author | martin.trojer@nokia.com |
Fri, 31 Jul 2009 15:01:17 +0100 | |
changeset 1 | 2fb8b9db1c86 |
permissions | -rw-r--r-- |
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.. _curses-howto: |
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********************************** |
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Curses Programming with Python |
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********************************** |
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:Author: A.M. Kuchling, Eric S. Raymond |
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:Release: 2.03 |
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.. topic:: Abstract |
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This document describes how to write text-mode programs with Python 2.x, using |
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the :mod:`curses` extension module to control the display. |
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What is curses? |
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=============== |
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The curses library supplies a terminal-independent screen-painting and |
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keyboard-handling facility for text-based terminals; such terminals include |
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VT100s, the Linux console, and the simulated terminal provided by X11 programs |
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such as xterm and rxvt. Display terminals support various control codes to |
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perform common operations such as moving the cursor, scrolling the screen, and |
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erasing areas. Different terminals use widely differing codes, and often have |
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their own minor quirks. |
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In a world of X displays, one might ask "why bother"? It's true that |
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character-cell display terminals are an obsolete technology, but there are |
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niches in which being able to do fancy things with them are still valuable. One |
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is on small-footprint or embedded Unixes that don't carry an X server. Another |
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is for tools like OS installers and kernel configurators that may have to run |
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before X is available. |
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The curses library hides all the details of different terminals, and provides |
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the programmer with an abstraction of a display, containing multiple |
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non-overlapping windows. The contents of a window can be changed in various |
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ways-- adding text, erasing it, changing its appearance--and the curses library |
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will automagically figure out what control codes need to be sent to the terminal |
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to produce the right output. |
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The curses library was originally written for BSD Unix; the later System V |
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versions of Unix from AT&T added many enhancements and new functions. BSD curses |
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is no longer maintained, having been replaced by ncurses, which is an |
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open-source implementation of the AT&T interface. If you're using an |
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open-source Unix such as Linux or FreeBSD, your system almost certainly uses |
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ncurses. Since most current commercial Unix versions are based on System V |
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code, all the functions described here will probably be available. The older |
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versions of curses carried by some proprietary Unixes may not support |
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everything, though. |
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No one has made a Windows port of the curses module. On a Windows platform, try |
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the Console module written by Fredrik Lundh. The Console module provides |
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cursor-addressable text output, plus full support for mouse and keyboard input, |
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and is available from http://effbot.org/zone/console-index.htm. |
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The Python curses module |
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------------------------ |
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Thy Python module is a fairly simple wrapper over the C functions provided by |
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curses; if you're already familiar with curses programming in C, it's really |
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easy to transfer that knowledge to Python. The biggest difference is that the |
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Python interface makes things simpler, by merging different C functions such as |
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:func:`addstr`, :func:`mvaddstr`, :func:`mvwaddstr`, into a single |
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:meth:`addstr` method. You'll see this covered in more detail later. |
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This HOWTO is simply an introduction to writing text-mode programs with curses |
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and Python. It doesn't attempt to be a complete guide to the curses API; for |
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that, see the Python library guide's section on ncurses, and the C manual pages |
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for ncurses. It will, however, give you the basic ideas. |
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Starting and ending a curses application |
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======================================== |
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Before doing anything, curses must be initialized. This is done by calling the |
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:func:`initscr` function, which will determine the terminal type, send any |
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required setup codes to the terminal, and create various internal data |
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structures. If successful, :func:`initscr` returns a window object representing |
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the entire screen; this is usually called ``stdscr``, after the name of the |
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corresponding C variable. :: |
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import curses |
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stdscr = curses.initscr() |
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Usually curses applications turn off automatic echoing of keys to the screen, in |
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order to be able to read keys and only display them under certain circumstances. |
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This requires calling the :func:`noecho` function. :: |
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curses.noecho() |
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Applications will also commonly need to react to keys instantly, without |
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requiring the Enter key to be pressed; this is called cbreak mode, as opposed to |
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the usual buffered input mode. :: |
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curses.cbreak() |
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Terminals usually return special keys, such as the cursor keys or navigation |
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keys such as Page Up and Home, as a multibyte escape sequence. While you could |
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write your application to expect such sequences and process them accordingly, |
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curses can do it for you, returning a special value such as |
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:const:`curses.KEY_LEFT`. To get curses to do the job, you'll have to enable |
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keypad mode. :: |
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106 |
