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.

3 files changed, 24 insertions, 158 deletions

diff --git a/sys/src/9/omap/beagle b/sys/src/9/omap/beagle
index 8852bd7d4..3dea87477 100644
--- a/sys/src/9/omap/beagle
+++ b/sys/src/9/omap/beagle
@@ -24,7 +24,7 @@ dev
 	ether		netif
 	ip		arp chandial ip ipv6 ipaux iproute netlog nullmedium pktmedium ptclbsum inferno
 
-	draw		screen
+	draw		screen swcursor
 	dss
 	mouse
 
diff --git a/sys/src/9/omap/screen.c b/sys/src/9/omap/screen.c
index e47fd2821..f2ec47054 100644
--- a/sys/src/9/omap/screen.c
+++ b/sys/src/9/omap/screen.c
@@ -346,174 +346,33 @@ screenpower(int on)
 	blankscreen(on == 0);
 }
 
-/*
- * 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.
- */
-void
-swcursorhide(void)
-{
-	if(swvisible == 0)
-		return;
-	if(swback == nil)
-		return;
-	swvisible = 0;
-	memimagedraw(gscreen, swrect, swback, ZP, memopaque, ZP, S);
-	flushmemscreen(swrect);
-}
-
-void
-swcursoravoid(Rectangle r)
-{
-	if(swvisible && rectXrect(r, swrect))
-		swcursorhide();
-}
-
-void
-swcursordraw(void)
-{
-	if(swvisible)
-		return;
-	if(swenabled == 0)
-		return;
-	if(swback == nil || swimg1 == nil || swmask1 == nil)
-		return;
-//	assert(!canqlock(&drawlock));		// assertion fails on omap
-	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;
-}
-
-int
-cursoron(int dolock)
-{
-	if (dolock)
-		lock(&oscreen);
-	cursoroff(0);
-	swcursordraw();
-	if (dolock)
-		unlock(&oscreen);
-	return 0;
-}
-
 void
-cursoroff(int dolock)
+cursoron(void)
 {
-	if (dolock)
-		lock(&oscreen);
+	qlock(&drawlock);
+	lock(&cursor);
 	swcursorhide();
-	if (dolock)
-		unlock(&oscreen);
+	swcursordraw(mousexy());
+	unlock(&cursor);
+	qunlock(&drawlock);
 }
 
 void
-swload(Cursor *curs)
+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(1);
 	oscreen.Cursor = *curs;
-	swload(curs);
-	cursoron(1);
-}
-
-int
-swmove(Point p)
-{
-	swpt = addpt(p, swoffset);
-	return 0;
-}
-
-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);
-	}
-	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);
 }
 
 /* called from main and possibly later from devdss to change resolution */
diff --git a/sys/src/9/omap/screen.h b/sys/src/9/omap/screen.h
index 6eff3649c..6083aea15 100644
--- a/sys/src/9/omap/screen.h
+++ b/sys/src/9/omap/screen.h
@@ -20,12 +20,13 @@ extern Point mousexy(void);
 
 extern void	mouseaccelerate(int);
 extern void	mouseresize(void);
+extern void	mouseredraw(void);
 
 /* screen.c */
 extern uchar* attachscreen(Rectangle*, ulong*, int*, int*, int*);
 extern void	flushmemscreen(Rectangle);
-extern int	cursoron(int);
-extern void	cursoroff(int);
+extern void	cursoron(void);
+extern void	cursoroff(void);
 extern void	setcursor(Cursor*);
 extern int	screensize(int, int, int, ulong);
 extern int	screenaperture(int, int);
@@ -49,6 +50,13 @@ extern QLock	drawlock;
 
 #define ishwimage(i)	0		/* for ../port/devdraw.c */
 
+/* swcursor.c */
+void		swcursorhide(void);
+void		swcursoravoid(Rectangle);
+void		swcursordraw(Point);
+void		swcursorload(Cursor *);
+void		swcursorinit(void);
+
 /* for communication between devdss.c and screen.c */
 
 enum {
@@ -93,7 +101,6 @@ struct Settings {
 };
 
 struct OScreen {
-	Lock;
 	Cursor;
 	Settings *settings;
 	int	open;