Transcript CURSES!!!!! - Bridgewater State University

CURSES!!!!!
FOILED AGAIN!!
Liam O’Leary
12/3/07
Seminar: Ruby V. Python
Pr. John Santore
Curses and its Purposes:
• The curses library is used for displays on various
terminals (like the Linux console) and controls
simple things like text input, cursor movement,
etc.
• A common use for curses is on things like OS
installers and kernel configurators which run
before more complicated graphics and text
editors are available
Starting Curses…
import curses
stdscr = curses.initscr()
• initscr() initializes curses and sets up any
necessary code to connect to the terminal.
• initscr(), creates a window, usually taking
up the entire screen, to display curses
graphics
Curses functions Pt. I
• newwin(height, width, begin y, begin x) –
Creates a new curses window (Note: window
coordinates in curses are the same as in
pygame)
• noecho() - Prevents curses from displaying
keystrokes on the screen
• echo() – Allows curses to display user input from
the keyboard
• cbreak() – Used to allow curses programs to
automatically react to keys, without needing
Enter to be pressed
Curses Functions Pt. II (Featuring
pad)
• refresh() – Refreshes the window, like blit()
in pygame
• newpad() – Creates a “pad”, which can be
bigger than the actual window or just a
small section of a window which curses
will use
• curs_set(0) – Allows you to hide the
cursor, should your application not need it
Displaying Text in Curses
• Curses in python uses addch/str(y, x, str or ch,
attr) to draw characters or strings onto the
screen.
• The y and x in addstr() is optional, allowing you
to specfically place the text where you want it. If
omitted, the text is displayed in the upper left
corner (0, 0)
• addstr() (and initscr) replaces mvaddstr() and
waddstr() from the C version of curses,
waddstr() creates a new window for the new
string and mvaddstr() moves the string to a
specified location
Attributes of Curses…
• A_BLINK – Causes any string or character
written with this attribute to flash on screen
• A_BOLD – Makes strings or characters
bold or extra bright
• A_DIM – Decreases brightness of text by
half
• A_REVERSE – Puts text in reverse video
More Curses Attributes…
• A_STANDOUT – Sets the text to the
brightest possible highlight
• A_UNDERLINE – Underlines all text with
this attribute
Curses in Color
• start_color() – Initializes the default color
set, needs to be called shortly after
initscr()
• has_colors() – Returns true if the terminal
has the ability to display colors
• Init_pair (x, foreground_color,
background_color) – Initializes a color pair,
with x being the number of the pair
Curses in Color Pt. II
• color_pair() – A designated foreground
and background color fair curses output,
default, color_pair(0), is white on black
and can’t be changed
• curses eight normal color possibilities are
0) black, 1) red, 2) green, 3) yellow, 4)
blue, 5) magenta, 6) cyan (blue-green),
and 7) white. Colors are called by the
function curses.COLOR_(RED)
Curses and You…
• getch() – Allows the user to input text into a curses
window, it pauses, waits for a keystroke (assuming
echo() was already called) and displays it to the screen.
A (y, x) position can be given with getch() if desired
• getstr() – Just like getch(), but instead, accepts a string
of a user-given length
• getmouse() – Accepts mouse clicks as events,
represented by a 5-tuple (id, x, y, z, bit-state) id is a
value used to distinguish between multiple devices, x
and y are the events’ coordinates (z is unused) bit-state
is a value used to determine what type of event it is; a
button press, a button release, a double click, etc.
Curses and You Pt. II
• nodelay() – Turns off the default delay for
getch() and gives an error if no input is
received
• halfdelay(x) – Essentially sets a timer for
getch(), if no input is received within the
number of milliseconds equal to x, and
exception is thrown
Curses and You Pt. III
• During getch(), curses only outputs numbers
with ASCII values between 0 and 255, the
following are functions for keys beyond that
scope
• curses.KEY_HOME – A function to determine if
a keystroke from getch() is, in fact, the HOME
key, can used in a function to set the cursor back
to the origin
• curses.KEY_LEFT (etc) – Same as KEY_HOME,
only instead to be used to move the cursor by
individual spaces
Fancy Curses…
• stdscr.hline(y, x, ch, n) – Draws a
horizontal line of n length, starting at (y, x)
made of the character ch
• stdscr.vline(y, x, ch, n) – Draws a vertical
line of n length, starting at (y, x), made of
the character ch
• beep() – Let’s out a short beeping sound
Curses on the Menu…
• Curses can give the appearance of
menus, using addstr() and the proper
amount of spacing
• Creating real menus with curses requires
using either Tkinter or another library
called dialog to create real menus and
buttons
Cursed Curses!!!
• Upon finishing an application, curses has a
tendency to mess up the terminal, either leaving
it the last color used by the application, or not
displaying any further input
• This problem is solved (at least on csdev01) by
typing in reset, while you won’t see it appear on
the screen, it will still work, setting the terminal
back to normal
More Cursed Curses…
• Curses can set colors through RGB with a
function called init_color(color, r, g, b). Color is a
number representing one of the normal curses
colors, (r, g, b) are numerical representations of
the amount of red, green or blue desired,
ranging from between 0 and 1000
• However, init_color() will only work if the terminal
is capable of doing so, which can be determined
using can_change_color() (1 indicates true,
meaning the terminal can use RGB to determine
colors)