From 6b126f4049b9821f42418a8f3ae1c34b2d6aa453 Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Sun, 7 Feb 2021 18:31:31 -0500
Subject: [PATCH] add notcurses_canbraille() capability test

---
 NEWS.md                                  | 3 +++
 USAGE.md                                 | 6 ++++++
 doc/man/man3/notcurses_capabilities.3.md | 5 ++++-
 include/notcurses/notcurses.h            | 3 +++
 src/lib/notcurses.c                      | 4 ++++
 tests/plot.cpp                           | 6 ++++++
 6 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/NEWS.md b/NEWS.md
index ec528a946..6ae751d1b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,6 +1,9 @@
 This document attempts to list user-visible changes and any major internal
 rearrangements of Notcurses.
 
+* 2.1.9 (not yet released)
+  * Add `notcurses_canbraille()` capability predicate.
+
 * 2.1.8 (2021-02-03):
   * The `notcurses-tetris` binary has been renamed `nctetris`.
   * The new function `channel_set_palindex()` has been added.
diff --git a/USAGE.md b/USAGE.md
index 799f7e3cd..ca91870a3 100644
--- a/USAGE.md
+++ b/USAGE.md
@@ -300,6 +300,12 @@ bool notcurses_canutf8(const struct notcurses* nc);
 
 // Can we blit to Sixel? This requires being built against libsixel.
 bool notcurses_cansixel(const struct notcurses* nc);
+
+// Can we draw sextants? This requires Unicode 13.
+bool notcurses_cansextants(const struct notcurses* nc);
+
+// Can we draw Braille? The Linux console cannot.
+bool notcurses_canbraille(const struct notcurses* nc);
 ```
 
 ## Direct mode
diff --git a/doc/man/man3/notcurses_capabilities.3.md b/doc/man/man3/notcurses_capabilities.3.md
index 2208fca37..38d52b7fe 100644
--- a/doc/man/man3/notcurses_capabilities.3.md
+++ b/doc/man/man3/notcurses_capabilities.3.md
@@ -28,6 +28,8 @@ notcurses_capabilities - runtime capability detection
 
 **bool notcurses_cansextant(const struct notcurses* ***nc***);**
 
+**bool notcurses_canbraille(const struct notcurses* ***nc***);**
+
 **bool notcurses_cansixel(const struct notcurses* ***nc***);**
 
 # DESCRIPTION
@@ -64,7 +66,8 @@ UTF-8 encoding, and the locale was successfully loaded.
 that the terminal can properly render Unicode 13 sextants.
 
 **notcurses_cansixel** returns **true** if the terminal advertises
-support for Sixel.
+support for Sixel. **notcurses_canbraille** returns **true** if Braille
+is expected to work on the terminal.
 
 # BUGS
 
diff --git a/include/notcurses/notcurses.h b/include/notcurses/notcurses.h
index 135262fcb..2e0cb985b 100644
--- a/include/notcurses/notcurses.h
+++ b/include/notcurses/notcurses.h
@@ -1228,6 +1228,9 @@ API bool notcurses_canutf8(const struct notcurses* nc);
 // Can we reliably use Unicode 13 sextants?
 API bool notcurses_cansextant(const struct notcurses* nc);
 
+// Can we reliably use Unicode Braille?
+API bool notcurses_canbraille(const struct notcurses* nc);
+
 // Can we blit to Sixel?
 API bool notcurses_cansixel(const struct notcurses* nc);
 
diff --git a/src/lib/notcurses.c b/src/lib/notcurses.c
index 49152e73e..627b48ecc 100644
--- a/src/lib/notcurses.c
+++ b/src/lib/notcurses.c
@@ -2053,6 +2053,10 @@ bool notcurses_cansextant(const notcurses* nc){
   return nc->tcache.sextants && nc->tcache.utf8;
 }
 
+bool notcurses_canbraille(const notcurses* nc){
+  return nc->tcache.braille && nc->tcache.utf8;
+}
+
 bool notcurses_canfade(const notcurses* nc){
   return nc->tcache.CCCflag || nc->tcache.RGBflag;
 }
diff --git a/tests/plot.cpp b/tests/plot.cpp
index 007152d0f..ed5a519fb 100644
--- a/tests/plot.cpp
+++ b/tests/plot.cpp
@@ -146,6 +146,9 @@ TEST_CASE("Plot") {
   }
 
   SUBCASE("BraillePlot") {
+    if(!notcurses_canbraille(nc_)){
+      return;
+    }
     ncplane_options nopts = {
       .y = 1, .x = 1, .rows = 6, .cols = 50,
       .userptr = nullptr, .name = "plot", .resizecb = nullptr, .flags = 0,
@@ -250,6 +253,9 @@ TEST_CASE("Plot") {
   }
 
   SUBCASE("BraillePlot1Row") {
+    if(!notcurses_canbraille(nc_)){
+      return;
+    }
     ncplane_options nopts = {
       .y = 1, .x = 1, .rows = 1, .cols = 25,
       .userptr = nullptr, .name = "plot", .resizecb = nullptr, .flags = 0,