terminal-util: add terminal_get_cursor_position() helper
This commit is contained in:
Lennart Poettering
+220
-111
@@ -1855,6 +1855,226 @@ int terminal_set_cursor_position(int fd, unsigned row, unsigned column) {
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return loop_write(fd, cursor_position, SIZE_MAX);
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}
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static int terminal_verify_same(int input_fd, int output_fd) {
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assert(input_fd >= 0);
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assert(output_fd >= 0);
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/* Validates that the specified fds reference the same TTY */
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if (input_fd != output_fd) {
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struct stat sti;
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if (fstat(input_fd, &sti) < 0)
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return -errno;
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if (!S_ISCHR(sti.st_mode)) /* TTYs are character devices */
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return -ENOTTY;
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struct stat sto;
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if (fstat(output_fd, &sto) < 0)
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return -errno;
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if (!S_ISCHR(sto.st_mode))
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return -ENOTTY;
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if (sti.st_rdev != sto.st_rdev)
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return -ENOLINK;
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}
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if (!isatty_safe(input_fd)) /* The check above was just for char device, but now let's ensure it's actually a tty */
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return -ENOTTY;
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return 0;
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}
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typedef enum CursorPositionState {
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CURSOR_TEXT,
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CURSOR_ESCAPE,
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CURSOR_ROW,
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CURSOR_COLUMN,
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} CursorPositionState;
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typedef struct CursorPositionContext {
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CursorPositionState state;
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unsigned row, column;
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} CursorPositionContext;
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static int scan_cursor_position_response(
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CursorPositionContext *context,
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const char *buf,
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size_t size,
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size_t *ret_processed) {
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assert(context);
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assert(buf);
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assert(ret_processed);
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for (size_t i = 0; i < size; i++) {
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char c = buf[i];
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switch (context->state) {
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case CURSOR_TEXT:
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context->state = c == '\x1B' ? CURSOR_ESCAPE : CURSOR_TEXT;
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break;
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case CURSOR_ESCAPE:
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context->state = c == '[' ? CURSOR_ROW : CURSOR_TEXT;
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break;
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case CURSOR_ROW:
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if (c == ';')
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context->state = context->row > 0 ? CURSOR_COLUMN : CURSOR_TEXT;
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else {
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int d = undecchar(c);
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/* We read a decimal character, let's suffix it to the number we so far read,
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* but let's do an overflow check first. */
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if (d < 0 || context->row > (UINT_MAX-d)/10)
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context->state = CURSOR_TEXT;
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else
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context->row = context->row * 10 + d;
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}
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break;
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case CURSOR_COLUMN:
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if (c == 'R') {
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if (context->column > 0) {
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*ret_processed = i + 1;
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return 1; /* success! */
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}
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context->state = CURSOR_TEXT;
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} else {
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int d = undecchar(c);
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/* As above, add the decimal character to our column number */
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if (d < 0 || context->column > (UINT_MAX-d)/10)
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context->state = CURSOR_TEXT;
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else
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context->column = context->column * 10 + d;
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}
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break;
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}
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/* Reset any positions we might have picked up */
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if (IN_SET(context->state, CURSOR_TEXT, CURSOR_ESCAPE))
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context->row = context->column = 0;
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}
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*ret_processed = size;
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return 0; /* all good, but not enough data yet */
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}
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int terminal_get_cursor_position(
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int input_fd,
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int output_fd,
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unsigned *ret_row,
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unsigned *ret_column) {
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_cleanup_close_ int nonblock_input_fd = -EBADF;
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int r;
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assert(input_fd >= 0);
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assert(output_fd >= 0);
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if (terminal_is_dumb())
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return -EOPNOTSUPP;
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r = terminal_verify_same(input_fd, output_fd);
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if (r < 0)
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return log_debug_errno(r, "Called with distinct input/output fds: %m");
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struct termios old_termios;
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if (tcgetattr(input_fd, &old_termios) < 0)
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return log_debug_errno(errno, "Failed to get terminal settings: %m");
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struct termios new_termios = old_termios;
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termios_disable_echo(&new_termios);
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if (tcsetattr(input_fd, TCSANOW, &new_termios) < 0)
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return log_debug_errno(errno, "Failed to set new terminal settings: %m");
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/* Request cursor position (DSR/CPR) */
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r = loop_write(output_fd, "\x1B[6n", SIZE_MAX);
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if (r < 0)
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goto finish;
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/* Open a 2nd input fd, in non-blocking mode, so that we won't ever hang in read() should someone
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* else process the POLLIN. */
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nonblock_input_fd = r = fd_reopen(input_fd, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
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if (r < 0)
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goto finish;
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usec_t end = usec_add(now(CLOCK_MONOTONIC), CONSOLE_REPLY_WAIT_USEC);
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char buf[STRLEN("\x1B[1;1R")]; /* The shortest valid reply possible */
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size_t buf_full = 0;
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CursorPositionContext context = {};
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for (bool first = true;; first = false) {
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if (buf_full == 0) {
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usec_t n = now(CLOCK_MONOTONIC);
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if (n >= end) {
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r = -EOPNOTSUPP;
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goto finish;
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}
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r = fd_wait_for_event(nonblock_input_fd, POLLIN, usec_sub_unsigned(end, n));
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if (r < 0)
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goto finish;
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if (r == 0) {
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r = -EOPNOTSUPP;
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goto finish;
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}
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/* On the first try, read multiple characters, i.e. the shortest valid
