curses and use_default_colors()

[Brian Victor]

I am attempting to write a curses-based program. I would like to use
the default terminal background rather than a black one (a significant
difference with transluscent terminals, regardless of one's opinion of
them).

It appears that in the C ncurses interface, this is accomplished via
use_default_colors() and assume_default_colors(). However, these
functions don't seem to have parallels in the python binding. Is there
some way to accomplish what I want?

Thanks,

 

[Chris Reay]

I am attempting to write a curses-based program. I would like to use
the default terminal background rather than a black one (a significant
difference with transluscent terminals, regardless of one's opinion of
them).

<snip>

I don't know how much this'll help, but my home-brewed curses TextApp
class has a white-on-blue default, and TextApp.startWin() contains
these lines (inter alia) ...

# ... blah, blah, blah.
curses.start_color()
curses.init_pair(1, curses.COLOR_WHITE, curses.COLOR_BLUE)
# ... blah, blah, blah ...
self.scrn = self.stdscr.subwin(self.height, self.width, 0, 0)
self.scrn.bkgd(curses.color_pair(1))
# Blah, blah, blah ...

Fwiw

Chris

 

[Brian Victor]

I don't know how much this'll help, but my home-brewed curses TextApp
class has a white-on-blue default, and TextApp.startWin() contains
these lines (inter alia) ...

[snip]

Thanks, but that's not quite what I'm looking for. Getting a solid
background isn't a problem. Getting a subtly textured background to
show through (or other windows on Mac) seems to be a bit tricker.

Still hoping someone will hop in with "just use this curses extension"
or "you can write a wrapper around that one function and integrate it
with python's curses like this." But thanks for the input, anyway!

 

[Brian Victor]

Still hoping someone will hop in with "just use this curses extension"
or "you can write a wrapper around that one function and integrate it
with python's curses like this." But thanks for the input, anyway!

I guess that someone is me. I love replying to my own posts...

I just hacked this bit of code up and it seems to do the trick.
importing usedefault and calling usedefault.use_default_colors() sets
color pair 0 to use the default colors for the terminal. This allows
translucency on terminals that support it. The packaging could use some
work, but the following should be enough to get future readers going.

This is the first C extension I've written, and it's almost straight
from the docs. If anyone has any pointers, I'd be happy to hear them.

usedefault.c
#v+
#include <Python.h>
#include <ncurses.h>

static PyObject *
pyuse_default_colors(PyObject *self, PyObject *args)
{
use_default_colors();
Py_INCREF(Py_None);
return Py_None;
}

static PyMethodDef SpamMethods[] = {
{"use_default_colors", pyuse_default_colors, METH_VARARGS,
"Use Default Colors."},
{NULL, NULL, 0, NULL} /* Sentinel */
};

/* PyMODINIT_FUNC */
/* The docs say to use the above, but it doesn't exist in my copy of
* Python.h. */
void initusedefault()
{
(void) Py_InitModule("usedefault", SpamMethods);
}
#v-

setup.py
#v+
from distutils.core import setup, Extension

module1 = Extension('usedefault',
libraries = ["ncurses"],
sources = ['usedefault.c'])

setup (name = 'usedefault',
version = '1.0',
description = 'Use default colors in curses',
ext_modules = [module1])
#v-

 

[A.M. Kuchling]

static PyObject *
pyuse_default_colors(PyObject *self, PyObject *args)
{
use_default_colors();
Py_INCREF(Py_None);
return Py_None;
}

static PyMethodDef SpamMethods[] = {
{"use_default_colors", pyuse_default_colors, METH_VARARGS,
"Use Default Colors."},
{NULL, NULL, 0, NULL} /* Sentinel */

Use METH_NOARGS instead of METH_VARARGS; as written, this code will accept
any number of arguments to the Python use_default_colors() method and not
raise any error. An alternative would be to leave METH_VARARGS and put "if
(!PyArg_NoArgs(args)) return NULL;" in pyuse_default_colors(); this would
work with older versions of Python at the cost of being slightly slower.

I'll add this function to the curses module, so at least it'll be in 2.4;
thanks for writing it. Anyone know if it's possible to test it on MacOS X?
Does the Terminal support transparency?

--amk

};

/* PyMODINIT_FUNC */
/* The docs say to use the above, but it doesn't exist in my copy of
* Python.h. */
void initusedefault()
{
(void) Py_InitModule("usedefault", SpamMethods);
}
#v-

setup.py
#v+
from distutils.core import setup, Extension

module1 = Extension('usedefault',
libraries = ["ncurses"],
sources = ['usedefault.c'])

setup (name = 'usedefault',
version = '1.0',
description = 'Use default colors in curses',
ext_modules = [module1])
#v-

 

[Brian Victor]

Interestingly, both Terminal and iTerm seem to make everything
transparent, so use_default_colors has no significant effect. That is,
a black background is indistinguishable from a transparent/default
background.

I forgot to mention that I hit a compile error on OSX's ncurses header
file. I believe it came from the December dev tools. It dealt with
redefining wchar_t:

#ifndef _WCHAR_T
typedef unsigned long wchar_t;
#endif /* _WCHAR_T */

I have no idea why the mac version does that (fink's does also). My
linux copy of the headers has nothing like that. #defining _WCHAR_T
before including ncurses.h fixed that, but I don't know if that's a
permanent solution. FWIW, I was doing this with python 2.3a1.