notcurses_input(3)

nick black

v1.7.4

NAME

notcurses_input - input via notcurses

SYNOPSIS

#include <notcurses/notcurses.h>

struct timespec;
struct notcurses;

typedef struct ncinput {
  char32_t id;     // Unicode codepoint
  int y;           // Y cell coordinate of event, -1 for undefined
  int x;           // X cell coordinate of event, -1 for undefined
  bool alt;        // Was Alt held during the event?
  bool shift;      // Was Shift held during the event?
  bool ctrl;       // Was Ctrl held during the event?
  uint64_t seqnum; // Monotonically increasing input event counter
} ncinput;

bool nckey_mouse_p(char32_t r);

char32_t notcurses_getc(struct notcurses* n, const struct timespec* ts, sigset_t* sigmask, ncinput* ni);

char32_t notcurses_getc_nblock(struct notcurses* n, ncinput* ni);

char32_t notcurses_getc_blocking(struct notcurses* n, ncinput* ni);

int notcurses_mouse_enable(struct notcurses* n);

int notcurses_mouse_disable(struct notcurses* n);

int notcurses_inputready_fd(struct notcurses* n);

DESCRIPTION

notcurses supports input from keyboards and mice, and any device that looks like them. Mouse support requires a broker such as GPM, Wayland, or Xorg, and must be explicitly enabled via notcurses_mouse_enable. The full 32-bit range of Unicode is supported (see unicode(7)), with synthesized events mapped into the Supplementary Private Use Area-B. Unicode characters are returned directly as UCS-32, one codepoint at a time.

notcurses takes its keyboard input from stdin, which will be placed into non-blocking mode for the duration of operation. The terminal is put into raw mode (see cfmakeraw(3)), and thus keys are received without line-buffering. notcurses maintains its own buffer of input characters, which it will attempt to fill whenever it reads.

notcurses_getc allows a struct timespec to be specified as a timeout. If ts is NULL, notcurses_getc will block until it reads input, or is interrupted by a signal. If its values are zeroes, there will be no blocking. Otherwise, ts specifies a minimum time to wait for input before giving up. On timeout, 0 is returned. Signals in sigmask will be masked and blocked in the same manner as a call to ppoll(2). sigmask may be NULL. Event details will be reported in ni, unless ni is NULL.

notcurses_inputready_fd provides a file descriptor suitable for use with I/O multiplexors such as poll(2). This file descriptor might or might not be the actual input file descriptor. If it readable, notcurses_getc can be called without the possibility of blocking.

Mice

For mouse events, the additional fields y and x are set. These fields are not meaningful for keypress events. Mouse events can be distinguished using the nckey_mouse_p predicate. Once enabled, mouse button presses are detected, as are mouse motions made while a button is held down. If no button is depressed, mouse movement does not result in events. This is known as “button-event tracking” mode in the nomenclature of Xterm Control Sequences.

Synthesized keypresses

Many keys do not have a Unicode representation, let alone ASCII. Examples include the modifier keys (Alt, Meta, etc.), the “function” keys, and the arrow keys on the numeric keypad. The special keys available to the terminal are defined in the terminfo(5) entry, which notcurses loads on startup. Upon receiving an escape code matching a terminfo input capability, notcurses synthesizes a special value. An escape sequence must arrive in its entirety to notcurses; running out of input in the middle of an escape sequence will see it rejected. Likewise, any error while handling an escape sequence will see the lex aborted, and the sequence thus far played back as independent literal keystrokes.

The full list of synthesized keys (there are well over one hundred) can be found in <notcurses/notcurses.h>. For more details, consult terminfo(5).

NCKEY_RESIZE

Unless the SIGWINCH handler has been inhibited (see notcurses_init), notcurses will automatically catch screen resizes, and synthesize an NCKEY_RESIZE event. Upon receiving this event, the user may call notcurses_refresh to force an immediate reflow, or just wait until the next call to notcurses_render, when notcurses will pick up the resize itself. If the SIGWINCH handler is inhibited, NCKEY_RESIZE is never generated.

RETURN VALUES

On error, the **_getc** family of functions returns (char32_t)-1. The cause of the error may be determined using errno(3). Unless the error was a temporary one (especially e.g. EINTR), notcurses_getc probably cannot be usefully called forthwith. On a timeout, 0 is returned. Otherwise, the UCS-32 value of a Unicode codepoint, or a synthesized event, is returned.

notcurses_mouse_enable returns 0 on success, and non-zero on failure, as does notcurses_mouse_disable.

NOTES

Like any other notcurses function, it is an error to call notcurses_getc during or after a call to notcurses_stop. If a thread is always sitting on blocking input, it can be tricky to guarantee that this doesn’t happen.

Only one thread may call into the input stack at once, but unlike almost every other function in notcurses, notcurses_getc and friends can be called concurrently with notcurses_render.

Do not simply poll the input file descriptor. Instead, use the file descriptor returned by notcurses_inputready_fd to ensure compatibility with future versions of Notcurses (it is possible that future versions will process input in their own contexts).

BUGS

Failed escape sequences are not yet played back in their entirety; only an ESC (ASCII 0x1b) will be seen by the application.

The Shift key is only indicated in conjunction with mouse button presses. If e.g. Shift is used to generate a capital letter ‘A’, id will equal ‘A’, and shift will be false. This should be fixed in the future.

When Ctrl is pressed along with a letter, the letter will currently always be reported in its uppercase form. E.g., if Shift, Ctrl, and ‘a’ are all pressed, this is indistinguishable from Ctrl and ‘a’ without Shift. This should be fixed in the future.

Ctrl pressed along with ‘J’ or ‘M’, whether Shift is pressed or not, currently registers as NCKEY_ENTER. This will likely change in the future.

SEE ALSO

poll(2), cfmakeraw(3), notcurses(3), notcurses_refresh(3), notcurses_render(3), termios(3), terminfo(5), ascii(7), signal(7), unicode(7)