separate out

13 files changed, 1062 insertions, 0 deletions

diff --git a/src/libmemlayer/draw.c b/src/libmemlayer/draw.c
new file mode 100644
index 00000000..c352a0b2
--- /dev/null
+++ b/src/libmemlayer/draw.c
@@ -0,0 +1,192 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+struct Draw
+{
+	Point	deltas;
+	Point	deltam;
+	Memlayer		*dstlayer;
+	Memimage	*src;
+	Memimage	*mask;
+	int	op;
+};
+
+static
+void
+ldrawop(Memimage *dst, Rectangle screenr, Rectangle clipr, void *etc, int insave)
+{
+	struct Draw *d;
+	Point p0, p1;
+	Rectangle oclipr, srcr, r, mr;
+	int ok;
+
+	d = etc;
+	if(insave && d->dstlayer->save==nil)
+		return;
+
+	p0 = addpt(screenr.min, d->deltas);
+	p1 = addpt(screenr.min, d->deltam);
+
+	if(insave){
+		r = rectsubpt(screenr, d->dstlayer->delta);
+		clipr = rectsubpt(clipr, d->dstlayer->delta);
+	}else
+		r = screenr;
+
+	/* now in logical coordinates */
+
+	/* clipr may have narrowed what we should draw on, so clip if necessary */
+	if(!rectinrect(r, clipr)){
+		oclipr = dst->clipr;
+		dst->clipr = clipr;
+		ok = drawclip(dst, &r, d->src, &p0, d->mask, &p1, &srcr, &mr);
+		dst->clipr = oclipr;
+		if(!ok)
+			return;
+	}
+	memdraw(dst, r, d->src, p0, d->mask, p1, d->op);
+}
+
+void
+memdraw(Memimage *dst, Rectangle r, Memimage *src, Point p0, Memimage *mask, Point p1, int op)
+{
+	struct Draw d;
+	Rectangle srcr, tr, mr;
+	Memlayer *dl, *sl;
+
+	if(drawdebug)
+		iprint("memdraw %p %R %p %P %p %P\n", dst, r, src, p0, mask, p1);
+
+	if(mask == nil)
+		mask = memopaque;
+
+	if(mask->layer){
+if(drawdebug)	iprint("mask->layer != nil\n");
+		return;	/* too hard, at least for now */
+	}
+
+    Top:
+	if(dst->layer==nil && src->layer==nil){
+		memimagedraw(dst, r, src, p0, mask, p1, op);
+		return;
+	}
+
+	if(drawclip(dst, &r, src, &p0, mask, &p1, &srcr, &mr) == 0){
+if(drawdebug)	iprint("drawclip dstcr %R srccr %R maskcr %R\n", dst->clipr, src->clipr, mask->clipr);
+		return;
+	}
+
+	/*
+ 	 * Convert to screen coordinates.
+	 */
+	dl = dst->layer;
+	if(dl != nil){
+		r.min.x += dl->delta.x;
+		r.min.y += dl->delta.y;
+		r.max.x += dl->delta.x;
+		r.max.y += dl->delta.y;
+	}
+    Clearlayer:
+	if(dl!=nil && dl->clear){
+		if(src == dst){
+			p0.x += dl->delta.x;
+			p0.y += dl->delta.y;
+			src = dl->screen->image;
+		}
+		dst = dl->screen->image;
+		goto Top;
+	}
+
+	sl = src->layer;
+	if(sl != nil){
+		p0.x += sl->delta.x;
+		p0.y += sl->delta.y;
+		srcr.min.x += sl->delta.x;
+		srcr.min.y += sl->delta.y;
+		srcr.max.x += sl->delta.x;
+		srcr.max.y += sl->delta.y;
+	}
+
+	/*
+	 * Now everything is in screen coordinates.
+	 * mask is an image.  dst and src are images or obscured layers.
+	 */
+
+	/*
+	 * if dst and src are the same layer, just draw in save area and expose.
