Index: safekill.c
==================================================================
--- safekill.c
+++ safekill.c
@@ -1,34 +1,37 @@
 /* [ʞ] safekill.c <c.hale.su/lexi/util>
  *  ~ lexi hale <lexi@hale.su>
- *  $ cc -Ofast safekill.c -lX11 -lc -osafekill
+ *  $ cc -Ofast safekill.c -lX11 -osafekill
  *  © affero general public license
  
  * a utility to make it harder to accidentally nuke
- * important windows on i3wm or whatever. */
+ * important windows on i3wm or whatever.
+
+ TODO add option to run as daemon that listens for
+      key chords, for wms that don't have built-in
+      support for user keybindings */
 
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #include <X11/Xatom.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 typedef enum { false, true } bool;
-char* isvital(char* str) {
-	start: // tail calls for dipshits
-		if (*str != '{') {
-			if (*str == 0) return 0;
-			++str; goto start;
-		} else {
-			if (str[1] == 'V' && str[2] == '}')
-				return str;
-			else { ++str; goto start; }
-		}
-}
 
 Display *display;
+Atom xvital;
+
+bool isvital(Window w) {
+	unsigned char* value;
+	int _i; long _l;
+	Atom type;
+	XGetWindowProperty(display,w, xvital, 0,1,False,xvital,
+				&type,&_i,&_l,&_l, &value);
+	return type != None;
+}
 
 void killwin(Window w) {
 	XEvent ev;
 	long mask = SubstructureRedirectMask | SubstructureNotifyMask;
 	ev.xclient.type       = ClientMessage;
@@ -50,27 +53,68 @@
 			fprintf(stderr," falling back to XDestroyWindow, but this may wreck your shit - lots of multi-win apps do *not* like it.\n");
 			XDestroyWindow(display,w);
 		}
 	}
 }
+
+bool isnum(const char* str) {
+	// is the string passed something strtoul can interpret as a
+	// number? decimal, hex, or octal?
+	if (*str == '0' && str[1] == 0) return true;
+
+	enum { hex, dec, oct } mode;
+	if (*str == '0' && str[1] == 'x') mode = hex, str += 2;
+	            else if (*str == '0') mode = oct, str += 1;
+			                     else mode = dec;
+	bool first = true;
+	eval: if(*str == 0) return !first;
+		  first = false;
+		  if(*str >= '0' && *str <= '7') {
+			  ++ str; goto eval;
+		  } else if ((mode == dec || mode == hex) && *str >= '0' && *str <= '9') {
+			  ++ str; goto eval;
+		  } else if (mode == hex && (
+				  (*str >= 'a' && *str <= 'f') ||
+				  (*str >= 'A' && *str <= 'F'))) {
+			  ++ str; goto eval;
+		  } else return false;
+}
+
+int bad(Display* d, XErrorEvent* e) {
+	printf("\x1b[1merror:\x1b[m no such window\n");
+	exit(1);
+}
+
 int main(const int argc, const char** argv) {
 	Window focus;
 	int revert;
 
 	bool active;
 	enum { vitalize, devitalize, hardkill, softkill } op;
 
-	if (argc > 3) goto usage;
-	if (argc == 1)
+	const char* winp = argv[2];
+	if (argc >  3) goto usage; // nope
+	if (argc == 1) // no parameters, implied softkill on active win
 		op = softkill, active = true;
 	else {
-		if (argc == 2) active = true;
-		else           active = false;
+		if (argc == 2) { // single argument; what kind is it?
+			if (isnum(argv[1])) { // single numeric argument = win id 
+				active = false; // window is specified for us
+				op     = softkill; // implied softkill
+				winp   = argv[1]; // interpret argv[1] as window id
+				goto   go_go_go; // skip the rest of this nonsense;
+					// we already know there's no switch
+			} else {
+				active = true; // no number passed, so it's either a
+				// switch with an implied active window or bad syntax
+				// now we need to figure out which
+			}
+		} else if (argc == 3) active = false; // win id AND opt
 
+		// determine mission parameters
 		if (argv[1][0] == '-' && argv[1][2] == 0) { // opt is short switch
 			switch (argv[1][1]) { // opt char
-
 				// make window mission-critical
 				case 'v': op = vitalize; break;
 
 				// make window acceptable loss
 				case 'c': op = devitalize; break;
@@ -82,16 +126,19 @@
 				default: goto usage;
 			}
 		} else goto usage;
 	}
 
+go_go_go:
 	display = XOpenDisplay(NULL);
+	xvital = XInternAtom(display, "_k_vital", False);
+	XSetErrorHandler(bad);
 
 	if (active) {
 		XGetInputFocus(display, &focus, &revert);
 	} else {
-		unsigned long temp = strtoul(argv[2], NULL, 0);
+		unsigned long temp = strtoul(winp, NULL, 0);
 		if (errno == EINVAL || errno == ERANGE) goto usage;
 		if (temp == 0) goto usage;
 		focus = (Window)temp;
 	}
 
@@ -99,45 +146,32 @@
 		killwin(focus);
 		XSync(display,false);
 		return 0;
 	}
 
-	XClassHint xclh;
-	if (XGetClassHint(display,focus,&xclh)) {
-		char* v;
-		if(v = isvital(xclh.res_class)) {
-
-			if (op == vitalize) return 0; // nothing need be done
-			else if (op == devitalize) {
-				strcpy(v, v+3);
-				XSetClassHint(display,focus,&xclh);
-				XSync(display,false);
-			} else if (op == softkill) {
-				fprintf(stderr, "softkill forbidden\n");
-				return 1; // ACCESS DENIED
-			}
-		} else {
-			if (op == vitalize) {
-				size_t sz=strlen(xclh.res_class); // TODO: remove double-walk
-				xclh.res_class=realloc(xclh.res_class, sz+4);
-				xclh.res_class[sz]='{';
-				xclh.res_class[sz+1]='V';
-				xclh.res_class[sz+2]='}';
-				xclh.res_class[sz+3]=0;
-				XSetClassHint(display,focus,&xclh);
-				XSync(display,false);
-			} else if (op == devitalize) return 0;
-			else if (op == softkill) {
-				// ice that motherfucker
-				killwin(focus);
-				XSync(display,false);
-				return 3;
-			}
+	char* v;
+	if(isvital(focus)) {
+		if        (op == vitalize) return 0; // nothing need be done
+		else if   (op == devitalize) {
+			XDeleteProperty(display, focus, xvital);
+			XSync(display,false);
+		} else if (op == softkill) {
+			fprintf(stderr, "softkill forbidden\n");
+			return 1; // ACCESS DENIED
 		}
 	} else {
-		fprintf(stderr,"\x1b[1merror:\x1b[m bad window\n");
-		goto usage;
+		if        (op == vitalize) {
+			char* yes="\01"; //arbitrary
+			XChangeProperty(display,focus, xvital,xvital,8,PropModeReplace, yes, 1);
+			XSync(display,false);
+		} else if (op == devitalize) return 0;
+		else if   (op == softkill) {
+			// ice that motherfucker
+			killwin(focus);
+			XSync(display,false);
+			return 3;
+		}
 	}
 
 	return 0;
 
 usage: