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c38508c262
forever loop is gone (use repeat without iteration count). struct literal is now same as array literal [...] to avoid parsing ambiguity with scope blocks.
253 lines
8.5 KiB
Lua
253 lines
8.5 KiB
Lua
%import c64lib
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; bitmap pixel graphics module for the C64
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; only black/white monchrome for now
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; you could put this code at $4000 which is after the bitmap screen in memory ($2000-$3fff),
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; this leaves more space for user program code.
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graphics {
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const uword bitmap_address = $2000
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sub enable_bitmap_mode() {
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; enable bitmap screen, erase it and set colors to black/white.
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c64.SCROLY |= %00100000
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c64.VMCSB = (c64.VMCSB & %11110000) | %00001000 ; $2000-$3fff
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memset(bitmap_address, 320*200/8, 0)
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c64scr.clear_screen($10, 0) ; pixel color $1 (white) backround $0 (black)
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}
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sub line(uword x1, ubyte y1, uword x2, ubyte y2) {
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; Bresenham algorithm.
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; This code special cases various quadrant loops to allow simple ++ and -- operations.
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if y1>y2 {
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; make sure dy is always positive to avoid 8 instead of just 4 special cases
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swap(x1, x2)
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swap(y1, y2)
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}
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word d = 0
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ubyte positive_ix = true
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word dx = x2 - x1 as word
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word dy = y2 as word - y1 as word
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if dx < 0 {
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dx = -dx
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positive_ix = false
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}
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dx *= 2
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dy *= 2
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plotx = x1
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if dx >= dy {
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if positive_ix {
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repeat {
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plot(y1)
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if plotx==x2
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return
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plotx++
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d += dy
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if d > dx {
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y1++
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d -= dx
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}
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}
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} else {
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repeat {
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plot(y1)
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if plotx==x2
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return
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plotx--
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d += dy
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if d > dx {
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y1++
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d -= dx
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}
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}
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}
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}
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else {
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if positive_ix {
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repeat {
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plot(y1)
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if y1 == y2
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return
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y1++
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d += dx
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if d > dy {
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plotx++
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d -= dy
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}
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}
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} else {
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repeat {
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plot(y1)
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if y1 == y2
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return
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y1++
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d += dx
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if d > dy {
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plotx--
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d -= dy
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}
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}
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}
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}
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}
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sub circle(uword xcenter, ubyte ycenter, ubyte radius) {
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; Midpoint algorithm
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ubyte ploty
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ubyte xx = radius
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ubyte yy = 0
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byte decisionOver2 = 1-xx as byte
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while xx>=yy {
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plotx = xcenter + xx
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ploty = ycenter + yy
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plot(ploty)
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plotx = xcenter - xx
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plot(ploty)
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plotx = xcenter + xx
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ploty = ycenter - yy
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plot(ploty)
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plotx = xcenter - xx
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plot(ploty)
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plotx = xcenter + yy
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ploty = ycenter + xx
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plot(ploty)
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plotx = xcenter - yy
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plot(ploty)
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plotx = xcenter + yy
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ploty = ycenter - xx
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plot(ploty)
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plotx = xcenter - yy
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plot(ploty)
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yy++
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if decisionOver2<=0
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decisionOver2 += 2*yy+1
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else {
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xx--
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decisionOver2 += 2*(yy-xx)+1
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}
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}
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}
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sub disc(uword cx, ubyte cy, ubyte radius) {
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; Midpoint algorithm, filled