+	 */
+	if(dl!=nil && dst==src){
+		if(dl->save == nil)
+			return;	/* refresh function makes this case unworkable */
+		if(rectXrect(r, srcr)){
+			tr = r;
+			if(srcr.min.x < tr.min.x){
+				p1.x += tr.min.x - srcr.min.x;
+				tr.min.x = srcr.min.x;
+			}
+			if(srcr.min.y < tr.min.y){
+				p1.y += tr.min.x - srcr.min.x;
+				tr.min.y = srcr.min.y;
+			}
+			if(srcr.max.x > tr.max.x)
+				tr.max.x = srcr.max.x;
+			if(srcr.max.y > tr.max.y)
+				tr.max.y = srcr.max.y;
+			memlhide(dst, tr);
+		}else{
+			memlhide(dst, r);
+			memlhide(dst, srcr);
+		}
+		memdraw(dl->save, rectsubpt(r, dl->delta), dl->save,
+			subpt(srcr.min, src->layer->delta), mask, p1, op);
+		memlexpose(dst, r);
+		return;
+	}
+
+	if(sl){
+		if(sl->clear){
+			src = sl->screen->image;
+			if(dl != nil){
+				r.min.x -= dl->delta.x;
+				r.min.y -= dl->delta.y;
+				r.max.x -= dl->delta.x;
+				r.max.y -= dl->delta.y;
+			}
+			goto Top;
+		}
+		/* relatively rare case; use save area */
+		if(sl->save == nil)
+			return;	/* refresh function makes this case unworkable */
+		memlhide(src, srcr);
+		/* convert back to logical coordinates */
+		p0.x -= sl->delta.x;
+		p0.y -= sl->delta.y;
+		srcr.min.x -= sl->delta.x;
+		srcr.min.y -= sl->delta.y;
+		srcr.max.x -= sl->delta.x;
+		srcr.max.y -= sl->delta.y;
+		src = src->layer->save;
+	}
+
+	/*
+	 * src is now an image.  dst may be an image or a clear layer
+	 */
+	if(dst->layer==nil)
+		goto Top;
+	if(dst->layer->clear)
+		goto Clearlayer;
+
+	/*
+	 * dst is an obscured layer
+	 */
+	d.deltas = subpt(p0, r.min);
+	d.deltam = subpt(p1, r.min);
+	d.dstlayer = dl;
+	d.src = src;
+	d.op = op;
+	d.mask = mask;
+	_memlayerop(ldrawop, dst, r, r, &d);
+}
diff --git a/src/libmemlayer/lalloc.c b/src/libmemlayer/lalloc.c
new file mode 100644
index 00000000..17d934d3
--- /dev/null
+++ b/src/libmemlayer/lalloc.c
@@ -0,0 +1,79 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+Memimage*
+memlalloc(Memscreen *s, Rectangle screenr, Refreshfn refreshfn, void *refreshptr, u32int val)
+{
+	Memlayer *l;
+	Memimage *n;
+	static Memimage *paint;
+
+	if(paint == nil){
+		paint = allocmemimage(Rect(0,0,1,1), RGBA32);
+		if(paint == nil)
+			return nil;
+		paint->flags |= Frepl;
+		paint->clipr = Rect(-0x3FFFFFF, -0x3FFFFFF, 0x3FFFFFF, 0x3FFFFFF);
+	}
+
+	n = allocmemimaged(screenr, s->image->chan, s->image->data, nil);
+	if(n == nil)
+		return nil;
+	l = malloc(sizeof(Memlayer));
+	if(l == nil){
+		free(n);
+		return nil;
+	}
+
+	l->screen = s;
+	if(refreshfn)
+		l->save = nil;
+	else{
+		l->save = allocmemimage(screenr, s->image->chan);
+		if(l->save == nil){
+			free(l);
+			free(n);
+			return nil;
+		}
+		/* allocmemimage doesn't initialize memory; this paints save area */
+		if(val != DNofill)
+			memfillcolor(l->save, val);
+	}
+	l->refreshfn = refreshfn;
+	l->refreshptr = nil;	/* don't set it until we're done */
+	l->screenr = screenr;
+	l->delta = Pt(0,0);
+
+	n->data->ref++;
+	n->zero = s->image->zero;
+	n->width = s->image->width;
+	n->layer = l;
+
+	/* start with new window behind all existing ones */
+	l->front = s->rearmost;
+	l->rear = nil;
+	if(s->rearmost)
+		s->rearmost->layer->rear = n;
+	s->rearmost = n;
+	if(s->frontmost == nil)
+		s->frontmost = n;
+	l->clear = 0;
+
+	/* now pull new window to front */
+	_memltofrontfill(n, val != DNofill);
+	l->refreshptr = refreshptr;
+
+	/*
+	 * paint with requested color; previously exposed areas are already right
+	 * if this window has backing store, but just painting the whole thing is simplest.