stdscr.keypad(1) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
107 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
108 |
Terminating a curses application is much easier than starting one. You'll need |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
109 |
to call :: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
110 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
111 |
curses.nocbreak(); stdscr.keypad(0); curses.echo() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
112 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
113 |
to reverse the curses-friendly terminal settings. Then call the :func:`endwin` |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
114 |
function to restore the terminal to its original operating mode. :: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
115 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
116 |
curses.endwin() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
117 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
118 |
A common problem when debugging a curses application is to get your terminal |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
119 |
messed up when the application dies without restoring the terminal to its |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
120 |
previous state. In Python this commonly happens when your code is buggy and |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
121 |
raises an uncaught exception. Keys are no longer be echoed to the screen when |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
122 |
you type them, for example, which makes using the shell difficult. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
123 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
124 |
In Python you can avoid these complications and make debugging much easier by |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
125 |
importing the module :mod:`curses.wrapper`. It supplies a :func:`wrapper` |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
126 |
function that takes a callable. It does the initializations described above, |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
127 |
and also initializes colors if color support is present. It then runs your |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
128 |
provided callable and finally deinitializes appropriately. The callable is |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
129 |
called inside a try-catch clause which catches exceptions, performs curses |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
130 |
deinitialization, and then passes the exception upwards. Thus, your terminal |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
131 |
won't be left in a funny state on exception. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
132 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
133 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
134 |
Windows and Pads |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
135 |
================ |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
136 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
137 |
Windows are the basic abstraction in curses. A window object represents a |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
138 |
rectangular area of the screen, and supports various methods to display text, |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
139 |
erase it, allow the user to input strings, and so forth. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
140 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
141 |
The ``stdscr`` object returned by the :func:`initscr` function is a window |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
142 |
object that covers the entire screen. Many programs may need only this single |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
143 |
window, but you might wish to divide the screen into smaller windows, in order |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
144 |
to redraw or clear them separately. The :func:`newwin` function creates a new |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
145 |
window of a given size, returning the new window object. :: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
146 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
147 |
begin_x = 20 ; begin_y = 7 |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
148 |
height = 5 ; width = 40 |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
149 |
win = curses.newwin(height, width, begin_y, begin_x) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
150 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
151 |
A word about the coordinate system used in curses: coordinates are always passed |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
152 |
in the order *y,x*, and the top-left corner of a window is coordinate (0,0). |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
153 |
This breaks a common convention for handling coordinates, where the *x* |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
154 |
coordinate usually comes first. This is an unfortunate difference from most |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
155 |
other computer applications, but it's been part of curses since it was first |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
156 |
written, and it's too late to change things now. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
157 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
158 |
When you call a method to display or erase text, the effect doesn't immediately |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
159 |
show up on the display. This is because curses was originally written with slow |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
160 |
300-baud terminal connections in mind; with these terminals, minimizing the time |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
161 |
required to redraw the screen is very important. This lets curses accumulate |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
162 |
changes to the screen, and display them in the most efficient manner. For |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
163 |
example, if your program displays some characters in a window, and then clears |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
164 |
the window, there's no need to send the original characters because they'd never |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
165 |
be visible. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
166 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
167 |
Accordingly, curses requires that you explicitly tell it to redraw windows, |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
168 |
using the :func:`refresh` method of window objects. In practice, this doesn't |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
169 |
really complicate programming with curses much. Most programs go into a flurry |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
170 |
of activity, and then pause waiting for a keypress or some other action on the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
171 |
part of the user. All you have to do is to be sure that the screen has been |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
172 |
redrawn before pausing to wait for user input, by simply calling |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
173 |
``stdscr.refresh()`` or the :func:`refresh` method of some other relevant |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
174 |
window. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
175 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
176 |
A pad is a special case of a window; it can be larger than the actual display |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
177 |
screen, and only a portion of it displayed at a time. Creating a pad simply |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
178 |
requires the pad's height and width, while refreshing a pad requires giving the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
179 |
coordinates of the on-screen area where a subsection of the pad will be |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
180 |
displayed. :: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
181 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
182 |
pad = curses.newpad(100, 100) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
183 |
# These loops fill the pad with letters; this is |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
184 |
# explained in the next section |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
185 |
for y in range(0, 100): |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
186 |
for x in range(0, 100): |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
187 |
try: pad.addch(y,x, ord('a') + (x*x+y*y) % 26 ) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
188 |
except curses.error: pass |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
189 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
190 |
# Displays a section of the pad in the middle of the screen |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
191 |
