prog8/compiler/res/prog8lib/cx16/gfx2.p8

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; Bitmap pixel graphics routines for the CommanderX16
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; Custom routines to use the full-screen 640x480 and 320x240 screen modes.
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; (These modes are not supported by the documented GRAPH_xxxx kernal routines)
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;
; No text layer is currently shown, text can be drawn as part of the bitmap itself.
; Note: for similar graphics routines that also work on the C-64, use the "graphics" module instead.
; Note: for color palette manipulation, use the "palette" module or write Vera registers yourself.
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; Note: this library implements code for various resolutions and color depths. This takes up memory.
; If you're memory constrained you should probably not use this built-in library,
; but make a copy in your project only containing the code for the required resolution.
;
;
; SCREEN MODE LIST:
; mode 0 = reset back to default text mode
; mode 1 = bitmap 320 x 240 monochrome
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; mode 2 = bitmap 320 x 240 x 4c (TODO not yet implemented)
; mode 3 = bitmap 320 x 240 x 16c (TODO not yet implemented)
; mode 4 = bitmap 320 x 240 x 256c
; mode 5 = bitmap 640 x 480 monochrome
; mode 6 = bitmap 640 x 480 x 4c
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; higher color dephts in highres are not supported due to lack of VRAM
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; TODO can we make a FB vector table and emulation routines for the Cx16s' GRAPH_init() call? to replace the builtin 320x200 fb driver?
gfx2 {
; read-only control variables:
ubyte active_mode = 0
uword width = 0
uword height = 0
ubyte bpp = 0
ubyte monochrome_dont_stipple_flag = false ; set to false to enable stippling mode in monochrome displaymodes
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sub screen_mode(ubyte mode) {
when mode {
1 -> {
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; lores monochrome
cx16.VERA_DC_VIDEO = (cx16.VERA_DC_VIDEO & %11001111) | %00100000 ; enable only layer 1
cx16.VERA_DC_HSCALE = 64
cx16.VERA_DC_VSCALE = 64
cx16.VERA_L1_CONFIG = %00000100
cx16.VERA_L1_MAPBASE = 0
cx16.VERA_L1_TILEBASE = 0
width = 320
height = 240
bpp = 1
}
; TODO modes 2, 3 not yet implemented
4 -> {
; lores 256c
cx16.VERA_DC_VIDEO = (cx16.VERA_DC_VIDEO & %11001111) | %00100000 ; enable only layer 1
cx16.VERA_DC_HSCALE = 64
cx16.VERA_DC_VSCALE = 64
cx16.VERA_L1_CONFIG = %00000111
cx16.VERA_L1_MAPBASE = 0
cx16.VERA_L1_TILEBASE = 0
width = 320
height = 240
bpp = 8
}
5 -> {
; highres monochrome
cx16.VERA_DC_VIDEO = (cx16.VERA_DC_VIDEO & %11001111) | %00100000 ; enable only layer 1
cx16.VERA_DC_HSCALE = 128
cx16.VERA_DC_VSCALE = 128
cx16.VERA_L1_CONFIG = %00000100
cx16.VERA_L1_MAPBASE = 0
cx16.VERA_L1_TILEBASE = %00000001
width = 640
height = 480
bpp = 1
}
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6 -> {
; highres 4c
cx16.VERA_DC_VIDEO = (cx16.VERA_DC_VIDEO & %11001111) | %00100000 ; enable only layer 1
cx16.VERA_DC_HSCALE = 128
cx16.VERA_DC_VSCALE = 128
cx16.VERA_L1_CONFIG = %00000101
cx16.VERA_L1_MAPBASE = 0
cx16.VERA_L1_TILEBASE = %00000001
width = 640
height = 480
bpp = 2
}
else -> {
; back to default text mode and colors
cx16.VERA_CTRL = %10000000 ; reset VERA and palette
c64.CINT() ; back to text mode
width = 0
