plan9port

draw.c (56850B)

---

 #include <u.h>
 #include <libc.h>
 #include <draw.h>
 #include <memdraw.h>
 
 int drawdebug;
 static int	tablesbuilt;
 
 /* perfect approximation to NTSC = .299r+.587g+.114b when 0 ≤ r,g,b < 256 */
 #define RGB2K(r,g,b)	((156763*(r)+307758*(g)+59769*(b))>>19)
 
 /*
  * For 16-bit values, x / 255 == (t = x+1, (t+(t>>8)) >> 8).
  * We add another 127 to round to the nearest value rather
  * than truncate.
  *
  * CALCxy does x bytewise calculations on y input images (x=1,4; y=1,2).
  * CALC2x does two parallel 16-bit calculations on y input images (y=1,2).
  */
 #define CALC11(a, v, tmp) \
 	(tmp=(a)*(v)+128, (tmp+(tmp>>8))>>8)
 
 #define CALC12(a1, v1, a2, v2, tmp) \
 	(tmp=(a1)*(v1)+(a2)*(v2)+128, (tmp+(tmp>>8))>>8)
 
 #define MASK 0xFF00FF
 
 #define CALC21(a, vvuu, tmp) \
 	(tmp=(a)*(vvuu)+0x00800080, ((tmp+((tmp>>8)&MASK))>>8)&MASK)
 
 #define CALC41(a, rgba, tmp1, tmp2) \
 	(CALC21(a, rgba & MASK, tmp1) | \
 	 (CALC21(a, (rgba>>8)&MASK, tmp2)<<8))
 
 #define CALC22(a1, vvuu1, a2, vvuu2, tmp) \
 	(tmp=(a1)*(vvuu1)+(a2)*(vvuu2)+0x00800080, ((tmp+((tmp>>8)&MASK))>>8)&MASK)
 
 #define CALC42(a1, rgba1, a2, rgba2, tmp1, tmp2) \
 	(CALC22(a1, rgba1 & MASK, a2, rgba2 & MASK, tmp1) | \
 	 (CALC22(a1, (rgba1>>8) & MASK, a2, (rgba2>>8) & MASK, tmp2)<<8))
 
 static void mktables(void);
 typedef int Subdraw(Memdrawparam*);
 static Subdraw chardraw, alphadraw, memoptdraw;
 
 static Memimage*	memones;
 static Memimage*	memzeros;
 Memimage *memwhite;
 Memimage *memblack;
 Memimage *memtransparent;
 Memimage *memopaque;
 
 int	__ifmt(Fmt*);
 
 void
 memimageinit(void)
 {
 	static int didinit = 0;
 
 	if(didinit)
 		return;
 
 	didinit = 1;
 
 	mktables();
 	_memmkcmap();
 
 	fmtinstall('R', Rfmt);
 	fmtinstall('P', Pfmt);
 	fmtinstall('b', __ifmt);
 
 	memones = allocmemimage(Rect(0,0,1,1), GREY1);
 	memones->flags |= Frepl;
 	memones->clipr = Rect(-0x3FFFFFF, -0x3FFFFFF, 0x3FFFFFF, 0x3FFFFFF);
 	*byteaddr(memones, ZP) = ~0;
 
 	memzeros = allocmemimage(Rect(0,0,1,1), GREY1);
 	memzeros->flags |= Frepl;
 	memzeros->clipr = Rect(-0x3FFFFFF, -0x3FFFFFF, 0x3FFFFFF, 0x3FFFFFF);
 	*byteaddr(memzeros, ZP) = 0;
 
 	if(memones == nil || memzeros == nil)
 		assert(0 /*cannot initialize memimage library */);	/* RSC BUG */
 
 	memwhite = memones;
 	memblack = memzeros;
 	memopaque = memones;
 	memtransparent = memzeros;
 }
 
 u32int _imgtorgba(Memimage*, u32int);
 u32int _rgbatoimg(Memimage*, u32int);
 u32int _pixelbits(Memimage*, Point);
 
 #define DBG if(drawdebug)
 static Memdrawparam par;
 
 Memdrawparam*
 _memimagedrawsetup(Memimage *dst, Rectangle r, Memimage *src, Point p0, Memimage *mask, Point p1, int op)
 {
 	if(mask == nil)
 		mask = memopaque;
 
 DBG	print("memimagedraw %p/%luX %R @ %p %p/%luX %P %p/%luX %P... ", dst, dst->chan, r, dst->data->bdata, src, src->chan, p0, mask, mask->chan, p1);
 
 	if(drawclip(dst, &r, src, &p0, mask, &p1, &par.sr, &par.mr) == 0){
 /*		if(drawdebug) */
 /*			iprint("empty clipped rectangle\n"); */
 		return nil;
 	}
 
 	if(op < Clear || op > SoverD){
 /*		if(drawdebug) */
 /*			iprint("op out of range: %d\n", op); */
 		return nil;
 	}
 
 	par.op = op;
 	par.dst = dst;
 	par.r = r;
 	par.src = src;
 	/* par.sr set by drawclip */
 	par.mask = mask;
 	/* par.mr set by drawclip */
 
 	par.state = 0;
 	if(src->flags&Frepl){
 		par.state |= Replsrc;
 		if(Dx(src->r)==1 && Dy(src->r)==1){
 			par.sval = pixelbits(src, src->r.min);
 			par.state |= Simplesrc;
 			par.srgba = _imgtorgba(src, par.sval);
 			par.sdval = _rgbatoimg(dst, par.srgba);
 			if((par.srgba&0xFF) == 0 && (op&DoutS)){
 /*				if (drawdebug) iprint("fill with transparent source\n"); */
 				return nil;	/* no-op successfully handled */
 			}
 			if((par.srgba&0xFF) == 0xFF)
 				par.state |= Fullsrc;
 		}
 	}
 
 	if(mask->flags & Frepl){
 		par.state |= Replmask;
 		if(Dx(mask->r)==1 && Dy(mask->r)==1){
 			par.mval = pixelbits(mask, mask->r.min);
 			if(par.mval == 0 && (op&DoutS)){
 /*				if(drawdebug) iprint("fill with zero mask\n"); */
 				return nil;	/* no-op successfully handled */
 			}
 			par.state |= Simplemask;
 			if(par.mval == ~0)
 				par.state |= Fullmask;
 			par.mrgba = _imgtorgba(mask, par.mval);
 		}
 	}
 
 /*	if(drawdebug) */
 /*		iprint("dr %R sr %R mr %R...", r, par.sr, par.mr); */
 DBG print("draw dr %R sr %R mr %R %lux\n", r, par.sr, par.mr, par.state);
 
 	return &par;
 }
 
 void
 _memimagedraw(Memdrawparam *par)
 {
 	/*
 	 * Now that we've clipped the parameters down to be consistent, we
 	 * simply try sub-drawing routines in order until we find one that was able
 	 * to handle us.  If the sub-drawing routine returns zero, it means it was
 	 * unable to satisfy the request, so we do not return.
 	 */
 
 	/*
 	 * Hardware support.  Each video driver provides this function,
 	 * which checks to see if there is anything it can help with.
 	 * There could be an if around this checking to see if dst is in video memory.
 	 */
 DBG print("test hwdraw\n");
 	if(hwdraw(par)){
 /*if(drawdebug) iprint("hw handled\n"); */
 DBG print("hwdraw handled\n");
 		return;
 	}
 	/*
 	 * Optimizations using memmove and memset.
 	 */
 DBG print("test memoptdraw\n");
 	if(memoptdraw(par)){
 /*if(drawdebug) iprint("memopt handled\n"); */
 DBG print("memopt handled\n");
 		return;
 	}
 
 	/*
 	 * Character drawing.
 	 * Solid source color being painted through a boolean mask onto a high res image.
 	 */
 DBG print("test chardraw\n");
 	if(chardraw(par)){
 /*if(drawdebug) iprint("chardraw handled\n"); */
 DBG print("chardraw handled\n");
 		return;
 	}
 
 	/*
 	 * General calculation-laden case that does alpha for each pixel.
 	 */
 DBG print("do alphadraw\n");
 	alphadraw(par);
 /*if(drawdebug) iprint("alphadraw handled\n"); */
 DBG print("alphadraw handled\n");
 }
 #undef DBG
 
 /*
  * Clip the destination rectangle further based on the properties of the
  * source and mask rectangles.  Once the destination rectangle is properly
  * clipped, adjust the source and mask rectangles to be the same size.
  * Then if source or mask is replicated, move its clipped rectangle
  * so that its minimum point falls within the repl rectangle.
  *
  * Return zero if the final rectangle is null.
  */
 int
 drawclip(Memimage *dst, Rectangle *r, Memimage *src, Point *p0, Memimage *mask, Point *p1, Rectangle *sr, Rectangle *mr)
 {
 	Point rmin, delta;
 	int splitcoords;
 	Rectangle omr;
 
 	if(r->min.x>=r->max.x || r->min.y>=r->max.y)
 		return 0;
 	splitcoords = (p0->x!=p1->x) || (p0->y!=p1->y);
 	/* clip to destination */
 	rmin = r->min;
 	if(!rectclip(r, dst->r) || !rectclip(r, dst->clipr))
 		return 0;
 	/* move mask point */
 	p1->x += r->min.x-rmin.x;
 	p1->y += r->min.y-rmin.y;
 	/* move source point */
 	p0->x += r->min.x-rmin.x;
 	p0->y += r->min.y-rmin.y;
 	/* map destination rectangle into source */
 	sr->min = *p0;
 	sr->max.x = p0->x+Dx(*r);
 	sr->max.y = p0->y+Dy(*r);
 	/* sr is r in source coordinates; clip to source */
 	if(!(src->flags&Frepl) && !rectclip(sr, src->r))
 		return 0;
 	if(!rectclip(sr, src->clipr))
 		return 0;
 	/* compute and clip rectangle in mask */
 	if(splitcoords){
 		/* move mask point with source */
 		p1->x += sr->min.x-p0->x;
 		p1->y += sr->min.y-p0->y;
 		mr->min = *p1;
 		mr->max.x = p1->x+Dx(*sr);
 		mr->max.y = p1->y+Dy(*sr);
 		omr = *mr;
 		/* mr is now rectangle in mask; clip it */
 		if(!(mask->flags&Frepl) && !rectclip(mr, mask->r))
 			return 0;
 		if(!rectclip(mr, mask->clipr))
 			return 0;
 		/* reflect any clips back to source */
 		sr->min.x += mr->min.x-omr.min.x;
 		sr->min.y += mr->min.y-omr.min.y;
 		sr->max.x += mr->max.x-omr.max.x;
 		sr->max.y += mr->max.y-omr.max.y;
 		*p1 = mr->min;
 	}else{
 		if(!(mask->flags&Frepl) && !rectclip(sr, mask->r))
 			return 0;
 		if(!rectclip(sr, mask->clipr))
 			return 0;
 		*p1 = sr->min;
 	}
 
