notcurses_cell(3)

NAME

notcurses_cell - operations on nccell objects

SYNOPSIS

#include <notcurses/notcurses.h>

    // See DESCRIPTION below for information on EGC encoding
    typedef struct nccell {
      uint32_t gcluster;          // 4B → 4B
      uint8_t gcluster_backstop;  // 1B → 5B (8 bits of zero)
      uint8_t width;              // 1B → 6B (8 bits of column width)
      uint16_t stylemask;         // 2B → 8B (16 bits of NCSTYLE_* attributes)
      uint64_t channels;
    } nccell;
    #define CELL_TRIVIAL_INITIALIZER \
     { .gcluster = '\0', .stylemask = 0, .channels = 0, }
    #define CELL_SIMPLE_INITIALIZER(c) \
     { .gcluster = (c), .stylemask = 0, .channels = 0, }
    #define CELL_INITIALIZER(c, s, chan) \
     { .gcluster = (c), .stylemask = (s), .channels = (chan), }
    #define NCALPHA_HIGHCONTRAST  0x30000000ull
    #define NCALPHA_TRANSPARENT   0x20000000ull
    #define NCALPHA_BLEND         0x10000000ull
    #define NCALPHA_OPAQUE        0x00000000ull

void nccell_init(nccell* c);

int nccell_load(struct ncplane* n, nccell* c, const char* gcluster);

int nccell_prime(struct ncplane* n, nccell* c, const char* gcluster, uint32_t stylemask, uint64_t channels);

int nccell_duplicate(struct ncplane* n, nccell* targ, const nccell* c);

void nccell_release(struct ncplane* n, nccell* c);

int nccell_cols(const nccell* c);

void nccell_styles_set(nccell* c, unsigned stylebits);

unsigned nccell_styles(const nccell* c);

bool nccellcmp(const struct ncplane* n1, const nccell* c1, const struct ncplane* n2, const nccell* c2);

void nccell_on_styles(nccell* c, unsigned stylebits);

void nccell_off_styles(nccell* c, unsigned stylebits);

void nccell_set_fg_default(nccell* c);

void nccell_set_bg_default(nccell* c);

int nccell_set_fg_alpha(nccell* c, unsigned alpha);

int nccell_set_bg_alpha(nccell* c, unsigned alpha);

bool nccell_double_wide_p(const nccell* c);

const char* nccell_extended_gcluster(const struct ncplane* n, const nccell* c);

char* nccell_strdup(const struct ncplane* n, const nccell* c);

int nccell_load_char(struct ncplane* n, nccell* c, char ch);

int nccell_load_egc32(struct ncplane* n, nccell* c, uint32_t egc);

int nccell_load_ucs32(struct ncplane* n, nccell* c, uint32_t u);

char* nccell_extract(const struct ncplane* n, const nccell* c, uint16_t* stylemask, uint64_t* channels);

uint64_t nccell_channels(const nccell* c);

uint32_t nccell_bchannel(const nccell* c);

uint32_t nccell_fchannel(const nccell* c);

uint64_t nccell_set_channels(nccell* c, uint64_t channels);

uint64_t nccell_set_bchannel(nccell* c, uint32_t channel);

uint64_t nccell_set_fchannel(nccell* c, uint32_t channel);

uint32_t nccell_fg_rgb(const nccell* c);

uint32_t nccell_bg_rgb(const nccell* c);

unsigned nccell_fg_alpha(const nccell* c);

unsigned nccell_bg_alpha(const nccell* c);

unsigned nccell_fg_rgb8(const nccell* c, unsigned* r, unsigned* g, unsigned* b);

unsigned nccell_bg_rgb8(const ncell* c, unsigned* r, unsigned* g, unsigned* b);

int nccell_set_fg_rgb8(nccell* c, unsigned r, unsigned g, unsigned b);

int nccell_set_bg_rgb8(nccell* c, unsigned r, unsigned g, unsigned b);

void nccell_set_fg_rgb8_clipped(nccell* c, int r, int g, int b);

