NAME

notcurses - TUI library for modern terminal emulators

SYNOPSIS

#include <notcurses.h>

-lnotcurses

DESCRIPTION

notcurses builds atop the terminfo(5) abstraction layer to provide reasonably portable vivid character displays. It is an intellectual descendant of ncurses(3NCURSES), but goes beyond that library (and the X/Open Curses API it implements). notcurses is capable of subregion fades, 24bpp DirectColor, transparency, multimedia, and safe multithreaded use.

A program wishing to use notcurses will need to link it, ideally using the output of pkg-config --libs notcurses (see pkg-config(1)). It is advised to compile with the output of pkg-config --cflags notcurses. If using CMake, a support file is provided, and can be accessed as notcurses (see cmake(1)).

notcurses_init(3) can then be used to initialize a notcurses instance for a given FILE (usually stdout), after calling setlocale(3) to prepare a UTF-8 locale (see [Construction][]).

Construction

Before calling into notcurses—and usually as one of the first calls of the program—be sure to call setlocale with an appropriate UTF-8 LC_ALL locale. It is usually appropriate to use setlocale(LC_ALL, ""), relying on the user to properly set the LANG environment variable. notcurses will refuse to start if nl_langinfo(3) doesn't indicate UTF-8.

notcurses_init(3) accepts a struct notcurses_options allowing fine-grained control of notcurses behavior, including signal handlers, alternative screens, and overriding the TERM environment variable. A terminfo entry appropriate for the actual terminal must be available.

Output

All output is performed on struct ncplanes (see [Ncplanes][] below). Output is not visible until explicitly rendered via notcurses_render(3). It is safe to output from multiple threads. Information on drawing functions is available at notcurses_output(3).

Input

notcurses supports input from keyboards (via stdin) and pointing devices (via a broker such as GPM, X, or Wayland). Input is delivered as 32-bit Unicode code points. Synthesized events such as mouse button presses and arrow keys are mapped into Unicode's Supplementary Private Use Area-B. Information on input is available at notcurses_input(3).

Ncplanes

Following initialization, a single ncplane exists, the "standard plane" (see notcurses_stdplane(3)). This plane cannot be destoyed nor manually resized, and is always exactly as large as the screen. Further ncplanes can be created with ncplane_new(3). A total z-ordering always exists on the set of ncplanes, and new ncplanes are placed at the top of the z-buffer. Ncplanes can be larger, smaller, or the same size as the physical screen, and can be placed anywhere relative to it (including entirely off-screen). Ncplanes are made up of cells (see [Cells][] below). Information on ncplanes is available at notcurses_ncplane(3).

Cells

Cells make up the framebuffers backing each ncplane, one cell per coordinate, one extended grapheme cluster (see unicode(7)) per cell. A cell consists of a gcluster (either a directly-encoded 7-bit ASCII character (see ascii(7)), or a 25-bit index into the ncplane's egcpool), a set of attributes, and two channels (one for the foreground, and one for the background—see notcurses_channels(3)). Information on cells is available at notcurses_cell(3).

It is not usually necessary for users to interact directly with cells. They are typically encountered when retrieving data from ncplanes or the rendered scene (see e.g. ncplane_at_yx(3)), or to achieve peak performance when a particular EGC is heavily reused within a plane.

Threads

Notcurses explicitly supports use in multithreaded environments. Most functions are safe to call concurrently, with exceptions including those which destroy resources (ncplane_destroy(3), ncvisual_destroy(3), notcurses_stop(3), etc.). Multiple threads interacting with the same ncplane will block one another, but threads operating on distinct ncplanes can run concurrently. notcurses_render(3) blocks the majority of functions. Input functions only block other input functions, not ncplane manipulation.

Since multiple threads can concurrently manipulate distinct ncplanes, peak performance sometimes requires dividing the screen into several planes, and manipulating them from multiple threads.

Destruction

Before exiting, notcurses_stop(3) should be called. In addition to freeing up resources, this is necessary to restore the terminal to a state useful for the shell. By default, notcurses_init(3) installs signal handlers to catch all signals which would normally terminate the process. The new handlers will try to call notcurses_stop(3), and then propagate the received signal to the previous action.

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