From 88522172152013a281590f2714f45adac6d2d679 Mon Sep 17 00:00:00 2001
From: agatan <agatan039@gmail.com>
Date: Fri, 30 Nov 2018 10:30:12 +0900
Subject: [PATCH] Define ColorDefault and pass it to ColorPair#init

---
 src/ncurses/attribute.cr | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/ncurses/attribute.cr b/src/ncurses/attribute.cr
index c96fe20..8b5aa8e 100644
--- a/src/ncurses/attribute.cr
+++ b/src/ncurses/attribute.cr
@@ -2,15 +2,29 @@ require "./libncurses"
 
 module NCurses
   alias Attribute = LibNCurses::Attribute
+
+  struct ColorDefault
+  end
+
   alias Color = LibNCurses::Color
 
   struct ColorPair
     def initialize(@id : Int32)
     end
 
-    def init(fg : Color, bg : Color)
-      if LibNCurses.init_pair(@id, fg.value, bg.value) == LibNCurses::Result::ERR
-        raise "ncurses failure: init_pair"
+    def init(fg : Color | ColorDefault, bg : Color | ColorDefault)
+      fg = if fg.is_a?(Color)
+             fg.value
+           else
+             -1
+           end
+      bg = if bg.is_a?(Color)
+             bg.value
+           else
+             -1
+           end
+      if LibNCurses.init_pair(@id, fg, bg) == LibNCurses::Result::ERR
+        raise "ncurses failure: init_pair, #{@id}, #{fg}, #{bg}"
       end
       self
     end