notcurses/doc/man/man3/notcurses_cell.3.md
nick black 0657267274
v1.5.1
2020-06-14 17:17:49 -04:00

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% notcurses_cell(3)
% nick black <nickblack@linux.com>
% v1.5.1
# NAME
notcurses_cell - operations on notcurses cells
# SYNOPSIS
**#include <notcurses/notcurses.h>**
```c
// See DESCRIPTION below for information on EGC encoding
typedef struct cell {
uint32_t gcluster;
uint32_t attrword;
uint64_t channels;
} cell;
#define CELL_TRIVIAL_INITIALIZER \
{ .gcluster = '\0', .attrword = 0, .channels = 0, }
#define CELL_SIMPLE_INITIALIZER(c) \
{ .gcluster = (c), .attrword = 0, .channels = 0, }
#define CELL_INITIALIZER(c, a, chan) \
{ .gcluster = (c), .attrword = (a), .channels = (chan), }
#define CELL_WIDEASIAN_MASK 0x8000000080000000ull
#define CELL_BGDEFAULT_MASK 0x0000000040000000ull
#define CELL_FGDEFAULT_MASK (CELL_BGDEFAULT_MASK << 32u)
#define CELL_BG_MASK 0x0000000000ffffffull
#define CELL_FG_MASK (CELL_BG_MASK << 32u)
#define CELL_BG_PALETTE 0x0000000008000000ull
#define CELL_FG_PALETTE (CELL_BG_PALETTE << 32u)
#define CELL_ALPHA_MASK 0x0000000030000000ull
#define CELL_ALPHA_SHIFT 28u
#define CELL_ALPHA_HIGHCONTRAST 3
#define CELL_ALPHA_TRANSPARENT 2
#define CELL_ALPHA_BLEND 1
#define CELL_ALPHA_OPAQUE 0
```
**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 attr, 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, int alpha);**
**int cell_set_bg_alpha(cell* c, int alpha);**
**bool cell_double_wide_p(const cell* c);**
**bool cell_simple_p(const cell* c);**
**const char* cell_extended_gcluster(const struct ncplane* n, const cell* c);**
**bool cell_noforeground_p(const cell* c);**
**int cell_load_simple(struct ncplane* n, cell* c, char ch);**
**uint32_t cell_egc_idx(const cell* c);**
**unsigned cell_bchannel(const cell* cl);**
**unsigned 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);**
**uint64_t cell_blend_fchannel(cell* cl, unsigned channel, unsigned blends)**
**uint64_t cell_blend_bchannel(cell* cl, unsigned channel, unsigned blends)**
**unsigned cell_fg(const cell* cl);**
**unsigned cell_bg(const cell* cl);**
**unsigned cell_fg_alpha(const cell* cl);**
**unsigned cell_bg_alpha(const cell* cl);**
**unsigned cell_fg_rgb(const cell* cl, unsigned* r, unsigned* g, unsigned* b);**
**unsigned cell_bg_rgb(const cell* cl, unsigned* r, unsigned* g, unsigned* b);**
**int cell_set_fg_rgb(cell* cl, int r, int g, int b);**
**int cell_set_bg_rgb(cell* cl, int r, int g, int b);**
**void cell_set_fg_rgb_clipped(cell* cl, int r, int g, int b);**
**void cell_set_bg_rgb_clipped(cell* cl, int r, int g, int b);**
**int cell_set_fg(cell* c, uint32_t channel);**
**int cell_set_bg(cell* c, uint32_t channel);**
**bool cell_fg_default_p(const cell* cl);**
**bool cell_bg_default_p(const cell* cl);**
# 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 happens
to be a single ASCII character, i.e. a single character with a value less than
128, it is encoded directly into the **cell**'s **gcluster** field, and no
additional storage is necessary. In this case, **cell_simple_p()** is **true**.
Otherwise, the EGC is stored as a UTF-8 string in some backing egcpool. Egcpools
are associated with **ncplane**s, so **cell**s must be considered associated
with **ncplane**s. 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 **cell**s can eventually block new
output.
# 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_rgb()** 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)**