+	 */
+	if(val != DNofill){
+		memsetchan(paint, n->chan);
+		memfillcolor(paint, val);
+		memdraw(n, n->r, paint, n->r.min, nil, n->r.min, S);
+	}
+	return n;
+}
diff --git a/src/libmemlayer/layerop.c b/src/libmemlayer/layerop.c
new file mode 100644
index 00000000..800ffc85
--- /dev/null
+++ b/src/libmemlayer/layerop.c
@@ -0,0 +1,112 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+#define	RECUR(a,b,c,d)	_layerop(fn, i, Rect(a.x, b.y, c.x, d.y), clipr, etc, front->layer->rear);
+
+static void
+_layerop(
+	void (*fn)(Memimage*, Rectangle, Rectangle, void*, int),
+	Memimage *i,
+	Rectangle r,
+	Rectangle clipr,
+	void *etc,
+	Memimage *front)
+{
+	Rectangle fr;
+
+    Top:
+	if(front == i){
+		/* no one is in front of this part of window; use the screen */
+		fn(i->layer->screen->image, r, clipr, etc, 0);
+		return;
+	}
+	fr = front->layer->screenr;
+	if(rectXrect(r, fr) == 0){
+		/* r doesn't touch this window; continue on next rearmost */
+		/* assert(front && front->layer && front->layer->screen && front->layer->rear); */
+		front = front->layer->rear;
+		goto Top;
+	}
+	if(fr.max.y < r.max.y){
+		RECUR(r.min, fr.max, r.max, r.max);
+		r.max.y = fr.max.y;
+	}
+	if(r.min.y < fr.min.y){
+		RECUR(r.min, r.min, r.max, fr.min);
+		r.min.y = fr.min.y;
+	}
+	if(fr.max.x < r.max.x){
+		RECUR(fr.max, r.min, r.max, r.max);
+		r.max.x = fr.max.x;
+	}
+	if(r.min.x < fr.min.x){
+		RECUR(r.min, r.min, fr.min, r.max);
+		r.min.x = fr.min.x;
+	}
+	/* r is covered by front, so put in save area */
+	(*fn)(i->layer->save, r, clipr, etc, 1);
+}
+
+/*
+ * Assumes incoming rectangle has already been clipped to i's logical r and clipr
+ */
+void
+_memlayerop(
+	void (*fn)(Memimage*, Rectangle, Rectangle, void*, int),
+	Memimage *i,
+	Rectangle screenr,	/* clipped to window boundaries */
+	Rectangle clipr,		/* clipped also to clipping rectangles of hierarchy */
+	void *etc)
+{
+	Memlayer *l;
+	Rectangle r, scr;
+
+	l = i->layer;
+	if(!rectclip(&screenr, l->screenr))
+		return;
+	if(l->clear){
+		fn(l->screen->image, screenr, clipr, etc, 0);
+		return;
+	}
+	r = screenr;
+	scr = l->screen->image->clipr;
+
+	/*
+	 * Do the piece on the screen
+	 */
+	if(rectclip(&screenr, scr))
+		_layerop(fn, i, screenr, clipr, etc, l->screen->frontmost);
+	if(rectinrect(r, scr))
+		return;
+
+	/*
+	 * Do the piece off the screen
+	*/
+	if(!rectXrect(r, scr)){
+		/* completely offscreen; easy */
+		fn(l->save, r, clipr, etc, 1);
+		return;
+	}
+	if(r.min.y < scr.min.y){
+		/* above screen */
+		fn(l->save, Rect(r.min.x, r.min.y, r.max.x, scr.min.y), clipr, etc, 1);
+		r.min.y = scr.min.y;
+	}
+	if(r.max.y > scr.max.y){
+		/* below screen */
+		fn(l->save, Rect(r.min.x, scr.max.y, r.max.x, r.max.y), clipr, etc, 1);
+		r.max.y = scr.max.y;
+	}
+	if(r.min.x < scr.min.x){
+		/* left of screen */
+		fn(l->save, Rect(r.min.x, r.min.y, scr.min.x, r.max.y), clipr, etc, 1);
+		r.min.x = scr.min.x;
+	}
+	if(r.max.x > scr.max.x){
+		/* right of screen */
+		fn(l->save, Rect(scr.max.x, r.min.y, r.max.x, r.max.y), clipr, etc, 1);
+	}
+}
diff --git a/src/libmemlayer/ldelete.c b/src/libmemlayer/ldelete.c
new file mode 100644
index 00000000..34cd6ead
--- /dev/null
+++ b/src/libmemlayer/ldelete.c
@@ -0,0 +1,67 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+void
