reduce software cursor flickering

the software cursor starts flickering and reacts bumby if a process
spends most of its time with drawlock acquired because the timer interrupt
thats supposed to redraw the cursor fails to acquire the lock at the time
the timer fires.

instead of trying to draw the cursor on the screen from a timer interrupt
30 times per second, devmouse now creates a process calling cursoron() and
cursoroff() when the cursor needs to be redrawn. this allows the swcursor
to schedule a redraw while holding the drawlock in swcursoravoid() and
cursoron()/cursoroff() are now able to wait for a qlock (drawlock) because
they get called from process context.

the overall responsiveness is also improved with this change as the cursor
redraw rate isnt limited to 30 times a second anymore.

6 files changed, 27 insertions, 192 deletions

diff --git a/sys/src/9/bcm/fns.h b/sys/src/9/bcm/fns.h
index 92615d9ed..1c480cc14 100644
--- a/sys/src/9/bcm/fns.h
+++ b/sys/src/9/bcm/fns.h
@@ -64,7 +64,6 @@ extern void setpower(int, int);
 extern void setr13(int, u32int*);
 extern int splfhi(void);
 extern int splflo(void);
-extern void swcursorinit(void);
 extern int tas(void *);
 extern void touser(uintptr);
 extern void trapinit(void);
diff --git a/sys/src/9/bcm/main.c b/sys/src/9/bcm/main.c
index 4a00d1b13..1b78c80d1 100644
--- a/sys/src/9/bcm/main.c
+++ b/sys/src/9/bcm/main.c
@@ -249,8 +249,6 @@ main(void)
 	clockinit();
 	printinit();
 	timersinit();
-	if(conf.monitor)
-		swcursorinit();
 	cpuidprint();
 	archreset();
 
diff --git a/sys/src/9/bcm/picpuf b/sys/src/9/bcm/picpuf
index 7ec5d9881..fcdc080dd 100644
--- a/sys/src/9/bcm/picpuf
+++ b/sys/src/9/bcm/picpuf
@@ -14,7 +14,7 @@ dev
 	cap
 	fs
 	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium ptclbsum inferno
-	draw	screen
+	draw	screen swcursor
 	mouse	mouse
 	uart
 
diff --git a/sys/src/9/bcm/pif b/sys/src/9/bcm/pif
index cf3c66485..f209a1211 100644
--- a/sys/src/9/bcm/pif
+++ b/sys/src/9/bcm/pif
@@ -14,7 +14,7 @@ dev
 	cap
 	fs
 	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium ptclbsum inferno
-	draw	screen
+	draw	screen swcursor
 	mouse	mouse
 	uart
 
diff --git a/sys/src/9/bcm/screen.c b/sys/src/9/bcm/screen.c
index e96fa4fdf..fe7ed6c93 100644
--- a/sys/src/9/bcm/screen.c
+++ b/sys/src/9/bcm/screen.c
@@ -69,203 +69,32 @@ static void myscreenputs(char *s, int n);
 static void screenputc(char *buf);
 static void screenwin(void);
 
-/*
- * Software cursor. 
- */
-static int	swvisible;	/* is the cursor visible? */
-static int	swenabled;	/* is the cursor supposed to be on the screen? */
-static Memimage *swback;	/* screen under cursor */
-static Memimage *swimg;		/* cursor image */
-static Memimage *swmask;	/* cursor mask */
-static Memimage *swimg1;
-static Memimage *swmask1;
-
-static Point	swoffset;
-static Rectangle swrect;	/* screen rectangle in swback */
-static Point	swpt;		/* desired cursor location */
-static Point	swvispt;	/* actual cursor location */
-static int	swvers;		/* incremented each time cursor image changes */
-static int	swvisvers;	/* the version on the screen */
-
-/*
- * called with drawlock locked for us, most of the time.
- * kernel prints at inopportune times might mean we don't
- * hold the lock, but memimagedraw is now reentrant so
- * that should be okay: worst case we get cursor droppings.
- */
-static void
-swcursorhide(void)
-{
-	if(swvisible == 0)
-		return;
-	if(swback == nil)
-		return;
-	swvisible = 0;
-	memimagedraw(gscreen, swrect, swback, ZP, memopaque, ZP, S);
-	flushmemscreen(swrect);
-}
-
-static void
-swcursoravoid(Rectangle r)
-{
-	if(swvisible && rectXrect(r, swrect))
-		swcursorhide();
-}
-
-static void
-swcursordraw(void)
-{
-	int dounlock;
-
-	if(swvisible)
-		return;
-	if(swenabled == 0)
-		return;
-	if(swback == nil || swimg1 == nil || swmask1 == nil)
-		return;
-	dounlock = canqlock(&drawlock);
-	swvispt = swpt;
-	swvisvers = swvers;
-	swrect = rectaddpt(Rect(0,0,16,16), swvispt);
-	memimagedraw(swback, swback->r, gscreen, swpt, memopaque, ZP, S);
-	memimagedraw(gscreen, swrect, swimg1, ZP, swmask1, ZP, SoverD);
-	flushmemscreen(swrect);
-	swvisible = 1;
-	if(dounlock)
-		qunlock(&drawlock);
-}
-
-int
-cursoron(int dolock)
-{
-	int retry;
-
-	if (dolock)
-		lock(&cursor);
-	if (canqlock(&drawlock)) {
-		retry = 0;
-		swcursorhide();
-		swcursordraw();
-		qunlock(&drawlock);
-	} else
-		retry = 1;
-	if (dolock)
-		unlock(&cursor);
-	return retry;
-}
-
 void
-cursoroff(int dolock)
+cursoron(void)
 {
-	if (dolock)
-		lock(&cursor);
+	qlock(&drawlock);
+	lock(&cursor);
 	swcursorhide();
-	if (dolock)
-		unlock(&cursor);
+	swcursordraw(mousexy());
+	unlock(&cursor);
+	qunlock(&drawlock);
 }
 
