Re: lib/55220: Possible color problem in curses and/or py-curses

[Brett Lymn <blymn%internode.on.net@localhost>]

The following reply was made to PR lib/55220; it has been noted by GNATS.

From: Brett Lymn <blymn%internode.on.net@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: blymn%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost,
        Thomas Klausner <wiz%NetBSD.org@localhost>
Subject: Re: lib/55220: Possible color problem in curses and/or py-curses
Date: Fri, 3 Dec 2021 07:51:43 +1030

 On Tue, Oct 26, 2021 at 09:10:01AM +0000, Thomas Klausner wrote:
 >  
 >  The position where I'm at is reverse (in my case, gray on black). When
 >  I move the cursor, the new byte under the cursor position gets that
 >  color scheme, but the old one keeps it (it stays gray on black). I
 >  don't think this is intended behaviour.
 >  
 >  Can you please check that?
 >  
 
 I agree, I don't think this is intended but I don't think it is a curses
 problem.  If I run this test code:
 
 #!/usr/pkg/bin/python3.8
 #
 import curses
 
 stdscr = curses.initscr()
 curses.start_color()
 
 win = curses.newwin(20, 80, 0, 0)
 
 win.addstr(0, 0, "Current testing", curses.A_UNDERLINE)
 win.getch()
 
 curses.init_pair(1, curses.COLOR_RED, curses.COLOR_WHITE)
 curses.init_pair(2, curses.COLOR_GREEN, curses.COLOR_WHITE)
 win.addstr(1, 0, "Color testing", curses.color_pair(1))
 win.getch()
 
 win.chgat(1, 3, 4, curses.color_pair(2))
 win.getch()
 
 curses.endwin()
 
 Then the win.chgat call results in the 4 characters are set to a black
 background with white writing (default colour pair) instead of green on
 a white background.  Ramping up the debug in curses I see:
 
 1638479121.598015: mvwchgat: x: 3 y: 1 count: 4 attr: 0x0 color pair 0
 
 Which is also what I see when running debug on fileobj too - the
 attributes and colour are _always_ 0 which translates to attribute
 A_NORMAL and white text on a black background.  Having a look at the
 py-curses library code in the chgat handling there is:
 
 
     color = (short)((attr >> 8) & 0xff);
     attr = attr - (color << 8);
 
 
 This really doesn't map well to the NetBSD curses colour and attributes
 so it isn't surprising that the NetBSD curses is always getting 0's.
 
 So, it looks like the py-curses needs to be fixed.
 
 -- 
 Brett Lymn
 --
 Sent from my NetBSD device.
 
 "We are were wolves",
 "You mean werewolves?",
 "No we were wolves, now we are something else entirely",
 "Oh"