pad.refresh( 0,0, 5,5, 20,75) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
192 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
193 |
The :func:`refresh` call displays a section of the pad in the rectangle |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
194 |
extending from coordinate (5,5) to coordinate (20,75) on the screen; the upper |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
195 |
left corner of the displayed section is coordinate (0,0) on the pad. Beyond |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
196 |
that difference, pads are exactly like ordinary windows and support the same |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
197 |
methods. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
198 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
199 |
If you have multiple windows and pads on screen there is a more efficient way to |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
200 |
go, which will prevent annoying screen flicker at refresh time. Use the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
201 |
:meth:`noutrefresh` method of each window to update the data structure |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
202 |
representing the desired state of the screen; then change the physical screen to |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
203 |
match the desired state in one go with the function :func:`doupdate`. The |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
204 |
normal :meth:`refresh` method calls :func:`doupdate` as its last act. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
205 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
206 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
207 |
Displaying Text |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
208 |
=============== |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
209 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
210 |
From a C programmer's point of view, curses may sometimes look like a twisty |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
211 |
maze of functions, all subtly different. For example, :func:`addstr` displays a |
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|
212 |
string at the current cursor location in the ``stdscr`` window, while |
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|
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:func:`mvaddstr` moves to a given y,x coordinate first before displaying the |
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|
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string. :func:`waddstr` is just like :func:`addstr`, but allows specifying a |
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|
215 |
window to use, instead of using ``stdscr`` by default. :func:`mvwaddstr` follows |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
216 |
similarly. |
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|
217 |
|
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|
218 |
Fortunately the Python interface hides all these details; ``stdscr`` is a window |
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|
219 |
object like any other, and methods like :func:`addstr` accept multiple argument |
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|
220 |
forms. Usually there are four different forms. |
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|
221 |
|
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222 |
+---------------------------------+-----------------------------------------------+ |
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223 |
| Form | Description | |
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|
224 |
+=================================+===============================================+ |
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225 |
| *str* or *ch* | Display the string *str* or character *ch* at | |
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226 |
| | the current position | |
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227 |
+---------------------------------+-----------------------------------------------+ |
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228 |
| *str* or *ch*, *attr* | Display the string *str* or character *ch*, | |
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229 |
| | using attribute *attr* at the current | |
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230 |
| | position | |
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231 |
+---------------------------------+-----------------------------------------------+ |
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232 |
| *y*, *x*, *str* or *ch* | Move to position *y,x* within the window, and | |
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233 |
| | display *str* or *ch* | |
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|
234 |
+---------------------------------+-----------------------------------------------+ |
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235 |
| *y*, *x*, *str* or *ch*, *attr* | Move to position *y,x* within the window, and | |
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|
236 |
| | display *str* or *ch*, using attribute *attr* | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
237 |
+---------------------------------+-----------------------------------------------+ |
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|
238 |
|
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|
239 |
Attributes allow displaying text in highlighted forms, such as in boldface, |
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|
240 |
underline, reverse code, or in color. They'll be explained in more detail in |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
241 |
the next subsection. |
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|
242 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
243 |
The :func:`addstr` function takes a Python string as the value to be displayed, |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
244 |
while the :func:`addch` functions take a character, which can be either a Python |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
245 |
string of length 1 or an integer. If it's a string, you're limited to |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
246 |
displaying characters between 0 and 255. SVr4 curses provides constants for |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
247 |
extension characters; these constants are integers greater than 255. For |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
248 |
example, :const:`ACS_PLMINUS` is a +/- symbol, and :const:`ACS_ULCORNER` is the |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
249 |
upper left corner of a box (handy for drawing borders). |
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|
250 |
|
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|
251 |
Windows remember where the cursor was left after the last operation, so if you |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
252 |
leave out the *y,x* coordinates, the string or character will be displayed |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
253 |
wherever the last operation left off. You can also move the cursor with the |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
254 |
``move(y,x)`` method. Because some terminals always display a flashing cursor, |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
255 |
you may want to ensure that the cursor is positioned in some location where it |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
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|
256 |
won't be distracting; it can be confusing to have the cursor blinking at some |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
257 |
apparently random location. |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
258 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
259 |
If your application doesn't need a blinking cursor at all, you can call |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
260 |
``curs_set(0)`` to make it invisible. Equivalently, and for compatibility with |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
261 |
older curses versions, there's a ``leaveok(bool)`` function. When *bool* is |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
262 |
true, the curses library will attempt to suppress the flashing cursor, and you |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
263 |
won't need to worry about leaving it in odd locations. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
264 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
265 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
266 |
Attributes and Color |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
267 |
-------------------- |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
268 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
changeset
|
269 |
Characters can be displayed in different ways. Status lines in a text-based |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
270 |
application are commonly shown in reverse video; a text viewer may need to |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
271 |
