta G+9
lda #1
sta G+11
jsr geo_ellipse
lda #0
sta COMMAND
lda #239
sta COMMAND+1Read G+10 after return: 1 means accepted, 0 means rejected. An accepted shape can be completely outside the scissor and draw nothing. Change the inputs and call again; G holds no hidden scene or list of shapes.
The calling contract
All words use little-endian byte order. Screen origin is top left; Y increases downwards. Pen is ignored by this monochrome backend; initialise it to 1 for a caller that also ports to CPC.
| G offset | Supply or read |
|---|---|
| 0,2 | Signed x0,y0 for a line; centre cx,cy for curves |
| 4,6 | Signed x1,y1 for a line; radii rx,ry for an ellipse; a circle uses rx and ignores ry |
| 8 | Operation: 0 set/replace, 1 clear, 2 XOR |
| 9 | Line: 0 includes both ends, 1 omits the original caller’s final end; curves require 0 |
| 10 | Output: 1 accepted, 0 rejected |
| 11 | Pen index (ignored on mono backends) |
| 12,14,16,18 | Unsigned scissor left,top,right,bottom; right/bottom exclusive |
| 20 | Output: 32-bit destination-byte writes |
| 24 | Output: 16-bit backend calls |
| 26–159 | Private scratch |
Call geo_line, geo_circle, geo_ellipse, geo_fill_circle or geo_fill_ellipse. Coordinates must be −512..511, radii 0..255. The scissor must be nonempty and inside the 320×256 display. Invalid bounds, radii, operation, flags or pen reject before any destination write, with zero counters. Inputs at 0–9 and 11–19 survive. Unused circle ry is ignored. A zero radius becomes a point or straight span rather than an error.
Keep the line you asked for
The line uses accumulated integer error in all eight octants. It orders endpoints consistently before choosing half-way pixels, so reversing a line produces the same pixels. A horizontal or vertical line uses a span fast path. A zero-length inclusive line draws one pixel.
For a closed XOR polyline, give every edge flag 1. Each omits its original final endpoint, so the next edge owns that shared vertex. Leaving both endpoints on both edges would toggle the vertex twice and erase it. A zero-length omit-final line draws nothing.
The scissor discards outside pixels from the original raster, preserving its rounding phase. It does not replace the endpoints with rounded intersections. Offscreen steps still cost work: the accepted coordinate range bounds the major-axis delta at 1023. Filled curves instead intersect each row span with the scissor before calling the backend.
Draw with integer error works through a short line, symmetry, span filling and overflow. Place a point explains the origin difference; for integer screen rows here, convert an upwards world Y with screenY=height-1-worldY.
Fill rows, not thousands of point calls
Outline ellipses update an integer decision and reflect points into four quadrants. Axis points are emitted once. Filled ellipses select the widest interval for each row and emit that span once; they do not repeatedly XOR the same row as the edge advances. Circles use equal ellipse radii through this same kernel. A specialised eight-way circle implementation could reduce work further.
An ellipse with radii (37,15) covers 1,833 logical pixels here but needs only 31 span calls when filled. Those calls made 258 byte writes on this backend. That is actual destination work, not elapsed cycles. Four-pixel CPC packing and eight-pixel mono packing produce different counts, and partial edge bytes still need protection.
The geometry occupies 5,533 assembled bytes, the backend 526, plus the 208 RAM bytes for G and BP. A further 512-byte scanline table is required. Reset code, stack, display and assets are additional. The checked 32-bit curve arithmetic buys a clear range contract but has a code/time cost. Cache static shapes or specialise a hot path when measurement shows a need. No frame-budget claim has been measured here.
A logical circle has equal X/Y radii. Its displayed shape still depends on the display mode, pixel aspect and capture presentation. Choose the presentation deliberately; changing radius to compensate is a separate mapping decision, not a change to the circle equation.
Own the resources
Clobbered: A/X/Y and flags; keep decimal mode clear. Reserve a conservative 64-byte stack budget, plus your other calls and interrupts. The component is non-re-entrant. It does not change interrupt state or negotiate display access. Keep G/BP private and coordinate another renderer or interrupt user yourself. Reset fixtures own the machine; integration under a live OS needs its own loading and coexistence checks.
Open the complete reusable 6502 geometry include
Include this CPU component once
6502.inc
; SPDX-License-Identifier: MIT
; Copyright (c) 2020 zingl; assembly adaptation Code198x (2026).
; Integer geometry over the existing bp_pixel/bp_hspan/bp_vspan backend.
; G is 160 caller-owned RAM bytes. BP is a separate 48-byte workspace.
; Read README.md for signed inputs, scissor, endpoint flags and ownership.
; Bresenham/ellipse recurrences adapted from Alois Zingl; see LICENSE-Zingl.txt.
g_a = G+0
g_b = G+2
g_c = G+4
g_d = G+6
g_op = G+8
g_flags = G+9
g_status = G+10
g_pen = G+11
g_clip_l = G+12
g_clip_t = G+14
g_clip_r = G+16
g_clip_b = G+18
g_writes = G+20
g_calls = G+24
g_mode = G+32
g_first = G+33
g_swap = G+34
g_fill = G+35
g_x = G+40
g_y = G+42
g_end_x = G+44
g_end_y = G+46
g_dx = G+48
g_dy = G+50
g_sy = G+54
g_err = G+56
g_e2 = G+58
g_temp = G+60
g_last_y = G+62
g_rx = G+64
g_ry = G+66
g_px = G+68
g_py = G+70
g_right = G+72
g_bottom = G+74
g_a2 = G+80
g_b2 = G+84
g_curve_dx = G+88
g_curve_dy = G+92
g_curve_err = G+96
g_curve_e2 = G+100
g_step_x = G+104
g_step_y = G+108
g_work = G+112
g_mul = G+158
g_cmp = G+159
bp_writes = BP+40
bp_status = BP+9
bp_op = BP+8
bp_pen = BP+11
bp_x0 = BP+0
bp_y0 = BP+2
bp_x1 = BP+4
bp_y1 = BP+6
geo_line:
lda #$00
sta g_mode
jmp geo_enter
geo_circle:
lda #$01
sta g_mode
jmp geo_enter
geo_ellipse:
lda #$02
sta g_mode
jmp geo_enter
geo_fill_circle:
lda #$03
sta g_mode
jmp geo_enter
geo_fill_ellipse:
lda #$04
sta g_mode
jmp geo_enter
geo_enter:
lda #$00
sta g_status
lda #$00
sta g_writes
lda #$00
sta g_writes+1
lda #$00
sta g_writes+2
lda #$00
sta g_writes+3
lda #$00
sta g_calls
lda #$00
sta g_calls+1
; Validate the entire request before the first backend write.