 	/* move source clipping back to destination */
 	delta.x = r->min.x - p0->x;
 	delta.y = r->min.y - p0->y;
 	r->min.x = sr->min.x + delta.x;
 	r->min.y = sr->min.y + delta.y;
 	r->max.x = sr->max.x + delta.x;
 	r->max.y = sr->max.y + delta.y;
 
 	/* move source rectangle so sr->min is in src->r */
 	if(src->flags&Frepl) {
 		delta.x = drawreplxy(src->r.min.x, src->r.max.x, sr->min.x) - sr->min.x;
 		delta.y = drawreplxy(src->r.min.y, src->r.max.y, sr->min.y) - sr->min.y;
 		sr->min.x += delta.x;
 		sr->min.y += delta.y;
 		sr->max.x += delta.x;
 		sr->max.y += delta.y;
 	}
 	*p0 = sr->min;
 
 	/* move mask point so it is in mask->r */
 	*p1 = drawrepl(mask->r, *p1);
 	mr->min = *p1;
 	mr->max.x = p1->x+Dx(*sr);
 	mr->max.y = p1->y+Dy(*sr);
 
 	assert(Dx(*sr) == Dx(*mr) && Dx(*mr) == Dx(*r));
 	assert(Dy(*sr) == Dy(*mr) && Dy(*mr) == Dy(*r));
 	assert(ptinrect(*p0, src->r));
 	assert(ptinrect(*p1, mask->r));
 	assert(ptinrect(r->min, dst->r));
 
 	return 1;
 }
 
 /*
  * Conversion tables.
  */
 static uchar replbit[1+8][256];		/* replbit[x][y] is the replication of the x-bit quantity y to 8-bit depth */
 static uchar conv18[256][8];		/* conv18[x][y] is the yth pixel in the depth-1 pixel x */
 static uchar conv28[256][4];		/* ... */
 static uchar conv48[256][2];
 
 /*
  * bitmap of how to replicate n bits to fill 8, for 1 ≤ n ≤ 8.
  * the X's are where to put the bottom (ones) bit of the n-bit pattern.
  * only the top 8 bits of the result are actually used.
  * (the lower 8 bits are needed to get bits in the right place
  * when n is not a divisor of 8.)
  *
  * Should check to see if its easier to just refer to replmul than
  * use the precomputed values in replbit.  On PCs it may well
  * be; on machines with slow multiply instructions it probably isn't.
  */
 #define a ((((((((((((((((0
 #define X *2+1)
 #define _ *2)
 static int replmul[1+8] = {
 	0,
 	a X X X X X X X X X X X X X X X X,
 	a _ X _ X _ X _ X _ X _ X _ X _ X,
 	a _ _ X _ _ X _ _ X _ _ X _ _ X _,
 	a _ _ _ X _ _ _ X _ _ _ X _ _ _ X,
 	a _ _ _ _ X _ _ _ _ X _ _ _ _ X _,
 	a _ _ _ _ _ X _ _ _ _ _ X _ _ _ _,
 	a _ _ _ _ _ _ X _ _ _ _ _ _ X _ _,
 	a _ _ _ _ _ _ _ X _ _ _ _ _ _ _ X,
 };
 #undef a
 #undef X
 #undef _
 
 static void
 mktables(void)
 {
 	int i, j, mask, sh, small;
 
 	if(tablesbuilt)
 		return;
 
 	fmtinstall('R', Rfmt);
 	fmtinstall('P', Pfmt);
 	tablesbuilt = 1;
 
 	/* bit replication up to 8 bits */
 	for(i=0; i<256; i++){
 		for(j=0; j<=8; j++){	/* j <= 8 [sic] */
 			small = i & ((1<<j)-1);
 			replbit[j][i] = (small*replmul[j])>>8;
 		}
 	}
 
 	/* bit unpacking up to 8 bits, only powers of 2 */
 	for(i=0; i<256; i++){
 		for(j=0, sh=7, mask=1; j<8; j++, sh--)
 			conv18[i][j] = replbit[1][(i>>sh)&mask];
 
 		for(j=0, sh=6, mask=3; j<4; j++, sh-=2)
 			conv28[i][j] = replbit[2][(i>>sh)&mask];
 
 		for(j=0, sh=4, mask=15; j<2; j++, sh-=4)
 			conv48[i][j] = replbit[4][(i>>sh)&mask];
 	}
 }
 
 static uchar ones = 0xff;
 
 /*
  * General alpha drawing case.  Can handle anything.
  */
 typedef struct	Buffer	Buffer;
 struct Buffer {
 	/* used by most routines */
 	uchar	*red;
 	uchar	*grn;
 	uchar	*blu;
 	uchar	*alpha;
 	uchar	*grey;
 	u32int	*rgba;
 	int	delta;	/* number of bytes to add to pointer to get next pixel to the right */
 
 	/* used by boolcalc* for mask data */
 	uchar	*m;		/* ptr to mask data r.min byte; like p->bytermin */
 	int		mskip;	/* no. of left bits to skip in *m */
 	uchar	*bm;		/* ptr to mask data img->r.min byte; like p->bytey0s */
 	int		bmskip;	/* no. of left bits to skip in *bm */
 	uchar	*em;		/* ptr to mask data img->r.max.x byte; like p->bytey0e */
 	int		emskip;	/* no. of right bits to skip in *em */
 };
 
 typedef struct	Param	Param;
 typedef Buffer	Readfn(Param*, uchar*, int);
 typedef void	Writefn(Param*, uchar*, Buffer);
 typedef Buffer	Calcfn(Buffer, Buffer, Buffer, int, int, int);
 
 enum {
 	MAXBCACHE = 16
 };
 
 /* giant rathole to customize functions with */
 struct Param {
 	Readfn	*replcall;
 	Readfn	*greymaskcall;
 	Readfn	*convreadcall;
 	Writefn	*convwritecall;
 
 	Memimage *img;
 	Rectangle	r;
 	int	dx;	/* of r */
 	int	needbuf;
 	int	convgrey;
 	int	alphaonly;
 
 	uchar	*bytey0s;		/* byteaddr(Pt(img->r.min.x, img->r.min.y)) */
 	uchar	*bytermin;	/* byteaddr(Pt(r.min.x, img->r.min.y)) */
 	uchar	*bytey0e;		/* byteaddr(Pt(img->r.max.x, img->r.min.y)) */
 	int		bwidth;
 
 	int	replcache;	/* if set, cache buffers */
 	Buffer	bcache[MAXBCACHE];
 	u32int	bfilled;
 	uchar	*bufbase;
 	int	bufoff;
 	int	bufdelta;
 
 	int	dir;
 
 	int	convbufoff;
 	uchar	*convbuf;
 	Param	*convdpar;
 	int	convdx;
 };
 
 static uchar *drawbuf;
 static int	ndrawbuf;
 static int	mdrawbuf;
 static Param spar, mpar, dpar;	/* easier on the stacks */
 static Readfn	greymaskread, replread, readptr;
 static Writefn	nullwrite;
 static Calcfn	alphacalc0, alphacalc14, alphacalc2810, alphacalc3679, alphacalc5, alphacalc11, alphacalcS;
 static Calcfn	boolcalc14, boolcalc236789, boolcalc1011;
 
 static Readfn*	readfn(Memimage*);
 static Readfn*	readalphafn(Memimage*);
 static Writefn*	writefn(Memimage*);
 
 static Calcfn*	boolcopyfn(Memimage*, Memimage*);
 static Readfn*	convfn(Memimage*, Param*, Memimage*, Param*);
 
 static Calcfn *alphacalc[Ncomp] =
 {
 	alphacalc0,		/* Clear */
 	alphacalc14,		/* DoutS */
 	alphacalc2810,		/* SoutD */
 	alphacalc3679,		/* DxorS */
 	alphacalc14,		/* DinS */
 	alphacalc5,		/* D */
 	alphacalc3679,		/* DatopS */
 	alphacalc3679,		/* DoverS */
 	alphacalc2810,		/* SinD */
 	alphacalc3679,		/* SatopD */
 	alphacalc2810,		/* S */
 	alphacalc11,		/* SoverD */
 };
 
 static Calcfn *boolcalc[Ncomp] =
 {
 	alphacalc0,		/* Clear */
 	boolcalc14,		/* DoutS */
 	boolcalc236789,		/* SoutD */
 	boolcalc236789,		/* DxorS */
 	boolcalc14,		/* DinS */
 	alphacalc5,		/* D */
 	boolcalc236789,		/* DatopS */
 	boolcalc236789,		/* DoverS */
 	boolcalc236789,		/* SinD */
 	boolcalc236789,		/* SatopD */
 	boolcalc1011,		/* S */
 	boolcalc1011,		/* SoverD */
 };
 
 static int
 allocdrawbuf(void)
 {
 	uchar *p;
 
 	if(ndrawbuf > mdrawbuf){
 		p = realloc(drawbuf, ndrawbuf);
 		if(p == nil){
 			werrstr("memimagedraw out of memory");
 			return -1;
 		}
 		drawbuf = p;
 		mdrawbuf = ndrawbuf;
 	}
 	return 0;
 }
 
 static void
 getparam(Param *p, Memimage *img, Rectangle r, int convgrey, int needbuf)
 {
 	int nbuf;
 
 	memset(p, 0, sizeof *p);
 
 	p->img = img;
 	p->r = r;
 	p->dx = Dx(r);
 	p->needbuf = needbuf;
 	p->convgrey = convgrey;
 
 	assert(img->r.min.x <= r.min.x && r.min.x < img->r.max.x);
 
 	p->bytey0s = byteaddr(img, Pt(img->r.min.x, img->r.min.y));
 	p->bytermin = byteaddr(img, Pt(r.min.x, img->r.min.y));
 	p->bytey0e = byteaddr(img, Pt(img->r.max.x, img->r.min.y));
 	p->bwidth = sizeof(u32int)*img->width;
 
