dont flush screen when hiding software cursor

we can avoid some flickering when removing the software cursor
from the shadow framebuffer by avoiding the flushscreenimage()
call.

once the cursor is redrawn, we flush the combined rect of its
old and new position in one go.

1 files changed, 5 insertions, 2 deletions

diff --git a/sys/src/9/port/swcursor.c b/sys/src/9/port/swcursor.c
index 55ea014d0..75b658460 100644
--- a/sys/src/9/port/swcursor.c
+++ b/sys/src/9/port/swcursor.c
@@ -42,7 +42,6 @@ swcursorhide(void)
 		return;
 	swvisible = 0;
 	memimagedraw(gscreen, swrect, swback, ZP, memopaque, ZP, S);
-	flushmemscreen(swrect);
 }
 
 void
@@ -57,16 +56,20 @@ swcursoravoid(Rectangle r)
 void
 swcursordraw(Point p)
 {
+	Rectangle flushr;
+
 	if(swvisible)
 		return;
 	if(swback == nil || swimg1 == nil || swmask1 == nil || gscreen == nil)
 		return;
 	assert(!canqlock(&drawlock));
 	swvispt = addpt(swoffset, p);
+	flushr = swrect; 
 	swrect = rectaddpt(Rect(0,0,16,16), swvispt);
+	combinerect(&flushr, swrect);
 	memimagedraw(swback, swback->r, gscreen, swvispt, memopaque, ZP, S);
 	memimagedraw(gscreen, swrect, swimg1, ZP, swmask1, ZP, SoverD);
-	flushmemscreen(swrect);
+	flushmemscreen(flushr);
 	swvisible = 1;
 }