Support ncurses extended colors API

[shugo]

Support ncurses extended colors API

Use init_extended_pair/init_extended_color/extended_color_content/
extended_pair_content when available (ncurses 6+), removing the 256
color pair limitation. Window#color_set is upgraded to use wattr_set
internally when available, allowing pair numbers > 255.

New methods:

• Curses.support_extended_colors? — runtime check for extended support
• Curses.reset_color_pairs — reset all pairs to undefined (ncurses 6.1+)

[Copilot]

Pull request overview

This PR updates the Ruby curses extension to take advantage of ncurses’ extended colors API (ncurses 6+) when available, lifting the historical 256 color-pair limitation and updating Window#color_set behavior to better support large pair numbers.

Changes:

• Prefer init_extended_pair / init_extended_color and extended content getters when available.
• Add Curses.support_extended_colors? and Curses.reset_color_pairs.
• Update sample + README to reflect/support extended color pairs usage.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
sample/colors.rb	Demonstrates extended color-pair usage and avoids color_pair() for pairs > 255.
ext/curses/extconf.rb	Detects extended-color-related ncurses functions/macros at build time.
ext/curses/curses.c	Implements extended-color-aware wrappers and adds new Ruby-facing APIs.
README.md	Updates limitation docs to reflect extended color support on ncurses 6+.

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[Copilot]

reset_color_pairs() returns a status code (OK/ERR). The wrapper currently ignores the return value and always returns nil, making failures silent. Consider returning true/false (consistent with other wrappers) or raising on ERR.

Suggested change

	reset_color_pairs();
	int ret = reset_color_pairs();
	if (ret == ERR) {
	rb_sys_fail("reset_color_pairs");
	}

[Copilot]

extended_color_content/color_content return OK/ERR, but the code ignores the return value and then returns potentially uninitialized r/g/b when the call fails. Handle the return code and raise/return nil on ERR to avoid undefined behavior.

Suggested change

	extended_color_content(NUM2INT(color), &r, &g, &b);
	return rb_ary_new3(3, INT2FIX(r), INT2FIX(g), INT2FIX(b));
	}
	#else
	{
	short r, g, b;
	color_content(NUM2INT(color), &r, &g, &b);
	int rc = extended_color_content(NUM2INT(color), &r, &g, &b);
	if (rc == ERR) {
	return Qnil;
	}
	return rb_ary_new3(3, INT2FIX(r), INT2FIX(g), INT2FIX(b));
	}
	#else
	{
	short r, g, b;
	int rc = color_content(NUM2INT(color), &r, &g, &b);
	if (rc == ERR) {
	return Qnil;
	}

[Copilot]

extended_pair_content/pair_content return OK/ERR, but the code ignores the return value and then returns potentially uninitialized f/b when the call fails. Handle the return code and raise/return nil on ERR to avoid undefined behavior.

Suggested change

	extended_pair_content(NUM2INT(pair), &f, &b);
	return rb_ary_new3(2, INT2FIX(f), INT2FIX(b));
	}
	#else
	{
	short f, b;
	pair_content(NUM2INT(pair), &f, &b);
	int rc = extended_pair_content(NUM2INT(pair), &f, &b);
	if (rc == ERR) return Qnil;
	return rb_ary_new3(2, INT2FIX(f), INT2FIX(b));
	}
	#else
	{
	short f, b;
	int rc = pair_content(NUM2INT(pair), &f, &b);
	if (rc == ERR) return Qnil;

[Copilot]

In the extended branch, init_pair(i, i%256, ...) can pass invalid color numbers when colors < 256 (e.g., a 16-color terminal built against an extended-capable ncurses). Consider using i % colors (and choosing a background within range) so the sample works on low-color terminals too.

Suggested change

	Curses.init_pair(i, i%256, i>=256 ? 8 : 0)
	fg_color = i % colors
	bg_color = (i / colors) % colors
	Curses.init_pair(i, fg_color, bg_color)

[Copilot]

The loop initializes color pair 0 (Curses.init_pair(0, ...)). In ncurses, pair 0 is the default pair and typically cannot be redefined (init_pair(0, ...) returns ERR). Consider starting the loop at 1 (or skipping 0) to avoid silent errors in this sample.

Suggested change

	(extended ? [512, color_pairs].min : colors).times { |i|
	(extended ? [512, color_pairs].min : colors).times { |i|
	next if i == 0

[Copilot]

Window#color_set now uses wattr_set(..., 0, pair, ...) when available. Passing attrs = 0 will clear any existing window attributes (bold/underline/etc.), which changes behavior compared to wcolor_set (and to the method’s intent of only changing the color pair). Preserve the current attributes when switching pairs (e.g., fetch current attrs via wattr_get if available, or prefer wcolor_set when it exists and only fall back to wattr_set when needed).

Suggested change

	#ifdef 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;
	#ifdef HAVE_WCOLOR_SET
	/* Prefer wcolor_set when available, as it only changes the color pair. */
	return (wcolor_set(winp->window, NUM2INT(col), NULL) == OK) ? Qtrue : Qfalse;
	#elif defined(HAVE_WATTR_SET)
	# ifdef HAVE_WATTR_GET
	/*
	* When wcolor_set is unavailable but wattr_set/wattr_get are,
	* preserve existing attributes and only change the color pair.
	*/
	attr_t attrs;
	short current_pair;
	if (wattr_get(winp->window, &attrs, &current_pair, NULL) == ERR) {
	return Qfalse;
	}
	return (wattr_set(winp->window, attrs, NUM2INT(col), NULL) == OK) ? Qtrue : Qfalse;
	# else
	/*
	* Fallback: wcolor_set and wattr_get are unavailable; use wattr_set
	* with attrs = 0 (may clear attributes, but there is no way to
	* query and preserve them portably here).
	*/
	return (wattr_set(winp->window, 0, NUM2INT(col), NULL) == OK) ? Qtrue : Qfalse;
	# endif

[Copilot]

Curses.reset_color_pairs should follow the pattern of other color APIs by calling curses_stdscr() before invoking ncurses functions. As written, calling it before init_screen can behave inconsistently vs. the rest of the API.

Suggested change

	{
	{
	curses_stdscr();