+memldelete(Memimage *i)
+{
+	Memscreen *s;
+	Memlayer *l;
+
+	l = i->layer;
+	/* free backing store and disconnect refresh, to make pushback fast */
+	freememimage(l->save);
+	l->save = nil;
+	l->refreshptr = nil;
+	memltorear(i);
+
+	/* window is now the rearmost;  clean up screen structures and deallocate */
+	s = i->layer->screen;
+	if(s->fill){
+		i->clipr = i->r;
+		memdraw(i, i->r, s->fill, i->r.min, nil, i->r.min, S);
+	}
+	if(l->front){
+		l->front->layer->rear = nil;
+		s->rearmost = l->front;
+	}else{
+		s->frontmost = nil;
+		s->rearmost = nil;
+	}
+	free(l);
+	freememimage(i);
+}
+
+/*
+ * Just free the data structures, don't do graphics
+ */
+void
+memlfree(Memimage *i)
+{
+	Memlayer *l;
+
+	l = i->layer;
+	freememimage(l->save);
+	free(l);
+	freememimage(i);
+}
+
+void
+_memlsetclear(Memscreen *s)
+{
+	Memimage *i, *j;
+	Memlayer *l;
+
+	for(i=s->rearmost; i; i=i->layer->front){
+		l = i->layer;
+		l->clear = rectinrect(l->screenr, l->screen->image->clipr);
+		if(l->clear)
+			for(j=l->front; j; j=j->layer->front)
+				if(rectXrect(l->screenr, j->layer->screenr)){
+					l->clear = 0;
+					break;
+				}
+	}
+}
diff --git a/src/libmemlayer/lhide.c b/src/libmemlayer/lhide.c
new file mode 100644
index 00000000..d6aaa55f
--- /dev/null
+++ b/src/libmemlayer/lhide.c
@@ -0,0 +1,67 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+/*
+ * Hide puts that portion of screenr now on the screen into the window's save area.
+ * Expose puts that portion of screenr now in the save area onto the screen.
+ *
+ * Hide and Expose both require that the layer structures in the screen
+ * match the geometry they are being asked to update, that is, they update the
+ * save area (hide) or screen (expose) based on what those structures tell them.
+ * This means they must be called at the correct time during window shuffles.
+ */
+
+static
+void
+lhideop(Memimage *src, Rectangle screenr, Rectangle clipr, void *etc, int insave)
+{
+	Rectangle r;
+	Memlayer *l;
+
+	USED(clipr.min.x);
+	USED(insave);
+	l = etc;
+	if(src != l->save){	/* do nothing if src is already in save area */
+		r = rectsubpt(screenr, l->delta);
+		memdraw(l->save, r, src, screenr.min, nil, screenr.min, S);
+	}
+}
+
+void
+memlhide(Memimage *i, Rectangle screenr)
+{
+	if(i->layer->save == nil)
+		return;
+	if(rectclip(&screenr, i->layer->screen->image->r) == 0)
+		return;
+	_memlayerop(lhideop, i, screenr, screenr, i->layer);
+}
+
+static
+void
+lexposeop(Memimage *dst, Rectangle screenr, Rectangle clipr, void *etc, int insave)
+{
+	Memlayer *l;
+	Rectangle r;
+
+	USED(clipr.min.x);
+	if(insave)	/* if dst is save area, don't bother */
+		return;
+	l = etc;
+	r = rectsubpt(screenr, l->delta);
+	if(l->save)
+		memdraw(dst, screenr, l->save, r.min, nil, r.min, S);
+	else
+		l->refreshfn(dst, r, l->refreshptr);
+}
+
+void
+memlexpose(Memimage *i, Rectangle screenr)
+{
+	if(rectclip(&screenr, i->layer->screen->image->r) == 0)
+		return;
+	_memlayerop(lexposeop, i, screenr, screenr, i->layer);
+}
diff --git a/src/libmemlayer/line.c b/src/libmemlayer/line.c
new file mode 100644
index 00000000..f74930ef
--- /dev/null
+++ b/src/libmemlayer/line.c
@@ -0,0 +1,122 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+struct Lline