lda #$02
sta g_cmp
lda g_op
cmp g_cmp
bcs geo_branch_2
jmp geo_branch_1
geo_branch_2:
beq geo_branch_3
jmp geo_done
geo_branch_3:
geo_branch_1:
lda g_pen
cmp #GEO_PEN_MAX
bcs geo_branch_5
jmp geo_branch_4
geo_branch_5:
bne geo_branch_6
jmp geo_branch_4
geo_branch_6:
jmp geo_done
geo_branch_4:
lda #$fe
eor #$80
sta g_cmp
lda g_a+1
eor #$80
cmp g_cmp
bcs geo_branch_8
jmp geo_done
geo_branch_8:
beq geo_branch_9
jmp geo_branch_7
geo_branch_9:
lda #$00
sta g_cmp
lda g_a
cmp g_cmp
bcs geo_branch_10
jmp geo_done
geo_branch_10:
geo_branch_7:
lda #$01
eor #$80
sta g_cmp
lda g_a+1
eor #$80
cmp g_cmp
bcs geo_branch_12
jmp geo_branch_11
geo_branch_12:
beq geo_branch_13
jmp geo_done
geo_branch_13:
lda #$ff
sta g_cmp
lda g_a
cmp g_cmp
bcs geo_branch_14
jmp geo_branch_11
geo_branch_14:
beq geo_branch_15
jmp geo_done
geo_branch_15:
geo_branch_11:
lda #$fe
eor #$80
sta g_cmp
lda g_b+1
eor #$80
cmp g_cmp
bcs geo_branch_17
jmp geo_done
geo_branch_17:
beq geo_branch_18
jmp geo_branch_16
geo_branch_18:
lda #$00
sta g_cmp
lda g_b
cmp g_cmp
bcs geo_branch_19
jmp geo_done
geo_branch_19:
geo_branch_16:
lda #$01
eor #$80
sta g_cmp
lda g_b+1
eor #$80
cmp g_cmp
bcs geo_branch_21
jmp geo_branch_20
geo_branch_21:
beq geo_branch_22
jmp geo_done
geo_branch_22:
lda #$ff
sta g_cmp
lda g_b
cmp g_cmp
bcs geo_branch_23
jmp geo_branch_20
geo_branch_23:
beq geo_branch_24
jmp geo_done
geo_branch_24:
geo_branch_20:
lda #$00
eor #$80
sta g_cmp
lda g_clip_l+1
eor #$80
cmp g_cmp
bcs geo_branch_26
jmp geo_done
geo_branch_26:
beq geo_branch_27
jmp geo_branch_25
geo_branch_27:
lda #$00
sta g_cmp
lda g_clip_l
cmp g_cmp
bcs geo_branch_28
jmp geo_done
geo_branch_28:
geo_branch_25:
lda #$00
eor #$80
sta g_cmp
lda g_clip_t+1
eor #$80
cmp g_cmp
bcs geo_branch_30
jmp geo_done
geo_branch_30:
beq geo_branch_31
jmp geo_branch_29
geo_branch_31:
lda #$00
sta g_cmp
lda g_clip_t
cmp g_cmp
bcs geo_branch_32
jmp geo_done
geo_branch_32:
geo_branch_29:
lda g_clip_r+1
eor #$80
sta g_cmp
lda g_clip_l+1
eor #$80
cmp g_cmp
bcs geo_branch_34
jmp geo_branch_33
geo_branch_34:
beq geo_branch_35
jmp geo_done
geo_branch_35:
lda g_clip_r
sta g_cmp
lda g_clip_l
cmp g_cmp
bcs geo_branch_36
jmp geo_branch_33
geo_branch_36:
jmp geo_done
geo_branch_33:
lda g_clip_b+1
eor #$80
sta g_cmp
lda g_clip_t+1
eor #$80
cmp g_cmp
bcs geo_branch_38
jmp geo_branch_37
geo_branch_38:
beq geo_branch_39
jmp geo_done
geo_branch_39:
lda g_clip_b
sta g_cmp
lda g_clip_t
cmp g_cmp
bcs geo_branch_40
jmp geo_branch_37
geo_branch_40:
jmp geo_done
geo_branch_37:
lda #<GEO_WIDTH
sta g_temp
lda #>GEO_WIDTH
sta g_temp+1
lda g_temp+1
eor #$80
sta g_cmp
lda g_clip_r+1
eor #$80
cmp g_cmp
bcs geo_branch_42
jmp geo_branch_41
geo_branch_42:
beq geo_branch_43
jmp geo_done
geo_branch_43:
lda g_temp
sta g_cmp
lda g_clip_r
cmp g_cmp
bcs geo_branch_44
jmp geo_branch_41
geo_branch_44:
beq geo_branch_45
jmp geo_done
geo_branch_45:
geo_branch_41:
lda #<GEO_HEIGHT
sta g_temp
lda #>GEO_HEIGHT
sta g_temp+1
lda g_temp+1
eor #$80
sta g_cmp
lda g_clip_b+1
eor #$80
cmp g_cmp
bcs geo_branch_47
jmp geo_branch_46
geo_branch_47:
beq geo_branch_48
jmp geo_done
geo_branch_48:
lda g_temp
sta g_cmp
lda g_clip_b
cmp g_cmp
bcs geo_branch_49
jmp geo_branch_46
geo_branch_49:
beq geo_branch_50
jmp geo_done
geo_branch_50:
geo_branch_46:
lda #$00
sta g_cmp
lda g_mode
cmp g_cmp
beq geo_branch_52
jmp geo_curve_validate
geo_branch_52:
geo_branch_51:
lda #$01
sta g_cmp
lda g_flags
cmp g_cmp
bcs geo_branch_54
jmp geo_branch_53
geo_branch_54:
beq geo_branch_55
jmp geo_done
geo_branch_55:
geo_branch_53:
lda #$fe
eor #$80
sta g_cmp
lda g_c+1
eor #$80
cmp g_cmp
bcs geo_branch_57
jmp geo_done
geo_branch_57:
beq geo_branch_58
jmp geo_branch_56
geo_branch_58:
lda #$00
sta g_cmp
lda g_c
cmp g_cmp
bcs geo_branch_59
jmp geo_done
geo_branch_59:
geo_branch_56:
lda #$01
eor #$80
sta g_cmp
lda g_c+1
eor #$80
cmp g_cmp
bcs geo_branch_61
jmp geo_branch_60
geo_branch_61:
beq geo_branch_62
jmp geo_done
geo_branch_62:
lda #$ff
sta g_cmp
lda g_c
cmp g_cmp
bcs geo_branch_63
jmp geo_branch_60
geo_branch_63:
beq geo_branch_64
jmp geo_done
geo_branch_64:
geo_branch_60:
lda #$fe
eor #$80
sta g_cmp
lda g_d+1
eor #$80
cmp g_cmp
bcs geo_branch_66
jmp geo_done
geo_branch_66:
beq geo_branch_67
jmp geo_branch_65
geo_branch_67:
lda #$00
sta g_cmp
lda g_d
cmp g_cmp
bcs geo_branch_68
jmp geo_done
geo_branch_68:
geo_branch_65:
lda #$01
eor #$80
sta g_cmp
lda g_d+1
eor #$80
cmp g_cmp
bcs geo_branch_70
jmp geo_branch_69
geo_branch_70:
beq geo_branch_71
jmp geo_done
geo_branch_71:
lda #$ff
sta g_cmp
lda g_d
cmp g_cmp
bcs geo_branch_72
jmp geo_branch_69
geo_branch_72:
beq geo_branch_73
jmp geo_done
geo_branch_73:
geo_branch_69:
lda #$01
sta g_status
jmp geo_line_start