 	assert(p->bytey0s <= p->bytermin && p->bytermin <= p->bytey0e);
 
 	if(p->r.min.x == p->img->r.min.x)
 		assert(p->bytermin == p->bytey0s);
 
 	nbuf = 1;
 	if((img->flags&Frepl) && Dy(img->r) <= MAXBCACHE && Dy(img->r) < Dy(r)){
 		p->replcache = 1;
 		nbuf = Dy(img->r);
 	}
 	p->bufdelta = 4*p->dx;
 	p->bufoff = ndrawbuf;
 	ndrawbuf += p->bufdelta*nbuf;
 }
 
 static void
 clipy(Memimage *img, int *y)
 {
 	int dy;
 
 	dy = Dy(img->r);
 	if(*y == dy)
 		*y = 0;
 	else if(*y == -1)
 		*y = dy-1;
 	assert(0 <= *y && *y < dy);
 }
 
 static void
 dumpbuf(char *s, Buffer b, int n)
 {
 	int i;
 	uchar *p;
 
 	print("%s", s);
 	for(i=0; i<n; i++){
 		print(" ");
 		if(p=b.grey){
 			print(" k%.2uX", *p);
 			b.grey += b.delta;
 		}else{
 			if(p=b.red){
 				print(" r%.2uX", *p);
 				b.red += b.delta;
 			}
 			if(p=b.grn){
 				print(" g%.2uX", *p);
 				b.grn += b.delta;
 			}
 			if(p=b.blu){
 				print(" b%.2uX", *p);
 				b.blu += b.delta;
 			}
 		}
 		if((p=b.alpha) != &ones){
 			print(" α%.2uX", *p);
 			b.alpha += b.delta;
 		}
 	}
 	print("\n");
 }
 
 /*
  * For each scan line, we expand the pixels from source, mask, and destination
  * into byte-aligned red, green, blue, alpha, and grey channels.  If buffering is not
  * needed and the channels were already byte-aligned (grey8, rgb24, rgba32, rgb32),
  * the readers need not copy the data: they can simply return pointers to the data.
  * If the destination image is grey and the source is not, it is converted using the NTSC
  * formula.
  *
  * Once we have all the channels, we call either rgbcalc or greycalc, depending on
  * whether the destination image is color.  This is allowed to overwrite the dst buffer (perhaps
  * the actual data, perhaps a copy) with its result.  It should only overwrite the dst buffer
  * with the same format (i.e. red bytes with red bytes, etc.)  A new buffer is returned from
  * the calculator, and that buffer is passed to a function to write it to the destination.
  * If the buffer is already pointing at the destination, the writing function is a no-op.
  */
 #define DBG if(drawdebug)
 static int
 alphadraw(Memdrawparam *par)
 {
 	int isgrey, starty, endy, op;
 	int needbuf, dsty, srcy, masky;
 	int y, dir, dx, dy;
 	Buffer bsrc, bdst, bmask;
 	Readfn *rdsrc, *rdmask, *rddst;
 	Calcfn *calc;
 	Writefn *wrdst;
 	Memimage *src, *mask, *dst;
 	Rectangle r, sr, mr;
 
 	if(drawdebug)
 		print("alphadraw %R\n", par->r);
 	r = par->r;
 	dx = Dx(r);
 	dy = Dy(r);
 
 	ndrawbuf = 0;
 
 	src = par->src;
 	mask = par->mask;
 	dst = par->dst;
 	sr = par->sr;
 	mr = par->mr;
 	op = par->op;
 
 	isgrey = dst->flags&Fgrey;
 
 	/*
 	 * Buffering when src and dst are the same bitmap is sufficient but not
 	 * necessary.  There are stronger conditions we could use.  We could
 	 * check to see if the rectangles intersect, and if simply moving in the
 	 * correct y direction can avoid the need to buffer.
 	 */
 	needbuf = (src->data == dst->data);
 
 	getparam(&spar, src, sr, isgrey, needbuf);
 	getparam(&dpar, dst, r, isgrey, needbuf);
 	getparam(&mpar, mask, mr, 0, needbuf);
 
 	dir = (needbuf && byteaddr(dst, r.min) > byteaddr(src, sr.min)) ? -1 : 1;
 	spar.dir = mpar.dir = dpar.dir = dir;
 
 	/*
 	 * If the mask is purely boolean, we can convert from src to dst format
 	 * when we read src, and then just copy it to dst where the mask tells us to.
 	 * This requires a boolean (1-bit grey) mask and lack of a source alpha channel.
 	 *
 	 * The computation is accomplished by assigning the function pointers as follows:
 	 *	rdsrc - read and convert source into dst format in a buffer
 	 * 	rdmask - convert mask to bytes, set pointer to it
 	 * 	rddst - fill with pointer to real dst data, but do no reads
 	 *	calc - copy src onto dst when mask says to.
 	 *	wrdst - do nothing
 	 * This is slightly sleazy, since things aren't doing exactly what their names say,
 	 * but it avoids a fair amount of code duplication to make this a case here
 	 * rather than have a separate booldraw.
 	 */
 /*if(drawdebug) iprint("flag %lud mchan %lux=?%x dd %d\n", src->flags&Falpha, mask->chan, GREY1, dst->depth); */
 	if(!(src->flags&Falpha) && mask->chan == GREY1 && dst->depth >= 8 && op == SoverD){
 /*if(drawdebug) iprint("boolcopy..."); */
 		rdsrc = convfn(dst, &dpar, src, &spar);
 		rddst = readptr;
 		rdmask = readfn(mask);
 		calc = boolcopyfn(dst, mask);
 		wrdst = nullwrite;
 	}else{
 		/* usual alphadraw parameter fetching */
 		rdsrc = readfn(src);
 		rddst = readfn(dst);
 		wrdst = writefn(dst);
 		calc = alphacalc[op];
 
 		/*
 		 * If there is no alpha channel, we'll ask for a grey channel
 		 * and pretend it is the alpha.
 		 */
 		if(mask->flags&Falpha){
 			rdmask = readalphafn(mask);
 			mpar.alphaonly = 1;
 		}else{
 			mpar.greymaskcall = readfn(mask);
 			mpar.convgrey = 1;
 			rdmask = greymaskread;
 
 			/*
 			 * Should really be above, but then boolcopyfns would have
 			 * to deal with bit alignment, and I haven't written that.
 			 *
 			 * This is a common case for things like ellipse drawing.
 			 * When there's no alpha involved and the mask is boolean,
 			 * we can avoid all the division and multiplication.
 			 */
 			if(mask->chan == GREY1 && !(src->flags&Falpha))
 				calc = boolcalc[op];
 			else if(op == SoverD && !(src->flags&Falpha))
 				calc = alphacalcS;
 		}
 	}
 
 	/*
 	 * If the image has a small enough repl rectangle,
 	 * we can just read each line once and cache them.
 	 */
 	if(spar.replcache){
 		spar.replcall = rdsrc;
 		rdsrc = replread;
 	}
 	if(mpar.replcache){
 		mpar.replcall = rdmask;
 		rdmask = replread;
 	}
 
 	if(allocdrawbuf() < 0)
 		return 0;
 
 	/*
 	 * Before we were saving only offsets from drawbuf in the parameter
 	 * structures; now that drawbuf has been grown to accomodate us,
 	 * we can fill in the pointers.
 	 */
 	spar.bufbase = drawbuf+spar.bufoff;
 	mpar.bufbase = drawbuf+mpar.bufoff;
 	dpar.bufbase = drawbuf+dpar.bufoff;
 	spar.convbuf = drawbuf+spar.convbufoff;
 
 	if(dir == 1){
 		starty = 0;
 		endy = dy;
 	}else{
 		starty = dy-1;
 		endy = -1;
 	}
 
 	/*
 	 * srcy, masky, and dsty are offsets from the top of their
 	 * respective Rectangles.  they need to be contained within
 	 * the rectangles, so clipy can keep them there without division.
  	 */
 	srcy = (starty + sr.min.y - src->r.min.y)%Dy(src->r);
 	masky = (starty + mr.min.y - mask->r.min.y)%Dy(mask->r);
 	dsty = starty + r.min.y - dst->r.min.y;
 
 	assert(0 <= srcy && srcy < Dy(src->r));
 	assert(0 <= masky && masky < Dy(mask->r));
 	assert(0 <= dsty && dsty < Dy(dst->r));
 
 	if(drawdebug)
 		print("alphadraw: rdsrc=%p rdmask=%p rddst=%p calc=%p wrdst=%p\n",
 			rdsrc, rdmask, rddst, calc, wrdst);
 	for(y=starty; y!=endy; y+=dir, srcy+=dir, masky+=dir, dsty+=dir){
 		clipy(src, &srcy);
 		clipy(dst, &dsty);
 		clipy(mask, &masky);
 
 		bsrc = rdsrc(&spar, spar.bufbase, srcy);
 DBG print("[");
 		bmask = rdmask(&mpar, mpar.bufbase, masky);
 DBG print("]\n");
 		bdst = rddst(&dpar, dpar.bufbase, dsty);
 DBG		dumpbuf("src", bsrc, dx);
 DBG		dumpbuf("mask", bmask, dx);
 DBG		dumpbuf("dst", bdst, dx);
 		bdst = calc(bdst, bsrc, bmask, dx, isgrey, op);
 DBG		dumpbuf("bdst", bdst, dx);
 		wrdst(&dpar, dpar.bytermin+dsty*dpar.bwidth, bdst);
 	}
 
 	return 1;
 }
 #undef DBG
 
 static Buffer
 alphacalc0(Buffer bdst, Buffer b1, Buffer b2, int dx, int grey, int op)
 {
 	USED(grey);
 	USED(op);
 	memset(bdst.rgba, 0, dx*bdst.delta);
 	return bdst;
 }
 
 /*
  * Do the channels in the buffers match enough
  * that we can do word-at-a-time operations
  * on the pixels?
  */
 static int
 chanmatch(Buffer *bdst, Buffer *bsrc)
 {
 	uchar *drgb, *srgb;
 
 	/*
 	 * first, r, g, b must be in the same place
 	 * in the rgba word.
 	 */
 	drgb = (uchar*)bdst->rgba;
 	srgb = (uchar*)bsrc->rgba;
 	if(bdst->red - drgb != bsrc->red - srgb
 	|| bdst->blu - drgb != bsrc->blu - srgb
 	|| bdst->grn - drgb != bsrc->grn - srgb)
 		return 0;
 
