Issue #8659 has been updated by ThomasDickey (Thomas dickey).


agree: not just ncurses, but any implementation of SVr4 or X/Open curses will use >8 bits for chtype.
8-bit values were for BSD-curses, which is rarely used (essentially only for antique programs).
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Bug #8659: Curses::Window#bkgdset does not handle color correctly
https://bugs.ruby-lang.org/issues/8659#change-40591

Author: inferiorhumanorgans (Alex Zepeda)
Status: Open
Priority: Normal
Assignee: 
Category: ext
Target version: 
ruby -v: ruby 1.9.3p385 (2013-02-06 revision 39114) [x86_64-darwin12.2.1]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


=begin
Colors in curses are handled as high bits on a character.  Logically ORing a character with a color pair should allow bkgdset to configure a colored background.  This can be seen in the source for the Python curses module.  The Python function takes one or two arguments (color + character).  If there are two arguments they are ORed together and passed to curses as such.  Back in ruby land, with one argument it should be possible to specify a background color for the whole screen thusly:

 # Define a color pair
 Curses.init_pair(1, Curses::COLOR_GREEN, Curses::COLOR_BLUE)
 # Set the screen background to blue
 Curses.bkgdset(' '.ord | Curses.color_pair(1))

The following:

 #!/usr/bin/env ruby

 require 'curses'

 Curses.init_screen
 Curses.start_color

 Curses.init_pair(1, Curses::COLOR_YELLOW, Curses::COLOR_BLUE)
 Curses.bkgdset('='.ord | Curses.color_pair(1))
 Curses.clear
 Curses.refresh

 Curses.addstr('Press_any_key_to_continue')
 Curses.getch

Should fill the screen with equals signs (yellow on blue background), and prompt the user to press any key to continue.  With Ruby 1.9.3 this doesn't work.  The curses module assumes curses characters are one byte (typeof(chtype) == char).  Yet GNU ncurses defines the chtype data type as an unsigned integer (OSX 10.8) or an unsigned long (FreeBSD 9.1, RedHat 7.3).  The curses module defines a macro "NUM2CH" to convert from ruby objects to chtype objects.  At present NUM2CH is defined as NUM2CHR.  Instead NUM2CH should be defined as NUM2INT to allow for values > 255 (ex: character + color).

=end


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