Support ncurses extended colors API

README.md

@@ -53,7 +53,7 @@ Type the following command, and see `[rdoc]` of curses:
 
 ## Limitations
 
-* curses.gem doesn't support more than 256 color pairs.  See https://reversed.top/2019-02-05/more-than-256-curses-color-pairs/ for details.
+* On ncurses 6+ compiled with extended color support, more than 256 color pairs are supported transparently via the extended colors API (`init_extended_pair`, etc.). Use `Curses.support_extended_colors?` to check at runtime.
 
 ## Developers
 

ext/curses/curses.c

@@ -1321,7 +1321,11 @@ curses_init_pair(VALUE obj, VALUE pair, VALUE f, VALUE b)
 {
     /* may have to raise exception on ERR */
     curses_stdscr();
+#ifdef HAVE_INIT_EXTENDED_PAIR
+    return (init_extended_pair(NUM2INT(pair), NUM2INT(f), NUM2INT(b)) == OK) ? Qtrue : Qfalse;
+#else
     return (init_pair(NUM2INT(pair),NUM2INT(f),NUM2INT(b)) == OK) ? Qtrue : Qfalse;
+#endif
 }
 
 /*
@@ -1345,8 +1349,13 @@ curses_init_color(VALUE obj, VALUE color, VALUE r, VALUE g, VALUE b)
 {
     /* may have to raise exception on ERR */
     curses_stdscr();
+#ifdef HAVE_INIT_EXTENDED_COLOR
+    return (init_extended_color(NUM2INT(color), NUM2INT(r),
+				NUM2INT(g), NUM2INT(b)) == OK) ? Qtrue : Qfalse;
+#else
     return (init_color(NUM2INT(color),NUM2INT(r),
 		       NUM2INT(g),NUM2INT(b)) == OK) ? Qtrue : Qfalse;
+#endif
 }
 
 /*
@@ -1397,11 +1406,22 @@ curses_colors(VALUE obj)
 static VALUE
 curses_color_content(VALUE obj, VALUE color)
 {
-    short r,g,b;
-
     curses_stdscr();
-    color_content(NUM2INT(color),&r,&g,&b);
-    return rb_ary_new3(3,INT2FIX(r),INT2FIX(g),INT2FIX(b));
+#ifdef HAVE_EXTENDED_COLOR_CONTENT
+    {
+	int r, g, b;
+	if (extended_color_content(NUM2INT(color), &r, &g, &b) == ERR)
+	    return Qnil;
+	return rb_ary_new3(3, INT2FIX(r), INT2FIX(g), INT2FIX(b));
+    }
+#else
+    {
+	short r, g, b;
+	if (color_content(NUM2INT(color), &r, &g, &b) == ERR)
+	    return Qnil;
+	return rb_ary_new3(3, INT2FIX(r), INT2FIX(g), INT2FIX(b));
+    }
+#endif
 }
 
 
@@ -1430,11 +1450,22 @@ curses_color_pairs(VALUE obj)
 static VALUE
 curses_pair_content(VALUE obj, VALUE pair)
 {
-    short f,b;
-
     curses_stdscr();
-    pair_content(NUM2INT(pair),&f,&b);
-    return rb_ary_new3(2,INT2FIX(f),INT2FIX(b));
+#ifdef HAVE_EXTENDED_PAIR_CONTENT
+    {
+	int f, b;
+	if (extended_pair_content(NUM2INT(pair), &f, &b) == ERR)
+	    return Qnil;
+	return rb_ary_new3(2, INT2FIX(f), INT2FIX(b));
+    }
+#else
+    {
+	short f, b;
+	if (pair_content(NUM2INT(pair), &f, &b) == ERR)
+	    return Qnil;
+	return rb_ary_new3(2, INT2FIX(f), INT2FIX(b));
+    }
+#endif
 }
 
 /*
@@ -1465,6 +1496,41 @@ curses_pair_number(VALUE obj, VALUE attrs)
     curses_stdscr();
     return INT2FIX(PAIR_NUMBER(NUM2CHTYPE(attrs)));
 }
+
+/*
+ * Document-method: Curses.support_extended_colors?
+ *
+ * Returns +true+ if the ncurses library was compiled with extended color
+ * support (i.e., init_extended_pair, init_extended_color, etc. are available),
+ * +false+ otherwise.
+ */
+static VALUE
+curses_support_extended_colors(VALUE obj)
+{
+#if defined(HAVE_INIT_EXTENDED_PAIR) && defined(HAVE_INIT_EXTENDED_COLOR) && \
+    defined(HAVE_EXTENDED_COLOR_CONTENT) && defined(HAVE_EXTENDED_PAIR_CONTENT)
+    return Qtrue;
+#else
+    return Qfalse;
+#endif
+}
+
+/*
+ * Document-method: Curses.reset_color_pairs
+ *
+ * Resets all color pairs to undefined. Requires ncurses 6.1+.
+ */
+#ifdef HAVE_RESET_COLOR_PAIRS
+static VALUE
+curses_reset_color_pairs(VALUE obj)
+{
+    curses_stdscr();
+    reset_color_pairs();
+    return Qnil;
+}
+#else
+#define curses_reset_color_pairs rb_f_notimplement
+#endif
 #endif /* USE_COLOR */
 
 #ifdef USE_MOUSE
@@ -2717,7 +2783,7 @@ window_setscrreg(VALUE obj, VALUE top, VALUE bottom)
 #endif
 }
 
