engine: redraw when the picture changes, not when the state might have

Every key copied the whole Im and Search rune by rune, compared them
after the transition, and combined the answer with 'eaten', a commit
count that is always zero, and a force flag for caret and owner changes,
while redraw() kept a separate 'visible' bit to know when to send an
empty popup. redraw() now compares the snapshot with the last one sent
and treats two empty popups as equal, so imhandlekey just ends in
redraw(). keystroke() was only a test entry point and moves there.

strans.c

@@ -2,11 +2,11 @@
 #include "fn.h"
 
 static Im im;
-static int visible = 0;
 static void *activeowner;
 static int activecap;
 static Caret caret;
 static int candidatechosen;
+static Drawcmd lastdraw;
 static Emit transjp(Im*, Rune);
 static void backjp(Im*);
 static int maplookup(Trie*, Str*, Str*);
@@ -167,18 +167,48 @@ snapshot(Drawcmd *dc)
 		dc->kouho[i] = im.kouho[first + i];
 }
 
+static int
+careteq(Caret *a, Caret *b)
+{
+	return a->valid == b->valid && a->x == b->x && a->y == b->y &&
+		a->h == b->h;
+}
+
+static int
+shown(Drawcmd *dc)
+{
+	return dc->pre.n != 0 || dc->nkouho != 0;
+}
+
+static int
+samedraw(Drawcmd *a, Drawcmd *b)
+{
+	int i;
+
+	if(!shown(a) && !shown(b))
+		return 1;
+	if(a->nkouho != b->nkouho || a->sel != b->sel ||
+	   a->first != b->first || a->total != b->total ||
+	   scmp(&a->pre, &b->pre) != 0 || !careteq(&a->caret, &b->caret))
+		return 0;
+	for(i = 0; i < a->nkouho; i++)
+		if(scmp(&a->kouho[i], &b->kouho[i]) != 0)
+			return 0;
+	return 1;
+}
+
+/* Sends the popup a new picture only when it would look different. */
 static void
 redraw(void)
 {
-	static Drawcmd old;
-	Drawcmd dc;
+	Drawcmd dc, junk;
 
 	snapshot(&dc);
-	if(dc.pre.n == 0 && dc.nkouho == 0 && !visible)
+	if(samedraw(&dc, &lastdraw))
 		return;
-	visible = dc.pre.n != 0 || dc.nkouho != 0;
+	lastdraw = dc;
 	/* imthread is the sole producer; keep only the newest pending draw. */
-	while(channbrecv(drawc, &old) > 0)
+	while(channbrecv(drawc, &junk) > 0)
 		;
 	channbsend(drawc, &dc);
 }
@@ -744,63 +774,6 @@ transition(u32int ks, u32int mod, Str *com)
 	return n;
 }
 
-static int
-samestate(Im *a, Search *as, Im *b, Search *bs)
-{
-	int i;
-
-	if(a->l != b->l || scmp(&a->pre, &b->pre) != 0 ||
-	   scmp(&a->raw, &b->raw) != 0 || a->nkouho != b->nkouho ||
-	   a->sel != b->sel || as->lang != bs->lang ||
-	   scmp(&as->raw, &bs->raw) != 0 || scmp(&as->text, &bs->text) != 0)
-		return 0;
-	for(i = 0; i < a->nkouho; i++)
-		if(scmp(&a->kouho[i], &b->kouho[i]) != 0)
-			return 0;
-	return 1;
-}
-
-static void
-savestate(Im *p, Search *s)
-{
-	int i;
-
-	memset(p, 0, sizeof *p);
-	memset(s, 0, sizeof *s);
-	p->l = im.l;
-	sappend(&p->pre, &im.pre);
-	sappend(&p->raw, &im.raw);
-	p->nkouho = im.nkouho;
-	p->sel = im.sel;
-	for(i = 0; i < im.nkouho; i++)
-		sappend(&p->kouho[i], &im.kouho[i]);
-	s->lang = search.lang;
-	sappend(&s->raw, &search.raw);
-	sappend(&s->text, &search.text);
-}
-
-static int
-keystrokeforce(u32int ks, u32int mod, Str *com, int force)
-{
-	Im oldim;
-	Search oldsearch;
-	int eaten, ncom;
-
-	savestate(&oldim, &oldsearch);
-	ncom = com->n;
-	eaten = transition(ks, mod, com);
-	if(force || eaten || com->n != ncom ||
-	   !samestate(&oldim, &oldsearch, &im, &search))
-		redraw();
-	return eaten;
-}
-
-static int
-keystroke(u32int ks, u32int mod, Str *com)
-{
-	return keystrokeforce(ks, mod, com, 0);
-}
-
 static void
 init(void)
 {
@@ -812,7 +785,7 @@ init(void)
 	activeowner = nil;
 	activecap = 0;
 	candidatechosen = 0;
-	visible = 0;
+	memset(&lastdraw, 0, sizeof lastdraw);
 }
 