+{
+	Point			p0;
+	Point			p1;
+	Point			delta;
+	int			end0;
+	int			end1;
+	int			radius;
+	Point			sp;
+	Memlayer		*dstlayer;
+	Memimage	*src;
+	int			op;
+};
+
+static void llineop(Memimage*, Rectangle, Rectangle, void*, int);
+
+static
+void
+_memline(Memimage *dst, Point p0, Point p1, int end0, int end1, int radius, Memimage *src, Point sp, Rectangle clipr, int op)
+{
+	Rectangle r;
+	struct Lline ll;
+	Point d;
+	int srcclipped;
+	Memlayer *dl;
+
+	if(radius < 0)
+		return;
+	if(src->layer)	/* can't draw line with layered source */
+		return;
+	srcclipped = 0;
+
+   Top:
+	dl = dst->layer;
+	if(dl == nil){
+		_memimageline(dst, p0, p1, end0, end1, radius, src, sp, clipr, op);
+		return;
+	}
+	if(!srcclipped){
+		d = subpt(sp, p0);
+		if(rectclip(&clipr, rectsubpt(src->clipr, d)) == 0)
+			return;
+		if((src->flags&Frepl)==0 && rectclip(&clipr, rectsubpt(src->r, d))==0)
+			return;
+		srcclipped = 1;
+	}
+
+	/* dst is known to be a layer */
+	p0.x += dl->delta.x;
+	p0.y += dl->delta.y;
+	p1.x += dl->delta.x;
+	p1.y += dl->delta.y;
+	clipr.min.x += dl->delta.x;
+	clipr.min.y += dl->delta.y;
+	clipr.max.x += dl->delta.x;
+	clipr.max.y += dl->delta.y;
+	if(dl->clear){
+		dst = dst->layer->screen->image;
+		goto Top;
+	}
+
+	/* XXX */
+	/* this is not the correct set of tests */
+/*	if(log2[dst->depth] != log2[src->depth] || log2[dst->depth]!=3) */
+/*		return; */
+
+	/* can't use sutherland-cohen clipping because lines are wide */
+	r = memlinebbox(p0, p1, end0, end1, radius);
+	/*
+	 * r is now a bounding box for the line;
+	 * use it as a clipping rectangle for subdivision
+	 */
+	if(rectclip(&r, clipr) == 0)
+		return;
+	ll.p0 = p0;
+	ll.p1 = p1;
+	ll.end0 = end0;
+	ll.end1 = end1;
+	ll.sp = sp;
+	ll.dstlayer = dst->layer;
+	ll.src = src;
+	ll.radius = radius;
+	ll.delta = dl->delta;
+	ll.op = op;
+	_memlayerop(llineop, dst, r, r, &ll);
+}
+
+static
+void
+llineop(Memimage *dst, Rectangle screenr, Rectangle clipr, void *etc, int insave)
+{
+	struct Lline *ll;
+	Point p0, p1;
+
+	USED(screenr.min.x);
+	ll = etc;
+	if(insave && ll->dstlayer->save==nil)
+		return;
+	if(!rectclip(&clipr, screenr))
+		return;
+	if(insave){
+		p0 = subpt(ll->p0, ll->delta);
+		p1 = subpt(ll->p1, ll->delta);
+		clipr = rectsubpt(clipr, ll->delta);
+	}else{
+		p0 = ll->p0;
+		p1 = ll->p1;
+	}
+	_memline(dst, p0, p1, ll->end0, ll->end1, ll->radius, ll->src, ll->sp, clipr, ll->op);
+}
+
+void
+memline(Memimage *dst, Point p0, Point p1, int end0, int end1, int radius, Memimage *src, Point sp, int op)
+{
+	_memline(dst, p0, p1, end0, end1, radius, src, sp, dst->clipr, op);
+}
diff --git a/src/libmemlayer/load.c b/src/libmemlayer/load.c
new file mode 100644
index 00000000..d211564b
--- /dev/null
+++ b/src/libmemlayer/load.c
@@ -0,0 +1,55 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+int
+memload(Memimage *dst, Rectangle r, uchar *data, int n, int iscompressed)
+{
+	int (*loadfn)(Memimage*, Rectangle, uchar*, int);
+	Memimage *tmp;
+	Memlayer *dl;
+	Rectangle lr;
+	int dx;
+
+	loadfn = loadmemimage;
+	if(iscompressed)
+		loadfn = cloadmemimage;
+
+    Top:
+	dl = dst->layer;
+	if(dl == nil)
+		return loadfn(dst, r, data, n);
+
+	/*
+ 	 * Convert to screen coordinates.