height = 0
bpp = 0
mode = 0
}
}
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active_mode = mode
if bpp
clear_screen()
}
sub clear_screen() {
monochrome_stipple(false)
position(0, 0)
when active_mode {
1 -> {
; lores monochrome
repeat 240/2/8
cs_innerloop640()
}
; TODO mode 2, 3
4 -> {
; lores 256c
repeat 240/2
cs_innerloop640()
}
5 -> {
; highres monochrome
repeat 480/8
cs_innerloop640()
}
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6 -> {
; highres 4c
repeat 480/4
cs_innerloop640()
}
; modes 7 and 8 not supported due to lack of VRAM
}
position(0, 0)
}
sub monochrome_stipple(ubyte enable) {
monochrome_dont_stipple_flag = not enable
}
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sub rect(uword x, uword y, uword width, uword height, ubyte color) {
if width==0 or height==0
return
horizontal_line(x, y, width, color)
if height==1
return
horizontal_line(x, y+height-1, width, color)
vertical_line(x, y+1, height-2, color)
if width==1
return
vertical_line(x+width-1, y+1, height-2, color)
}
sub fillrect(uword x, uword y, uword width, uword height, ubyte color) {
if width==0
return
repeat height {
horizontal_line(x, y, width, color)
y++
}
}
sub horizontal_line(uword x, uword y, uword length, ubyte color) {
if length==0
return
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when active_mode {
1, 5 -> {
; monochrome modes, either resolution
ubyte separate_pixels = (8-lsb(x)) & 7
if separate_pixels as uword > length
separate_pixels = lsb(length)
repeat separate_pixels {
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; TODO optimize this by writing a masked byte in 1 go
plot(x, y, color)
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x++
}
length -= separate_pixels
if length {
position(x, y)
separate_pixels = lsb(length) & 7
x += length & $fff8
%asm {{
lsr length+1
ror length
lsr length+1
ror length
lsr length+1
ror length
lda color
bne +
ldy #0 ; black
bra _loop
+ lda monochrome_dont_stipple_flag
beq _stipple
ldy #255 ; don't stipple
bra _loop
_stipple lda y
and #1 ; determine stipple pattern to use
bne +
ldy #%01010101
bra _loop
+ ldy #%10101010
_loop lda length
ora length+1
beq _done
sty cx16.VERA_DATA0
lda length
bne +
dec length+1
+ dec length
bra _loop
_done
}}
repeat separate_pixels {
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; TODO optimize this by writing a masked byte in 1 go
plot(x, y, color)
x++
}
}
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cx16.VERA_ADDR_H &= %00000111 ; vera auto-increment off again
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}
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4 -> {
; lores 256c
position(x, y)
%asm {{
lda color
phx
ldx length+1
beq +
ldy #0
- sta cx16.VERA_DATA0
iny
bne -
dex
bne -
+ ldy length ; remaining
beq +
- sta cx16.VERA_DATA0
dey
bne -
+ plx
}}
}
6 -> {
; highres 4c
; TODO also mostly usable for lores 4c?
color &= 3
ubyte[4] colorbits
ubyte ii
for ii in 3 downto 0 {
colorbits[ii] = color
color <<= 2
}
void addr_mul_24_for_highres_4c(y, x) ; 24 bits result is in r0 and r1L (highest byte)
%asm {{
lda cx16.VERA_ADDR_H
and #%00000111 ; no auto advance
sta cx16.VERA_ADDR_H
stz cx16.VERA_CTRL ; setup vera addr 0
lda cx16.r1
and #1
sta cx16.VERA_ADDR_H
lda cx16.r0
sta cx16.VERA_ADDR_L
lda cx16.r0+1
sta cx16.VERA_ADDR_M
phx
ldx x
}}
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repeat length {
%asm {{
txa
and #3
tay
lda cx16.VERA_DATA0
and gfx2.plot.mask4c,y
ora colorbits,y
sta cx16.VERA_DATA0
cpy #%00000011 ; next vera byte?