 	/*
 	 * that implies alpha is in the same place,
 	 * if it is there at all (it might be == &ones).
 	 * if the destination is &ones, we can scribble
 	 * over the rgba slot just fine.
 	 */
 	if(bdst->alpha == &ones)
 		return 1;
 
 	/*
 	 * if the destination is not ones but the src is,
 	 * then the simultaneous calculation will use
 	 * bogus bytes from the src's rgba.  no good.
 	 */
 	if(bsrc->alpha == &ones)
 		return 0;
 
 	/*
 	 * otherwise, alphas are in the same place.
 	 */
 	return 1;
 }
 
 static Buffer
 alphacalc14(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int fd, sadelta;
 	int i, sa, ma, q;
 	u32int t, t1;
 
 	obdst = bdst;
 	sadelta = bsrc.alpha == &ones ? 0 : bsrc.delta;
 	q = bsrc.delta == 4 && bdst.delta == 4 && chanmatch(&bdst, &bsrc);
 
 	for(i=0; i<dx; i++){
 		sa = *bsrc.alpha;
 		ma = *bmask.alpha;
 		fd = CALC11(sa, ma, t);
 		if(op == DoutS)
 			fd = 255-fd;
 
 		if(grey){
 			*bdst.grey = CALC11(fd, *bdst.grey, t);
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			if(q){
 				*bdst.rgba = CALC41(fd, *bdst.rgba, t, t1);
 				bsrc.rgba++;
 				bdst.rgba++;
 				bsrc.alpha += sadelta;
 				bmask.alpha += bmask.delta;
 				continue;
 			}
 			*bdst.red = CALC11(fd, *bdst.red, t);
 			*bdst.grn = CALC11(fd, *bdst.grn, t);
 			*bdst.blu = CALC11(fd, *bdst.blu, t);
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		if(bdst.alpha != &ones){
 			*bdst.alpha = CALC11(fd, *bdst.alpha, t);
 			bdst.alpha += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		bsrc.alpha += sadelta;
 	}
 	return obdst;
 }
 
 static Buffer
 alphacalc2810(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int fs, sadelta;
 	int i, ma, da, q;
 	u32int t, t1;
 
 	obdst = bdst;
 	sadelta = bsrc.alpha == &ones ? 0 : bsrc.delta;
 	q = bsrc.delta == 4 && bdst.delta == 4 && chanmatch(&bdst, &bsrc);
 
 	for(i=0; i<dx; i++){
 		ma = *bmask.alpha;
 		da = *bdst.alpha;
 		if(op == SoutD)
 			da = 255-da;
 		fs = ma;
 		if(op != S)
 			fs = CALC11(fs, da, t);
 
 		if(grey){
 			*bdst.grey = CALC11(fs, *bsrc.grey, t);
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			if(q){
 				*bdst.rgba = CALC41(fs, *bsrc.rgba, t, t1);
 				bsrc.rgba++;
 				bdst.rgba++;
 				bmask.alpha += bmask.delta;
 				bdst.alpha += bdst.delta;
 				continue;
 			}
 			*bdst.red = CALC11(fs, *bsrc.red, t);
 			*bdst.grn = CALC11(fs, *bsrc.grn, t);
 			*bdst.blu = CALC11(fs, *bsrc.blu, t);
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		if(bdst.alpha != &ones){
 			*bdst.alpha = CALC11(fs, *bsrc.alpha, t);
 			bdst.alpha += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		bsrc.alpha += sadelta;
 	}
 	return obdst;
 }
 
 static Buffer
 alphacalc3679(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int fs, fd, sadelta;
 	int i, sa, ma, da, q;
 	u32int t, t1;
 
 	obdst = bdst;
 	sadelta = bsrc.alpha == &ones ? 0 : bsrc.delta;
 	q = bsrc.delta == 4 && bdst.delta == 4 && chanmatch(&bdst, &bsrc);
 
 	for(i=0; i<dx; i++){
 		sa = *bsrc.alpha;
 		ma = *bmask.alpha;
 		da = *bdst.alpha;
 		if(op == SatopD)
 			fs = CALC11(ma, da, t);
 		else
 			fs = CALC11(ma, 255-da, t);
 		if(op == DoverS)
 			fd = 255;
 		else{
 			fd = CALC11(sa, ma, t);
 			if(op != DatopS)
 				fd = 255-fd;
 		}
 
 		if(grey){
 			*bdst.grey = CALC12(fs, *bsrc.grey, fd, *bdst.grey, t);
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			if(q){
 				*bdst.rgba = CALC42(fs, *bsrc.rgba, fd, *bdst.rgba, t, t1);
 				bsrc.rgba++;
 				bdst.rgba++;
 				bsrc.alpha += sadelta;
 				bmask.alpha += bmask.delta;
 				bdst.alpha += bdst.delta;
 				continue;
 			}
 			*bdst.red = CALC12(fs, *bsrc.red, fd, *bdst.red, t);
 			*bdst.grn = CALC12(fs, *bsrc.grn, fd, *bdst.grn, t);
 			*bdst.blu = CALC12(fs, *bsrc.blu, fd, *bdst.blu, t);
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		if(bdst.alpha != &ones){
 			*bdst.alpha = CALC12(fs, sa, fd, da, t);
 			bdst.alpha += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		bsrc.alpha += sadelta;
 	}
 	return obdst;
 }
 
 static Buffer
 alphacalc5(Buffer bdst, Buffer b1, Buffer b2, int dx, int grey, int op)
 {
 	USED(dx);
 	USED(grey);
 	USED(op);
 	return bdst;
 }
 
 static Buffer
 alphacalc11(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int fd, sadelta;
 	int i, sa, ma, q;
 	u32int t, t1;
 
 	USED(op);
 	obdst = bdst;
 	sadelta = bsrc.alpha == &ones ? 0 : bsrc.delta;
 	q = bsrc.delta == 4 && bdst.delta == 4 && chanmatch(&bdst, &bsrc);
 
 	for(i=0; i<dx; i++){
 		sa = *bsrc.alpha;
 		ma = *bmask.alpha;
 		fd = 255-CALC11(sa, ma, t);
 
 		if(grey){
 			*bdst.grey = CALC12(ma, *bsrc.grey, fd, *bdst.grey, t);
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			if(q){
 				*bdst.rgba = CALC42(ma, *bsrc.rgba, fd, *bdst.rgba, t, t1);
 				bsrc.rgba++;
 				bdst.rgba++;
 				bsrc.alpha += sadelta;
 				bmask.alpha += bmask.delta;
 				continue;
 			}
 			*bdst.red = CALC12(ma, *bsrc.red, fd, *bdst.red, t);
 			*bdst.grn = CALC12(ma, *bsrc.grn, fd, *bdst.grn, t);
 			*bdst.blu = CALC12(ma, *bsrc.blu, fd, *bdst.blu, t);
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		if(bdst.alpha != &ones){
 			*bdst.alpha = CALC12(ma, sa, fd, *bdst.alpha, t);
 			bdst.alpha += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		bsrc.alpha += sadelta;
 	}
 	return obdst;
 }
 
 /*
 not used yet
 source and mask alpha 1
 static Buffer
 alphacalcS0(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int i;
 
 	USED(op);
 	obdst = bdst;
 	if(bsrc.delta == bdst.delta){
 		memmove(bdst.rgba, bsrc.rgba, dx*bdst.delta);
 		return obdst;
 	}
 	for(i=0; i<dx; i++){
 		if(grey){
 			*bdst.grey = *bsrc.grey;
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			*bdst.red = *bsrc.red;
 			*bdst.grn = *bsrc.grn;
 			*bdst.blu = *bsrc.blu;
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		if(bdst.alpha != &ones){
 			*bdst.alpha = 255;
 			bdst.alpha += bdst.delta;
 		}
 	}
 	return obdst;
 }
 */
 
 /* source alpha 1 */
 static Buffer
 alphacalcS(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int fd;
 	int i, ma;
 	u32int t;
 
 	USED(op);
 	obdst = bdst;
 
 	for(i=0; i<dx; i++){
 		ma = *bmask.alpha;
 		fd = 255-ma;
 
 		if(grey){
 			*bdst.grey = CALC12(ma, *bsrc.grey, fd, *bdst.grey, t);
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			*bdst.red = CALC12(ma, *bsrc.red, fd, *bdst.red, t);
 			*bdst.grn = CALC12(ma, *bsrc.grn, fd, *bdst.grn, t);
 			*bdst.blu = CALC12(ma, *bsrc.blu, fd, *bdst.blu, t);
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		if(bdst.alpha != &ones){
 			*bdst.alpha = ma+CALC11(fd, *bdst.alpha, t);
 			bdst.alpha += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 	}
 	return obdst;
 }
 
 static Buffer
 boolcalc14(Buffer bdst, Buffer b1, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int i, ma, zero;
 
 	obdst = bdst;
 
 	for(i=0; i<dx; i++){
 		ma = *bmask.alpha;
 		zero = ma ? op == DoutS : op == DinS;
 
 		if(grey){
 			if(zero)
 				*bdst.grey = 0;
 			bdst.grey += bdst.delta;
 		}else{
 			if(zero)
 				*bdst.red = *bdst.grn = *bdst.blu = 0;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		if(bdst.alpha != &ones){
 			if(zero)
 				*bdst.alpha = 0;
 			bdst.alpha += bdst.delta;
 		}
 	}
 	return obdst;
 }
 
 static Buffer
 boolcalc236789(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int fs, fd;
 	int i, ma, da, zero;
 	u32int t;
 
 	obdst = bdst;
 	zero = !(op&1);
 
 	for(i=0; i<dx; i++){
 		ma = *bmask.alpha;
 		da = *bdst.alpha;
 		fs = da;
 		if(op&2)
 			fs = 255-da;
 		fd = 0;
 		if(op&4)
 			fd = 255;
 
 		if(grey){
 			if(ma)
 				*bdst.grey = CALC12(fs, *bsrc.grey, fd, *bdst.grey, t);
 			else if(zero)
 				*bdst.grey = 0;
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			if(ma){
 				*bdst.red = CALC12(fs, *bsrc.red, fd, *bdst.red, t);
 				*bdst.grn = CALC12(fs, *bsrc.grn, fd, *bdst.grn, t);
 				*bdst.blu = CALC12(fs, *bsrc.blu, fd, *bdst.blu, t);
 			}
 			else if(zero)
 				*bdst.red = *bdst.grn = *bdst.blu = 0;
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		if(bdst.alpha != &ones){
 			if(ma)
 				*bdst.alpha = fs+CALC11(fd, da, t);
 			else if(zero)
 				*bdst.alpha = 0;
 			bdst.alpha += bdst.delta;
 		}
 	}
 	return obdst;
 }
 
