Set default lock command to vlock on Linux if present at build time, from Josh

Boyer in GitHub issue 3527.

Makefile.am

@@ -14,6 +14,7 @@ dist_EXTRA_tmux_SOURCES = compat/*.[ch]
 AM_CPPFLAGS += @XOPEN_DEFINES@ \
 	-DTMUX_VERSION='"@VERSION@"' \
 	-DTMUX_CONF='"$(sysconfdir)/tmux.conf:~/.tmux.conf:$$XDG_CONFIG_HOME/tmux/tmux.conf:~/.config/tmux/tmux.conf"' \
+	-DTMUX_LOCK_CMD='"@DEFAULT_LOCK_CMD@"' \
 	-DTMUX_TERM='"@DEFAULT_TERM@"'
 
 # Additional object files.

configure.ac

@@ -936,6 +936,19 @@ AM_CONDITIONAL(IS_HPUX, test "x$PLATFORM" = xhpux)
 AM_CONDITIONAL(IS_HAIKU, test "x$PLATFORM" = xhaiku)
 AM_CONDITIONAL(IS_UNKNOWN, test "x$PLATFORM" = xunknown)
 
+# Set the default lock command
+DEFAULT_LOCK_CMD="lock -np"
+AC_MSG_CHECKING(lock-command)
+if test "x$PLATFORM" = xlinux; then
+	AC_CHECK_PROG(found_vlock, vlock, yes, no)
+	if test "x$found_vlock" = xyes; then
+		DEFAULT_LOCK_CMD="vlock"
+	fi
+fi
+AC_MSG_RESULT($DEFAULT_LOCK_CMD)
+AC_SUBST(DEFAULT_LOCK_CMD)
+
+
 # Save our CFLAGS/CPPFLAGS/LDFLAGS for the Makefile and restore the old user
 # variables.
 AC_SUBST(AM_CPPFLAGS)

options-table.c

@@ -530,7 +530,7 @@ const struct options_table_entry options_table[] = {
 	{ .name = "lock-command",
 	  .type = OPTIONS_TABLE_STRING,
 	  .scope = OPTIONS_TABLE_SESSION,
-	  .default_str = "lock -np",
+	  .default_str = TMUX_LOCK_CMD,
 	  .text = "Shell command to run to lock a client."
 	},
 

tmux.h

@@ -81,6 +81,9 @@ struct winlink;
 #ifndef TMUX_TERM
 #define TMUX_TERM "screen"
 #endif
+#ifndef TMUX_LOCK_CMD
+#define TMUX_LOCK_CMD "lock -np"
+#endif
 
 /* Minimum layout cell size, NOT including border lines. */
 #define PANE_MINIMUM 1