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bne ++
inc cx16.VERA_ADDR_L
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bne ++
inc cx16.VERA_ADDR_M
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+ bne +
inc cx16.VERA_ADDR_H
+ inx ; next pixel
}}
}
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%asm {{
plx
}}
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}
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}
}
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sub vertical_line(uword x, uword y, uword height, ubyte color) {
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when active_mode {
1, 5 -> {
; monochrome, lo-res
cx16.r15L = gfx2.plot.bits[x as ubyte & 7] ; bitmask
if color {
if monochrome_dont_stipple_flag {
; draw continuous line.
position2(x,y,true)
if active_mode==1
set_both_strides(11) ; 40 increment = 1 line in 320 px monochrome
else
set_both_strides(12) ; 80 increment = 1 line in 640 px monochrome
repeat height {
%asm {{
lda cx16.VERA_DATA0
ora cx16.r15L
sta cx16.VERA_DATA1
}}
}
} else {
; draw stippled line.
if x&1 {
y++
height--
}
position2(x,y,true)
if active_mode==1
set_both_strides(12) ; 80 increment = 2 line in 320 px monochrome
else
set_both_strides(13) ; 160 increment = 2 line in 640 px monochrome
repeat height/2 {
%asm {{
lda cx16.VERA_DATA0
ora cx16.r15L
sta cx16.VERA_DATA1
}}
}
}
} else {
position2(x,y,true)
cx16.r15 = ~cx16.r15 ; erase pixels
if active_mode==1
set_both_strides(11) ; 40 increment = 1 line in 320 px monochrome
else
set_both_strides(12) ; 80 increment = 1 line in 640 px monochrome
repeat height {
%asm {{
lda cx16.VERA_DATA0
and cx16.r15L
sta cx16.VERA_DATA1
}}
}
}
}
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4 -> {
; lores 256c
; set vera auto-increment to 320 pixel increment (=next line)
position(x,y)
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cx16.VERA_ADDR_H = cx16.VERA_ADDR_H & %00000111 | (14<<4)
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%asm {{
ldy height
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beq +
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lda color
- sta cx16.VERA_DATA0
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dey
bne -
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+
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}}
}
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6 -> {
; highres 4c
; use TWO vera adress pointers simultaneously one for reading, one for writing, so auto-increment is possible
if height==0
return
position2(x,y,true)
set_both_strides(13) ; 160 increment = 1 line in 640 px 4c mode
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color &= 3
color <<= gfx2.plot.shift4c[lsb(x) & 3]
ubyte mask = gfx2.plot.mask4c[lsb(x) & 3]
repeat height {
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%asm {{
lda cx16.VERA_DATA0
and mask
ora color
sta cx16.VERA_DATA1
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}}
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}
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}
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}
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sub set_both_strides(ubyte stride) {
stride <<= 4
cx16.VERA_CTRL = 0
cx16.VERA_ADDR_H = cx16.VERA_ADDR_H & %00000111 | stride
cx16.VERA_CTRL = 1
cx16.VERA_ADDR_H = cx16.VERA_ADDR_H & %00000111 | stride
}
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}
sub line(uword @zp x1, uword @zp y1, uword @zp x2, uword @zp y2, ubyte color) {
; Bresenham algorithm.
; This code special-cases various quadrant loops to allow simple ++ and -- operations.