highlight certain words. curses supports this by allowing you to specify an |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
272 |
attribute for each cell on the screen. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
273 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
changeset
|
274 |
An attribute is a integer, each bit representing a different attribute. You can |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
275 |
try to display text with multiple attribute bits set, but curses doesn't |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
276 |
guarantee that all the possible combinations are available, or that they're all |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
changeset
|
277 |
visually distinct. That depends on the ability of the terminal being used, so |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
278 |
it's safest to stick to the most commonly available attributes, listed here. |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
279 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
280 |
+----------------------+--------------------------------------+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
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|
281 |
| Attribute | Description | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
282 |
+======================+======================================+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
283 |
| :const:`A_BLINK` | Blinking text | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
284 |
+----------------------+--------------------------------------+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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|
285 |
| :const:`A_BOLD` | Extra bright or bold text | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
286 |
+----------------------+--------------------------------------+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
287 |
| :const:`A_DIM` | Half bright text | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
288 |
+----------------------+--------------------------------------+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
289 |
| :const:`A_REVERSE` | Reverse-video text | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
changeset
|
290 |
+----------------------+--------------------------------------+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
291 |
| :const:`A_STANDOUT` | The best highlighting mode available | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
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|
292 |
+----------------------+--------------------------------------+ |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
293 |
| :const:`A_UNDERLINE` | Underlined text | |
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
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|
294 |
+----------------------+--------------------------------------+ |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
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changeset
|
295 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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diff
changeset
|
296 |
So, to display a reverse-video status line on the top line of the screen, you |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
297 |
could code:: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
298 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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changeset
|
299 |
stdscr.addstr(0, 0, "Current mode: Typing mode", |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
300 |
curses.A_REVERSE) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
301 |
stdscr.refresh() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
302 |
|
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Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
303 |
The curses library also supports color on those terminals that provide it, The |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
304 |
most common such terminal is probably the Linux console, followed by color |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
305 |
xterms. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
306 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
307 |
To use color, you must call the :func:`start_color` function soon after calling |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
308 |
:func:`initscr`, to initialize the default color set (the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
309 |
:func:`curses.wrapper.wrapper` function does this automatically). Once that's |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
310 |
done, the :func:`has_colors` function returns TRUE if the terminal in use can |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
311 |
actually display color. (Note: curses uses the American spelling 'color', |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
312 |
instead of the Canadian/British spelling 'colour'. If you're used to the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
313 |
British spelling, you'll have to resign yourself to misspelling it for the sake |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
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parents:
diff
changeset
|
314 |
of these functions.) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
315 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
316 |
The curses library maintains a finite number of color pairs, containing a |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
317 |
foreground (or text) color and a background color. You can get the attribute |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
318 |
value corresponding to a color pair with the :func:`color_pair` function; this |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
319 |
can be bitwise-OR'ed with other attributes such as :const:`A_REVERSE`, but |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
320 |
again, such combinations are not guaranteed to work on all terminals. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
321 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
322 |
An example, which displays a line of text using color pair 1:: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
323 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
324 |
stdscr.addstr( "Pretty text", curses.color_pair(1) ) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
325 |
stdscr.refresh() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
326 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
327 |
As I said before, a color pair consists of a foreground and background color. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
328 |
:func:`start_color` initializes 8 basic colors when it activates color mode. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
329 |
They are: 0:black, 1:red, 2:green, 3:yellow, 4:blue, 5:magenta, 6:cyan, and |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
330 |
7:white. The curses module defines named constants for each of these colors: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
331 |
:const:`curses.COLOR_BLACK`, :const:`curses.COLOR_RED`, and so forth. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
332 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
333 |
The ``init_pair(n, f, b)`` function changes the definition of color pair *n*, to |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
334 |
foreground color f and background color b. Color pair 0 is hard-wired to white |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
335 |
on black, and cannot be changed. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
336 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
337 |
Let's put all this together. To change color 1 to red text on a white |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
338 |
background, you would call:: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
339 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
340 |
curses.init_pair(1, curses.COLOR_RED, curses.COLOR_WHITE) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
341 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
342 |
When you change a color pair, any text already displayed using that color pair |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
343 |
will change to the new colors. You can also display new text in this color |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
344 |
with:: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
345 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
346 |
stdscr.addstr(0,0, "RED ALERT!", curses.color_pair(1) ) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
347 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
348 |
Very fancy terminals can change the definitions of the actual colors to a given |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
349 |
RGB value. This lets you change color 1, which is usually red, to purple or |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
350 |
blue or any other color you like. Unfortunately, the Linux console doesn't |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
351 |
