Add xsswin and a README

Makefile

@@ -1,4 +1,6 @@
 CFLAGS = -Wall
-LDLIBS = -lX11 -lXss
+LDLIBS = -lX11
 
-all: xss
+all: xss xsswin
+
+xss: LDLIBS += -lXss

README

@@ -0,0 +1,53 @@
+== xss ==
+
+xss uses the nearly 20-year-old MIT-SCREEN-SAVER extension to launch a
+program when the X server turns on the built-in screen saver.
+
+xsswin makes a full-screen black window and runs some other program,
+passing along the window ID in the environment ($XSS_WINDOW) and
+possibly as an argument (XSS_WINDOW gets replaced with the id).
+
+
+Examples
+--------
+
+Tell the X server to launch the screen saver after 90 seconds idle:
+
+    xset s 90
+
+
+Run like xautolock:
+
+    xss xlock -mode qix &
+
+
+Run like xscreensaver (no locking):
+
+    xss xsswin /usr/lib/xscreensaver/flurry -window-id XSS_WINDOW
+
+
+Shell script to run an xscreensaver hack and xtrlock at the same time:
+
+    #! /bin/sh
+    xsswin /usr/lib/xscreensaver/qix -window-id XSS_WINDOW &
+    pid=$!
+    xtrlock
+    kill $pid
+
+
+History
+-------
+
+AIX apparently had something also called `xss` which did almost exactly
+what my xss does, but had some command-line options.
+
+I'm not aware of anything else like `xsswin`.
+
+I lifted some code from `beforelight` from the X11 distribution, and
+from `slock` from [suckless.org](http://suckless.org/).  Both have a
+BSD/X11-like license.
+
+
+------
+
+Neale Pickett <neale@woozle.org>

xss.c

@@ -15,17 +15,16 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
 #include <signal.h>
 #include <stdio.h>
-#include <stdlib.h>
 
 #include <X11/Xlib.h>
-#include <X11/Xatom.h>
 #include <X11/extensions/scrnsaver.h>
 
+#include "obj.h"
+
 int child = 0;
 
 void
@@ -39,30 +38,22 @@ int
 main(int argc, char *argv[])
 {
   Display *display = NULL;
-  char    *errtxt  = "bummer dude.";
-  Pixmap   blank;
-  int      ss_event, ss_error;
-  Window   root;
-  XEvent   event;
 
   if (argc < 2) {
     fprintf(stderr, "Usage: %s PROGRAM [ARGUMENT ...]\n", argv[0]);
-    exit(1);
+    return 64;                  /* EX_USAGE */
   }
   signal(SIGCHLD, sigchld);
 
-  do {
-    display = XOpenDisplay(NULL);
-    if (! display) {
-      errtxt = "Cannot open display";
-      break;
-    }
-    root = DefaultRootWindow(display);
+  try {
+    int    ss_event, ss_error;
+    XEvent event;
+
+    if (! (display = XOpenDisplay(NULL))) raise("cannot open display");
     if (! XScreenSaverQueryExtension(display, &ss_event, &ss_error)) {
-      errtxt = "X server does not support MIT-SCREEN-SAVER extension.";
-      break;
+      raise("X server does not support MIT-SCREEN-SAVER extension.");
     }
-    XScreenSaverSelectInput(display, root, ScreenSaverNotifyMask);
+    XScreenSaverSelectInput(display, DefaultRootWindow(display), ScreenSaverNotifyMask);
     while (! XNextEvent(display, &event)) {
       if (event.type == ss_event) {
         XScreenSaverNotifyEvent *sevent = (XScreenSaverNotifyEvent *)&event;
@@ -79,16 +70,15 @@ main(int argc, char *argv[])
         }
       }
     }
-    errtxt = NULL;
   } while (0);
 
   if (display) {
-    (void)XFreePixmap(display, blank);
     (void)XCloseDisplay(display);
   }
-  if (errtxt) {
-    fprintf(stderr, "Error: %s\n", errtxt);
-    return 1;
+
+  except {
+    fprintf(stderr, "Error: %s\n", exception);
+    return 69;                  /* EX_UNAVAILABLE */
   }
 
   return 0;

xsswin.c

@@ -0,0 +1,104 @@
+/* xsswin -- create a screensaver window
+ * Copyright (C) 2008  Neale Pickett <neale@woozle.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#include <X11/Xlib.h>
+
+#include "obj.h"
+
+int
+main(int argc, char * const argv[])
+{
+  Display *display;
+  Cursor   invisible;
+  Pixmap   pmap;
+  Window   w;
+
+  if (argc < 2) {
+    fprintf(stderr, "Usage: %s PROGRAM [ARGUMENT ...]\n", argv[0]);
+    return 64;                  /* EX_USAGE */
+  }
+
+  try {
+    int                  screen;
+    XSetWindowAttributes wa;
+    Window               root;
+    XColor               black;
+    int                  child;
+
+    zero(wa);
+    zero(black);
+
+    if (! (display = XOpenDisplay(NULL))) raise("cannot open display");
+    screen = DefaultScreen(display);
+    root = RootWindow(display, screen);
+
+    wa.override_redirect = 1;
+    wa.background_pixel = BlackPixel(display, screen);
+    w = XCreateWindow(display, root,
+                      0, 0,
+                      DisplayWidth(display, screen), DisplayHeight(display, screen), 0,
+                      CopyFromParent, InputOutput, CopyFromParent,
+                      CWOverrideRedirect | CWBackPixel,
+                      &wa);
+    XAllocColor(display, DefaultColormap(display, screen), &black);
+    pmap = XCreateBitmapFromData(display, w, "\0", 1, 1);
+    invisible = XCreatePixmapCursor(display, pmap, pmap, &black, &black, 0, 0);
+    XDefineCursor(display, w, invisible);
+    XMapRaised(display, w);
+    XSync(display, False);
+
+    child = fork();
+    if (0 == child) {
+      char *nargv[argc + 1];
+      char id[50];
+      int i;
+
+      (void)snprintf(id, sizeof(id), "0x%lx", (unsigned long)w);
+      (void)setenv("XSS_WINDOW", id, 1);
+      for (i = 0; i < argc; i += 1) {
+        if (0 == strcmp(argv[i], "XSS_WINDOW")) {
+          nargv[i] = id;
+        } else {
+          nargv[i] = argv[i];
+        }
+      }
+      nargv[argc] = NULL;
+      (void)execvp(nargv[1], nargv + 1);
+      perror("exec");
+      exit(1);
+    }
+
+    /* XXX: maybe important to also watch for X events? */
+    (void)waitpid(-1, NULL, 0);
+  }
+
+  if (display) {
+    (void)XUndefineCursor(display, w);
+    (void)XFreePixmap(display, pmap);
+    (void)XCloseDisplay(display);
+  }
+
+  except {
+    fprintf(stderr, "Error: %s\n", exception);
+    return 69;                  /* EX_UNAVAILABLE */
+  }
+  return 0;
+}