if y1>y2 {
; make sure dy is always positive to have only 4 instead of 8 special cases
swap(x1, x2)
swap(y1, y2)
}
word @zp dx = (x2 as word)-x1
word @zp dy = (y2 as word)-y1
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if dx==0 {
vertical_line(x1, y1, abs(dy) as uword +1, color)
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return
}
if dy==0 {
if x1>x2
x1=x2
horizontal_line(x1, y1, abs(dx) as uword +1, color)
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return
}
word @zp d = 0
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cx16.r13 = true ; 'positive_ix'
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if dx < 0 {
dx = -dx
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cx16.r13 = false
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}
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word @zp dx2 = dx*2
word @zp dy2 = dy*2
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cx16.r14 = x1 ; internal plot X
if dx >= dy {
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if cx16.r13 {
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repeat {
plot(cx16.r14, y1, color)
if cx16.r14==x2
return
cx16.r14++
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d += dy2
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if d > dx {
y1++
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d -= dx2
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}
}
} else {
repeat {
plot(cx16.r14, y1, color)
if cx16.r14==x2
return
cx16.r14--
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d += dy2
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if d > dx {
y1++
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d -= dx2
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}
}
}
}
else {
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if cx16.r13 {
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repeat {
plot(cx16.r14, y1, color)
if y1 == y2
return
y1++
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d += dx2
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if d > dy {
cx16.r14++
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d -= dy2
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}
}
} else {
repeat {
plot(cx16.r14, y1, color)
if y1 == y2
return
y1++
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d += dx2
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if d > dy {
cx16.r14--
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d -= dy2
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}
}
}
}
}
sub circle(uword @zp xcenter, uword @zp ycenter, ubyte radius, ubyte color) {
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; Midpoint algorithm.
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if radius==0
return
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ubyte @zp xx = radius
ubyte @zp yy = 0
word @zp decisionOver2 = (1 as word)-xx
; R14 = internal plot X
; R15 = internal plot Y
while xx>=yy {
cx16.r14 = xcenter + xx
cx16.r15 = ycenter + yy
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter - xx
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter + xx
cx16.r15 = ycenter - yy
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter - xx
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter + yy
cx16.r15 = ycenter + xx
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter - yy
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter + yy
cx16.r15 = ycenter - xx
plot(cx16.r14, cx16.r15, color)
cx16.r14 = xcenter - yy
plot(cx16.r14, cx16.r15, color)
yy++
if decisionOver2<=0
decisionOver2 += (yy as word)*2+1
else {
xx--
decisionOver2 += (yy as word -xx)*2+1
}
}
}
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sub disc(uword @zp xcenter, uword @zp ycenter, ubyte @zp radius, ubyte color) {
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; Midpoint algorithm, filled
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if radius==0
return
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ubyte @zp yy = 0
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word @zp decisionOver2 = (1 as word)-radius
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while radius>=yy {
horizontal_line(xcenter-radius, ycenter+yy, radius*$0002+1, color)
horizontal_line(xcenter-radius, ycenter-yy, radius*$0002+1, color)
horizontal_line(xcenter-yy, ycenter+radius, yy*$0002+1, color)
horizontal_line(xcenter-yy, ycenter-radius, yy*$0002+1, color)
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yy++
if decisionOver2<=0
decisionOver2 += (yy as word)*2+1
else {
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radius--