geo_curve_validate:
lda #$00
sta g_cmp
lda g_flags
cmp g_cmp
beq geo_branch_75
jmp geo_done
geo_branch_75:
geo_branch_74:
lda #$00
eor #$80
sta g_cmp
lda g_c+1
eor #$80
cmp g_cmp
bcs geo_branch_77
jmp geo_done
geo_branch_77:
beq geo_branch_78
jmp geo_branch_76
geo_branch_78:
lda #$00
sta g_cmp
lda g_c
cmp g_cmp
bcs geo_branch_79
jmp geo_done
geo_branch_79:
geo_branch_76:
lda #$00
eor #$80
sta g_cmp
lda g_c+1
eor #$80
cmp g_cmp
bcs geo_branch_81
jmp geo_branch_80
geo_branch_81:
beq geo_branch_82
jmp geo_done
geo_branch_82:
lda #$ff
sta g_cmp
lda g_c
cmp g_cmp
bcs geo_branch_83
jmp geo_branch_80
geo_branch_83:
beq geo_branch_84
jmp geo_done
geo_branch_84:
geo_branch_80:
lda g_c
sta g_rx
lda g_c+1
sta g_rx+1
lda #$01
sta g_cmp
lda g_mode
cmp g_cmp
beq geo_branch_86
jmp geo_branch_85
geo_branch_86:
jmp geo_equal_axes
geo_branch_85:
lda #$03
sta g_cmp
lda g_mode
cmp g_cmp
beq geo_branch_88
jmp geo_branch_87
geo_branch_88:
jmp geo_equal_axes
geo_branch_87:
lda #$00
eor #$80
sta g_cmp
lda g_d+1
eor #$80
cmp g_cmp
bcs geo_branch_90
jmp geo_done
geo_branch_90:
beq geo_branch_91
jmp geo_branch_89
geo_branch_91:
lda #$00
sta g_cmp
lda g_d
cmp g_cmp
bcs geo_branch_92
jmp geo_done
geo_branch_92:
geo_branch_89:
lda #$00
eor #$80
sta g_cmp
lda g_d+1
eor #$80
cmp g_cmp
bcs geo_branch_94
jmp geo_branch_93
geo_branch_94:
beq geo_branch_95
jmp geo_done
geo_branch_95:
lda #$ff
sta g_cmp
lda g_d
cmp g_cmp
bcs geo_branch_96
jmp geo_branch_93
geo_branch_96:
beq geo_branch_97
jmp geo_done
geo_branch_97:
geo_branch_93:
lda g_d
sta g_ry
lda g_d+1
sta g_ry+1
jmp geo_axes_ready
geo_equal_axes:
lda g_c
sta g_ry
lda g_c+1
sta g_ry+1
geo_axes_ready:
lda #$01
sta g_status
lda #$00
sta g_fill
lda #$03
sta g_cmp
lda g_mode
cmp g_cmp
bcs geo_branch_99
jmp geo_curve_start
geo_branch_99:
geo_branch_98:
lda #$01
sta g_fill
jmp geo_curve_start
geo_done:
rts
geo_line_start:
; Canonical ordering gives the same tie pixels when endpoints are reversed.
lda g_a
sta g_x
lda g_a+1
sta g_x+1
lda g_b
sta g_y
lda g_b+1
sta g_y+1
lda g_c
sta g_end_x
lda g_c+1
sta g_end_x+1
lda g_d
sta g_end_y
lda g_d+1
sta g_end_y+1
lda #$00
sta g_swap
lda g_end_x+1
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
bcs geo_branch_101
jmp geo_branch_100
geo_branch_101:
beq geo_branch_102
jmp geo_swap_endpoints
geo_branch_102:
lda g_end_x
sta g_cmp
lda g_x
cmp g_cmp
bcs geo_branch_103
jmp geo_branch_100
geo_branch_103:
beq geo_branch_104
jmp geo_swap_endpoints
geo_branch_104:
geo_branch_100:
lda g_end_x+1
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
beq geo_branch_106
jmp geo_line_ordered
geo_branch_106:
lda g_end_x
sta g_cmp
lda g_x
cmp g_cmp
beq geo_branch_107
jmp geo_line_ordered
geo_branch_107:
geo_branch_105:
lda g_end_y+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
bcs geo_branch_109
jmp geo_line_ordered
geo_branch_109:
beq geo_branch_110
jmp geo_branch_108
geo_branch_110:
lda g_end_y
sta g_cmp
lda g_y
cmp g_cmp
bcs geo_branch_111
jmp geo_line_ordered
geo_branch_111:
bne geo_branch_112
jmp geo_line_ordered
geo_branch_112:
geo_branch_108:
geo_swap_endpoints:
lda g_x
sta g_temp
lda g_x+1
sta g_temp+1
lda g_end_x
sta g_x
lda g_end_x+1
sta g_x+1
lda g_temp
sta g_end_x
lda g_temp+1
sta g_end_x+1
lda g_y
sta g_temp
lda g_y+1
sta g_temp+1
lda g_end_y
sta g_y
lda g_end_y+1
sta g_y+1
lda g_temp
sta g_end_y
lda g_temp+1
sta g_end_y+1
lda #$01
sta g_swap
geo_line_ordered:
lda g_end_y+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
beq geo_branch_114
jmp geo_branch_113
geo_branch_114:
lda g_end_y
sta g_cmp
lda g_y
cmp g_cmp
beq geo_branch_115
jmp geo_branch_113
geo_branch_115:
jmp geo_horizontal
geo_branch_113:
lda g_end_x+1
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
beq geo_branch_117
jmp geo_branch_116
geo_branch_117:
lda g_end_x
sta g_cmp
lda g_x
cmp g_cmp
beq geo_branch_118
jmp geo_branch_116
geo_branch_118:
jmp geo_vertical_line
geo_branch_116:
lda g_end_x
sta g_dx
lda g_end_x+1
sta g_dx+1
sec
lda g_dx
sbc g_x
sta g_dx
lda g_dx+1
sbc g_x+1
sta g_dx+1
lda g_end_y
sta g_dy
lda g_end_y+1
sta g_dy+1
sec
lda g_dy
sbc g_y
sta g_dy
lda g_dy+1
sbc g_y+1
sta g_dy+1
lda #$01
sta g_sy
lda #$00
sta g_sy+1
lda #$00
eor #$80
sta g_cmp
lda g_dy+1
eor #$80
cmp g_cmp
bcs geo_branch_121
jmp geo_branch_120
geo_branch_121:
beq geo_branch_122
jmp geo_branch_119
geo_branch_122:
lda #$00
sta g_cmp
lda g_dy
cmp g_cmp
bcs geo_branch_123
jmp geo_branch_120
geo_branch_123:
jmp geo_branch_119
geo_branch_120:
lda #$ff
sta g_sy
lda #$ff
sta g_sy+1
lda g_dy
eor #$ff
sta g_dy
lda g_dy+1
eor #$ff
sta g_dy+1
clc
lda g_dy
adc #$01
sta g_dy
lda g_dy+1
adc #$00
sta g_dy+1
geo_branch_119:
lda g_dy
eor #$ff
sta g_dy
lda g_dy+1
eor #$ff
sta g_dy+1
clc
lda g_dy
