Curses Key Definition Doesn't Work

[zhepyrval]

I was learning curses (using Pluto Project PDCurses) when I found out the keypad key definitions doesn't really work.

For example, this program shows nothing after I press the up arrow key on my keyboard.

#include <curses.h>

int main()
{
    int ch;

    initscr();
    keypad(stdscr, TRUE);

    ch = getch();
    if(ch == KEY_UP)
        printw("IT WORKS!");

    getch();
    endwin();

    return 0;
}

After a bit of debugging I learned that up arrow key is interpreted as the number 60419. I tried changing KEY_UP to that number and the program works.

The problem only happens when I test the value of ch with non ASCII characters. I did everything on CodeBlocks in a Windows machine.

I have two questions about this:

1. What is this number? I know it's not ASCII or Alt Codes. I tried Google but I got a bank somewhere in England.
2. If this is system related, should I mess around with curses.h file to associate every key with this number? I think this is a really really bad idea.

For reference, I tried to check what number is associated with each arrow key and this is the result

http://puu.sh/jnzF0.JPG (top to bottom: a, s, d, f, g, h, j, k, l, ;, up arrow, right arrow, down arrow, left arrow, up arrow, right arrow, down arrow, left arrow)

Curses are weird.

[Duthomhas]

Are you sure you are using the correct curses.h header file?
(Check again!)

The number means nothing -- it's a magic number.
It makes perfect sense, though. Print it (and other 'extended key' values) in hexadecimal to see what's going on.

curses.h

/*----------------------------------------------------------------------
 *
 *  Function and Keypad Key Definitions.
 *  Many are just for compatibility.
 *
 */

#ifdef PDC_WIDE
   #define KEY_OFFSET 0xec00
#else
   #define KEY_OFFSET 0x100
#endif

#define KEY_CODE_YES     (KEY_OFFSET + 0x00) /* If get_wch() gives a key code */

#define KEY_BREAK        (KEY_OFFSET + 0x01) /* Not on PC KBD */
#define KEY_DOWN         (KEY_OFFSET + 0x02) /* Down arrow key */
#define KEY_UP           (KEY_OFFSET + 0x03) /* Up arrow key */
#define KEY_LEFT         (KEY_OFFSET + 0x04) /* Left arrow key */
#define KEY_RIGHT        (KEY_OFFSET + 0x05) /* Right arrow key */
#define KEY_HOME         (KEY_OFFSET + 0x06) /* home key */
#define KEY_BACKSPACE    (KEY_OFFSET + 0x07) /* not on pc */
#define KEY_F0           (KEY_OFFSET + 0x08) /* function keys; 64 reserved */ 

Curses is weird because it works with so many different terminals, all of varying functionality. The IBM PC was unique, in part, because it set a clear standard for how devices attached to the system, like the keyboard, were to behave. Responding to keyboard interrupts is just a matter of table-lookup of make/break codes.

Many other systems, even today, are nowhere near as easy to handle. On an old SunSPARC station I used to use at school, pressing an arrow key required the system to handle a seven or eight character escape sequence.

Likewise, handling the Esc character is a hassle, because of a commonly-perpetuated bad design decision to use \033 as the first in a sequence of formatted control codes -- hence the ESCDELAY -- how long does Curses want to wait to see if Esc is just a single Esc key press or a control sequence? On a dial-up tty, it might be a lot longer than you would think.

Anyway, fix your curses.h header.

Hope this helps.

[zhepyrval]

That part in my curses.h is exactly the same as yours.

Weird update:
I found out the weird number appears when I declare ch as an integer. When I declared it as char, I got 2, 3, 4, 5 for down, up, left, and right.

However, this code still only works

#include <curses.h>

int main()
{
    char ch;

    initscr();
    keypad(stdscr, TRUE);

    ch = getch();
    if(ch == KEY_UP)
        printw("IT WORKS!");

    getch();
    endwin();

    return 0;
}

when I replace KEY_UP with 3.



Another thing, this is the tutorial I tried to follow (first example)

http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/windows.html

#include <ncurses.h>


WINDOW *create_newwin(int height, int width, int starty, int startx);
void destroy_win(WINDOW *local_win);

int main(int argc, char *argv[])
{	WINDOW *my_win;
	int startx, starty, width, height;
	int ch;

	initscr();			/* Start curses mode 		*/
	cbreak();			/* Line buffering disabled, Pass on
					 * everty thing to me 		*/
	keypad(stdscr, TRUE);		/* I need that nifty F1 	*/

	height = 3;
	width = 10;
	starty = (LINES - height) / 2;	/* Calculating for a center placement */
	startx = (COLS - width) / 2;	/* of the window		*/
	printw("Press F1 to exit");
	refresh();
	my_win = create_newwin(height, width, starty, startx);

	while((ch = getch()) != KEY_F(1))
	{	switch(ch)
		{	case KEY_LEFT:
				destroy_win(my_win);
				my_win = create_newwin(height, width, starty,--startx);
				break;
			case KEY_RIGHT:
				destroy_win(my_win);
				my_win = create_newwin(height, width, starty,++startx);
				break;
			case KEY_UP:
				destroy_win(my_win);
				my_win = create_newwin(height, width, --starty,startx);
				break;
			case KEY_DOWN:
				destroy_win(my_win);
				my_win = create_newwin(height, width, ++starty,startx);
				break;	
		}
	}
		
	endwin();			/* End curses mode		  */
	return 0;
}

I declared ch as a character and I got

warning: case label value exceeds maximum value for type [enabled by default]|

If the value of KEY_DOWN, KEY_UP, KEY_LEFT, KEY_RIGHT are 2, 3, 4, 5, how come it exceeds the maximum value of char (128 if I'm not mistaken)?

[Duthomhas]

'ch' should be an int.

(The returned key codes aren't just characters.)

BTW, the code works perfectly for me (except for having to change <ncurses.h> to <curses.h>).

I'm still not sure what's causing you problems.