decisionOver2 += (yy as word -radius)*2+1
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}
}
}
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sub plot(uword @zp x, uword y, ubyte color) {
ubyte[8] bits = [128, 64, 32, 16, 8, 4, 2, 1]
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ubyte[4] mask4c = [%00111111, %11001111, %11110011, %11111100]
ubyte[4] shift4c = [6,4,2,0]
when active_mode {
1 -> {
; lores monochrome
%asm {{
lda x
eor y
ora monochrome_dont_stipple_flag
and #1
}}
if_nz {
cx16.r0L = lsb(x) & 7 ; xbits
x /= 8
x += y*(320/8)
%asm {{
stz cx16.VERA_CTRL
stz cx16.VERA_ADDR_H
lda x+1
sta cx16.VERA_ADDR_M
lda x
sta cx16.VERA_ADDR_L
ldy cx16.r0L ; xbits
lda bits,y
ldy color
beq +
tsb cx16.VERA_DATA0
bra ++
+ trb cx16.VERA_DATA0
+
}}
}
}
; TODO mode 2,3
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4 -> {
; lores 256c
void addr_mul_24_for_lores_256c(y, x) ; 24 bits result is in r0 and r1L (highest byte)
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%asm {{
stz cx16.VERA_CTRL
lda cx16.r1
ora #%00010000 ; enable auto-increment so next_pixel() can be used after this
sta cx16.VERA_ADDR_H
lda cx16.r0+1
sta cx16.VERA_ADDR_M
lda cx16.r0
sta cx16.VERA_ADDR_L
lda color
sta cx16.VERA_DATA0
}}
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}
5 -> {
; highres monochrome
%asm {{
lda x
eor y
ora monochrome_dont_stipple_flag
and #1
}}
if_nz {
cx16.r0L = lsb(x) & 7 ; xbits
x /= 8
x += y*(640/8)
%asm {{
stz cx16.VERA_CTRL
stz cx16.VERA_ADDR_H
lda x+1
sta cx16.VERA_ADDR_M
lda x
sta cx16.VERA_ADDR_L
ldy cx16.r0L ; xbits
lda bits,y
ldy color
beq +
tsb cx16.VERA_DATA0
bra ++
+ trb cx16.VERA_DATA0
+
}}
}
}
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6 -> {
; highres 4c
; TODO also mostly usable for lores 4c?
void addr_mul_24_for_highres_4c(y, x) ; 24 bits result is in r0 and r1L (highest byte)
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cx16.r2L = lsb(x) & 3 ; xbits
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color &= 3
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color <<= shift4c[cx16.r2L]
%asm {{
stz cx16.VERA_CTRL
lda cx16.r1L
sta cx16.VERA_ADDR_H
lda cx16.r0H
sta cx16.VERA_ADDR_M
lda cx16.r0L
sta cx16.VERA_ADDR_L
ldy cx16.r2L ; xbits
lda mask4c,y
and cx16.VERA_DATA0
ora color
sta cx16.VERA_DATA0
}}
}
}
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}
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sub position(uword @zp x, uword y) {
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ubyte bank
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when active_mode {
1 -> {
; lores monochrome
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cx16.r0 = y*(320/8) + x/8
cx16.vaddr(0, cx16.r0, 0, 1)
}
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; TODO modes 2,3
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4 -> {
; lores 256c
void addr_mul_24_for_lores_256c(y, x) ; 24 bits result is in r0 and r1L (highest byte)
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bank = lsb(cx16.r1)
cx16.vaddr(bank, cx16.r0, 0, 1)
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}
5 -> {
; highres monochrome
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cx16.r0 = y*(640/8) + x/8
cx16.vaddr(0, cx16.r0, 0, 1)
}
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6 -> {
; highres 4c
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void addr_mul_24_for_highres_4c(y, x) ; 24 bits result is in r0 and r1L (highest byte)
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bank = lsb(cx16.r1)
cx16.vaddr(bank, cx16.r0, 0, 1)
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}
}
}
sub position2(uword @zp x, uword y, ubyte also_port_1) {
position(x, y)
if also_port_1 {
when active_mode {
1, 5 -> cx16.vaddr(0, cx16.r0, 1, 1)
; TODO modes 2, 3
4, 6 -> {
ubyte bank = lsb(cx16.r1)
cx16.vaddr(bank, cx16.r0, 1, 1)
}
}
}
}
inline asmsub next_pixel(ubyte color @A) {
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; -- sets the next pixel byte to the graphics chip.
; for 8 bpp screens this will plot 1 pixel.
; for 1 bpp screens it will plot 8 pixels at once (color = bit pattern).
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; for 2 bpp screens it will plot 4 pixels at once (color = bit pattern).
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%asm {{
sta cx16.VERA_DATA0
}}
}
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asmsub next_pixels(uword pixels @AY, uword amount @R0) clobbers(A, Y) {
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; -- sets the next bunch of pixels from a prepared array of bytes.
; for 8 bpp screens this will plot 1 pixel per byte.