adc #$01
sta g_dy
lda g_dy+1
adc #$00
sta g_dy+1
lda g_dx
sta g_err
lda g_dx+1
sta g_err+1
clc
lda g_err
adc g_dy
sta g_err
lda g_err+1
adc g_dy+1
sta g_err+1
lda #$01
sta g_first
geo_line_loop:
lda #$00
sta g_cmp
lda g_flags
cmp g_cmp
beq geo_branch_127
jmp geo_branch_126
geo_branch_127:
jmp geo_branch_124
geo_branch_126:
lda #$00
sta g_cmp
lda g_swap
cmp g_cmp
beq geo_branch_130
jmp geo_branch_129
geo_branch_130:
jmp geo_branch_128
geo_branch_129:
lda #$00
sta g_cmp
lda g_first
cmp g_cmp
beq geo_branch_132
jmp geo_branch_125
geo_branch_132:
geo_branch_131:
jmp geo_branch_124
geo_branch_128:
lda g_end_x+1
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
beq geo_branch_134
jmp geo_branch_124
geo_branch_134:
lda g_end_x
sta g_cmp
lda g_x
cmp g_cmp
beq geo_branch_135
jmp geo_branch_124
geo_branch_135:
geo_branch_133:
lda g_end_y+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
beq geo_branch_137
jmp geo_branch_136
geo_branch_137:
lda g_end_y
sta g_cmp
lda g_y
cmp g_cmp
beq geo_branch_138
jmp geo_branch_136
geo_branch_138:
jmp geo_done
geo_branch_136:
geo_branch_124:
lda g_x
sta g_px
lda g_x+1
sta g_px+1
lda g_y
sta g_py
lda g_y+1
sta g_py+1
jsr geo_point
geo_branch_125:
lda #$00
sta g_first
lda g_end_x+1
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
beq geo_branch_141
jmp geo_branch_139
geo_branch_141:
lda g_end_x
sta g_cmp
lda g_x
cmp g_cmp
beq geo_branch_142
jmp geo_branch_139
geo_branch_142:
geo_branch_140:
lda g_end_y+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
beq geo_branch_144
jmp geo_branch_143
geo_branch_144:
lda g_end_y
sta g_cmp
lda g_y
cmp g_cmp
beq geo_branch_145
jmp geo_branch_143
geo_branch_145:
jmp geo_done
geo_branch_143:
geo_branch_139:
lda g_err
sta g_e2
lda g_err+1
sta g_e2+1
asl g_e2
rol g_e2+1
lda g_dy+1
eor #$80
sta g_cmp
lda g_e2+1
eor #$80
cmp g_cmp
bcs geo_branch_148
jmp geo_branch_146
geo_branch_148:
beq geo_branch_149
jmp geo_branch_147
geo_branch_149:
lda g_dy
sta g_cmp
lda g_e2
cmp g_cmp
bcs geo_branch_150
jmp geo_branch_146
geo_branch_150:
geo_branch_147:
clc
lda g_err
adc g_dy
sta g_err
lda g_err+1
adc g_dy+1
sta g_err+1
clc
lda g_x
adc #$01
sta g_x
lda g_x+1
adc #$00
sta g_x+1
geo_branch_146:
lda g_dx+1
eor #$80
sta g_cmp
lda g_e2+1
eor #$80
cmp g_cmp
bcs geo_branch_153
jmp geo_branch_152
geo_branch_153:
beq geo_branch_154
jmp geo_branch_151
geo_branch_154:
lda g_dx
sta g_cmp
lda g_e2
cmp g_cmp
bcs geo_branch_155
jmp geo_branch_152
geo_branch_155:
beq geo_branch_156
jmp geo_branch_151
geo_branch_156:
geo_branch_152:
clc
lda g_err
adc g_dx
sta g_err
lda g_err+1
adc g_dx+1
sta g_err+1
clc
lda g_y
adc g_sy
sta g_y
lda g_y+1
adc g_sy+1
sta g_y+1
geo_branch_151:
jmp geo_line_loop
geo_horizontal:
lda #$00
sta g_cmp
lda g_flags
cmp g_cmp
beq geo_branch_159
jmp geo_branch_158
geo_branch_159:
jmp geo_branch_157
geo_branch_158:
lda #$00
sta g_cmp
lda g_swap
cmp g_cmp
beq geo_branch_162
jmp geo_branch_161
geo_branch_162:
jmp geo_branch_160
geo_branch_161:
clc
lda g_x
adc #$01
sta g_x
lda g_x+1
adc #$00
sta g_x+1
jmp geo_branch_157
geo_branch_160:
clc
lda g_end_x
adc #$ff
sta g_end_x
lda g_end_x+1
adc #$ff
sta g_end_x+1
geo_branch_157:
lda g_end_x+1
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
bcs geo_branch_164
jmp geo_branch_163
geo_branch_164:
beq geo_branch_165
jmp geo_done
geo_branch_165:
lda g_end_x
sta g_cmp
lda g_x
cmp g_cmp
bcs geo_branch_166
jmp geo_branch_163
geo_branch_166:
beq geo_branch_167
jmp geo_done
geo_branch_167:
geo_branch_163:
lda g_x
sta g_px
lda g_x+1
sta g_px+1
lda g_end_x
sta g_right
lda g_end_x+1
sta g_right+1
lda g_y
sta g_py
lda g_y+1
sta g_py+1
jsr geo_span
jmp geo_done
geo_vertical_line:
lda #$00
sta g_cmp
lda g_flags
cmp g_cmp
beq geo_branch_170
jmp geo_branch_169
geo_branch_170:
jmp geo_branch_168
geo_branch_169:
lda #$00
sta g_cmp
lda g_swap
cmp g_cmp
beq geo_branch_173
jmp geo_branch_172
geo_branch_173:
jmp geo_branch_171
geo_branch_172:
clc
lda g_y
adc #$01
sta g_y
lda g_y+1
adc #$00
sta g_y+1
jmp geo_branch_168
geo_branch_171:
clc
lda g_end_y
adc #$ff
sta g_end_y
lda g_end_y+1
adc #$ff
sta g_end_y+1
geo_branch_168:
lda g_end_y+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
bcs geo_branch_175
jmp geo_branch_174
geo_branch_175:
beq geo_branch_176
jmp geo_done
geo_branch_176:
lda g_end_y
sta g_cmp
lda g_y
cmp g_cmp
bcs geo_branch_177
jmp geo_branch_174
geo_branch_177:
beq geo_branch_178
jmp geo_done
geo_branch_178:
geo_branch_174:
lda g_x
sta g_px
lda g_x+1
sta g_px+1
lda g_y
sta g_py
lda g_y+1
sta g_py+1
lda g_end_y
sta g_bottom
lda g_end_y+1
sta g_bottom+1
jsr geo_vspan
jmp geo_done
geo_curve_start:
; Collapsed axes are an inclusive point or straight span, never a division by zero.
