this patch fixes subpixel highlighting.  it also elimintes the read from
the screen's memory to draw the new text.  on many new graphics cards
(e.g. nvidia.) this improves draw performance.  commented out are two
 lines that also address this problem, but they cause
some flicker.

the new function is somewhat large due to the fact that there are really 5
regions to draw.  (1) unhighlighted boxes (2) one partially highlighted box
(3) 0-n highlighted boxes (4) 0,1 partially highlighted box (may be the same
box as 2) (5) 0,n unhighlighted boxes.  

frdrawsel0 does a similar but inverse, redrawing the background but not the
text.

Notes:
Tue Sep 18 00:59:09 EDT 2007 geoff
Tue Sep 18 01:00:08 EDT 2007 geoff
    deferring this at least until it's refactored, per rsc.


Reference: /n/sources/patch/saved/libframe-subpixfix
Date: Mon Aug 20 03:30:57 CES 2007
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/include/frame.h	Mon Aug 20 03:15:18 2007
+++ /sys/include/frame.h	Mon Aug 20 03:15:17 2007
@@ -80,7 +80,7 @@
 int	_frnewwid(Frame*, Point, Frbox*);
 int	_frnewwid0(Frame*, Point, Frbox*);
 void	_frclean(Frame*, Point, int, int);
-void	_frredraw(Frame*, Point, Image*, Image*);
+void	_frredraw(Frame*, Point, Image*, Image*, Image*);
 void	_fraddbox(Frame*, int, int);
 Point	_frptofcharptb(Frame*, ulong, Point, int);
 Point	_frptofcharnb(Frame*, ulong, int);
--- /sys/src/cmd/rio/wind.c	Mon Aug 20 03:15:33 2007
+++ /sys/src/cmd/rio/wind.c	Mon Aug 20 03:15:26 2007
@@ -709,8 +709,11 @@
 wrepaint(Window *w)
 {
 	wsetcols(w);
-	if(!w->mouseopen)
-		_frredraw(w, w->Frame.r.min, w->cols[TEXT], nil);
+	if(!w->mouseopen){
+		_frredraw(w, w->Frame.r.min, w->cols[TEXT], w->cols[BACK], w->cols[HIGH]);
+//		_frredraw(w, w->Frame.r.min, w->cols[TEXT], w->cols[BACK]);
+//		frdrawsel(w, frptofchar(w, w->p0), w->p0, w->p1, 1);
+	}
 	if(w == input){
 		wborder(w, Selborder);
 		wsetcursor(w, 0);
--- /sys/src/libframe/frinsert.c	Mon Aug 20 03:15:41 2007
+++ /sys/src/libframe/frinsert.c	Mon Aug 20 03:15:39 2007
@@ -262,7 +262,7 @@
 	else
 		col = f->cols[BACK];
 	frselectpaint(f, ppt0, ppt1, col);
-	_frredraw(&frame, ppt0, f->cols[TEXT], col);
+	_frredraw(&frame, ppt0, f->cols[TEXT], col, col);
 	_fraddbox(f, nn0, frame.nbox);
 	for(n=0; n<frame.nbox; n++)
 		f->box[nn0+n] = frame.box[n];
--- /sys/src/libframe/frdraw.c	Mon Aug 20 03:15:51 2007
+++ /sys/src/libframe/frdraw.c	Mon Aug 20 03:15:49 2007
@@ -6,7 +6,7 @@
 #include <frame.h>
 
 void
-_frredraw(Frame *f, Point pt, Image *text, Image *back)
+_frredraw0(Frame *f, Point pt, Image *text, Image *back)
 {
 	Frbox *b;
 	int nb;
@@ -31,6 +31,78 @@
 	while(--nr >= 0)
 		s += chartorune(&r, s);
 	return s-s0;
+}
+
+void
+_frredraw(Frame *f, Point pt, Image *text, Image *back, Image *hiback)
+{
+	Frbox *b;
+	int nb, nr, trim;
+	Point qt, xt;
+	uint p;
+	char *ptr;
+
+	if(f->p0 == f->p1){
+		_frredraw0(f, pt, text, back);
+		return;
+	}
+
+	p = nr = 0;
+	/* draw up to the box with the selection */
+	for(nb=0,b=f->box; nb<f->nbox; nb++, b++){
+		nr = NRUNE(b);
+		_frcklinewrap(f, &pt, b);
+		if(p+nr > f->p0)
+			break;
+		if(b->nrune >= 0)
+			stringbg(f->b, pt, text, ZP, f->font, (char *)b->ptr, back, ZP);
+		pt.x += b->wid;
+		p += nr;
+	}
+
+	qt = pt;
+	ptr = (char*)b->ptr;
+	if(p < f->p0){	/* beginning of region: advance into box */
+		if(b->nrune >= 0){
+			stringnbg(f->b, pt, text, ZP, f->font, ptr, f->p0-p, back, ZP);
+			pt.x += stringnwidth(f->font, ptr, f->p0-p);
+		}
+		ptr += nbytes(ptr, f->p0-p);
+		nr -= (f->p0-p);
+		p = f->p0;
+	}
+
+	for(; nb<f->nbox && p<f->p1; ){
+		trim = 0;
+		if(p+nr > f->p1){	/* end of region: trim box */
+			trim = (p+nr)-f->p1;
+			nr -= trim;
+		}
+		if(b->nrune < 0)
+			goto next;
+		xt = stringnbg(f->b, pt, text, ZP, f->font, ptr, nr, hiback, ZP);
+		if(trim)
+			stringbg(f->b, xt, text, ZP, f->font, ptr+nr, back, ZP);
+	next:
+		pt = qt;
+		pt.x += b->wid;
+		p += nr;
+
+		nb++;
+		b++;
+		ptr = (char*)b->ptr;
+		nr = NRUNE(b);
+		_frcklinewrap(f, &pt, b);
+		qt = pt;
+	}
+
+	for(; nb<f->nbox; nb++, b++){
+		_frcklinewrap(f, &pt, b);
+		if(b->nrune >= 0){
+			stringbg(f->b, pt, text, ZP, f->font, (char *)b->ptr, back, ZP);
+		}
+		pt.x += b->wid;
+	}
 }
 
 void