[docs] add notcurses_canpixel() to notcurses_capabilities.3

NEWS.md

@@ -35,7 +35,7 @@ rearrangements of Notcurses.
     now a `struct notcurses*` rather than a `struct ncplane*`.
   * `ncvisual_render()` has been deprecated in favor of the new function
     `ncvisual_blit()`. When a `NULL` `vopts->n` is passed to `ncvisual_blit()`,
-    a new plane is created (as it was in `ncvisual_render()`, but that plane
+    a new plane is created (as it was in `ncvisual_render()`), but that plane
     is the root of a new pile, rather than a child of the standard plane.
     The only tricky conversion is if you previously had `vopts.n` as `NULL`,
     and were not using `NCVISUAL_OPTION_CHILDPLANE` (or were passing `NULL`

doc/man/man3/notcurses_capabilities.3.md

@@ -36,6 +36,20 @@ notcurses_capabilities - runtime capability detection
 
 **bool notcurses_canbraille(const struct notcurses* ***nc***);**
 
+**bool notcurses_canpixel(const struct notcurses* ***nc***);**
+
+```c
+typedef enum {
+  NCPIXEL_NONE = 0,
+  NCPIXEL_SIXEL,           // sixel
+  NCPIXEL_LINUXFB,         // linux framebuffer
+  NCPIXEL_ITERM2,          // iTerm2
+  NCPIXEL_KITTY_STATIC,    // kitty pre-0.20.0
+  NCPIXEL_KITTY_ANIMATED,  // kitty pre-0.22.0
+  NCPIXEL_KITTY_SELFREF,   // kitty 0.22.0+, wezterm
+} ncpixelimpl_e;
+```
+
 **ncpixelimpl_e notcurses_check_pixel_support(struct notcurses* ***nc***);**
 
 # DESCRIPTION
@@ -88,7 +102,7 @@ these functions return **true** unless UTF-8 encoding is in use.
 
 **notcurses_check_pixel_support** returns a non-zero pixel implementation
 if bitmap support (via any mechanism) has been detected, and otherwise 0
-(**NCPIXEL_NONE**).
+(**NCPIXEL_NONE**). **notcurses_canpixel** folds this down to a boolean.
 
 # NOTES