+	 */
+	lr = r;
+	r.min.x += dl->delta.x;
+	r.min.y += dl->delta.y;
+	r.max.x += dl->delta.x;
+	r.max.y += dl->delta.y;
+	dx = dl->delta.x&(7/dst->depth);
+	if(dl->clear && dx==0){
+		dst = dl->screen->image;
+		goto Top;
+	}
+
+	/*
+	 * dst is an obscured layer or data is unaligned
+	 */
+	if(dl->save && dx==0){
+		n = loadfn(dl->save, lr, data, n);
+		if(n > 0)
+			memlexpose(dst, r);
+		return n;
+	}
+	tmp = allocmemimage(lr, dst->chan);
+	if(tmp == nil)
+		return -1;
+	n = loadfn(tmp, lr, data, n);
+	memdraw(dst, lr, tmp, lr.min, nil, lr.min, S);
+	freememimage(tmp);
+	return n;
+}
diff --git a/src/libmemlayer/lorigin.c b/src/libmemlayer/lorigin.c
new file mode 100644
index 00000000..0926ee8d
--- /dev/null
+++ b/src/libmemlayer/lorigin.c
@@ -0,0 +1,107 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+/*
+ * Place i so i->r.min = log, i->layer->screenr.min == scr.
+*/
+int
+memlorigin(Memimage *i, Point log, Point scr)
+{
+	Memlayer *l;
+	Memscreen *s;
+	Memimage *t, *shad, *nsave;
+	Rectangle x, newr, oldr;
+	Point delta;
+	int overlap, eqlog, eqscr, wasclear;
+
+	l = i->layer;
+	s = l->screen;
+	oldr = l->screenr;
+	newr = Rect(scr.x, scr.y, scr.x+Dx(oldr), scr.y+Dy(oldr));
+	eqscr = eqpt(scr, oldr.min);
+	eqlog = eqpt(log, i->r.min);
+	if(eqscr && eqlog)
+		return 0;
+	nsave = nil;
+	if(eqlog==0 && l->save!=nil){
+		nsave = allocmemimage(Rect(log.x, log.y, log.x+Dx(oldr), log.y+Dy(oldr)), i->chan);
+		if(nsave == nil)
+			return -1;
+	}
+
+	/*
+	 * Bring it to front and move logical coordinate system.
+	 */
+	memltofront(i);
+	wasclear = l->clear;
+	if(nsave){
+		if(!wasclear)
+			memimagedraw(nsave, nsave->r, l->save, l->save->r.min, nil, Pt(0,0), S);
+		freememimage(l->save);
+		l->save = nsave;
+	}
+	delta = subpt(log, i->r.min);
+	i->r = rectaddpt(i->r, delta);
+	i->clipr = rectaddpt(i->clipr, delta);
+	l->delta = subpt(l->screenr.min, i->r.min);
+	if(eqscr)
+		return 0;
+
+	/*
+	 * To clean up old position, make a shadow window there, don't paint it,
+	 * push it behind this one, and (later) delete it.  Because the refresh function
+	 * for this fake window is a no-op, this will cause no graphics action except
+	 * to restore the background and expose the windows previously hidden.
+	 */
+	shad = memlalloc(s, oldr, memlnorefresh, nil, DNofill);
+	if(shad == nil)
+		return -1;
+	s->frontmost = i;
+	if(s->rearmost == i)
+		s->rearmost = shad;
+	else
+		l->rear->layer->front = shad;
+	shad->layer->front = i;
+	shad->layer->rear = l->rear;
+	l->rear = shad;
+	l->front = nil;
+	shad->layer->clear = 0;
+
+	/*
+	 * Shadow is now holding down the fort at the old position.
