shithub: riscv

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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.

--- a/sys/src/9/port/swcursor.c

+++ b/sys/src/9/port/swcursor.c

@@ -42,7 +42,6 @@

 		return;

 	swvisible = 0;

 	memimagedraw(gscreen, swrect, swback, ZP, memopaque, ZP, S);

-	flushmemscreen(swrect);

 }

 void

@@ -57,6 +56,8 @@

 void

 swcursordraw(Point p)

 {

+	Rectangle flushr;

+

 	if(swvisible)

 		return;

 	if(swback == nil || swimg1 == nil || swmask1 == nil || gscreen == nil)

@@ -63,10 +64,12 @@

 		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;

 }