lda #$00
eor #$80
sta g_cmp
lda g_rx+1
eor #$80
cmp g_cmp
beq geo_branch_180
jmp geo_branch_179
geo_branch_180:
lda #$00
sta g_cmp
lda g_rx
cmp g_cmp
beq geo_branch_181
jmp geo_branch_179
geo_branch_181:
jmp geo_curve_vertical
geo_branch_179:
lda #$00
eor #$80
sta g_cmp
lda g_ry+1
eor #$80
cmp g_cmp
beq geo_branch_183
jmp geo_branch_182
geo_branch_183:
lda #$00
sta g_cmp
lda g_ry
cmp g_cmp
beq geo_branch_184
jmp geo_branch_182
geo_branch_184:
jmp geo_curve_horizontal
geo_branch_182:
lda g_rx
sta g_x
lda g_rx+1
sta g_x+1
lda g_x
eor #$ff
sta g_x
lda g_x+1
eor #$ff
sta g_x+1
clc
lda g_x
adc #$01
sta g_x
lda g_x+1
adc #$00
sta g_x+1
lda #$00
sta g_y
lda #$00
sta g_y+1
lda #$ff
sta g_last_y
lda #$ff
sta g_last_y+1
; Squared radii and signed error increments use 32-bit storage. Radii <=255.
lda #$00
sta g_a2
lda #$00
sta g_a2+1
lda #$00
sta g_a2+2
lda #$00
sta g_a2+3
lda #$00
sta g_work
lda #$00
sta g_work+1
lda #$00
sta g_work+2
lda #$00
sta g_work+3
lda g_rx
sta g_work
lda g_rx+1
sta g_work+1
lda g_rx
sta g_mul
geo_branch_185:
lda #$00
sta g_cmp
lda g_mul
cmp g_cmp
beq geo_branch_188
jmp geo_branch_187
geo_branch_188:
jmp geo_branch_186
geo_branch_187:
lda g_mul
and #1
bne geo_branch_190
jmp geo_branch_189
geo_branch_190:
clc
lda g_a2
adc g_work
sta g_a2
lda g_a2+1
adc g_work+1
sta g_a2+1
lda g_a2+2
adc g_work+2
sta g_a2+2
lda g_a2+3
adc g_work+3
sta g_a2+3
geo_branch_189:
lsr g_mul
asl g_work
rol g_work+1
rol g_work+2
rol g_work+3
jmp geo_branch_185
geo_branch_186:
lda #$00
sta g_b2
lda #$00
sta g_b2+1
lda #$00
sta g_b2+2
lda #$00
sta g_b2+3
lda #$00
sta g_work
lda #$00
sta g_work+1
lda #$00
sta g_work+2
lda #$00
sta g_work+3
lda g_ry
sta g_work
lda g_ry+1
sta g_work+1
lda g_ry
sta g_mul
geo_branch_191:
lda #$00
sta g_cmp
lda g_mul
cmp g_cmp
beq geo_branch_194
jmp geo_branch_193
geo_branch_194:
jmp geo_branch_192
geo_branch_193:
lda g_mul
and #1
bne geo_branch_196
jmp geo_branch_195
geo_branch_196:
clc
lda g_b2
adc g_work
sta g_b2
lda g_b2+1
adc g_work+1
sta g_b2+1
lda g_b2+2
adc g_work+2
sta g_b2+2
lda g_b2+3
adc g_work+3
sta g_b2+3
geo_branch_195:
lsr g_mul
asl g_work
rol g_work+1
rol g_work+2
rol g_work+3
jmp geo_branch_191
geo_branch_192:
lda g_b2
sta g_step_x
lda g_b2+1
sta g_step_x+1
lda g_b2+2
sta g_step_x+2
lda g_b2+3
sta g_step_x+3
asl g_step_x
rol g_step_x+1
rol g_step_x+2
rol g_step_x+3
lda g_a2
sta g_step_y
lda g_a2+1
sta g_step_y+1
lda g_a2+2
sta g_step_y+2
lda g_a2+3
sta g_step_y+3
asl g_step_y
rol g_step_y+1
rol g_step_y+2
rol g_step_y+3
lda g_b2
sta g_curve_dx
lda g_b2+1
sta g_curve_dx+1
lda g_b2+2
sta g_curve_dx+2
lda g_b2+3
sta g_curve_dx+3
lda g_rx
sta g_temp
lda g_rx+1
sta g_temp+1
geo_branch_197:
sec
lda g_curve_dx
sbc g_step_x
sta g_curve_dx
lda g_curve_dx+1
sbc g_step_x+1
sta g_curve_dx+1
lda g_curve_dx+2
sbc g_step_x+2
sta g_curve_dx+2
lda g_curve_dx+3
sbc g_step_x+3
sta g_curve_dx+3
clc
lda g_temp
adc #$ff
sta g_temp
lda g_temp+1
adc #$ff
sta g_temp+1
lda #$00
eor #$80
sta g_cmp
lda g_temp+1
eor #$80
cmp g_cmp
beq geo_branch_199
jmp geo_branch_197
geo_branch_199:
lda #$00
sta g_cmp
lda g_temp
cmp g_cmp
beq geo_branch_200
jmp geo_branch_197
geo_branch_200:
geo_branch_198:
lda g_a2
sta g_curve_dy
lda g_a2+1
sta g_curve_dy+1
lda g_a2+2
sta g_curve_dy+2
lda g_a2+3
sta g_curve_dy+3
lda g_curve_dx
sta g_curve_err
lda g_curve_dx+1
sta g_curve_err+1
lda g_curve_dx+2
sta g_curve_err+2
lda g_curve_dx+3
sta g_curve_err+3
clc
lda g_curve_err
adc g_curve_dy
sta g_curve_err
lda g_curve_err+1
adc g_curve_dy+1
sta g_curve_err+1
lda g_curve_err+2
adc g_curve_dy+2
sta g_curve_err+2
lda g_curve_err+3
adc g_curve_dy+3
sta g_curve_err+3
geo_curve_loop:
jsr geo_emit_curve
lda g_curve_err
sta g_curve_e2
lda g_curve_err+1
sta g_curve_e2+1
lda g_curve_err+2
sta g_curve_e2+2
lda g_curve_err+3
sta g_curve_e2+3
asl g_curve_e2
rol g_curve_e2+1
rol g_curve_e2+2
rol g_curve_e2+3