 static Buffer
 boolcalc1011(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int grey, int op)
 {
 	Buffer obdst;
 	int i, ma, zero;
 
 	obdst = bdst;
 	zero = !(op&1);
 
 	for(i=0; i<dx; i++){
 		ma = *bmask.alpha;
 
 		if(grey){
 			if(ma)
 				*bdst.grey = *bsrc.grey;
 			else if(zero)
 				*bdst.grey = 0;
 			bsrc.grey += bsrc.delta;
 			bdst.grey += bdst.delta;
 		}else{
 			if(ma){
 				*bdst.red = *bsrc.red;
 				*bdst.grn = *bsrc.grn;
 				*bdst.blu = *bsrc.blu;
 			}
 			else if(zero)
 				*bdst.red = *bdst.grn = *bdst.blu = 0;
 			bsrc.red += bsrc.delta;
 			bsrc.blu += bsrc.delta;
 			bsrc.grn += bsrc.delta;
 			bdst.red += bdst.delta;
 			bdst.blu += bdst.delta;
 			bdst.grn += bdst.delta;
 		}
 		bmask.alpha += bmask.delta;
 		if(bdst.alpha != &ones){
 			if(ma)
 				*bdst.alpha = 255;
 			else if(zero)
 				*bdst.alpha = 0;
 			bdst.alpha += bdst.delta;
 		}
 	}
 	return obdst;
 }
 /*
  * Replicated cached scan line read.  Call the function listed in the Param,
  * but cache the result so that for replicated images we only do the work once.
  */
 static Buffer
 replread(Param *p, uchar *s, int y)
 {
 	Buffer *b;
 
 	USED(s);
 	b = &p->bcache[y];
 	if((p->bfilled & (1<<y)) == 0){
 		p->bfilled |= 1<<y;
 		*b = p->replcall(p, p->bufbase+y*p->bufdelta, y);
 	}
 	return *b;
 }
 
 /*
  * Alpha reading function that simply relabels the grey pointer.
  */
 static Buffer
 greymaskread(Param *p, uchar *buf, int y)
 {
 	Buffer b;
 
 	b = p->greymaskcall(p, buf, y);
 	b.alpha = b.grey;
 	return b;
 }
 
 #define DBG if(0)
 static Buffer
 readnbit(Param *p, uchar *buf, int y)
 {
 	Buffer b;
 	Memimage *img;
 	uchar *repl, *r, *w, *ow, bits;
 	int i, n, sh, depth, x, dx, npack, nbits;
 
 	memset(&b, 0, sizeof b);
 	b.rgba = (u32int*)buf;
 	b.grey = w = buf;
 	b.red = b.blu = b.grn = w;
 	b.alpha = &ones;
 	b.delta = 1;
 
 	dx = p->dx;
 	img = p->img;
 	depth = img->depth;
 	repl = &replbit[depth][0];
 	npack = 8/depth;
 	sh = 8-depth;
 
 	/* copy from p->r.min.x until end of repl rectangle */
 	x = p->r.min.x;
 	n = dx;
 	if(n > p->img->r.max.x - x)
 		n = p->img->r.max.x - x;
 
 	r = p->bytermin + y*p->bwidth;
 DBG print("readnbit dx %d %p=%p+%d*%d, *r=%d fetch %d ", dx, r, p->bytermin, y, p->bwidth, *r, n);
 	bits = *r++;
 	nbits = 8;
 	if(i=x&(npack-1)){
 DBG print("throwaway %d...", i);
 		bits <<= depth*i;
 		nbits -= depth*i;
 	}
 	for(i=0; i<n; i++){
 		if(nbits == 0){
 DBG print("(%.2ux)...", *r);
 			bits = *r++;
 			nbits = 8;
 		}
 		*w++ = repl[bits>>sh];
 DBG print("bit %x...", repl[bits>>sh]);
 		bits <<= depth;
 		nbits -= depth;
 	}
 	dx -= n;
 	if(dx == 0)
 		return b;
 
 	assert(x+i == p->img->r.max.x);
 
 	/* copy from beginning of repl rectangle until where we were before. */
 	x = p->img->r.min.x;
 	n = dx;
 	if(n > p->r.min.x - x)
 		n = p->r.min.x - x;
 
 	r = p->bytey0s + y*p->bwidth;
 DBG print("x=%d r=%p...", x, r);
 	bits = *r++;
 	nbits = 8;
 	if(i=x&(npack-1)){
 		bits <<= depth*i;
 		nbits -= depth*i;
 	}
 DBG print("nbits=%d...", nbits);
 	for(i=0; i<n; i++){
 		if(nbits == 0){
 			bits = *r++;
 			nbits = 8;
 		}
 		*w++ = repl[bits>>sh];
 DBG print("bit %x...", repl[bits>>sh]);
 		bits <<= depth;
 		nbits -= depth;
 DBG print("bits %x nbits %d...", bits, nbits);
 	}
 	dx -= n;
 	if(dx == 0)
 		return b;
 
 	assert(dx > 0);
 	/* now we have exactly one full scan line: just replicate the buffer itself until we are done */
 	ow = buf;
 	while(dx--)
 		*w++ = *ow++;
 
 	return b;
 }
 #undef DBG
 
 #define DBG if(0)
 static void
 writenbit(Param *p, uchar *w, Buffer src)
 {
 	uchar *r;
 	u32int bits;
 	int i, sh, depth, npack, nbits, x, ex;
 
 	assert(src.grey != nil && src.delta == 1);
 
 	x = p->r.min.x;
 	ex = x+p->dx;
 	depth = p->img->depth;
 	npack = 8/depth;
 
 	i=x&(npack-1);
 	bits = i ? (*w >> (8-depth*i)) : 0;
 	nbits = depth*i;
 	sh = 8-depth;
 	r = src.grey;
 
 	for(; x<ex; x++){
 		bits <<= depth;
 DBG print(" %x", *r);
 		bits |= (*r++ >> sh);
 		nbits += depth;
 		if(nbits == 8){
 			*w++ = bits;
 			nbits = 0;
 		}
 	}
 
 	if(nbits){
 		sh = 8-nbits;
 		bits <<= sh;
 		bits |= *w & ((1<<sh)-1);
 		*w = bits;
 	}
 DBG print("\n");
 	return;
 }
 #undef DBG
 
 static Buffer
 readcmap(Param *p, uchar *buf, int y)
 {
 	Buffer b;
 	int a, convgrey, copyalpha, dx, i, m;
 	uchar *q, *cmap, *begin, *end, *r, *w;
 
 	memset(&b, 0, sizeof b);
 	begin = p->bytey0s + y*p->bwidth;
 	r = p->bytermin + y*p->bwidth;
 	end = p->bytey0e + y*p->bwidth;
 	cmap = p->img->cmap->cmap2rgb;
 	convgrey = p->convgrey;
 	copyalpha = (p->img->flags&Falpha) ? 1 : 0;
 
 	w = buf;
 	dx = p->dx;
 	if(copyalpha){
 		b.alpha = buf++;
 		a = p->img->shift[CAlpha]/8;
 		m = p->img->shift[CMap]/8;
 		for(i=0; i<dx; i++){
 			*w++ = r[a];
 			q = cmap+r[m]*3;
 			r += 2;
 			if(r == end)
 				r = begin;
 			if(convgrey){
 				*w++ = RGB2K(q[0], q[1], q[2]);
 			}else{
 				*w++ = q[2];	/* blue */
 				*w++ = q[1];	/* green */
 				*w++ = q[0];	/* red */
 			}
 		}
 	}else{
 		b.alpha = &ones;
 		for(i=0; i<dx; i++){
 			q = cmap+*r++*3;
 			if(r == end)
 				r = begin;
 			if(convgrey){
 				*w++ = RGB2K(q[0], q[1], q[2]);
 			}else{
 				*w++ = q[2];	/* blue */
 				*w++ = q[1];	/* green */
 				*w++ = q[0];	/* red */
 			}
 		}
 	}
 
 	b.rgba = (u32int*)(buf-copyalpha);
 
 	if(convgrey){
 		b.grey = buf;
 		b.red = b.blu = b.grn = buf;
 		b.delta = 1+copyalpha;
 	}else{
 		b.blu = buf;
 		b.grn = buf+1;
 		b.red = buf+2;
 		b.grey = nil;
 		b.delta = 3+copyalpha;
 	}
 	return b;
 }
 
 static void
 writecmap(Param *p, uchar *w, Buffer src)
 {
 	uchar *cmap, *red, *grn, *blu;
 	int i, dx, delta;
 
 	cmap = p->img->cmap->rgb2cmap;
 
 	delta = src.delta;
 	red= src.red;
 	grn = src.grn;
 	blu = src.blu;
 
 	dx = p->dx;
 	for(i=0; i<dx; i++, red+=delta, grn+=delta, blu+=delta)
 		*w++ = cmap[(*red>>4)*256+(*grn>>4)*16+(*blu>>4)];
 }
 
 #define DBG if(drawdebug)
 static Buffer
 readbyte(Param *p, uchar *buf, int y)
 {
 	Buffer b;
 	Memimage *img;
 	int dx, isgrey, convgrey, alphaonly, copyalpha, i, nb;
 	uchar *begin, *end, *r, *w, *rrepl, *grepl, *brepl, *arepl, *krepl;
 	uchar ured, ugrn, ublu;
 	u32int u;
 
 	img = p->img;
 	begin = p->bytey0s + y*p->bwidth;
 	r = p->bytermin + y*p->bwidth;
 	end = p->bytey0e + y*p->bwidth;
 
 	w = buf;
 	dx = p->dx;
 	nb = img->depth/8;
 
 	convgrey = p->convgrey;	/* convert rgb to grey */
 	isgrey = img->flags&Fgrey;
 	alphaonly = p->alphaonly;
 	copyalpha = (img->flags&Falpha) ? 1 : 0;
 
