% notcurses_input(3)
% nick black <nickblack@linux.com>
% v1.5.3

# NAME

notcurses_input - input via notcurses

# SYNOPSIS

**#include <notcurses/notcurses.h>**

```c
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](https://unicode.org/charts/PDF/U1.0.10.pdf).
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](https://www.xfree86.org/current/ctlseqs.html).

## 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)**