; for 1 bpp screens it will plot 8 pixels at once (colors are the bit patterns per byte).
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; for 2 bpp screens it will plot 4 pixels at once (colors are the bit patterns per byte).
%asm {{
phx
sta P8ZP_SCRATCH_W1
sty P8ZP_SCRATCH_W1+1
ldx cx16.r0+1
beq +
ldy #0
- lda (P8ZP_SCRATCH_W1),y
sta cx16.VERA_DATA0
iny
bne -
inc P8ZP_SCRATCH_W1+1 ; next page of 256 pixels
dex
bne -
+ ldx cx16.r0 ; remaining pixels
beq +
ldy #0
- lda (P8ZP_SCRATCH_W1),y
sta cx16.VERA_DATA0
iny
dex
bne -
+ plx
}}
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}
asmsub set_8_pixels_from_bits(ubyte bits @R0, ubyte oncolor @A, ubyte offcolor @Y) {
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; this is only useful in 256 color mode where one pixel equals one byte value.
%asm {{
phx
ldx #8
- asl cx16.r0
bcc +
sta cx16.VERA_DATA0
bra ++
+ sty cx16.VERA_DATA0
+ dex
bne -
plx
rts
}}
}
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const ubyte charset_orig_bank = $0
const uword charset_orig_addr = $f800 ; in bank 0, so $0f800
const ubyte charset_bank = $1
const uword charset_addr = $f000 ; in bank 1, so $1f000
sub text_charset(ubyte charset) {
; -- make a copy of the selected character set to use with text()
; the charset number is the same as for the cx16.screen_set_charset() ROM function.
; 1 = ISO charset, 2 = PETSCII uppercase+graphs, 3= PETSCII uppercase+lowercase.
cx16.screen_set_charset(charset, 0)
cx16.vaddr(charset_orig_bank, charset_orig_addr, 0, 1)
cx16.vaddr(charset_bank, charset_addr, 1, 1)
repeat 256*8 {
cx16.VERA_DATA1 = cx16.VERA_DATA0
}
}
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sub text(uword @zp x, uword y, ubyte color, uword sctextptr) {
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; -- Write some text at the given pixel position. The text string must be in screencode encoding (not petscii!).
; You must also have called text_charset() first to select and prepare the character set to use.
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; NOTE: in monochrome (1bpp) screen modes, x position is currently constrained to multiples of 8 ! TODO allow per-pixel horizontal positioning
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; TODO draw whole horizontal spans using vera auto increment if possible, instead of per-character columns
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uword chardataptr
when active_mode {
1, 5 -> {
; monochrome mode, either resolution
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cx16.r2 = 40
if active_mode==5
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cx16.r2 = 80
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while @(sctextptr) {
chardataptr = charset_addr + (@(sctextptr) as uword)*8
cx16.vaddr(charset_bank, chardataptr, 1, 1)
position(x,y)
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%asm {{
lda cx16.VERA_ADDR_H
and #%111 ; don't auto-increment, we have to do that manually because of the ora
sta cx16.VERA_ADDR_H
lda color
sta P8ZP_SCRATCH_B1
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ldy #8
- lda P8ZP_SCRATCH_B1
bne + ; white color, plot normally
lda cx16.VERA_DATA1
eor #255 ; black color, keep only the other pixels
and cx16.VERA_DATA0
bra ++
+ lda cx16.VERA_DATA0
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ora cx16.VERA_DATA1
+ sta cx16.VERA_DATA0
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lda cx16.VERA_ADDR_L
clc
adc cx16.r2
sta cx16.VERA_ADDR_L
bcc +
inc cx16.VERA_ADDR_M
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+ inc x
bne +
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inc x+1
+ dey
bne -