 	/* if we can, avoid processing everything */
 	if(!(img->flags&Frepl) && !convgrey && (img->flags&Fbytes)){
 		memset(&b, 0, sizeof b);
 		if(p->needbuf){
 			memmove(buf, r, dx*nb);
 			r = buf;
 		}
 		b.rgba = (u32int*)r;
 		if(copyalpha)
 			b.alpha = r+img->shift[CAlpha]/8;
 		else
 			b.alpha = &ones;
 		if(isgrey){
 			b.grey = r+img->shift[CGrey]/8;
 			b.red = b.grn = b.blu = b.grey;
 		}else{
 			b.red = r+img->shift[CRed]/8;
 			b.grn = r+img->shift[CGreen]/8;
 			b.blu = r+img->shift[CBlue]/8;
 		}
 		b.delta = nb;
 		return b;
 	}
 
 	rrepl = replbit[img->nbits[CRed]];
 	grepl = replbit[img->nbits[CGreen]];
 	brepl = replbit[img->nbits[CBlue]];
 	arepl = replbit[img->nbits[CAlpha]];
 	krepl = replbit[img->nbits[CGrey]];
 
 	for(i=0; i<dx; i++){
 		u = r[0] | (r[1]<<8) | (r[2]<<16) | (r[3]<<24);
 		if(copyalpha)
 			*w++ = arepl[(u>>img->shift[CAlpha]) & img->mask[CAlpha]];
 
 		if(isgrey)
 			*w++ = krepl[(u >> img->shift[CGrey]) & img->mask[CGrey]];
 		else if(!alphaonly){
 			ured = rrepl[(u >> img->shift[CRed]) & img->mask[CRed]];
 			ugrn = grepl[(u >> img->shift[CGreen]) & img->mask[CGreen]];
 			ublu = brepl[(u >> img->shift[CBlue]) & img->mask[CBlue]];
 			if(convgrey){
 				*w++ = RGB2K(ured, ugrn, ublu);
 			}else{
 				*w++ = brepl[(u >> img->shift[CBlue]) & img->mask[CBlue]];
 				*w++ = grepl[(u >> img->shift[CGreen]) & img->mask[CGreen]];
 				*w++ = rrepl[(u >> img->shift[CRed]) & img->mask[CRed]];
 			}
 		}
 		r += nb;
 		if(r == end)
 			r = begin;
 	}
 
 	b.alpha = copyalpha ? buf : &ones;
 	b.rgba = (u32int*)buf;
 	if(alphaonly){
 		b.red = b.grn = b.blu = b.grey = nil;
 		if(!copyalpha)
 			b.rgba = nil;
 		b.delta = 1;
 	}else if(isgrey || convgrey){
 		b.grey = buf+copyalpha;
 		b.red = b.grn = b.blu = buf+copyalpha;
 		b.delta = copyalpha+1;
 	}else{
 		b.blu = buf+copyalpha;
 		b.grn = buf+copyalpha+1;
 		b.grey = nil;
 		b.red = buf+copyalpha+2;
 		b.delta = copyalpha+3;
 	}
 	return b;
 }
 #undef DBG
 
 #define DBG if(drawdebug)
 static void
 writebyte(Param *p, uchar *w, Buffer src)
 {
 	Memimage *img;
 	int i, isalpha, isgrey, nb, delta, dx, adelta;
 	uchar ff, *red, *grn, *blu, *grey, *alpha;
 	u32int u, mask;
 
 	img = p->img;
 
 	red = src.red;
 	grn = src.grn;
 	blu = src.blu;
 	alpha = src.alpha;
 	delta = src.delta;
 	grey = src.grey;
 	dx = p->dx;
 
 	nb = img->depth/8;
 	mask = (nb==4) ? 0 : ~((1<<img->depth)-1);
 
 	isalpha = img->flags&Falpha;
 	isgrey = img->flags&Fgrey;
 	adelta = src.delta;
 
 	if(isalpha && (alpha == nil || alpha == &ones)){
 		ff = 0xFF;
 		alpha = &ff;
 		adelta = 0;
 	}
 
 	for(i=0; i<dx; i++){
 		u = w[0] | (w[1]<<8) | (w[2]<<16) | (w[3]<<24);
 DBG print("u %.8lux...", u);
 		u &= mask;
 DBG print("&mask %.8lux...", u);
 		if(isgrey){
 			u |= ((*grey >> (8-img->nbits[CGrey])) & img->mask[CGrey]) << img->shift[CGrey];
 DBG print("|grey %.8lux...", u);
 			grey += delta;
 		}else{
 			u |= ((*red >> (8-img->nbits[CRed])) & img->mask[CRed]) << img->shift[CRed];
 			u |= ((*grn >> (8-img->nbits[CGreen])) & img->mask[CGreen]) << img->shift[CGreen];
 			u |= ((*blu >> (8-img->nbits[CBlue])) & img->mask[CBlue]) << img->shift[CBlue];
 			red += delta;
 			grn += delta;
 			blu += delta;
 DBG print("|rgb %.8lux...", u);
 		}
 
 		if(isalpha){
 			u |= ((*alpha >> (8-img->nbits[CAlpha])) & img->mask[CAlpha]) << img->shift[CAlpha];
 			alpha += adelta;
 DBG print("|alpha %.8lux...", u);
 		}
 
 		w[0] = u;
 		w[1] = u>>8;
 		w[2] = u>>16;
 		w[3] = u>>24;
 DBG print("write back %.8lux...", u);
 		w += nb;
 	}
 }
 #undef DBG
 
 static Readfn*
 readfn(Memimage *img)
 {
 	if(img->depth < 8)
 		return readnbit;
 	if(img->nbits[CMap] == 8)
 		return readcmap;
 	return readbyte;
 }
 
 static Readfn*
 readalphafn(Memimage *m)
 {
 	USED(m);
 	return readbyte;
 }
 
 static Writefn*
 writefn(Memimage *img)
 {
 	if(img->depth < 8)
 		return writenbit;
 	if(img->chan == CMAP8)
 		return writecmap;
 	return writebyte;
 }
 
 static void
 nullwrite(Param *p, uchar *s, Buffer b)
 {
 	USED(p);
 	USED(s);
 }
 
 static Buffer
 readptr(Param *p, uchar *s, int y)
 {
 	Buffer b;
 	uchar *q;
 
 	USED(s);
 	memset(&b, 0, sizeof b);
 	q = p->bytermin + y*p->bwidth;
 	b.red = q;	/* ptr to data */
 	b.grn = b.blu = b.grey = b.alpha = nil;
 	b.rgba = (u32int*)q;
 	b.delta = p->img->depth/8;
 	return b;
 }
 
 static Buffer
 boolmemmove(Buffer bdst, Buffer bsrc, Buffer b1, int dx, int i, int o)
 {
 	USED(i);
 	USED(o);
 	memmove(bdst.red, bsrc.red, dx*bdst.delta);
 	return bdst;
 }
 
 static Buffer
 boolcopy8(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int i, int o)
 {
 	uchar *m, *r, *w, *ew;
 
 	USED(i);
 	USED(o);
 	m = bmask.grey;
 	w = bdst.red;
 	r = bsrc.red;
 	ew = w+dx;
 	for(; w < ew; w++,r++)
 		if(*m++)
 			*w = *r;
 	return bdst;	/* not used */
 }
 
 static Buffer
 boolcopy16(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int i, int o)
 {
 	uchar *m;
 	ushort *r, *w, *ew;
 
 	USED(i);
 	USED(o);
 	m = bmask.grey;
 	w = (ushort*)bdst.red;
 	r = (ushort*)bsrc.red;
 	ew = w+dx;
 	for(; w < ew; w++,r++)
 		if(*m++)
 			*w = *r;
 	return bdst;	/* not used */
 }
 
 static Buffer
 boolcopy24(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int i, int o)
 {
 	uchar *m;
 	uchar *r, *w, *ew;
 
 	USED(i);
 	USED(o);
 	m = bmask.grey;
 	w = bdst.red;
 	r = bsrc.red;
 	ew = w+dx*3;
 	while(w < ew){
 		if(*m++){
 			*w++ = *r++;
 			*w++ = *r++;
 			*w++ = *r++;
 		}else{
 			w += 3;
 			r += 3;
 		}
 	}
 	return bdst;	/* not used */
 }
 
 static Buffer
 boolcopy32(Buffer bdst, Buffer bsrc, Buffer bmask, int dx, int i, int o)
 {
 	uchar *m;
 	u32int *r, *w, *ew;
 
 	USED(i);
 	USED(o);
 	m = bmask.grey;
 	w = (u32int*)bdst.red;
 	r = (u32int*)bsrc.red;
 	ew = w+dx;
 	for(; w < ew; w++,r++)
 		if(*m++)
 			*w = *r;
 	return bdst;	/* not used */
 }
 
 static Buffer
 genconv(Param *p, uchar *buf, int y)
 {
 	Buffer b;
 	int nb;
 	uchar *r, *w, *ew;
 
 	/* read from source into RGB format in convbuf */
 	b = p->convreadcall(p, p->convbuf, y);
 
 	/* write RGB format into dst format in buf */
 	p->convwritecall(p->convdpar, buf, b);
 
 	if(p->convdx){
 		nb = p->convdpar->img->depth/8;
 		r = buf;
 		w = buf+nb*p->dx;
 		ew = buf+nb*p->convdx;
 		while(w<ew)
 			*w++ = *r++;
 	}
 
 	b.red = buf;
 	b.blu = b.grn = b.grey = b.alpha = nil;
 	b.rgba = (u32int*)buf;
 	b.delta = 0;
 
 	return b;
 }
 
 static Readfn*
 convfn(Memimage *dst, Param *dpar, Memimage *src, Param *spar)
 {
 	if(dst->chan == src->chan && !(src->flags&Frepl)){
 /*if(drawdebug) iprint("readptr..."); */
 		return readptr;
 	}
 
 	if(dst->chan==CMAP8 && (src->chan==GREY1||src->chan==GREY2||src->chan==GREY4)){
 		/* cheat because we know the replicated value is exactly the color map entry. */
 /*if(drawdebug) iprint("Readnbit..."); */
 		return readnbit;
 	}
 
 	spar->convreadcall = readfn(src);
 	spar->convwritecall = writefn(dst);
 	spar->convdpar = dpar;
 
 	/* allocate a conversion buffer */
 	spar->convbufoff = ndrawbuf;
 	ndrawbuf += spar->dx*4;
 
 	if(spar->dx > Dx(spar->img->r)){
 		spar->convdx = spar->dx;
 		spar->dx = Dx(spar->img->r);
 	}
 