lda g_curve_dx+3
eor #$80
sta g_cmp
lda g_curve_e2+3
eor #$80
cmp g_cmp
bcs geo_branch_203
jmp geo_branch_201
geo_branch_203:
beq geo_branch_204
jmp geo_branch_202
geo_branch_204:
lda g_curve_dx+2
sta g_cmp
lda g_curve_e2+2
cmp g_cmp
bcs geo_branch_205
jmp geo_branch_201
geo_branch_205:
beq geo_branch_206
jmp geo_branch_202
geo_branch_206:
lda g_curve_dx+1
sta g_cmp
lda g_curve_e2+1
cmp g_cmp
bcs geo_branch_207
jmp geo_branch_201
geo_branch_207:
beq geo_branch_208
jmp geo_branch_202
geo_branch_208:
lda g_curve_dx
sta g_cmp
lda g_curve_e2
cmp g_cmp
bcs geo_branch_209
jmp geo_branch_201
geo_branch_209:
geo_branch_202:
clc
lda g_x
adc #$01
sta g_x
lda g_x+1
adc #$00
sta g_x+1
clc
lda g_curve_dx
adc g_step_x
sta g_curve_dx
lda g_curve_dx+1
adc g_step_x+1
sta g_curve_dx+1
lda g_curve_dx+2
adc g_step_x+2
sta g_curve_dx+2
lda g_curve_dx+3
adc g_step_x+3
sta g_curve_dx+3
clc
lda g_curve_err
adc g_curve_dx
sta g_curve_err
lda g_curve_err+1
adc g_curve_dx+1
sta g_curve_err+1
lda g_curve_err+2
adc g_curve_dx+2
sta g_curve_err+2
lda g_curve_err+3
adc g_curve_dx+3
sta g_curve_err+3
geo_branch_201:
lda g_curve_dy+3
eor #$80
sta g_cmp
lda g_curve_e2+3
eor #$80
cmp g_cmp
bcs geo_branch_212
jmp geo_branch_211
geo_branch_212:
beq geo_branch_213
jmp geo_branch_210
geo_branch_213:
lda g_curve_dy+2
sta g_cmp
lda g_curve_e2+2
cmp g_cmp
bcs geo_branch_214
jmp geo_branch_211
geo_branch_214:
beq geo_branch_215
jmp geo_branch_210
geo_branch_215:
lda g_curve_dy+1
sta g_cmp
lda g_curve_e2+1
cmp g_cmp
bcs geo_branch_216
jmp geo_branch_211
geo_branch_216:
beq geo_branch_217
jmp geo_branch_210
geo_branch_217:
lda g_curve_dy
sta g_cmp
lda g_curve_e2
cmp g_cmp
bcs geo_branch_218
jmp geo_branch_211
geo_branch_218:
beq geo_branch_219
jmp geo_branch_210
geo_branch_219:
geo_branch_211:
clc
lda g_y
adc #$01
sta g_y
lda g_y+1
adc #$00
sta g_y+1
clc
lda g_curve_dy
adc g_step_y
sta g_curve_dy
lda g_curve_dy+1
adc g_step_y+1
sta g_curve_dy+1
lda g_curve_dy+2
adc g_step_y+2
sta g_curve_dy+2
lda g_curve_dy+3
adc g_step_y+3
sta g_curve_dy+3
clc
lda g_curve_err
adc g_curve_dy
sta g_curve_err
lda g_curve_err+1
adc g_curve_dy+1
sta g_curve_err+1
lda g_curve_err+2
adc g_curve_dy+2
sta g_curve_err+2
lda g_curve_err+3
adc g_curve_dy+3
sta g_curve_err+3
geo_branch_210:
lda #$00
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
bcs geo_branch_221
jmp geo_curve_loop
geo_branch_221:
beq geo_branch_222
jmp geo_branch_220
geo_branch_222:
lda #$00
sta g_cmp
lda g_x
cmp g_cmp
bcs geo_branch_223
jmp geo_curve_loop
geo_branch_223:
bne geo_branch_224
jmp geo_curve_loop
geo_branch_224:
geo_branch_220:
lda #$00
sta g_x
lda #$00
sta g_x+1
geo_curve_tip:
lda g_ry+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
bcs geo_branch_226
jmp geo_branch_225
geo_branch_226:
beq geo_branch_227
jmp geo_done
geo_branch_227:
lda g_ry
sta g_cmp
lda g_y
cmp g_cmp
bcs geo_branch_228
jmp geo_branch_225
geo_branch_228:
jmp geo_done
geo_branch_225:
clc
lda g_y
adc #$01
sta g_y
lda g_y+1
adc #$00
sta g_y+1
jsr geo_emit_curve
jmp geo_curve_tip
geo_curve_vertical:
lda g_a
sta g_px
lda g_a+1
sta g_px+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
sec
lda g_py
sbc g_ry
sta g_py
lda g_py+1
sbc g_ry+1
sta g_py+1
lda g_b
sta g_bottom
lda g_b+1
sta g_bottom+1
clc
lda g_bottom
adc g_ry
sta g_bottom
lda g_bottom+1
adc g_ry+1
sta g_bottom+1
jsr geo_vspan
jmp geo_done
geo_curve_horizontal:
lda g_b
sta g_py
lda g_b+1
sta g_py+1
lda g_a
sta g_px
lda g_a+1
sta g_px+1
sec
lda g_px
sbc g_rx
sta g_px
lda g_px+1
sbc g_rx+1
sta g_px+1
lda g_a
sta g_right
lda g_a+1
sta g_right+1
clc
lda g_right
adc g_rx
sta g_right
lda g_right+1
adc g_rx+1
sta g_right+1
jsr geo_span
jmp geo_done
geo_emit_curve:
lda #$00
sta g_cmp
lda g_fill
cmp g_cmp
beq geo_branch_230
jmp geo_emit_fill
geo_branch_230:
geo_branch_229:
; Axis tests remove duplicate symmetric pixels, including XOR at the centre.