}}
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sctextptr++
}
}
4 -> {
; lores 256c
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while @(sctextptr) {
chardataptr = charset_addr + (@(sctextptr) as uword)*8
cx16.vaddr(charset_bank, chardataptr, 1, 1)
repeat 8 {
position(x,y)
y++
%asm {{
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phx
ldx #1
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lda cx16.VERA_DATA1
sta P8ZP_SCRATCH_B1
ldy #8
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- asl P8ZP_SCRATCH_B1
bcc +
stx cx16.VERA_DATA0 ; write a pixel
bra ++
+ lda cx16.VERA_DATA0 ; don't write a pixel, but do advance to the next address
+ dey
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bne -
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plx
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}}
}
x+=8
y-=8
sctextptr++
}
}
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6 -> {
; hires 4c
while @(sctextptr) {
chardataptr = charset_addr + (@(sctextptr) as uword)*8
repeat 8 {
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; TODO rewrite this inner loop partly in assembly
; requires expanding the charbits to 2-bits per pixel (based on color)
; also it's way more efficient to draw whole horizontal spans instead of per-character
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ubyte charbits = cx16.vpeek(charset_bank, chardataptr)
repeat 8 {
charbits <<= 1
if_cs
plot(x, y, color)
x++
}
x-=8
chardataptr++
y++
}
x+=8
y-=8
sctextptr++
}
}
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}
}
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asmsub cs_innerloop640() clobbers(Y) {
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%asm {{
ldy #80
- stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
stz cx16.VERA_DATA0
dey
bne -
rts
}}
}
asmsub addr_mul_24_for_highres_4c(uword yy @R2, uword xx @R3) clobbers(A, Y) -> uword @R0, uword @R1 {
; yy * 160 + xx/4 (24 bits calculation)
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; 24 bits result is in r0 and r1L (highest byte)
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%asm {{
ldy #5
- asl cx16.r2
rol cx16.r2+1
dey
bne -
lda cx16.r2
sta cx16.r0
lda cx16.r2+1
sta cx16.r0+1
asl cx16.r0
rol cx16.r0+1
asl cx16.r0
rol cx16.r0+1
; xx >>= 2 (xx=R3)
lsr cx16.r3+1
ror cx16.r3
lsr cx16.r3+1
ror cx16.r3
; add r2 and xx (r3) to r0 (24-bits)
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stz cx16.r1
clc
lda cx16.r0
adc cx16.r2
sta cx16.r0
lda cx16.r0+1
adc cx16.r2+1
sta cx16.r0+1
bcc +
inc cx16.r1
+ clc
lda cx16.r0
adc cx16.r3
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sta cx16.r0
lda cx16.r0+1
adc cx16.r3+1
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sta cx16.r0+1
bcc +
inc cx16.r1
+
rts
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}}
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}
asmsub addr_mul_24_for_lores_256c(uword yy @R0, uword xx @AY) clobbers(A) -> uword @R0, ubyte @R1 {
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; yy * 320 + xx (24 bits calculation)
%asm {{
sta P8ZP_SCRATCH_W1
sty P8ZP_SCRATCH_W1+1
lda cx16.r0
sta P8ZP_SCRATCH_B1
lda cx16.r0+1
sta cx16.r1
sta P8ZP_SCRATCH_REG
lda cx16.r0
asl a
rol P8ZP_SCRATCH_REG
asl a
rol P8ZP_SCRATCH_REG
asl a
rol P8ZP_SCRATCH_REG
asl a
rol P8ZP_SCRATCH_REG
asl a
rol P8ZP_SCRATCH_REG
asl a
rol P8ZP_SCRATCH_REG
sta cx16.r0
lda P8ZP_SCRATCH_B1
clc
adc P8ZP_SCRATCH_REG
sta cx16.r0+1
bcc +
inc cx16.r1
+ ; now add the value to this 24-bits number
lda cx16.r0
clc
adc P8ZP_SCRATCH_W1
sta cx16.r0
lda cx16.r0+1
adc P8ZP_SCRATCH_W1+1
sta cx16.r0+1
bcc +
inc cx16.r1
+ lda cx16.r1
rts
}}
}
}