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ubyte xx = radius
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ubyte yy = 0
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byte decisionOver2 = 1-xx as byte
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while xx>=yy {
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ubyte cy_plus_yy = cy + yy
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ubyte cy_min_yy = cy - yy
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ubyte cy_plus_xx = cy + xx
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ubyte cy_min_xx = cy - xx
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for plotx in cx to cx+xx {
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plot(cy_plus_yy)
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plot(cy_min_yy)
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}
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for plotx in cx-xx to cx-1 {
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plot(cy_plus_yy)
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plot(cy_min_yy)
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}
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for plotx in cx to cx+yy {
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plot(cy_plus_xx)
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plot(cy_min_xx)
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}
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for plotx in cx-yy to cx {
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plot(cy_plus_xx)
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plot(cy_min_xx)
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}
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yy++
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if decisionOver2<=0
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decisionOver2 += 2*yy+1
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else {
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xx--
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decisionOver2 += 2*(yy-xx)+1
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}
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}
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}
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; here is the non-asm code for the plot routine below:
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; sub plot_nonasm(uword px, ubyte py) {
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; ubyte[] ormask = [128, 64, 32, 16, 8, 4, 2, 1]
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; uword addr = bitmap_address + 320*(py>>3) + (py & 7) + (px & %0000000111111000)
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; @(addr) |= ormask[lsb(px) & 7]
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; }
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uword plotx ; 0..319 ; separate 'parameter' for plot()
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asmsub plot(ubyte ploty @A) { ; plotx is 16 bits 0 to 319... doesn't fit in a register
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%asm {{
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tay
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stx c64.SCRATCH_ZPREGX
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lda plotx+1
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sta c64.SCRATCH_ZPWORD2+1
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lsr a ; 0
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sta c64.SCRATCH_ZPWORD2
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lda plotx
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pha
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and #7
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tax
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lda _y_lookup_lo,y
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clc
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adc c64.SCRATCH_ZPWORD2
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sta c64.SCRATCH_ZPWORD2
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lda _y_lookup_hi,y
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adc c64.SCRATCH_ZPWORD2+1
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sta c64.SCRATCH_ZPWORD2+1
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pla ; plotx
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and #%11111000
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tay
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lda (c64.SCRATCH_ZPWORD2),y
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ora _ormask,x
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sta (c64.SCRATCH_ZPWORD2),y
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ldx c64.SCRATCH_ZPREGX
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rts
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_ormask .byte 128, 64, 32, 16, 8, 4, 2, 1
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; note: this can be even faster if we also have a 256 byte x-lookup table, but hey.
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; see http://codebase64.org/doku.php?id=base:various_techniques_to_calculate_adresses_fast_common_screen_formats_for_pixel_graphics
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; the y lookup tables encodes this formula: bitmap_address + 320*(py>>3) + (py & 7) (y from 0..199)
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_y_lookup_hi
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.byte $20, $20, $20, $20, $20, $20, $20, $20, $21, $21, $21, $21, $21, $21, $21, $21
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.byte $22, $22, $22, $22, $22, $22, $22, $22, $23, $23, $23, $23, $23, $23, $23, $23
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.byte $25, $25, $25, $25, $25, $25, $25, $25, $26, $26, $26, $26, $26, $26, $26, $26
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.byte $27, $27, $27, $27, $27, $27, $27, $27, $28, $28, $28, $28, $28, $28, $28, $28
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.byte $2a, $2a, $2a, $2a, $2a, $2a, $2a, $2a, $2b, $2b, $2b, $2b, $2b, $2b, $2b, $2b
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.byte $2c, $2c, $2c, $2c, $2c, $2c, $2c, $2c, $2d, $2d, $2d, $2d, $2d, $2d, $2d, $2d
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.byte $2f, $2f, $2f, $2f, $2f, $2f, $2f, $2f, $30, $30, $30, $30, $30, $30, $30, $30
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.byte $31, $31, $31, $31, $31, $31, $31, $31, $32, $32, $32, $32, $32, $32, $32, $32
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.byte $34, $34, $34, $34, $34, $34, $34, $34, $35, $35, $35, $35, $35, $35, $35, $35
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.byte $36, $36, $36, $36, $36, $36, $36, $36, $37, $37, $37, $37, $37, $37, $37, $37
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.byte $39, $39, $39, $39, $39, $39, $39, $39, $3a, $3a, $3a, $3a, $3a, $3a, $3a, $3a
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.byte $3b, $3b, $3b, $3b, $3b, $3b, $3b, $3b, $3c, $3c, $3c, $3c, $3c, $3c, $3c, $3c
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.byte $3e, $3e, $3e, $3e, $3e, $3e, $3e, $3e
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_y_lookup_lo
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.byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47
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.byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7
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.byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47
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.byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7
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.byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47
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.byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7
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.byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47
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.byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7
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.byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47
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.byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7
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.byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47
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.byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7
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.byte $00, $01, $02, $03, $04, $05, $06, $07
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}}
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}
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}
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