lda g_a
sta g_px
lda g_a+1
sta g_px+1
sec
lda g_px
sbc g_x
sta g_px
lda g_px+1
sbc g_x+1
sta g_px+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
clc
lda g_py
adc g_y
sta g_py
lda g_py+1
adc g_y+1
sta g_py+1
jsr geo_point
lda #$00
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
beq geo_branch_233
jmp geo_branch_232
geo_branch_233:
lda #$00
sta g_cmp
lda g_x
cmp g_cmp
beq geo_branch_234
jmp geo_branch_232
geo_branch_234:
jmp geo_branch_231
geo_branch_232:
lda g_a
sta g_px
lda g_a+1
sta g_px+1
clc
lda g_px
adc g_x
sta g_px
lda g_px+1
adc g_x+1
sta g_px+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
clc
lda g_py
adc g_y
sta g_py
lda g_py+1
adc g_y+1
sta g_py+1
jsr geo_point
geo_branch_231:
lda #$00
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
beq geo_branch_236
jmp geo_branch_235
geo_branch_236:
lda #$00
sta g_cmp
lda g_y
cmp g_cmp
beq geo_branch_237
jmp geo_branch_235
geo_branch_237:
jmp geo_emit_return
geo_branch_235:
lda g_a
sta g_px
lda g_a+1
sta g_px+1
sec
lda g_px
sbc g_x
sta g_px
lda g_px+1
sbc g_x+1
sta g_px+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
sec
lda g_py
sbc g_y
sta g_py
lda g_py+1
sbc g_y+1
sta g_py+1
jsr geo_point
lda #$00
eor #$80
sta g_cmp
lda g_x+1
eor #$80
cmp g_cmp
beq geo_branch_239
jmp geo_branch_238
geo_branch_239:
lda #$00
sta g_cmp
lda g_x
cmp g_cmp
beq geo_branch_240
jmp geo_branch_238
geo_branch_240:
jmp geo_emit_return
geo_branch_238:
lda g_a
sta g_px
lda g_a+1
sta g_px+1
clc
lda g_px
adc g_x
sta g_px
lda g_px+1
adc g_x+1
sta g_px+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
sec
lda g_py
sbc g_y
sta g_py
lda g_py+1
sbc g_y+1
sta g_py+1
jsr geo_point
geo_emit_return:
rts
geo_emit_fill:
; Only the first, widest extent for a row emits spans. Each row is written once.
lda g_last_y+1
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
beq geo_branch_242
jmp geo_branch_241
geo_branch_242:
lda g_last_y
sta g_cmp
lda g_y
cmp g_cmp
beq geo_branch_243
jmp geo_branch_241
geo_branch_243:
jmp geo_emit_return
geo_branch_241:
lda g_y
sta g_last_y
lda g_y+1
sta g_last_y+1
lda g_a
sta g_px
lda g_a+1
sta g_px+1
clc
lda g_px
adc g_x
sta g_px
lda g_px+1
adc g_x+1
sta g_px+1
lda g_a
sta g_right
lda g_a+1
sta g_right+1
sec
lda g_right
sbc g_x
sta g_right
lda g_right+1
sbc g_x+1
sta g_right+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
clc
lda g_py
adc g_y
sta g_py
lda g_py+1
adc g_y+1
sta g_py+1
jsr geo_span
lda #$00
eor #$80
sta g_cmp
lda g_y+1
eor #$80
cmp g_cmp
beq geo_branch_245
jmp geo_branch_244
geo_branch_245:
lda #$00
sta g_cmp
lda g_y
cmp g_cmp
beq geo_branch_246
jmp geo_branch_244
geo_branch_246:
jmp geo_emit_return
geo_branch_244:
lda g_a
sta g_px
lda g_a+1
sta g_px+1
clc
lda g_px
adc g_x
sta g_px
lda g_px+1
adc g_x+1
sta g_px+1
lda g_a
sta g_right
lda g_a+1
sta g_right+1
sec
lda g_right
sbc g_x
sta g_right
lda g_right+1
sbc g_x+1
sta g_right+1
lda g_b
sta g_py
lda g_b+1
sta g_py+1
sec
lda g_py
sbc g_y
sta g_py
lda g_py+1
sbc g_y+1
sta g_py+1
jsr geo_span
rts
geo_point:
; Scissor the original raster, preserving its decision phase outside the window.
lda g_clip_l+1
eor #$80
sta g_cmp
lda g_px+1
eor #$80
cmp g_cmp
bcs geo_branch_248
jmp geo_emit_return
geo_branch_248:
beq geo_branch_249
jmp geo_branch_247
geo_branch_249:
lda g_clip_l
sta g_cmp
lda g_px
cmp g_cmp
bcs geo_branch_250
jmp geo_emit_return
geo_branch_250:
geo_branch_247:
lda g_clip_r+1
eor #$80
sta g_cmp
lda g_px+1
eor #$80
cmp g_cmp
bcs geo_branch_252
jmp geo_branch_251
geo_branch_252:
beq geo_branch_253
jmp geo_emit_return
geo_branch_253:
lda g_clip_r
sta g_cmp
lda g_px
cmp g_cmp
bcs geo_branch_254
jmp geo_branch_251
geo_branch_254:
jmp geo_emit_return
geo_branch_251:
lda g_clip_t+1
eor #$80
sta g_cmp
lda g_py+1
eor #$80
cmp g_cmp
bcs geo_branch_256
jmp geo_emit_return
geo_branch_256:
beq geo_branch_257
jmp geo_branch_255
geo_branch_257:
lda g_clip_t
sta g_cmp
lda g_py
cmp g_cmp
bcs geo_branch_258
jmp geo_emit_return
geo_branch_258:
geo_branch_255:
lda g_clip_b+1
eor #$80
sta g_cmp
lda g_py+1
eor #$80
cmp g_cmp
bcs geo_branch_260
jmp geo_branch_259
geo_branch_260:
beq geo_branch_261
jmp geo_emit_return
geo_branch_261:
lda g_clip_b
sta g_cmp
lda g_py
cmp g_cmp
bcs geo_branch_262
jmp geo_branch_259
geo_branch_262:
jmp geo_emit_return
geo_branch_259:
lda g_px
sta bp_x0
lda g_px+1
sta bp_x0+1
lda g_py
sta bp_y0
lda g_py+1
sta bp_y0+1
jsr geo_backend_inputs
jsr bp_pixel
jmp geo_account
geo_span:
lda g_clip_t+1
eor #$80
sta g_cmp
lda g_py+1
eor #$80
cmp g_cmp
bcs geo_branch_264
jmp geo_emit_return
geo_branch_264:
beq geo_branch_265
jmp geo_branch_263
geo_branch_265:
lda g_clip_t
sta g_cmp
lda g_py
cmp g_cmp
bcs geo_branch_266
jmp geo_emit_return
geo_branch_266:
geo_branch_263:
lda g_clip_b+1
eor #$80
sta g_cmp
lda g_py+1
eor #$80
cmp g_cmp
bcs geo_branch_268
jmp geo_branch_267
geo_branch_268:
beq geo_branch_269
jmp geo_emit_return
geo_branch_269:
lda g_clip_b
sta g_cmp
lda g_py
cmp g_cmp
bcs geo_branch_270
jmp geo_branch_267
geo_branch_270:
jmp geo_emit_return
geo_branch_267:
lda g_clip_l+1
eor #$80
sta g_cmp
lda g_right+1
eor #$80
cmp g_cmp
bcs geo_branch_272
jmp geo_emit_return
