how to set the background color of a window with curses

[Jim Dennis]

In article <mailman.1015708997.5233.python-list at python.org>, Marco Herrn wrote:

> On Sat, Mar 09, 2002 at 05:42:04PM +0100, Gerhard H?ring wrote:
>> Le 09/03/02 ? 13:53, Marco Herrn ?crivit:
>>> Hi,

>>> I am trying to set a backround color for a window and did it with

>>> stdscr.bkgd(' ', curses.COLOR_BLUE)

>>> But that doesn't work. It seems to do nothing.
>>> What am I doing wrong?

>> You're confusing colors with attributes. I recently stumbled across that
>> one, too :)

> Hmm, that may be true.... ;)

>> This will do the trick:

>> # define color 1 as black on blue
>> curses.init_pair(1, curses.COLOR_BLACK, curses.COLOR_BLUE)
>> stdscr.bkgd(' ', curses.color_pair(1))

> No, that doesn't work for me.
> The whole screen remains black. I get no error message and any text that
> is displayed with color_pair(1) is correctly displayed in black on blue.

> Am I missing something else?

>> Btw. there's a curses howto on http://py-howto.sf.net/ in case you
>> didn't know.

> Yes, I did read it. It is a good starting point, but unfortunately
> doesn't go over my problem ;)

 I don't think that the Python Curses HOWTO is a good starting point
 for curses, especially regarding the use of color in ncurses.  

 Here's a working example of color and attributes in curses:


#!/usr/bin/env python2.2
""" Curses Clock: draw a colorful clock in the center of a terminal 
    		      and update it every second. Quit on first keystroke
		Bugs: handles window change (SIGWINCH) crudely
			  abends (exit code 1) if not curses.has_colors(), no error message
			  mouse events are so totally not working! 
			  	(may be cause of segfault?)
	by James T. Dennis <jimd at starshine.org> 
	Sun Mar 17 15:06:52 PST 2002
"""
import curses, time, random, string, sys

def main(w):
	w.keypad(1)
	w.leaveok(1) 
	w.immedok(0)
	w.nodelay(1) 
	w.scrollok(0)
	w.erase()
	norm = curses.A_NORMAL
	bold = curses.A_BOLD
	dim  = curses.A_DIM
	if curses.has_colors():
		colorlist = (("red", curses.COLOR_RED), 
					 ("green", curses.COLOR_GREEN),
					 ("yellow", curses.COLOR_YELLOW),
					 ("blue", curses.COLOR_BLUE),
					 ("cyan", curses.COLOR_CYAN),
					 ("magenta", curses.COLOR_MAGENTA),
					 ("black", curses.COLOR_BLACK),
					 ("white", curses.COLOR_WHITE))
		colors = {}
		colorpairs = 0
		for name,i in colorlist:
			colorpairs += 1 
			curses.init_pair(colorpairs, i, curses.COLOR_BLACK)
			colors[name]=curses.color_pair(i)
	else: 
		sys.exit(1)
	## (mousecap, mouseold) = curses.mousemask(0)
	## (mousecap, mouseold) = curses.mousemask(mouseold | mousecap)

	tpart = { "day":	 0, "month": 4, "date":	 8, "hour":	11,
			   "min":	14, "sec":	17, "year":	21 }
	key = 0		
	while 1:
		if key == 0 or key == 410:	# 410 is from SIGWINCH?
			w.erase()
			y,x=w.getmaxyx()
			mid = y / 2 
			ctr = x / 2 
			t = time.asctime()
			ctr -=  len(t) / 2 
		### k = w.getkey()
		### Warning: previous line causes segfault!
		key = w.getch()
		## if key == 410: continue
		if key == ord('q') or key == ord('Q'): 
			break
		else: 
			w.addstr(0, 0, "\t%s\t" % key, colors["yellow"])
			### w.addstr(0, 0, "\t%s\t" % curses.keyname(k), colors["yellow"])
			### Warning: previous line causes segfault!
		t = time.asctime()
		w.addstr(mid,ctr+tpart["day"],  t[0:3],colors["blue"]    | norm)
		w.addstr(mid,ctr+tpart["month"],t[4:8],colors["blue"]    | dim)
		w.addstr(mid,ctr+tpart["date"], t[8:11],colors["blue"]   | bold)
		w.addstr(mid,ctr+tpart["hour"], t[11:14],colors["red"]   | dim)
		w.addstr(mid,ctr+tpart["min"],  t[14:17],colors["red"]   | bold)
		w.addstr(mid,ctr+tpart["sec"],  t[17:20],colors["green"] | dim)
		w.addstr(mid,ctr+tpart["year"], t[20:],colors["magenta"] | dim)
		time.sleep(1)
	return key
	
if __name__ == "__main__":
	x = curses.wrapper(main)
	print x


 This may not be efficient, but it shows the basics of handling color and
 attributes.  BTW: the "dim" attribute looks just like "normal" on my
 terminals (xterms and Linux console).  So that may not be useful in most 
 cases.

 As you can see it isn't at all clever about terminals that lack ncurses 
 color support, and it can't handle dynamic window size changes (SIGWINCH)

 Separately I'm playing with the signal module to see if I can add SIGWINCH
 support my own version of curses.wrapper.  (Although it seems that
 getch() returns 410 on window resize events). I've also been mentally
 playing with possible ways to create an enhanced curses.wrapper with
 support for passing arguments to main() and return values back from
 it.  (Of course I can simply create a global mutable "retval = []" and
 do an assignment to that prior to a return.  Actually it seems I can
 call: r = curses.wrapper(foo) and get the return value from foo().

 Also NOTE the two lines where I get python to segfault (this is 
 Python2.2 from Debian "Unstable") but it does it under 2.1, too.
 (It segfaults on any reference to curses.keyname OR w.getkey() 
 the two are orthogonal paths to the failure)

 There are still some things I don't understand about this.  
 The mouse stuff is completely opaque (and virtually undocumented).

> Bye
> Marco

> Experience is something you don't get until just after you need it.
                                                       ^^^ the first time