+	 * Move the window and hide things obscured by new position.
+	 */
+	for(t=l->rear->layer->rear; t!=nil; t=t->layer->rear){
+		x = newr;
+		overlap = rectclip(&x, t->layer->screenr);
+		if(overlap){
+			memlhide(t, x);
+			t->layer->clear = 0;
+		}
+	}
+	l->screenr = newr;
+	l->delta = subpt(scr, i->r.min);
+	l->clear = rectinrect(newr, l->screen->image->clipr);
+
+	/*
+	 * Everything's covered.  Copy to new position and delete shadow window.
+	 */
+	if(wasclear)
+		memdraw(s->image, newr, s->image, oldr.min, nil, Pt(0,0), S);
+	else
+		memlexpose(i, newr);
+	memldelete(shad);
+
+	return 1;
+}
+
+void
+memlnorefresh(Memimage *l, Rectangle r, void *v)
+{
+	USED(l);
+	USED(r.min.x);
+	USED(v);
+}
diff --git a/src/libmemlayer/lsetrefresh.c b/src/libmemlayer/lsetrefresh.c
new file mode 100644
index 00000000..526bd668
--- /dev/null
+++ b/src/libmemlayer/lsetrefresh.c
@@ -0,0 +1,35 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+int
+memlsetrefresh(Memimage *i, Refreshfn fn, void *ptr)
+{
+	Memlayer *l;
+
+	l = i->layer;
+	if(l->refreshfn!=0 && fn!=0){	/* just change functions */
+		l->refreshfn = fn;
+		l->refreshptr = ptr;
+		return 1;
+	}
+
+	if(l->refreshfn == 0){	/* is using backup image; just free it */
+		freememimage(l->save);
+		l->save = nil;
+		l->refreshfn = fn;
+		l->refreshptr = ptr;
+		return 1;
+	}
+
+	l->save = allocmemimage(i->r, i->chan);
+	if(l->save == nil)
+		return 0;
+	/* easiest way is just to update the entire save area */
+	l->refreshfn(i, i->r, l->refreshptr);
+	l->refreshfn = 0;
+	l->refreshptr = nil;
+	return 1;
+}
diff --git a/src/libmemlayer/ltofront.c b/src/libmemlayer/ltofront.c
new file mode 100644
index 00000000..447b40bd
--- /dev/null
+++ b/src/libmemlayer/ltofront.c
@@ -0,0 +1,80 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+/*
+ * Pull i towards top of screen, just behind front
+*/
+static
+void
+_memltofront(Memimage *i, Memimage *front, int fill)
+{
+	Memlayer *l;
+	Memscreen *s;
+	Memimage *f, *ff, *rr;
+	Rectangle x;
+	int overlap;
+
+	l = i->layer;
+	s = l->screen;
+	while(l->front != front){
+		f = l->front;
+		x = l->screenr;
+		overlap = rectclip(&x, f->layer->screenr);
+		if(overlap){
+			memlhide(f, x);
+			f->layer->clear = 0;
+		}
+		/* swap l and f in screen's list */
+		ff = f->layer->front;
+		rr = l->rear;
+		if(ff == nil)
+			s->frontmost = i;
+		else
+			ff->layer->rear = i;
+		if(rr == nil)
+			s->rearmost = f;
+		else
+			rr->layer->front = f;
+		l->front = ff;
+		l->rear = f;
+		f->layer->front = i;
+		f->layer->rear = rr;
+		if(overlap && fill)
+			memlexpose(i, x);
+	}
+}
+
+void
+_memltofrontfill(Memimage *i, int fill)
+{
+	_memltofront(i, nil, fill);
+	_memlsetclear(i->layer->screen);
+}
+
+void
+memltofront(Memimage *i)
+{
+	_memltofront(i, nil, 1);
+	_memlsetclear(i->layer->screen);
+}
+
+void
+memltofrontn(Memimage **ip, int n)
+{
+	Memimage *i, *front;
+	Memscreen *s;
+
+	if(n == 0)
+		return;
+	front = nil;
+	while(--n >= 0){
+		i = *ip++;
+		_memltofront(i, front, 1);
+		front = i;