 /*if(drawdebug) iprint("genconv..."); */
 	return genconv;
 }
 
 /*
  * Do NOT call this directly.  pixelbits is a wrapper
  * around this that fetches the bits from the X server
  * when necessary.
  */
 u32int
 _pixelbits(Memimage *i, Point pt)
 {
 	uchar *p;
 	u32int val;
 	int off, bpp, npack;
 
 	val = 0;
 	p = byteaddr(i, pt);
 	switch(bpp=i->depth){
 	case 1:
 	case 2:
 	case 4:
 		npack = 8/bpp;
 		off = pt.x%npack;
 		val = p[0] >> bpp*(npack-1-off);
 		val &= (1<<bpp)-1;
 		break;
 	case 8:
 		val = p[0];
 		break;
 	case 16:
 		val = p[0]|(p[1]<<8);
 		break;
 	case 24:
 		val = p[0]|(p[1]<<8)|(p[2]<<16);
 		break;
 	case 32:
 		val = p[0]|(p[1]<<8)|(p[2]<<16)|(p[3]<<24);
 		break;
 	}
 	while(bpp<32){
 		val |= val<<bpp;
 		bpp *= 2;
 	}
 	return val;
 }
 
 static Calcfn*
 boolcopyfn(Memimage *img, Memimage *mask)
 {
 	if(mask->flags&Frepl && Dx(mask->r)==1 && Dy(mask->r)==1 && pixelbits(mask, mask->r.min)==~0)
 		return boolmemmove;
 
 	switch(img->depth){
 	case 8:
 		return boolcopy8;
 	case 16:
 		return boolcopy16;
 	case 24:
 		return boolcopy24;
 	case 32:
 		return boolcopy32;
 	default:
 		assert(0 /* boolcopyfn */);
 	}
 	return 0;
 }
 
 /*
  * Optimized draw for filling and scrolling; uses memset and memmove.
  */
 static void
 memsets(void *vp, ushort val, int n)
 {
 	ushort *p, *ep;
 
 	p = vp;
 	ep = p+n;
 	while(p<ep)
 		*p++ = val;
 }
 
 static void
 memsetl(void *vp, u32int val, int n)
 {
 	u32int *p, *ep;
 
 	p = vp;
 	ep = p+n;
 	while(p<ep)
 		*p++ = val;
 }
 
 static void
 memset24(void *vp, u32int val, int n)
 {
 	uchar *p, *ep;
 	uchar a,b,c;
 
 	p = vp;
 	ep = p+3*n;
 	a = val;
 	b = val>>8;
 	c = val>>16;
 	while(p<ep){
 		*p++ = a;
 		*p++ = b;
 		*p++ = c;
 	}
 }
 
 u32int
 _imgtorgba(Memimage *img, u32int val)
 {
 	uchar r, g, b, a;
 	int nb, ov, v;
 	u32int chan;
 	uchar *p;
 
 	a = 0xFF;
 	r = g = b = 0xAA;	/* garbage */
 	for(chan=img->chan; chan; chan>>=8){
 		nb = NBITS(chan);
 		ov = v = val&((1<<nb)-1);
 		val >>= nb;
 
 		while(nb < 8){
 			v |= v<<nb;
 			nb *= 2;
 		}
 		v >>= (nb-8);
 
 		switch(TYPE(chan)){
 		case CRed:
 			r = v;
 			break;
 		case CGreen:
 			g = v;
 			break;
 		case CBlue:
 			b = v;
 			break;
 		case CAlpha:
 			a = v;
 			break;
 		case CGrey:
 			r = g = b = v;
 			break;
 		case CMap:
 			p = img->cmap->cmap2rgb+3*ov;
 			r = *p++;
 			g = *p++;
 			b = *p;
 			break;
 		}
 	}
 	return (r<<24)|(g<<16)|(b<<8)|a;
 }
 
 u32int
 _rgbatoimg(Memimage *img, u32int rgba)
 {
 	u32int chan;
 	int d, nb;
 	u32int v;
 	uchar *p, r, g, b, a, m;
 
 	v = 0;
 	r = rgba>>24;
 	g = rgba>>16;
 	b = rgba>>8;
 	a = rgba;
 	d = 0;
 	for(chan=img->chan; chan; chan>>=8){
 		nb = NBITS(chan);
 		switch(TYPE(chan)){
 		case CRed:
 			v |= (r>>(8-nb))<<d;
 			break;
 		case CGreen:
 			v |= (g>>(8-nb))<<d;
 			break;
 		case CBlue:
 			v |= (b>>(8-nb))<<d;
 			break;
 		case CAlpha:
 			v |= (a>>(8-nb))<<d;
 			break;
 		case CMap:
 			p = img->cmap->rgb2cmap;
 			m = p[(r>>4)*256+(g>>4)*16+(b>>4)];
 			v |= (m>>(8-nb))<<d;
 			break;
 		case CGrey:
 			m = RGB2K(r,g,b);
 			v |= (m>>(8-nb))<<d;
 			break;
 		}
 		d += nb;
 	}
 /*	print("rgba2img %.8lux = %.*lux\n", rgba, 2*d/8, v); */
 	return v;
 }
 
 #define DBG if(0)
 static int
 memoptdraw(Memdrawparam *par)
 {
 	int m, y, dy, dx, op;
 	u32int v;
 	u16int u16;
 	Memimage *src;
 	Memimage *dst;
 
 	dx = Dx(par->r);
 	dy = Dy(par->r);
 	src = par->src;
 	dst = par->dst;
 	op = par->op;
 
 DBG print("state %lux mval %lux dd %d\n", par->state, par->mval, dst->depth);
 	/*
 	 * If we have an opaque mask and source is one opaque pixel we can convert to the
 	 * destination format and just replicate with memset.
 	 */
 	m = Simplesrc|Simplemask|Fullmask;
 	if((par->state&m)==m && (par->srgba&0xFF) == 0xFF && (op ==S || op == SoverD)){
 		uchar *dp, p[4];
 		int d, dwid, ppb, np, nb;
 		uchar lm, rm;
 
 DBG print("memopt, dst %p, dst->data->bdata %p\n", dst, dst->data->bdata);
 		dwid = dst->width*sizeof(u32int);
 		dp = byteaddr(dst, par->r.min);
 		v = par->sdval;
 DBG print("sdval %lud, depth %d\n", v, dst->depth);
 		switch(dst->depth){
 		case 1:
 		case 2:
 		case 4:
 			for(d=dst->depth; d<8; d*=2)
 				v |= (v<<d);
 			ppb = 8/dst->depth;	/* pixels per byte */
 			m = ppb-1;
 			/* left edge */
 			np = par->r.min.x&m;		/* no. pixels unused on left side of word */
 			dx -= (ppb-np);
 			nb = 8 - np * dst->depth;		/* no. bits used on right side of word */
 			lm = (1<<nb)-1;
 DBG print("np %d x %d nb %d lm %ux ppb %d m %ux\n", np, par->r.min.x, nb, lm, ppb, m);
 
 			/* right edge */
 			np = par->r.max.x&m;	/* no. pixels used on left side of word */
 			dx -= np;
 			nb = 8 - np * dst->depth;		/* no. bits unused on right side of word */
 			rm = ~((1<<nb)-1);
 DBG print("np %d x %d nb %d rm %ux ppb %d m %ux\n", np, par->r.max.x, nb, rm, ppb, m);
 
 DBG print("dx %d Dx %d\n", dx, Dx(par->r));
 			/* lm, rm are masks that are 1 where we should touch the bits */
 			if(dx < 0){	/* just one byte */
 				lm &= rm;
 				for(y=0; y<dy; y++, dp+=dwid)
 					*dp ^= (v ^ *dp) & lm;
 			}else if(dx == 0){	/* no full bytes */
 				if(lm)
 					dwid--;
 
 				for(y=0; y<dy; y++, dp+=dwid){
 					if(lm){
 DBG print("dp %p v %lux lm %ux (v ^ *dp) & lm %lux\n", dp, v, lm, (v^*dp)&lm);
 						*dp ^= (v ^ *dp) & lm;
 						dp++;
 					}
 					*dp ^= (v ^ *dp) & rm;
 				}
 			}else{		/* full bytes in middle */
 				dx /= ppb;
 				if(lm)
 					dwid--;
 				dwid -= dx;
 
 				for(y=0; y<dy; y++, dp+=dwid){
 					if(lm){
 						*dp ^= (v ^ *dp) & lm;
 						dp++;
 					}
 					memset(dp, v, dx);
 					dp += dx;
 					*dp ^= (v ^ *dp) & rm;
 				}
 			}
 			return 1;
 		case 8:
 			for(y=0; y<dy; y++, dp+=dwid)
 				memset(dp, v, dx);
 			return 1;
 		case 16:
 			p[0] = v;		/* make little endian */
 			p[1] = v>>8;
 			memmove(&u16, p, 2);
 			v = u16;
 DBG print("dp=%p; dx=%d; for(y=0; y<%d; y++, dp+=%d)\nmemsets(dp, v, dx);\n",
 	dp, dx, dy, dwid);
 			for(y=0; y<dy; y++, dp+=dwid)
 				memsets(dp, v, dx);
 			return 1;
 		case 24:
 			for(y=0; y<dy; y++, dp+=dwid)
 				memset24(dp, v, dx);
 			return 1;
 		case 32:
 			p[0] = v;		/* make little endian */
 			p[1] = v>>8;
 			p[2] = v>>16;
 			p[3] = v>>24;
 			memmove(&v, p, 4);
 			for(y=0; y<dy; y++, dp+=dwid)
 				memsetl(dp, v, dx);
 			return 1;
 		default:
 			assert(0 /* bad dest depth in memoptdraw */);
 		}
 	}
 
 	/*
 	 * If no source alpha, an opaque mask, we can just copy the
 	 * source onto the destination.  If the channels are the same and
 	 * the source is not replicated, memmove suffices.
 	 */
 	m = Simplemask|Fullmask;
 	if((par->state&(m|Replsrc))==m && src->depth >= 8
 	&& src->chan == dst->chan && !(src->flags&Falpha) && (op == S || op == SoverD)){
 		uchar *sp, *dp;
 		long swid, dwid, nb;
 		int dir;
 
 		if(src->data == dst->data && byteaddr(dst, par->r.min) > byteaddr(src, par->sr.min))
 			dir = -1;
 		else
 			dir = 1;
 
 		swid = src->width*sizeof(u32int);
 		dwid = dst->width*sizeof(u32int);
 		sp = byteaddr(src, par->sr.min);
 		dp = byteaddr(dst, par->r.min);
 		if(dir == -1){
 			sp += (dy-1)*swid;
 			dp += (dy-1)*dwid;
 			swid = -swid;
 			dwid = -dwid;
 		}
 		nb = (dx*src->depth)/8;
 		for(y=0; y<dy; y++, sp+=swid, dp+=dwid)
 			memmove(dp, sp, nb);
 		return 1;
 	}
 
