add notcurses_canhalfblock()/notcurses_canquadrant() #1575

NEWS.md

@@ -3,6 +3,7 @@ rearrangements of Notcurses.
 
 * 2.2.9 (not yet released)
   * Added two new stats, `sprixelemissions` and `sprixelelisions`.
+  * Added `notcurses_canhalfblock()` and `notcurses_canquadrant()`.
 
 * 2.2.8 (2021-04-18)
   * All remaining functions prefixed with `cell_` or `cells_` have been

USAGE.md

@@ -297,6 +297,12 @@ bool notcurses_canchangecolor(const struct notcurses* nc);
 // Is our encoding UTF-8? Requires LANG being set to a UTF-8 locale.
 bool notcurses_canutf8(const struct notcurses* nc);
 
+// Can we reliably use Unicode halfblocks?
+bool notcurses_canhalfblock(const struct notcurses* nc);
+
+// Can we reliably use Unicode quadrants?
+bool notcurses_canquadrant(const struct notcurses* nc);
+
 // Can we draw sextants? This requires Unicode 13.
 bool notcurses_cansextants(const struct notcurses* nc);
 

doc/man/man3/notcurses_capabilities.3.md

@@ -26,6 +26,10 @@ notcurses_capabilities - runtime capability detection
 
 **bool notcurses_canutf8(const struct notcurses* ***nc***);**
 
+**bool notcurses_canhalfblock(const struct notcurses* ***nc***);**
+
+**bool notcurses_canquadrant(const struct notcurses* ***nc***);**
+
 **bool notcurses_cansextant(const struct notcurses* ***nc***);**
 
 **bool notcurses_canbraille(const struct notcurses* ***nc***);**
@@ -63,10 +67,12 @@ multimedia support capable of decoding videos.
 UTF-8 encoding, and the locale was successfully loaded.
 
 **notcurses_cansextant** returns **true** if the heuristics suggest
-that the terminal can properly render Unicode 13 sextants.
+that the terminal can properly render Unicode 13 sextants. Likewise,
-
+**notcurses_canquadrant** and **notcurses_canhalfblock** return **true**
-**notcurses_canbraille** returns **true** if Braille is expected to work on the
+if the heuristics suggest that the terminal can properly render Unicode
-terminal.
+quadrants and halfblocks, respectively. **notcurses_canbraille** returns
+**true** if Unicode Braille is expected to work on the terminal. None of
+these functions return **true** unless UTF-8 encoding is in use.
 
 **notcurses_check_pixel_support** returns 1 if bitmap support (via any
 mechanism) is detected; **NCBLIT_PIXEL** can be used after such a return.

include/notcurses/notcurses.h

@@ -1262,6 +1262,12 @@ API bool notcurses_canopen_videos(const struct notcurses* nc);
 // Is our encoding UTF-8? Requires LANG being set to a UTF8 locale.
 API bool notcurses_canutf8(const struct notcurses* nc);
 
+// Can we reliably use Unicode halfblocks?
+API bool notcurses_canhalfblock(const struct notcurses* nc);
+
+// Can we reliably use Unicode quadrants?
+API bool notcurses_canquadrant(const struct notcurses* nc);
+
 // Can we reliably use Unicode 13 sextants?
 API bool notcurses_cansextant(const struct notcurses* nc);
 

src/lib/notcurses.c

@@ -2047,6 +2047,14 @@ bool notcurses_canutf8(const notcurses* nc){
   return nc->tcache.utf8;
 }
 
+bool notcurses_canhalfblock(const notcurses* nc){
+  return nc->tcache.utf8;
+}
+
+bool notcurses_canquadrant(const notcurses* nc){
+  return nc->tcache.quadrants && nc->tcache.utf8;
+}
+
 bool notcurses_cansextant(const notcurses* nc){
   return nc->tcache.sextants && nc->tcache.utf8;
 }