+	}
+	s = front->layer->screen;
+	_memlsetclear(s);
+}
diff --git a/src/libmemlayer/ltorear.c b/src/libmemlayer/ltorear.c
new file mode 100644
index 00000000..d53e8cc9
--- /dev/null
+++ b/src/libmemlayer/ltorear.c
@@ -0,0 +1,69 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+void
+_memltorear(Memimage *i, Memimage *rear)
+{
+	Memlayer *l;
+	Memscreen *s;
+	Memimage *f, *r, *rr;
+	Rectangle x;
+	int overlap;
+
+	l = i->layer;
+	s = l->screen;
+	while(l->rear != rear){
+		r = l->rear;
+		x = l->screenr;
+		overlap = rectclip(&x, r->layer->screenr);
+		if(overlap){
+			memlhide(i, x);
+			l->clear = 0;
+		}
+		/* swap l and r in screen's list */
+		rr = r->layer->rear;
+		f = l->front;
+		if(rr == nil)
+			s->rearmost = i;
+		else
+			rr->layer->front = i;
+		if(f == nil)
+			s->frontmost = r;
+		else
+			f->layer->rear = r;
+		l->rear = rr;
+		l->front = r;
+		r->layer->rear = i;
+		r->layer->front = f;
+		if(overlap)
+			memlexpose(r, x);
+	}
+}
+
+void
+memltorear(Memimage *i)
+{
+	_memltorear(i, nil);
+	_memlsetclear(i->layer->screen);
+}
+
+void
+memltorearn(Memimage **ip, int n)
+{
+	Memimage *i, *rear;
+	Memscreen *s;
+
+	if(n == 0)
+		return;
+	rear = nil;
+	while(--n >= 0){
+		i = *ip++;
+		_memltorear(i, rear);
+		rear = i;
+	}
+	s = rear->layer->screen;
+	_memlsetclear(s);
+}
diff --git a/src/libmemlayer/mkfile b/src/libmemlayer/mkfile
new file mode 100644
index 00000000..c1d05419
--- /dev/null
+++ b/src/libmemlayer/mkfile
@@ -0,0 +1,25 @@
+<$PLAN9/src/mkhdr
+
+LIB=libmemlayer.a
+
+OFILES=\
+	draw.$O\
+	lalloc.$O\
+	layerop.$O\
+	ldelete.$O\
+	lhide.$O\
+	line.$O\
+	load.$O\
+	lorigin.$O\
+	lsetrefresh.$O\
+	ltofront.$O\
+	ltorear.$O\
+	unload.$O\
+
+HFILES=\
+	$PLAN9/include/draw.h\
+	$PLAN9/include/memdraw.h\
+	$PLAN9/include/memlayer.h\
+
+<$PLAN9/src/mksyslib
+
diff --git a/src/libmemlayer/unload.c b/src/libmemlayer/unload.c
new file mode 100644
index 00000000..b9534117
--- /dev/null
+++ b/src/libmemlayer/unload.c
@@ -0,0 +1,52 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <memlayer.h>
+
+int
+memunload(Memimage *src, Rectangle r, uchar *data, int n)
+{
+	Memimage *tmp;
+	Memlayer *dl;
+	Rectangle lr;
+	int dx;
+
+    Top:
+	dl = src->layer;
+	if(dl == nil)
+		return unloadmemimage(src, r, data, n);
+
+	/*
+ 	 * Convert to screen coordinates.
+	 */
+	lr = r;
+	r.min.x += dl->delta.x;
+	r.min.y += dl->delta.y;
+	r.max.x += dl->delta.x;
+	r.max.y += dl->delta.y;
+	dx = dl->delta.x&(7/src->depth);
+	if(dl->clear && dx==0){
+		src = dl->screen->image;
+		goto Top;
+	}
+
+	/*
+	 * src is an obscured layer or data is unaligned
+	 */
+	if(dl->save && dx==0){
+		if(dl->refreshfn != 0)
+			return -1;	/* can't unload window if it's not Refbackup */
+		if(n > 0)
+			memlhide(src, r);
+		n = unloadmemimage(dl->save, lr, data, n);
+		return n;
+	}
+	tmp = allocmemimage(lr, src->chan);
+	if(tmp == nil)
+		return -1;
+	memdraw(tmp, lr, src, lr.min, nil, lr.min, S);
+	n = unloadmemimage(tmp, lr, data, n);
+	freememimage(tmp);
+	return n;
+}