geo_branch_272:
beq geo_branch_273
jmp geo_branch_271
geo_branch_273:
lda g_clip_l
sta g_cmp
lda g_right
cmp g_cmp
bcs geo_branch_274
jmp geo_emit_return
geo_branch_274:
geo_branch_271:
lda g_clip_r+1
eor #$80
sta g_cmp
lda g_px+1
eor #$80
cmp g_cmp
bcs geo_branch_276
jmp geo_branch_275
geo_branch_276:
beq geo_branch_277
jmp geo_emit_return
geo_branch_277:
lda g_clip_r
sta g_cmp
lda g_px
cmp g_cmp
bcs geo_branch_278
jmp geo_branch_275
geo_branch_278:
jmp geo_emit_return
geo_branch_275:
lda g_clip_l+1
eor #$80
sta g_cmp
lda g_px+1
eor #$80
cmp g_cmp
bcs geo_branch_281
jmp geo_branch_280
geo_branch_281:
beq geo_branch_282
jmp geo_branch_279
geo_branch_282:
lda g_clip_l
sta g_cmp
lda g_px
cmp g_cmp
bcs geo_branch_283
jmp geo_branch_280
geo_branch_283:
jmp geo_branch_279
geo_branch_280:
lda g_clip_l
sta g_px
lda g_clip_l+1
sta g_px+1
geo_branch_279:
lda g_clip_r+1
eor #$80
sta g_cmp
lda g_right+1
eor #$80
cmp g_cmp
bcs geo_branch_286
jmp geo_branch_284
geo_branch_286:
beq geo_branch_287
jmp geo_branch_285
geo_branch_287:
lda g_clip_r
sta g_cmp
lda g_right
cmp g_cmp
bcs geo_branch_288
jmp geo_branch_284
geo_branch_288:
geo_branch_285:
lda g_clip_r
sta g_right
lda g_clip_r+1
sta g_right+1
clc
lda g_right
adc #$ff
sta g_right
lda g_right+1
adc #$ff
sta g_right+1
geo_branch_284:
lda g_px
sta bp_x0
lda g_px+1
sta bp_x0+1
lda g_py
sta bp_y0
lda g_py+1
sta bp_y0+1
lda g_right
sta bp_x1
lda g_right+1
sta bp_x1+1
clc
lda bp_x1
adc #$01
sta bp_x1
lda bp_x1+1
adc #$00
sta bp_x1+1
jsr geo_backend_inputs
jsr bp_hspan
jmp geo_account
geo_vspan:
lda g_clip_l+1
eor #$80
sta g_cmp
lda g_px+1
eor #$80
cmp g_cmp
bcs geo_branch_290
jmp geo_emit_return
geo_branch_290:
beq geo_branch_291
jmp geo_branch_289
geo_branch_291:
lda g_clip_l
sta g_cmp
lda g_px
cmp g_cmp
bcs geo_branch_292
jmp geo_emit_return
geo_branch_292:
geo_branch_289:
lda g_clip_r+1
eor #$80
sta g_cmp
lda g_px+1
eor #$80
cmp g_cmp
bcs geo_branch_294
jmp geo_branch_293
geo_branch_294:
beq geo_branch_295
jmp geo_emit_return
geo_branch_295:
lda g_clip_r
sta g_cmp
lda g_px
cmp g_cmp
bcs geo_branch_296
jmp geo_branch_293
geo_branch_296:
jmp geo_emit_return
geo_branch_293:
lda g_clip_t+1
eor #$80
sta g_cmp
lda g_bottom+1
eor #$80
cmp g_cmp
bcs geo_branch_298
jmp geo_emit_return
geo_branch_298:
beq geo_branch_299
jmp geo_branch_297
geo_branch_299:
lda g_clip_t
sta g_cmp
lda g_bottom
cmp g_cmp
bcs geo_branch_300
jmp geo_emit_return
geo_branch_300:
geo_branch_297:
lda g_clip_b+1
eor #$80
sta g_cmp
lda g_py+1
eor #$80
cmp g_cmp
bcs geo_branch_302
jmp geo_branch_301
geo_branch_302:
beq geo_branch_303
jmp geo_emit_return
geo_branch_303:
lda g_clip_b
sta g_cmp
lda g_py
cmp g_cmp
bcs geo_branch_304
jmp geo_branch_301
geo_branch_304:
jmp geo_emit_return
geo_branch_301:
lda g_clip_t+1
eor #$80
sta g_cmp
lda g_py+1
eor #$80
cmp g_cmp
bcs geo_branch_307
jmp geo_branch_306
geo_branch_307:
beq geo_branch_308
jmp geo_branch_305
geo_branch_308:
lda g_clip_t
sta g_cmp
lda g_py
cmp g_cmp
bcs geo_branch_309
jmp geo_branch_306
geo_branch_309:
jmp geo_branch_305
geo_branch_306:
lda g_clip_t
sta g_py
lda g_clip_t+1
sta g_py+1
geo_branch_305:
lda g_clip_b+1
eor #$80
sta g_cmp
lda g_bottom+1
eor #$80
cmp g_cmp
bcs geo_branch_312
jmp geo_branch_310
geo_branch_312:
beq geo_branch_313
jmp geo_branch_311
geo_branch_313:
lda g_clip_b
sta g_cmp
lda g_bottom
cmp g_cmp
bcs geo_branch_314
jmp geo_branch_310
geo_branch_314:
geo_branch_311:
lda g_clip_b
sta g_bottom
lda g_clip_b+1
sta g_bottom+1
clc
lda g_bottom
adc #$ff
sta g_bottom
lda g_bottom+1
adc #$ff
sta g_bottom+1
geo_branch_310:
lda g_px
sta bp_x0
lda g_px+1
sta bp_x0+1
lda g_py
sta bp_y0
lda g_py+1
sta bp_y0+1
lda g_bottom
sta bp_y1
lda g_bottom+1
sta bp_y1+1
clc
lda bp_y1
adc #$01
sta bp_y1
lda bp_y1+1
adc #$00
sta bp_y1+1
jsr geo_backend_inputs
jsr bp_vspan
jmp geo_account
geo_backend_inputs:
lda g_op
sta bp_op
lda g_pen
sta bp_pen
rts
geo_account:
lda #$00
sta g_work
lda #$00
sta g_work+1
lda #$00
sta g_work+2
lda #$00
sta g_work+3
lda bp_writes
sta g_work
lda bp_writes+1
sta g_work+1
clc
lda g_writes
adc g_work
sta g_writes
lda g_writes+1
adc g_work+1
sta g_writes+1
lda g_writes+2
adc g_work+2
sta g_writes+2
lda g_writes+3
adc g_work+3
sta g_writes+3
clc
lda g_calls
adc #$01
sta g_calls
lda g_calls+1
adc #$00
sta g_calls+1
rts
geometry_end:What was verified
215 calls completed on this exact configuration using Asm198x 0.0.71 and Emu198x 0.39.0. Every call compares complete bitmap memory, neighbouring guards, public inputs, acceptance, byte writes and backend calls with an independent model. Cases cover all octants, reversal/ties, endpoint ownership, axes, zero radii, clipping, XOR, range extremes and rejected requests. Selected whole native frames match independently composed pixels. A wrong ellipse recurrence completed accepted draws and failed both memory and picture checks.
The radius bound also has a separate exhaustive arithmetic check: all 65,025 nonzero radius pairs fit the chosen 32-bit error path. That host check does not claim native execution of every pair. Real-hardware timing, stock-OS loading and tear-free live drawing remain separate.