void nccell_set_bg_rgb8_clipped(nccell* c, int r, int g, int b);

int nccell_set_fg_rgb(nccell* c, uint32_t channel);

int nccell_set_bg_rgb(nccell* c, uint32_t channel);

bool nccell_fg_default_p(const nccell* c);

bool nccell_bg_default_p(const nccell* c);

int nccell_set_fg_palindex(nccell* cl, unsigned idx);

int nccell_set_bg_palindex(nccell* cl, unsigned idx);

uint32_t nccell_fg_palindex(const nccell* cl);

uint32_t nccell_bg_palindex(const nccell* cl);

bool nccell_fg_palindex_p(const nccell* cl);

bool nccell_bg_palindex_p(const nccell* cl);

int ncstrwidth(const char* text);

int ncstrwidth_valid(const char* text, int* validbytes, int* validwidth);

DESCRIPTION

Cells make up the framebuffer associated with each plane, with one cell per addressable coordinate. You should not usually need to interact directly with nccells.

Each nccell contains exactly one extended grapheme cluster. If the EGC is encoded in UTF-8 with four or fewer bytes (all Unicode codepoints as of Unicode 13 can be encoded in no more than four UTF-8 bytes), it is encoded directly into the nccell's gcluster field, and no additional storage is necessary. Otherwise, the EGC is stored as a nul-terminated UTF-8 string in some backing egcpool. Egcpools are associated with ncplanes, so nccells must be considered associated with ncplanes. Indeed, ncplane_erase destroys the backing storage for all a plane's cells, invalidating them. This association is formed at the time of nccell_load, nccell_prime, or nccell_duplicate. All of these functions first call nccell_release, as do nccell_load_egc32, nccell_load_char, and nccell_load_ucs32. When done using a nccell entirely, call nccell_release. ncplane_destroy will free up the memory used by the nccell, but the backing egcpool has a maximum size of 16MiB, and failure to release nccells can eventually block new output. Writing over an ncplane's cells releases them automatically.

nccell_extended_gcluster provides a nul-terminated handle to the EGC. This ought be considered invalidated by changes to the nccell or egcpool. The handle is not heap-allocated; do not attempt to free(3) it. A heap-allocated copy can be acquired with nccell_strdup.

ncstrwidth_valid returns the number of columns occupied by a valid UTF-8 string, or -1 if an error is encountered. In either case, the number of valid bytes and columns, respectively, consumed before error into validbytes and validwidth (assuming them to not be NULL).

nccell_fg_palindex extracts the palette index from a cell's foreground channel. The channel must be palette-indexed, or the return value is meaningless. Verify palette indexing with nccell_fg_palindex_p. A cell's foreground channel can be set to palette-indexed mode (and have the index set) with nccell_set_fg_palindex. The index must be less than NCPALETTESIZE. Replace fg with bg to operate on the background channel.

RETURN VALUES

nccell_load and similar functions return the number of bytes loaded from the EGC, or -1 on failure. They can fail due to either an invalid UTF-8 input, or the backing egcpool reaching its maximum size.

nccell_set_fg_rgb8 and similar functions will return -1 if provided invalid inputs, and 0 otherwise.

nccellcmp returns a negative integer, 0, or a positive integer if c1 is less than, equal to, or more than c2, respectively.

nccell_extended_gcluster returns NULL if called on a sprixel (see notcurses_visual(3).

nccell_cols returns the number of columns occupied by c, according to wcwidth(3)*. ncstrwidth is an equivalent for strings. ncstrwidth_valid returns the same value as ncstrwidth.

NOTES

cell was renamed to nccell in Notcurses 2.2.0, so as not to bleed such a common term into the (single, global) C namespace. cell will be retained as an alias until Notcurses 3.0. Likewise, many functions prefixed with cell have been renamed to start with nccell.

SEE ALSO

notcurses(3), notcurses_channels(3), notcurses_plane(3), notcurses_output(3), notcurses_visual(3), wcwidth(3), utf8(7)

AUTHORS
nick black <nickblack@linux.com>.