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221 lines
9.4 KiB
Markdown
221 lines
9.4 KiB
Markdown
% notcurses_visual(3)
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% nick black <nickblack@linux.com>
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% v2.1.6
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# NAME
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notcurses_visual - notcurses multimedia
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# SYNOPSIS
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**#include <notcurses/notcurses.h>**
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```c
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typedef enum {
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NCSCALE_NONE,
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NCSCALE_SCALE,
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NCSCALE_STRETCH,
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NCSCALE_NONE_HIRES,
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NCSCALE_SCALE_HIRES,
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} ncscale_e;
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typedef enum {
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NCBLIT_DEFAULT, // let the ncvisual pick
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NCBLIT_1x1, // spaces only
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NCBLIT_2x1, // halves + 1x1
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NCBLIT_2x2, // quadrants + 2x1
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NCBLIT_3x2, // sextants + 1x1
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NCBLIT_4x1, // four vertical levels
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NCBLIT_BRAILLE, // 4 rows, 2 cols (braille)
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NCBLIT_8x1, // eight vertical levels
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NCBLIT_SIXEL, // not yet implemented
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} ncblitter_e;
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#define NCVISUAL_OPTION_NODEGRADE 0x0001
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#define NCVISUAL_OPTION_BLEND 0x0002
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struct ncvisual_options {
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struct ncplane* n;
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ncscale_e scaling;
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int ***y***, x;
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int begy, begx; // origin of rendered section
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int leny, lenx; // size of rendered section
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ncblitter_e blitter; // glyph set to use
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uint64_t flags; // bitmask over NCVISUAL_OPTION_*
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};
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typedef int (*streamcb)(struct notcurses*, struct ncvisual*, void*);
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```
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**bool notcurses_canopen_images(const struct notcurses* ***nc***);**
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**bool notcurses_canopen_videos(const struct notcurses* ***nc***);**
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**bool notcurses_cansixel(const struct notcurses* ***nc***);**
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**struct ncvisual* ncvisual_from_file(const char* ***file***);**
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**struct ncvisual* ncvisual_from_rgba(const void* ***rgba***, int ***rows***, int ***rowstride***, int ***cols***);**
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**struct ncvisual* ncvisual_from_bgra(const void* ***bgra***, int ***rows***, int ***rowstride***, int ***cols***);**
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**struct ncvisual* ncvisual_from_plane(struct ncplane* ***n***, ncblitter_e ***blit***, int ***begy***, int ***begx***, int ***leny***, int ***lenx***);**
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**int ncvisual_geom(const struct notcurses* ***nc***, const struct ncvisual* ***n***, const struct ncvisual_options* ***vopts***, int* ***y***, int* ***x***, int* ***toy***, int* ***tox***);**
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**void ncvisual_destroy(struct ncvisual* ***ncv***);**
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**int ncvisual_decode(struct ncvisual* ***ncv***);**
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**int ncvisual_decode_loop(struct ncvisual* ***ncv***);**
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**struct ncplane* ncvisual_render(struct notcurses* ***nc***, struct ncvisual* ***ncv***, const struct ncvisual_options* ***vopts***);**
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**int ncvisual_simple_streamer(struct ncplane* ***n***, struct ncvisual* ***ncv***, const struct timespec* ***disptime***, void* ***curry***);**
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**int ncvisual_stream(struct notcurses* ***nc***, struct ncvisual* ***ncv***, float ***timescale***, streamcb ***streamer***, const struct ncvisual_options* ***vopts***, void* ***curry***);**
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**int ncvisual_rotate(struct ncvisual* ***n***, double ***rads***);**
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**int ncvisual_resize(struct ncvisual* ***n***, int ***rows***, int ***cols***);**
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**int ncvisual_polyfill_yx(struct ncvisual* ***n***, int ***y***, int ***x***, uint32_t ***rgba***);**
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**int ncvisual_at_yx(const struct ncvisual* ***n***, int ***y***, int ***x***, uint32_t* ***pixel***);**
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**int ncvisual_set_yx(const struct ncvisual* ***n***, int ***y***, int ***x***, uint32_t ***pixel***);**
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**char* ncvisual_subtitle(const struct ncvisual* ***ncv***);**
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**int notcurses_lex_scalemode(const char* ***op***, ncscale_e* ***scaling***);**
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**const char* notcurses_str_scalemode(ncscale_e ***scaling***);**
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**int notcurses_lex_blitter(const char* ***op***, ncblitter_e* ***blitter***);**
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**const char* notcurses_str_blitter(ncblitter_e ***blitter***);**
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**ncblitter_e ncvisual_media_defblitter(const struct notcurses ***nc***, ncscale_e ***scaling***);**
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# DESCRIPTION
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An **ncvisual** is a virtual pixel framebuffer. They can be created from
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RGBA/BGRA data in memory (**ncvisual_from_rgba**/**ncvisual_from_bgra**),
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or from the content of a suitable **ncplane** (**ncvisual_from_ncplane**).
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If Notcurses was built against a multimedia engine (FFMpeg or OpenImageIO),
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image and video files can be loaded into visuals using
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**ncvisual_from_file**. **ncvisual_from_file** discovers the container
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and codecs, but does not verify that the entire file is well-formed.
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**ncvisual_decode** ought be invoked to recover subsequent frames, once
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per frame. **ncvisual_decode_loop** will return to the first frame,
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as if **ncvisual_decode** had never been called.
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Once the visual is loaded, it can be transformed using **ncvisual_rotate**
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and **ncvisual_resize**. These are persistent operations, unlike any scaling
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that takes place at render time. If a subtitle is associated with the frame,
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it can be acquired with **ncvisual_subtitle**.
