input: make the Ctrl+Arrow keys work on a Linux console

If this breaks your build, please send report or instructions or patch.

src/global.c

@@ -33,6 +33,8 @@ volatile sig_atomic_t sigwinch_counter = 0;
 	/* Is incremented by the handler whenever a SIGWINCH occurs. */
 #endif
 
+bool console;
+	/* Whether we're running on a Linux VC (TRUE) or under X (FALSE). */
 bool meta_key;
 	/* Whether the current keystroke is a Meta key. */
 bool focusing = TRUE;

src/nano.c

@@ -2482,6 +2482,9 @@ int main(int argc, char **argv)
     /* Set up the terminal state. */
     terminal_init();
 
+    /* Check whether we're running on a Linux console. */
+    console = (getenv("DISPLAY") == NULL);
+
 #ifdef DEBUG
     fprintf(stderr, "Main: set up windows\n");
 #endif

src/proto.h

@@ -30,6 +30,7 @@
 extern volatile sig_atomic_t sigwinch_counter;
 #endif
 
+extern bool console;
 extern bool meta_key;
 extern bool focusing;
 

src/winio.c

@@ -23,6 +23,8 @@
 #include "proto.h"
 #include "revision.h"
 
+#include <sys/ioctl.h>
+
 #include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
@@ -502,6 +504,24 @@ int parse_kbinput(WINDOW *win)
 	return sc_seq_or(do_next_block, 0);
 #endif
 
+    /* When not running under X, check for the bare arrow keys whether
+     * the Ctrl key is being held together with them. */
+    if (console && (retval == KEY_UP || retval == KEY_DOWN ||
+			retval == KEY_LEFT || retval == KEY_RIGHT)) {
+	unsigned char modifiers = 6;
+
+	if (ioctl(0, TIOCLINUX, &modifiers) >= 0 && (modifiers & 0x04)) {
+	    if (retval == KEY_UP)
+		return sc_seq_or(do_prev_block, 0);
+	    else if (retval == KEY_DOWN)
+		return sc_seq_or(do_next_block, 0);
+	    else if (retval == KEY_LEFT)
+		return sc_seq_or(do_prev_word_void, 0);
+	    else
+		return sc_seq_or(do_next_word_void, 0);
+	}
+    }
+
     switch (retval) {
 #ifdef KEY_SLEFT
 	/* Slang doesn't support KEY_SLEFT. */