-#if defined(USE_COLOR) && defined(HAVE_WCOLOR_SET)
+#if defined(USE_COLOR) && (defined(HAVE_WCOLOR_SET) || defined(HAVE_WATTR_SET))
 /*
  * Document-method: Curses::Window.color_set
  * call-seq: color_set(col)
@@ -2729,13 +2795,28 @@ static VALUE
 window_color_set(VALUE obj, VALUE col)
 {
     struct windata *winp;
-    int res;
 
     GetWINDOW(obj, winp);
-    res = wcolor_set(winp->window, NUM2INT(col), NULL);
-    return (res == OK) ? Qtrue : Qfalse;
+#if defined(HAVE_WATTR_SET) && defined(HAVE_WATTR_GET)
+    /* Use wattr_set to support pair numbers > 255; preserve existing attrs. */
+    {
+	attr_t attrs;
+#ifdef NCURSES_PAIRS_T
+	NCURSES_PAIRS_T current_pair;
+#else
+	short current_pair;
+#endif
+	if (wattr_get(winp->window, &attrs, &current_pair, NULL) == ERR)
+	    return Qfalse;
+	return (wattr_set(winp->window, attrs, NUM2INT(col), NULL) == OK) ? Qtrue : Qfalse;
+    }
+#elif defined(HAVE_WATTR_SET)
+    return (wattr_set(winp->window, 0, NUM2INT(col), NULL) == OK) ? Qtrue : Qfalse;
+#else
+    return (wcolor_set(winp->window, NUM2INT(col), NULL) == OK) ? Qtrue : Qfalse;
+#endif
 }
-#endif /* defined(USE_COLOR) && defined(HAVE_WCOLOR_SET) */
+#endif /* defined(USE_COLOR) && (defined(HAVE_WCOLOR_SET) || defined(HAVE_WATTR_SET)) */
 
 /*
  * Document-method: Curses::Window.scroll
@@ -5071,6 +5152,8 @@ Init_curses(void)
     rb_define_module_function(mCurses, "pair_content", curses_pair_content, 1);
     rb_define_module_function(mCurses, "color_pair", curses_color_pair, 1);
     rb_define_module_function(mCurses, "pair_number", curses_pair_number, 1);
+    rb_define_module_function(mCurses, "support_extended_colors?", curses_support_extended_colors, 0);
+    rb_define_module_function(mCurses, "reset_color_pairs", curses_reset_color_pairs, 0);
 #endif /* USE_COLOR */
 #ifdef USE_MOUSE
     rb_define_module_function(mCurses, "getmouse", curses_getmouse, 0);
@@ -5203,9 +5286,9 @@ Init_curses(void)
     rb_define_method(cWindow, "move", window_move, 2);
     rb_define_method(cWindow, "move_relative", window_move_relative, 2);
     rb_define_method(cWindow, "setpos", window_setpos, 2);
-#if defined(USE_COLOR) && defined(HAVE_WCOLOR_SET)
+#if defined(USE_COLOR) && (defined(HAVE_WCOLOR_SET) || defined(HAVE_WATTR_SET))
     rb_define_method(cWindow, "color_set", window_color_set, 1);
-#endif /* USE_COLOR && HAVE_WCOLOR_SET */
+#endif /* USE_COLOR && (HAVE_WCOLOR_SET || HAVE_WATTR_SET) */
     rb_define_method(cWindow, "cury", window_cury, 0);
     rb_define_method(cWindow, "curx", window_curx, 0);
     rb_define_method(cWindow, "maxy", window_maxy, 0);

ext/curses/extconf.rb

@@ -119,7 +119,9 @@ def exec_command(cmd)
               def_prog_mode reset_prog_mode timeout wtimeout nodelay
               init_color wcolor_set use_default_colors assume_default_colors
               newpad unget_wch get_wch wget_wch PDC_get_key_modifiers
-              chgat wchgat newterm)
+              chgat wchgat newterm
+              init_extended_color init_extended_pair extended_color_content
+              extended_pair_content reset_color_pairs wattr_set wattr_get)
     have_func(f) || (have_macro(f, curses) && $defs.push(format("-DHAVE_%s", f.upcase)))
   end
   convertible_int('chtype', [["#undef MOUSE_MOVED\n"]]+curses) or abort

sample/colors.rb

@@ -5,6 +5,7 @@
 
 # The TERM environment variable should be set to xterm-256color etc. to
 # use 256 colors.  Curses.colors returns the color numbers of the terminal.
+# With ncurses 6+ extended color support, color_pairs may exceed 256.
 
 begin
   init_screen
@@ -14,14 +15,24 @@
   else
     start_color
 
-    addstr "This Terminal supports #{colors} colors.\n"
-
-    Curses.colors.times { |i|
-      Curses.init_pair(i, i, 0)
-      attrset(color_pair(i))
+    extended = Curses.support_extended_colors?
+    addstr "This Terminal supports #{colors} colors, #{color_pairs} pairs"
+    addstr extended ? " (extended).\n" : ".\n"
+
+    (extended ? [512, color_pairs].min : colors).times { |i|
+      next if i == 0
+      Curses.init_pair(i, i % colors, (i / colors) % colors)
+      if extended
+        # color_pair() encodes into chtype and can't handle pairs > 255;
+        # use color_set on stdscr instead, which calls wattr_set internally.
+        stdscr.color_set(i)
+      else
+        attrset(color_pair(i))
+      end
       addstr("#{i.to_s.rjust(3)} ")
       addstr("\n") if i == 15 || (i > 16 && (i - 15) % 36 == 0)
     }
+    stdscr.color_set(0)
   end
 
   getch