notcurses_input - Man Page

input via notcurses

Synopsis

#include <notcurses/notcurses.h>

struct timespec;
struct notcurses;

typedef struct ncinput {
  uint32_t id;     // Unicode codepoint
  int y;           // Y cell coordinate of event, -1 for undefined
  int x;           // X cell coordinate of event, -1 for undefined
  char utf8[5];    // utf8 representation, when one exists
  bool alt;        // Was Alt held during the event?
  bool shift;      // Was Shift held during the event?
  bool ctrl;       // Was Ctrl held during the event?
  enum {
    EVTYPE_UNKNOWN,
    EVTYPE_PRESS,
    EVTYPE_REPEAT,
    EVTYPE_RELEASE,
  } evtype;
  int ypx, xpx;    // pixel offsets within cell, -1 for undefined
  unsigned modifiers;
} ncinput;

#define NCMICE_NO_EVENTS     0
#define NCMICE_MOVE_EVENT    0x1
#define NCMICE_BUTTON_EVENT  0x2
#define NCMICE_DRAG_EVENT    0x4
#define NCMICE_ALL_EVENTS    0x7

bool nckey_mouse_p(uint32_t r);

bool ncinput_nomod_p(const ncinput* ni);

uint32_t notcurses_get(struct notcurses* n, const struct timespec* ts, ncinput* ni);

int notcurses_getvec(struct notcurses* n, const struct timespec* ts, ncinput* ni, int vcount);

uint32_t notcurses_get_nblock(struct notcurses* n, ncinput* ni);

uint32_t notcurses_get_blocking(struct notcurses* n, ncinput* ni);

int cnotcurses_mice_enable(struct notcurses* n, unsigned eventmask);

int notcurses_mice_disable(struct notcurses* n);

int notcurses_inputready_fd(struct notcurses* n);

static inline bool ncinput_equal_p(const ncinput* n1, const ncinput* n2);

int notcurses_linesigs_disable(struct notcurses* n);

int notcurses_linesigs_enable(struct notcurses* n);

bool ncinput_shift_p(const struct ncinput* n);

bool ncinput_ctrl_p(const struct ncinput* n);

bool ncinput_alt_p(const struct ncinput* n);

bool ncinput_meta_p(const struct ncinput* 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_mice_enable. The full 32-bit range of Unicode is supported (see unicode(7)), with synthesized events mapped above the 1,114,112 codepoints of Unicode 14.0's seventeen Planes. Unicode characters are returned directly as UCS-32, one codepoint at a time. When the input has a UTF8 representation, it is written to utf8; this field is always NUL-terminated.

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 non-canonical mode (see termios(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_get allows a struct timespec to be specified as a timeout. If ts is NULL, notcurses_get 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 an absolute deadline (taken against CLOCK_MONOTONIC; see clock_gettime(2)). On timeout, 0 is returned. 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_get can be called without the possibility of blocking.

ncinput_equal_p compares two ncinput structs for data equality (i.e. not considering padding), returning true if they represent the same input (though not necessarily the same input event).

notcurses_linesigs_disable disables conversion of inputs INTR, QUIT, SUSP, and DSUSP into SIGINT, SIGQUIT, and SIGTSTP. These conversions are enabled by default. notcurses_linesigs_enable undoes this action, but signals in the interim are permanently lost.

ncinput_shift_p, ncinput_ctrl_p, ncinput_alt_p, and ncinput_meta_p test n to see if the relevant modifier is set. This is preferably to directly accessing the struct members.

Mice

For mouse events, the additional fields y, x, ypx, and xpx are set. These fields are not meaningful for keypress events. Mouse events can be distinguished using the nckey_mouse_p predicate. NCMICE_MOVE_EVENT requests events whenever the mouse moves when no buttons are held down. NCMICE_DRAG_EVENT requests events when the mouse is moving with buttons held down. NCMICE_BUTTON_EVENT requests events then the button state changes. NCMICE_ALL_EVENTS is provided for convenience and future-proofing against API (though not ABI) changes.

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.

Nckey_signal

Unless the SIGWINCH handler has been inhibited (see notcurses_init), Notcurses will catch SIGCONT, and synthesize an NCKEY_SIGNAL event. This typically indicates that the program has been restarted after being paused or placed in the background. The next rasterization will be a full rebuild of the screen, as if notcurses_refresh had been called; the user might wish to immediately call notcurses_refresh themselves.

Nckey_eof

Upon reaching the end of input, NCKEY_EOF will be returned. At this point, any further calls will immediately return NCKEY_EOF. Note that this does not necessarily result from pressing e.g. Ctrl+D.

Return Values

On error, the get family of functions return (uint32_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_get 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.

If an error is encountered before notcurses_getvec has read any input, it will return -1. If it times out before reading any input, it will return 0. Otherwise, it returns the number of ncinput objects written back.

notcurses_mice_enable returns 0 on success, and non-zero on failure, as does notcurses_mice_disable. Success does not necessarily mean that a mouse is available nor that all requested events will be generated.

ncinput_equal_p returns true if the two ncinput structs represent the same input (though not necessarily the same input event), and false otherwise.

Notes

Like any other notcurses function, it is an error to call notcurses_get 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_get and friends can be called concurrently with notcurses_render.

Do not simply poll the file descriptor associated with stdin to test for input readiness. 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).

The full list of synthesized events is available in <notcurses/nckeys.h>.

In API4, the various bool modifier fields will go away, and these statuses will be merged into the modifiers bitmask. You are encouraged to use ncinput_shift_p and friends to future-proof your code.

Bugs

Notcurses attempts to use the XTMODKEYS and Kitty keyboard disambiguation protocols. When supported, they eliminate most of these issues.

The Shift key is traditionally not indicated in conjunction with typical Unicode text. If e.g. Shift is used to generate a capital letter 'A', id will equal 'A', and shift will be false. Similarly, 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'.

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.

When the Kitty keyboard disambiguation protocol is used, most of these issues are resolved. You can determine whether the protocol is in use by examining the output of notcurses-info(1). If the kbd property is indicated, you're using the Kitty protocol.

Mouse events in the left margins will never be delivered to the application (as is intended), but mouse events in the bottom and right margins sometimes can be if the event occurs prior to a window resize.

The ypx and xpx fields are never currently valid (i.e. they are always -1). This ought be fixed in the future using the SGR PixelMode mouse protocol.

On some operating systems, CLOCK_REALTIME is used as the basis for timeouts instead of CLOCK_MONOTONIC. This ought be fixed.

See Also

notcurses-info(1), clock_gettime(2), poll(2), notcurses(3), notcurses_refresh(3), notcurses_render(3), termios(3), terminfo(5), ascii(7), signal(7), unicode(7)

Authors

nick black <nickblack@linux.com>.

Referenced By

notcurses(3), notcurses_init(3), notcurses-input(1), notcurses_menu(3), notcurses_multiselector(3), notcurses_reader(3), notcurses_reel(3), notcurses_refresh(3), notcurses_render(3), notcurses_selector(3), notcurses_tree(3).

v3.0.4