support this, so I'm unable to try it out, and can't provide any examples. You |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
352 |
can check if your terminal can do this by calling :func:`can_change_color`, |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
353 |
which returns TRUE if the capability is there. If you're lucky enough to have |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
354 |
such a talented terminal, consult your system's man pages for more information. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
355 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
356 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
357 |
User Input |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
358 |
========== |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
359 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
360 |
The curses library itself offers only very simple input mechanisms. Python's |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
361 |
support adds a text-input widget that makes up some of the lack. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
362 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
363 |
The most common way to get input to a window is to use its :meth:`getch` method. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
364 |
:meth:`getch` pauses and waits for the user to hit a key, displaying it if |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
365 |
:func:`echo` has been called earlier. You can optionally specify a coordinate |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
366 |
to which the cursor should be moved before pausing. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
367 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
368 |
It's possible to change this behavior with the method :meth:`nodelay`. After |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
369 |
``nodelay(1)``, :meth:`getch` for the window becomes non-blocking and returns |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
370 |
``curses.ERR`` (a value of -1) when no input is ready. There's also a |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
371 |
:func:`halfdelay` function, which can be used to (in effect) set a timer on each |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
372 |
:meth:`getch`; if no input becomes available within a specified |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
373 |
delay (measured in tenths of a second), curses raises an exception. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
374 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
375 |
The :meth:`getch` method returns an integer; if it's between 0 and 255, it |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
376 |
represents the ASCII code of the key pressed. Values greater than 255 are |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
377 |
special keys such as Page Up, Home, or the cursor keys. You can compare the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
378 |
value returned to constants such as :const:`curses.KEY_PPAGE`, |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
379 |
:const:`curses.KEY_HOME`, or :const:`curses.KEY_LEFT`. Usually the main loop of |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
380 |
your program will look something like this:: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
381 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
382 |
while 1: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
383 |
c = stdscr.getch() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
384 |
if c == ord('p'): PrintDocument() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
385 |
elif c == ord('q'): break # Exit the while() |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
386 |
elif c == curses.KEY_HOME: x = y = 0 |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
387 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
388 |
The :mod:`curses.ascii` module supplies ASCII class membership functions that |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
389 |
take either integer or 1-character-string arguments; these may be useful in |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
390 |
writing more readable tests for your command interpreters. It also supplies |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
391 |
conversion functions that take either integer or 1-character-string arguments |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
392 |
and return the same type. For example, :func:`curses.ascii.ctrl` returns the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
393 |
control character corresponding to its argument. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
394 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
395 |
There's also a method to retrieve an entire string, :const:`getstr()`. It isn't |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
396 |
used very often, because its functionality is quite limited; the only editing |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
397 |
keys available are the backspace key and the Enter key, which terminates the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
398 |
string. It can optionally be limited to a fixed number of characters. :: |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
399 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
400 |
curses.echo() # Enable echoing of characters |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
401 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
402 |
# Get a 15-character string, with the cursor on the top line |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
403 |
s = stdscr.getstr(0,0, 15) |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
404 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
405 |
The Python :mod:`curses.textpad` module supplies something better. With it, you |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
406 |
can turn a window into a text box that supports an Emacs-like set of |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
407 |
keybindings. Various methods of :class:`Textbox` class support editing with |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
408 |
input validation and gathering the edit results either with or without trailing |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
409 |
spaces. See the library documentation on :mod:`curses.textpad` for the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
410 |
details. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
411 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
412 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
413 |
For More Information |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
414 |
==================== |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
415 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
416 |
This HOWTO didn't cover some advanced topics, such as screen-scraping or |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
417 |
capturing mouse events from an xterm instance. But the Python library page for |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
418 |
the curses modules is now pretty complete. You should browse it next. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
419 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
420 |
If you're in doubt about the detailed behavior of any of the ncurses entry |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
421 |
points, consult the manual pages for your curses implementation, whether it's |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
422 |
ncurses or a proprietary Unix vendor's. The manual pages will document any |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
423 |
quirks, and provide complete lists of all the functions, attributes, and |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
424 |
:const:`ACS_\*` characters available to you. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
425 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
426 |
Because the curses API is so large, some functions aren't supported in the |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
427 |
Python interface, not because they're difficult to implement, but because no one |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
428 |
has needed them yet. Feel free to add them and then submit a patch. Also, we |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
429 |
don't yet have support for the menus or panels libraries associated with |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
430 |
ncurses; feel free to add that. |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
431 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
432 |
If you write an interesting little program, feel free to contribute it as |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
433 |
another demo. We can always use more of them! |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
434 |
|
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
435 |
The ncurses FAQ: http://invisible-island.net/ncurses/ncurses.faq.html |
2fb8b9db1c86
Initial QEMU (symbian-qemu-0.9.1-12) import
martin.trojer@nokia.com
parents:
diff
changeset
|
436 |