1 files changed, 122 insertions, 0 deletions
diff --git a/xkbdlock.c b/xkbdlock.c
new file mode 100644
index 0000000..0cdaedf
--- /dev/null
+++ b/xkbdlock.c
@@ -0,0 +1,122 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <X11/Xlib.h>
+#include <X11/keysym.h>
+
+struct named_mask {
+	const char *name;
+	unsigned int mask;
+};
+
+static const struct named_mask named_masks[] = {
+	{ "Shift", ShiftMask },
+	{ "Control", ControlMask },
+	{ "Ctrl", ControlMask },
+	{ "Alt", Mod1Mask },
+	{ "Super", Mod4Mask },
+	{ "Mod1", Mod1Mask },
+	{ "Mod2", Mod2Mask },
+	{ "Mod3", Mod3Mask },
+	{ "Mod4", Mod4Mask },
+	{ "Mod5", Mod5Mask }
+};
+#define len_named_masks (sizeof(named_masks) / sizeof(*named_masks))
+
+static unsigned int str_to_mask(const char *s)
+{
+	for (size_t i = 0; i < len_named_masks; ++i) {
+		const struct named_mask *m = named_masks + i;
+		if (!strcmp(s, m->name))
+			return m->mask;
+	}
+
+	return 0;
+}
+
+static void die(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+
+	char *s;
+	if (vasprintf(&s, fmt, ap) != -1)
+		fprintf(stderr, "xkbdlock: %s\n", s);
+	else
+		fprintf(stderr, "xkbdlock: unknown error\n");
+
+	va_end(ap);
+	exit(1);
+}
+
+static bool grab_kbd(Display *d, int screen)
+{
+	Window w = RootWindow(d, screen);
+	int res;
+
+	// attempt to grab keyboard for 500ms if already grabbed.
+	// thanks to slock code for the pointer.
+	for (int i = 0;;) {
+		res = XGrabKeyboard(d, w, True, GrabModeAsync, GrabModeAsync,
+			CurrentTime);
+		if (res != AlreadyGrabbed || ++i > 5)
+			break;
+
+		usleep(100000);
+	}
+
+	return (res == GrabSuccess);
+}
+
+static void wait_for_release(Display *d, KeySym key, unsigned int mask)
+{
+	XEvent ev;
+	while (!XNextEvent(d, &ev)) {
+		if (ev.type == KeyPress &&
+				XLookupKeysym(&ev.xkey, 0) == key &&
+				(mask & ev.xkey.state) == mask)
+			break;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	unsigned int mask = 0, arg_mask;
+	KeySym key = NoSymbol, arg_key;
+
+	for (int i = 1; i < argc; ++i) {
+		if ((arg_mask = str_to_mask(argv[i]))) {
+			mask = mask | arg_mask;
+		} else if (key != NoSymbol) {
+			die("more than one non-modifier key provided");
+		} else {
+			if ((arg_key = XStringToKeysym(argv[i])) == NoSymbol)
+				die("unknown key: %s", argv[i]);
+			if (arg_key >= XK_A && arg_key <= XK_Z)
+				die("use Shift modifier for uppercase key: %s",
+					argv[i]);
+			key = arg_key;
+		}
+	}
+
+	if (key == NoSymbol) {
+		if (mask)
+			die("no non-modifier key provided");
+		key = XK_Escape;
+	}
+
+	Display *d = XOpenDisplay(NULL);
+	if (!d)
+		die("cannot open display");
+
+	for (int i = 0; i < ScreenCount(d); ++i) {
+		if (!grab_kbd(d, i))
+			die("failed to grab keyboard");
+	}
+
+	wait_for_release(d, key, mask);
+	return 0;
+}