 static int
@@ -821,30 +794,16 @@ meaningful(Keyreq *kr)
 	return kr->ks != 0 && !ismodkey(kr->ks);
 }
 
-static int
-setactivecap(int cap)
-{
-	int old;
-
-	old = activecap & Cclientpreedit;
-	activecap &= ~Cclientpreedit;
-	activecap |= cap & Cclientpreedit;
-	return old != (activecap & Cclientpreedit);
-}
-
-static int
-careteq(Caret *a, Caret *b)
-{
-	return a->valid == b->valid && a->x == b->x && a->y == b->y &&
-		a->h == b->h;
-}
-
+/*
+ * The engine belongs to whichever context last typed a real key; only
+ * the owner's requests change state.  Every request ends in redraw(),
+ * which sends the popup a picture only if something visible changed.
+ */
 static void
 imhandlekey(Keyreq *kr)
 {
 	Keyres res;
 	void *oldowner;
-	int changed;
 
 	oldowner = activeowner;
 	sclear(&res.commit);
@@ -856,57 +815,38 @@ imhandlekey(Keyreq *kr)
 			reset();
 			activeowner = nil;
 			activecap = 0;
-			redraw();
 		}
 		break;
 	case Keyreset:
-		if(kr->owner == activeowner){
+		if(kr->owner == activeowner)
 			reset();
-			redraw();
-		}
 		break;
 	case Keycaret:
-		if(kr->owner == activeowner && !careteq(&caret, &kr->caret)){
+		if(kr->owner == activeowner)
 			caret = kr->caret;
-			if(visible)
-				redraw();
-		}
 		break;
 	case Keycap:
-		res.eaten = 0;
-		if(activeowner != nil && kr->owner == activeowner){
-			res.eaten = 1;
-			if(setactivecap(kr->cap))
-				redraw();
-		}
+		res.eaten = activeowner != nil && kr->owner == activeowner;
+		if(res.eaten)
+			activecap = kr->cap & Cclientpreedit;
 		break;
 	case Keypress:
 		res.eaten = 0;
-		changed = 0;
-		if(activeowner != nil && kr->owner == activeowner &&
-		   setactivecap(kr->cap))
-			changed = 1;
+		if(activeowner != nil && kr->owner == activeowner)
+			activecap = kr->cap & Cclientpreedit;
 		if(meaningful(kr)){
 			if(kr->owner != activeowner){
 				reset();
 				activeowner = kr->owner;
 				activecap = kr->cap & Cclientpreedit;
 				caret = kr->caret;
-				changed = 1;
-			}else if(kr->caret.valid &&
-			   !careteq(&caret, &kr->caret)){
+			}else if(kr->caret.valid)
 				caret = kr->caret;
-				changed = 1;
-			}
-			if(changed)
-				res.eaten = keystrokeforce(kr->ks, kr->mod,
-					&res.commit, 1);
-			else
-				res.eaten = keystroke(kr->ks, kr->mod, &res.commit);
-		}else if(changed)
-			redraw();
+			res.eaten = transition(kr->ks, kr->mod, &res.commit);
+		}
 		break;
 	}
+	redraw();
 	if(activeowner != oldowner)
 		ximownernotify();
 	if(kr->owner == activeowner){