notcurses_cell(3)

nick black

v1.7.4

NAME

notcurses_cell - operations on notcurses cells

SYNOPSIS

#include <notcurses/notcurses.h>

// See DESCRIPTION below for information on EGC encoding
typedef struct cell {
  uint32_t gcluster;          // 4B → 4B
  uint8_t gcluster_backstop;  // 1B → 5B (8 bits of zero)
  uint8_t reserved;           // 1B → 6B (8 reserved bits, ought be zero)
  uint16_t stylemask;         // 2B → 8B (16 bits of NCSTYLE_* attributes)
  uint64_t channels;
} cell;

#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 CELL_WIDEASIAN_MASK     0x8000000080000000ull
#define CELL_BGDEFAULT_MASK     0x0000000040000000ull
#define CELL_FGDEFAULT_MASK     (CELL_BGDEFAULT_MASK << 32u)
#define CELL_BG_RGB_MASK        0x0000000000ffffffull
#define CELL_FG_RGB_MASK        (CELL_BG_MASK << 32u)
#define CELL_BG_PALETTE         0x0000000008000000ull
#define CELL_FG_PALETTE         (CELL_BG_PALETTE << 32u)
#define CHANNEL_ALPHA_MASK      0x30000000ull
#define CELL_ALPHA_HIGHCONTRAST 0x30000000ull
#define CELL_ALPHA_TRANSPARENT  0x20000000ull
#define CELL_ALPHA_BLEND        0x10000000ull
#define CELL_ALPHA_OPAQUE       0x00000000ull

void cell_init(cell* c);

int cell_load(struct ncplane* n, cell* c, const char* gcluster);

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

int cell_duplicate(struct ncplane* n, cell* targ, const cell* c);

void cell_release(struct ncplane* n, cell* c);

void cell_styles_set(cell* c, unsigned stylebits);

unsigned cell_styles(const cell* c);

void cell_styles_on(cell* c, unsigned stylebits);

void cell_styles_off(cell* c, unsigned stylebits);

void cell_set_fg_default(cell* c);

void cell_set_bg_default(cell* c);

int cell_set_fg_alpha(cell* c, unsigned alpha);

int cell_set_bg_alpha(cell* c, unsigned alpha);

bool cell_double_wide_p(const cell* c);

const char* cell_extended_gcluster(const struct ncplane* n, const cell* c);

char* cell_strdup(const struct ncplane* n, const cell* c);

int cell_load_simple(struct ncplane* n, cell* c, char ch);

char* cell_extract(const struct ncplane* n, const cell* c, uint16_t* stylemask, uint64_t* channels);

uint32_t cell_bchannel(const cell* cl);

uint32_t cell_fchannel(const cell* cl);

uint64_t cell_set_bchannel(cell* cl, uint32_t channel);

uint64_t cell_set_fchannel(cell* cl, uint32_t channel);

uint32_t cell_fg_rgb(const cell* cl);

uint32_t cell_bg_rgb(const cell* cl);

unsigned cell_fg_alpha(const cell* cl);

unsigned cell_bg_alpha(const cell* cl);

unsigned cell_fg_rgb8(const cell* cl, unsigned* r, unsigned* g, unsigned* b);

unsigned cell_bg_rgb8(const cell* cl, unsigned* r, unsigned* g, unsigned* b);

int cell_set_fg_rgb8(cell* cl, int r, int g, int b);

int cell_set_bg_rgb8(cell* cl, int r, int g, int b);

void cell_set_fg_rgb8_clipped(cell* cl, int r, int g, int b);

void cell_set_bg_rgb8_clipped(cell* cl, int r, int g, int b);

int cell_set_fg_rgb(cell* c, uint32_t channel);

int cell_set_bg_rgb(cell* c, uint32_t channel);

bool cell_fg_default_p(const cell* cl);

bool cell_bg_default_p(const cell* cl);

int ncstrwidth(const char* text);

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 cells.

Each cell 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 cell’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 cells 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 cell_load(), cell_prime(), or cell_duplicate(). All of these functions first call cell_release(), as does cell_load_simple(). When done using a cell entirely, call cell_release(). ncplane_destroy() will free up the memory used by the cell, but the backing egcpool has a maximum size of 16MiB, and failure to release cells can eventually block new output.

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

RETURN VALUES

cell_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.

cell_set_fg_rgb8() and similar functions will return -1 if provided invalid inputs, and 0 otherwise.

SEE ALSO

notcurses(3), notcurses_channels(3), notcurses_plane(3), notcurses_output(3)