 	/*
 	 * If we have a 1-bit mask, 1-bit source, and 1-bit destination, and
 	 * they're all bit aligned, we can just use bit operators.  This happens
 	 * when we're manipulating boolean masks, e.g. in the arc code.
 	 */
 	if((par->state&(Simplemask|Simplesrc|Replmask|Replsrc))==0
 	&& dst->chan==GREY1 && src->chan==GREY1 && par->mask->chan==GREY1
 	&& (par->r.min.x&7)==(par->sr.min.x&7) && (par->r.min.x&7)==(par->mr.min.x&7)){
 		uchar *sp, *dp, *mp;
 		uchar lm, rm;
 		long swid, dwid, mwid;
 		int i, x, dir;
 
 		sp = byteaddr(src, par->sr.min);
 		dp = byteaddr(dst, par->r.min);
 		mp = byteaddr(par->mask, par->mr.min);
 		swid = src->width*sizeof(u32int);
 		dwid = dst->width*sizeof(u32int);
 		mwid = par->mask->width*sizeof(u32int);
 
 		if(src->data == dst->data && byteaddr(dst, par->r.min) > byteaddr(src, par->sr.min)){
 			dir = -1;
 		}else
 			dir = 1;
 
 		lm = 0xFF>>(par->r.min.x&7);
 		rm = 0xFF<<(8-(par->r.max.x&7));
 		dx -= (8-(par->r.min.x&7)) + (par->r.max.x&7);
 
 		if(dx < 0){	/* one byte wide */
 			lm &= rm;
 			if(dir == -1){
 				dp += dwid*(dy-1);
 				sp += swid*(dy-1);
 				mp += mwid*(dy-1);
 				dwid = -dwid;
 				swid = -swid;
 				mwid = -mwid;
 			}
 			for(y=0; y<dy; y++){
 				*dp ^= (*dp ^ *sp) & *mp & lm;
 				dp += dwid;
 				sp += swid;
 				mp += mwid;
 			}
 			return 1;
 		}
 
 		dx /= 8;
 		if(dir == 1){
 			i = (lm!=0)+dx+(rm!=0);
 			mwid -= i;
 			swid -= i;
 			dwid -= i;
 			for(y=0; y<dy; y++, dp+=dwid, sp+=swid, mp+=mwid){
 				if(lm){
 					*dp ^= (*dp ^ *sp++) & *mp++ & lm;
 					dp++;
 				}
 				for(x=0; x<dx; x++){
 					*dp ^= (*dp ^ *sp++) & *mp++;
 					dp++;
 				}
 				if(rm){
 					*dp ^= (*dp ^ *sp++) & *mp++ & rm;
 					dp++;
 				}
 			}
 			return 1;
 		}else{
 		/* dir == -1 */
 			i = (lm!=0)+dx+(rm!=0);
 			dp += dwid*(dy-1)+i-1;
 			sp += swid*(dy-1)+i-1;
 			mp += mwid*(dy-1)+i-1;
 			dwid = -dwid+i;
 			swid = -swid+i;
 			mwid = -mwid+i;
 			for(y=0; y<dy; y++, dp+=dwid, sp+=swid, mp+=mwid){
 				if(rm){
 					*dp ^= (*dp ^ *sp--) & *mp-- & rm;
 					dp--;
 				}
 				for(x=0; x<dx; x++){
 					*dp ^= (*dp ^ *sp--) & *mp--;
 					dp--;
 				}
 				if(lm){
 					*dp ^= (*dp ^ *sp--) & *mp-- & lm;
 					dp--;
 				}
 			}
 		}
 		return 1;
 	}
 	return 0;
 }
 #undef DBG
 
 /*
  * Boolean character drawing.
  * Solid opaque color through a 1-bit greyscale mask.
  */
 #define DBG if(0)
 static int
 chardraw(Memdrawparam *par)
 {
 	u32int bits;
 	int i, ddepth, dy, dx, x, bx, ex, y, npack, bsh, depth, op;
 	u32int v, maskwid, dstwid;
 	uchar *wp, *rp, *q, *wc;
 	ushort *ws;
 	u32int *wl;
 	uchar sp[4];
 	Rectangle r, mr;
 	Memimage *mask, *src, *dst;
 	union {
 		// black box to hide pointer conversions from gcc.
 		// we'll see how long this works.
 		uchar *u8;
 		u16int *u16;
 		u32int *u32;
 	} gcc_black_box;
 
 if(0) if(drawdebug) iprint("chardraw? mf %lux md %d sf %lux dxs %d dys %d dd %d ddat %p sdat %p\n",
 		par->mask->flags, par->mask->depth, par->src->flags,
 		Dx(par->src->r), Dy(par->src->r), par->dst->depth, par->dst->data, par->src->data);
 
 	mask = par->mask;
 	src = par->src;
 	dst = par->dst;
 	r = par->r;
 	mr = par->mr;
 	op = par->op;
 
 	if((par->state&(Replsrc|Simplesrc|Fullsrc|Replmask)) != (Replsrc|Simplesrc|Fullsrc)
 	|| mask->depth != 1 || dst->depth<8 || dst->data==src->data
 	|| op != SoverD)
 		return 0;
 
 /*if(drawdebug) iprint("chardraw..."); */
 
 	depth = mask->depth;
 	maskwid = mask->width*sizeof(u32int);
 	rp = byteaddr(mask, mr.min);
 	npack = 8/depth;
 	bsh = (mr.min.x % npack) * depth;
 
 	wp = byteaddr(dst, r.min);
 	dstwid = dst->width*sizeof(u32int);
 DBG print("bsh %d\n", bsh);
 	dy = Dy(r);
 	dx = Dx(r);
 
 	ddepth = dst->depth;
 
 	/*
 	 * for loop counts from bsh to bsh+dx
 	 *
 	 * we want the bottom bits to be the amount
 	 * to shift the pixels down, so for n≡0 (mod 8) we want
 	 * bottom bits 7.  for n≡1, 6, etc.
 	 * the bits come from -n-1.
 	 */
 
 	bx = -bsh-1;
 	ex = -bsh-1-dx;
 	SET(bits);
 	v = par->sdval;
 
 	/* make little endian */
 	sp[0] = v;
 	sp[1] = v>>8;
 	sp[2] = v>>16;
 	sp[3] = v>>24;
 
 /*print("sp %x %x %x %x\n", sp[0], sp[1], sp[2], sp[3]); */
 	for(y=0; y<dy; y++, rp+=maskwid, wp+=dstwid){
 		q = rp;
 		if(bsh)
 			bits = *q++;
 		switch(ddepth){
 		case 8:
 /*if(drawdebug) iprint("8loop..."); */
 			wc = wp;
 			for(x=bx; x>ex; x--, wc++){
 				i = x&7;
 				if(i == 8-1)
 					bits = *q++;
 DBG print("bits %lux sh %d...", bits, i);
 				if((bits>>i)&1)
 					*wc = v;
 			}
 			break;
 		case 16:
 			gcc_black_box.u8 = wp;
 			ws = gcc_black_box.u16;
 			gcc_black_box.u8 = sp;
 			v = *gcc_black_box.u16;
 			for(x=bx; x>ex; x--, ws++){
 				i = x&7;
 				if(i == 8-1)
 					bits = *q++;
 DBG print("bits %lux sh %d...", bits, i);
 				if((bits>>i)&1)
 					*ws = v;
 			}
 			break;
 		case 24:
 			wc = wp;
 			for(x=bx; x>ex; x--, wc+=3){
 				i = x&7;
 				if(i == 8-1)
 					bits = *q++;
 DBG print("bits %lux sh %d...", bits, i);
 				if((bits>>i)&1){
 					wc[0] = sp[0];
 					wc[1] = sp[1];
 					wc[2] = sp[2];
 				}
 			}
 			break;
 		case 32:
 			gcc_black_box.u8 = wp;
 			wl = gcc_black_box.u32;
 			gcc_black_box.u8 = sp;
 			v = *gcc_black_box.u32;
 			for(x=bx; x>ex; x--, wl++){
 				i = x&7;
 				if(i == 8-1)
 					bits = *q++;
 DBG iprint("bits %lux sh %d...", bits, i);
 				if((bits>>i)&1)
 					*wl = v;
 			}
 			break;
 		}
 	}
 
 DBG print("\n");
 	return 1;
 }
 #undef DBG
 
 
 /*
  * Fill entire byte with replicated (if necessary) copy of source pixel,
  * assuming destination ldepth is >= source ldepth.
  *
  * This code is just plain wrong for >8bpp.
  *
 u32int
 membyteval(Memimage *src)
 {
 	int i, val, bpp;
 	uchar uc;
 
 	unloadmemimage(src, src->r, &uc, 1);
 	bpp = src->depth;
 	uc <<= (src->r.min.x&(7/src->depth))*src->depth;
 	uc &= ~(0xFF>>bpp);
 	* pixel value is now in high part of byte. repeat throughout byte
 	val = uc;
 	for(i=bpp; i<8; i<<=1)
 		val |= val>>i;
 	return val;
 }
  *
  */
 
 void
 _memfillcolor(Memimage *i, u32int val)
 {
 	u32int bits;
 	int d, y;
 	uchar p[4];
 
 	if(val == DNofill)
 		return;
 
 	bits = _rgbatoimg(i, val);
 	switch(i->depth){
 	case 24:	/* 24-bit images suck */
 		for(y=i->r.min.y; y<i->r.max.y; y++)
 			memset24(byteaddr(i, Pt(i->r.min.x, y)), bits, Dx(i->r));
 		break;
 	default:	/* 1, 2, 4, 8, 16, 32 */
 		for(d=i->depth; d<32; d*=2)
 			bits = (bits << d) | bits;
 		p[0] = bits;		/* make little endian */
 		p[1] = bits>>8;
 		p[2] = bits>>16;
 		p[3] = bits>>24;
 		memmove(&bits, p, 4);
 		memsetl(wordaddr(i, i->r.min), bits, i->width*Dy(i->r));
 		break;
 	}
 }