-static void
-swload(Cursor *curs)
+void
+cursoroff(void)
 {
-	uchar *ip, *mp;
-	int i, j, set, clr;
-
-	if(!swimg || !swmask || !swimg1 || !swmask1)
-		return;
-	/*
-	 * Build cursor image and mask.
-	 * Image is just the usual cursor image
-	 * but mask is a transparent alpha mask.
-	 * 
-	 * The 16x16x8 memimages do not have
-	 * padding at the end of their scan lines.
-	 */
-	ip = byteaddr(swimg, ZP);
-	mp = byteaddr(swmask, ZP);
-	for(i=0; i<32; i++){
-		set = curs->set[i];
-		clr = curs->clr[i];
-		for(j=0x80; j; j>>=1){
-			*ip++ = set&j ? 0x00 : 0xFF;
-			*mp++ = (clr|set)&j ? 0xFF : 0x00;
-		}
-	}
-	swoffset = curs->offset;
-	swvers++;
-	memimagedraw(swimg1,  swimg1->r,  swimg,  ZP, memopaque, ZP, S);
-	memimagedraw(swmask1, swmask1->r, swmask, ZP, memopaque, ZP, S);
+	qlock(&drawlock);
+	lock(&cursor);
+	swcursorhide();
+	unlock(&cursor);
+	qunlock(&drawlock);
 }
 
 /* called from devmouse */
 void
 setcursor(Cursor* curs)
 {
-	cursoroff(0);
-	swload(curs);
-	cursoron(0);
-}
-
-static int
-swmove(Point p)
-{
-	swpt = addpt(p, swoffset);
-	return 0;
-}
-
-static void
-swcursorclock(void)
-{
-	int x;
-
-	if(!swenabled)
-		return;
-	swmove(mousexy());
-	if(swvisible && eqpt(swpt, swvispt) && swvers==swvisvers)
-		return;
-
-	x = splhi();
-	if(swenabled)
-	if(!swvisible || !eqpt(swpt, swvispt) || swvers!=swvisvers)
-	if(canqlock(&drawlock)){
-		swcursorhide();
-		swcursordraw();
-		qunlock(&drawlock);
-	}
-	splx(x);
-}
-
-void
-swcursorinit(void)
-{
-	static int init;
-
-	if(!init){
-		init = 1;
-		addclock0link(swcursorclock, 10);
-		swenabled = 1;
-	}
-	if(swback){
-		freememimage(swback);
-		freememimage(swmask);
-		freememimage(swmask1);
-		freememimage(swimg);
-		freememimage(swimg1);
-	}
-
-	swback  = allocmemimage(Rect(0,0,32,32), gscreen->chan);
-	swmask  = allocmemimage(Rect(0,0,16,16), GREY8);
-	swmask1 = allocmemimage(Rect(0,0,16,16), GREY1);
-	swimg   = allocmemimage(Rect(0,0,16,16), GREY8);
-	swimg1  = allocmemimage(Rect(0,0,16,16), GREY1);
-	if(swback==nil || swmask==nil || swmask1==nil || swimg==nil || swimg1 == nil){
-		print("software cursor: allocmemimage fails\n");
-		return;
-	}
-
-	memfillcolor(swmask, DOpaque);
-	memfillcolor(swmask1, DOpaque);
-	memfillcolor(swimg, DBlack);
-	memfillcolor(swimg1, DBlack);
+	swcursorload(curs);
 }
 
 int
@@ -348,6 +177,7 @@ screeninit(void)
 	memdefont = getmemdefont();
 	screenwin();
 	screenputs = myscreenputs;
+	swcursorinit();
 }
 
 void
diff --git a/sys/src/9/bcm/screen.h b/sys/src/9/bcm/screen.h
index 8703796a9..9c45e3a2f 100644
--- a/sys/src/9/bcm/screen.h
+++ b/sys/src/9/bcm/screen.h
@@ -21,16 +21,24 @@ extern Cursor arrow;
 /* mouse.c */
 extern void mousectl(Cmdbuf*);
 extern void mouseresize(void);
+extern void mouseredraw(void);
 
 /* screen.c */
 extern void	blankscreen(int);
 extern void	flushmemscreen(Rectangle);
 extern uchar*	attachscreen(Rectangle*, ulong*, int*, int*, int*);
-extern int	cursoron(int);
-extern void	cursoroff(int);
+extern void	cursoron(void);
+extern void	cursoroff(void);
 extern void	setcursor(Cursor*);
 
 /* devdraw.c */
 extern QLock	drawlock;
 
 #define ishwimage(i)	1		/* for ../port/devdraw.c */
+
+/* swcursor.c */
+void		swcursorhide(void);
+void		swcursoravoid(Rectangle);
+void		swcursordraw(Point);
+void		swcursorload(Cursor *);
+void		swcursorinit(void);