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**ncvisual_from_rgba** and **ncvisual_from_bgra** both require a number of
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**rows**, a number of image columns **cols**, and a virtual row length of
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**rowstride** / 4 columns. The input data must provide 32 bits per pixel, and
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thus must be at least **rowstride** * **rows** bytes, of which a
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**cols** * **rows** * 4-byte subset is used. It is not possible to **mmap(2)** an image
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file and use it directly--decompressed, decoded data is necessary. The
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resulting plane will be ceil(**rows**/2) rows, and **cols** columns.
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**ncvisual_from_plane** requires specification of a rectangle via **begy**,
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**begx**, **leny**, and **lenx**. The only valid characters within this
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region are those used by the **NCBLIT_2x2** blitter, though this may change
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in the future.
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**ncvisual_rotate** executes a rotation of **rads** radians, in the clockwise
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(positive) or counterclockwise (negative) direction.
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**ncvisual_subtitle** will return a UTF-8-encoded subtitle corresponding to
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the current frame if such a subtitle was decoded. Note that a subtitle might
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be returned for multiple frames, or might not.
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**ncvisual_render** blits the visual to an **ncplane**, based on the contents
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of its **struct ncvisual_options**. If **n** is not **NULL**, it specifies the
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plane on which to render, and **y**/**x** specify a location within that plane.
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Otherwise, a new plane will be created, and placed at **y**/**x** relative to
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the rendering area. **begy**/**begx** specify the upper left corner of a
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subsection of the **ncvisual** to render, while **leny**/**lenx** specify the
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geometry of same. **flags** is a bitfield over:
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* **NCVISUAL_OPTION_NODEGRADE** If the specified blitter is not available, fail rather than degrading.
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* **NCVISUAL_OPTION_BLEND**: Render with **CELL_ALPHA_BLEND**.
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# BLITTERS
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The different **ncblitter_e** values select from among available glyph sets:
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* **NCBLIT_DEFAULT**: Let the **ncvisual** choose its own blitter.
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* **NCBLIT_1x1**: Spaces only. Works in ASCII, unlike other blitters.
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* **NCBLIT_2x1**: Adds the half blocks (▄▀) to **NCBLIT_1x1**.
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* **NCBLIT_2x2**: Adds left and right half blocks (▌▐) and quadrants (▖▗▟▙) to **NCBLIT_2x1**.
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* **NCBLIT_3x2**: Adds sextants to **NCBLIT_1x1**.
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* **NCBLIT_4x1**: Adds ¼ and ¾ blocks (▂▆) to **NCBLIT_2x1**.
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* **NCBLIT_BRAILLE**: 4 rows and 2 columns of braille (⡀⡄⡆⡇⢀⣀⣄⣆⣇⢠⣠⣤⣦⣧⢰⣰⣴⣶⣷⢸⣸⣼⣾⣿).
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* **NCBLIT_8x1**: Adds ⅛, ⅜, ⅝, and ⅞ blocks (▇▅▃▁) to **NCBLIT_4x1**.
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* **NCBLIT_SIXEL**: Not yet implemented.
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**NCBLIT_4x1** and **NCBLIT_8x1** are intended for use with plots, and are
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not really applicable for general visuals.
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# RETURN VALUES
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**notcurses_canopen_images** and **notcurses_canopen_videos** returns true if
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images and videos, respecitvely, can be decoded, or false if Notcurses was
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built with insufficient multimedia support.
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**ncvisual_from_file** returns an **ncvisual** object on success, or **NULL**
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on failure. Success indicates that the specified **file** was opened, and
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enough data was read to make a firm codec identification. It does not imply
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that the entire file is properly-formed.
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**ncvisual_decode** returns 0 on success, or 1 on end of file, or -1 on
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failure. It is only necessary for multimedia-based visuals. It advances one
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frame for each call. **ncvisual_decode_loop** has the same return values: when
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called following decoding of the last frame, it will return 1, but a subsequent
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**ncvisual_render** will return the first frame.
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**ncvisual_from_plane** returns **NULL** if the **ncvisual** cannot be created
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and bound. This is usually due to illegal content in the source **ncplane**.
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**ncvisual_render** returns **NULL** on error, and otherwise the plane to
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which the visual was rendered. If **opts->n** is provided, this will be
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**opts->n**. Otherwise, a plane will be created, perfectly sized for the
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visual and the specified blitter.
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**ncvisual_geom** returns non-zero if the **blitter** is invalid.
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**ncvisual_media_defblitter** returns the blitter selected by **NCBLIT_DEFAULT**
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in the specified configuration. If UTF8 is not enabled, this will always be
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**NCBLIT_1x1**. If ***scale*** is **NCSCALE_NONE** or **NCSCALE_SCALE**, the
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aspect-preserving **NCBLIT_2x1** will be returned. If sextants are available
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(see **notcurses_cansextant**), this will be **NCBLIT_3x2**, or otherwise
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**NCBLIT_2x2**.
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# NOTES
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Multimedia decoding requires that Notcurses be built with either FFmpeg or
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OpenImageIO support. What formats can be decoded is totally dependent on the
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linked library. OpenImageIO does not support subtitles.
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# BUGS
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**ncvisual_rotate** currently supports only **M_PI**/2 and -**M_PI**/2
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radians for **rads**, but this will change soon.
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**NCBLIT_SIXEL** is not yet implemented, and is only infrequently supported
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among terminals.
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Bad font support can ruin **NCBLIT_2x2**, **NCBLIT_3x2**, **NCBLIT_4x1**,
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**NCBLIT_BRAILLE**, and **NCBLIT_8x1**.
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# SEE ALSO
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**notcurses(3)**,
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**notcurses_capabilities(3)**,
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**notcurses_plane(3)**,
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**utf-8(7)**
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