CURSES!!!!!

1
CURSES!!!!!

• FOILED AGAIN!!
• Liam OLeary
• 12/3/07
• Seminar Ruby V. Python
• Pr. John Santore

2
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

3
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

4
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

5
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

6
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

7
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

8
More Curses Attributes

• A_STANDOUT Sets the text to the brightest
  possible highlight
• A_UNDERLINE Underlines all text with this
  attribute

9
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

10
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 cant 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)

11
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.

12
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

13
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

14
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() Lets out a short beeping sound

15
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

16
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 wont see it appear on
  the screen, it will still work, setting the
  terminal back to normal

17
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)