Do not interpret CSI ? u as DECRC

The kitty keyboard protocol docs recommend CSI ? u to query support for
that protocol, see https://sw.kovidgoyal.net/kitty/keyboard-protocol/

For better or worse, fish shell uses this query to work around bugs
in other terminals triggered by requesting that protocol via CSI = 5 u.

Unfortunately, st interprets CSI ? u as DECRC (restore cursor
position). reproduce with 'printf "\x1b[?u"; cat'.

fish could work around this by switching to the alternate screen
before running this query; but that might cause tearing on terminals
that don't support Synchronized Output. I'm not sure.

In the meantime, let's correct our parser.

This adds a redundant else-after-return, for consistency with the
surrounding code.

config.def.h

@@ -53,7 +53,7 @@ int allowwindowops = 0;
  * near minlatency, but it waits longer for slow updates to avoid partial draw.
  * low minlatency will tear/flicker more, as it can "detect" idle too early.
  */
-static double minlatency = 8;
+static double minlatency = 2;
 static double maxlatency = 33;
 
 /*

config.mk

@@ -1,5 +1,5 @@
 # st version
-VERSION = 0.9
+VERSION = 0.9.2
 
 # Customize below to fit your system
 

st.c

@@ -86,8 +86,8 @@ enum escape_state {
 
 typedef struct {
 	Glyph attr; /* current char attributes */
-	int x; /* terminal column */
+	int x;
-	int y; /* terminal row */
+	int y;
 	char state;
 } TCursor;
 
@@ -1132,6 +1132,7 @@ csiparse(void)
 {
 	char *p = csiescseq.buf, *np;
 	long int v;
+	int sep = ';'; /* colon or semi-colon, but not both */
 
 	csiescseq.narg = 0;
 	if (*p == '?') {
@@ -1149,7 +1150,9 @@ csiparse(void)
 			v = -1;
 		csiescseq.arg[csiescseq.narg++] = v;
 		p = np;
-		if (*p != ';' || csiescseq.narg == ESC_ARG_SIZ)
+		if (sep == ';' && *p == ':')
+			sep = ':'; /* allow override to colon once */
+		if (*p != sep || csiescseq.narg == ESC_ARG_SIZ)
 			break;
 		p++;
 	}
@@ -1643,7 +1646,7 @@ csihandle(void)
 			ttywrite(vtiden, strlen(vtiden), 0);
 		break;
 	case 'b': /* REP -- if last char is printable print it <n> more times */
-		DEFAULT(csiescseq.arg[0], 1);
+		LIMIT(csiescseq.arg[0], 1, 65535);
 		if (term.lastc)
 			while (csiescseq.arg[0]-- > 0)
 				tputc(term.lastc);
@@ -1702,7 +1705,7 @@ csihandle(void)
 			}
 			break;
 		case 1: /* above */
-			if (term.c.y > 1)
+			if (term.c.y > 0)
 				tclearregion(0, 0, term.col-1, term.c.y-1);
 			tclearregion(0, term.c.y, term.c.x, term.c.y);
 			break;
@@ -1798,7 +1801,11 @@ csihandle(void)
 		tcursor(CURSOR_SAVE);
 		break;
 	case 'u': /* DECRC -- Restore cursor position (ANSI.SYS) */
-		tcursor(CURSOR_LOAD);
+		if (csiescseq.priv) {
+			goto unknown;
+		} else {
+			tcursor(CURSOR_LOAD);
+		}
 		break;
 	case ' ':
 		switch (csiescseq.mode[1]) {
@@ -2175,16 +2182,12 @@ tstrsequence(uchar c)
 void
 tcontrolcode(uchar ascii)
 {
-	size_t i;
-
 	switch (ascii) {
 	case '\t':   /* HT */
 		tputtab(1);
 		return;
 	case '\b':   /* BS */
-		for (i = 1; term.c.x && term.line[term.c.y][term.c.x - i].u == 0; ++i)
+		tmoveto(term.c.x-1, term.c.y);
-			;
-		tmoveto(term.c.x - i, term.c.y);
 		return;
 	case '\r':   /* CR */
 		tmoveto(0, term.c.y);

x.c

@@ -1131,7 +1131,7 @@ xinit(int cols, int rows)
 {
 	XGCValues gcvalues;
 	Cursor cursor;
-	Window parent;
+	Window parent, root;
 	pid_t thispid = getpid();
 	XColor xmousefg, xmousebg;
 
@@ -1168,16 +1168,19 @@ xinit(int cols, int rows)
 		| ButtonMotionMask | ButtonPressMask | ButtonReleaseMask;
 	xw.attrs.colormap = xw.cmap;
 
+	root = XRootWindow(xw.dpy, xw.scr);
 	if (!(opt_embed && (parent = strtol(opt_embed, NULL, 0))))
-		parent = XRootWindow(xw.dpy, xw.scr);
+		parent = root;
-	xw.win = XCreateWindow(xw.dpy, parent, xw.l, xw.t,
+	xw.win = XCreateWindow(xw.dpy, root, xw.l, xw.t,
 			win.w, win.h, 0, XDefaultDepth(xw.dpy, xw.scr), InputOutput,
 			xw.vis, CWBackPixel | CWBorderPixel | CWBitGravity
 			| CWEventMask | CWColormap, &xw.attrs);
+	if (parent != root)
+		XReparentWindow(xw.dpy, xw.win, parent, xw.l, xw.t);
 
 	memset(&gcvalues, 0, sizeof(gcvalues));
 	gcvalues.graphics_exposures = False;
-	dc.gc = XCreateGC(xw.dpy, parent, GCGraphicsExposures,
+	dc.gc = XCreateGC(xw.dpy, xw.win, GCGraphicsExposures,
 			&gcvalues);
 	xw.buf = XCreatePixmap(xw.dpy, xw.win, win.w, win.h,
 			DefaultDepth(xw.dpy, xw.scr));
@@ -1617,6 +1620,9 @@ xseticontitle(char *p)
 	XTextProperty prop;
 	DEFAULT(p, opt_title);
 
+	if (p[0] == '\0')
+		p = opt_title;
+
 	if (Xutf8TextListToTextProperty(xw.dpy, &p, 1, XUTF8StringStyle,
 	                                &prop) != Success)
 		return;
@@ -1631,6 +1637,9 @@ xsettitle(char *p)
 	XTextProperty prop;
 	DEFAULT(p, opt_title);
 
+	if (p[0] == '\0')
+		p = opt_title;
+
 	if (Xutf8TextListToTextProperty(xw.dpy, &p, 1, XUTF8StringStyle,
 	                                &prop) != Success)
 		return;