Implement logic to get FreeBSD ttyv device names.

In FreeBSD the virtual terminals used for Xorg are named ttyv.

Their device numbers are also base32 encoded.

Code mostly taken from swaywm/wlroots@fc6c0ca

src/x-server.c

@@ -181,13 +181,60 @@ x_server_connect_session (DisplayServer *display_server, Session *session)
         g_autofree gchar *tty_text = NULL;
         g_autofree gchar *vt_text = NULL;
 
+#ifdef __FreeBSD__
+        char vty_num32[6];
+        int num;
+        const int base = 32;
+        size_t offset = 0;
+
+        num = vt - 1;
+
+        if (num == 0) {
+            vty_num32[offset++] = '0';
+            vty_num32[offset] = '\0';
+        } else {
+            for (int remaning = num; remaning > 0; remaning /= base, offset++) {
+                if (offset + 1 >= 6) {
+                    g_error ("tty number buffer too small");
+                    goto error;
+                }
+
+                const int value = remaning % base;
+                if (value >= 10) {
+                    vty_num32[offset] = 'a' + value - 10;
+                } else {
+                    vty_num32[offset] = '0' + value;
+                }
+            }
+
+            for (size_t i = 0; i < offset / 2; i++) {
+                const size_t p1 = i;
+                const size_t p2 = offset - 1 - i;
+                const char tmp = vty_num32[p1];
+                vty_num32[p1] = vty_num32[p2];
+                vty_num32[p2] = tmp;
+            }
+
+            vty_num32[offset] = '\0';
+        }
+
+        tty_text = g_strdup_printf ("/dev/ttyv%s", vty_num32);
+#else
         tty_text = g_strdup_printf ("/dev/tty%d", vt);
+#endif
         session_set_tty (session, tty_text);
 
+#ifdef __FreeBSD__
+        vt_text = g_strdup_printf ("%d", num);
+#else
         vt_text = g_strdup_printf ("%d", vt);
+#endif
         session_set_env (session, "XDG_VTNR", vt_text);
     }
     else
+#ifdef __FreeBSD__
+error:
+#endif
         l_debug (session, "Not setting XDG_VTNR");
 
     session_set_env (session, "DISPLAY", x_server_get_address (X_SERVER (display_server)));