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* reply. Afterwards read byte-wise, since we don't want to read too much, and
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* unnecessarily drop too many characters from the input queue. */
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ssize_t l = read(nonblock_input_fd, buf, first ? sizeof(buf) : 1);
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if (l < 0) {
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if (errno == EAGAIN)
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continue;
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r = -errno;
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goto finish;
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}
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assert((size_t) l <= sizeof(buf));
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buf_full = l;
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}
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size_t processed;
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r = scan_cursor_position_response(&context, buf, buf_full, &processed);
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if (r < 0)
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goto finish;
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assert(processed <= buf_full);
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buf_full -= processed;
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memmove(buf, buf + processed, buf_full);
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if (r > 0) {
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/* Superficial validity check */
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if (context.row >= 32766 || context.column >= 32766) {
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r = -ENODATA;
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goto finish;
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}
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if (ret_row)
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*ret_row = context.row;
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if (ret_column)
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*ret_column = context.column;
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r = 0;
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goto finish;
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}
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}
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finish:
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RET_GATHER(r, RET_NERRNO(tcsetattr(input_fd, TCSANOW, &old_termios)));
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return r;
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}
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int terminal_reset_defensive(int fd, TerminalResetFlags flags) {
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int r = 0;
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@@ -1894,37 +2114,6 @@ void termios_disable_echo(struct termios *termios) {
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termios->c_cc[VTIME] = 0;
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}
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static int terminal_verify_same(int input_fd, int output_fd) {
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assert(input_fd >= 0);
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assert(output_fd >= 0);
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/* Validates that the specified fds reference the same TTY */
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if (input_fd != output_fd) {
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struct stat sti;
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if (fstat(input_fd, &sti) < 0)
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return -errno;
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if (!S_ISCHR(sti.st_mode)) /* TTYs are character devices */
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return -ENOTTY;
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struct stat sto;
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if (fstat(output_fd, &sto) < 0)
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return -errno;
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if (!S_ISCHR(sto.st_mode))
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return -ENOTTY;
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if (sti.st_rdev != sto.st_rdev)
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return -ENOLINK;
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}
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if (!isatty_safe(input_fd)) /* The check above was just for char device, but now let's ensure it's actually a tty */
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return -ENOTTY;
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return 0;
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}
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typedef enum BackgroundColorState {
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BACKGROUND_TEXT,
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BACKGROUND_ESCAPE,
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@@ -2174,86 +2363,6 @@ finish:
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return r;
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}
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typedef enum CursorPositionState {
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CURSOR_TEXT,
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CURSOR_ESCAPE,
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CURSOR_ROW,
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CURSOR_COLUMN,
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} CursorPositionState;
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typedef struct CursorPositionContext {
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CursorPositionState state;
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unsigned row, column;
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} CursorPositionContext;
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static int scan_cursor_position_response(
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CursorPositionContext *context,
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const char *buf,
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size_t size,
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size_t *ret_processed) {
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assert(context);
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assert(buf);
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assert(ret_processed);
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for (size_t i = 0; i < size; i++) {
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char c = buf[i];
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switch (context->state) {
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case CURSOR_TEXT:
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context->state = c == '\x1B' ? CURSOR_ESCAPE : CURSOR_TEXT;
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break;
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case CURSOR_ESCAPE:
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context->state = c == '[' ? CURSOR_ROW : CURSOR_TEXT;
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break;
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case CURSOR_ROW:
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if (c == ';')
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context->state = context->row > 0 ? CURSOR_COLUMN : CURSOR_TEXT;
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else {
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int d = undecchar(c);
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/* We read a decimal character, let's suffix it to the number we so far read,
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* but let's do an overflow check first. */
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if (d < 0 || context->row > (UINT_MAX-d)/10)
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context->state = CURSOR_TEXT;
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else
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context->row = context->row * 10 + d;
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}
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break;
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case CURSOR_COLUMN:
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if (c == 'R') {
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if (context->column > 0) {
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*ret_processed = i + 1;
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return 1; /* success! */
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}
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context->state = CURSOR_TEXT;
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} else {
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int d = undecchar(c);
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/* As above, add the decimal character to our column number */
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if (d < 0 || context->column > (UINT_MAX-d)/10)
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context->state = CURSOR_TEXT;
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else
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context->column = context->column * 10 + d;
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}
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break;
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}
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/* Reset any positions we might have picked up */
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if (IN_SET(context->state, CURSOR_TEXT, CURSOR_ESCAPE))
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context->row = context->column = 0;
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}
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*ret_processed = size;
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return 0; /* all good, but not enough data yet */
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}
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int terminal_get_size_by_dsr(
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int input_fd,
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int output_fd,
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@@ -46,6 +46,7 @@ int terminal_reset_defensive(int fd, TerminalResetFlags flags);
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int terminal_reset_defensive_locked(int fd, TerminalResetFlags flags);
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int terminal_set_cursor_position(int fd, unsigned row, unsigned column);
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int terminal_get_cursor_position(int input_fd, int output_fd, unsigned *ret_rows, unsigned *ret_column);
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int open_terminal(const char *name, int mode);
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