NCURSES- Arrow keys not detected?

[Tduck]

Within my code, there is a point where I am trying to see which arrow key a person pressed. No matter which key I press, the result is always default.
I have enabled keypad(stdscr, TRUE); and echo(); as well as raw();, and there is a refresh(); directly before the following code, if that helps at all.

char ch1 = getch();
switch(ch1)
{
    case KEY_LEFT: printw("You pressed left.\n"); break;
        
    case KEY_RIGHT: printw("You pressed right.\n"); break;
    
    case KEY_UP: printw("You pressed up.\n"); break;
        
    case KEY_DOWN: printw("You pressed down.\n"); break;
    default: printw("You didn't press an arrow key.\n");
}

Also, I'm not sure if I should be posting this on the normal windows forum or beginners, since NCURSES isn't taught in any c++ courses I've taken, and it seems more obscure than, well, the standard library. For future reference, should I post these kinds of questions here or elsewhere?

[mbozzi]

At the very least, refresh() must be called after you print to the buffer.
Here is a complete example:

#include <ncurses.h>

int main() {
  initscr();
  clear();
  noecho();
  cbreak();
  keypad(stdscr, true);

  printw("Press 'q' to quit.");
  refresh();

  for (int ch = getch(); ch != 'q'; ch = getch()) {
    mvprintw(1, 0,
               ch == KEY_UP    ? "up"
             : ch == KEY_DOWN  ? "down"
             : ch == KEY_LEFT  ? "left"
             : ch == KEY_RIGHT ? "right" : "");
    clrtoeol();
    refresh();
  }

  endwin();
}

I think it's fine to post here. It might be specific to Unix programming, but there is a port of NCurses (called PDCurses) for Windows anyway.

[dutch]

getch returns an int.

It's not so important where you post but it's definitely important to post something that can be run without helpers needing to add a bunch of boilerplate to.

[ne555]

https://linux.die.net/man/3/getch

int getch(void);

note that the function returns an int


> I have enabled keypad(stdscr, TRUE); and echo(); as well as raw();, and there is a refresh();
I'd rather have code, thanks.

[Tduck]

Why DOESN'T my code work?
In the code posted by mbozzi, it seems that on lines 15-20 or so, what is similar to if statements seems to be of use, I don't remember the name of the ? operator.

What's causing the input not to be evaluated properly, yet the evaluative expression by mbozzi seems to work fine?

[dutch]

Can't you read?
getch RETURNS AN INT!!!!
Just like getchar() in stdio.h.
That's a beginner mistake, dude.

[Tduck]

That's why I posted on beginner forums, I'd appreciate if you're not so rude. I don't find it helpful.

As I said, the code that mbozzi posted seems to work, and in my experience, all chars are associated with an integer in ASCII, so I would assume KEY_ has an integer value as well.

Edit: In fact, I've discovered this bout of code that made me assume as much would work:

printw("Type any character to see it in bold\n");
	ch = getch();			/* If raw() hadn't been called
					 * we have to press enter before it
					 * gets to the program 		*/
	if(ch == KEY_F(1))		/* Without keypad enabled this will */
		printw("F1 Key pressed")

It comes directly from the NCURSES how-to, here:
http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html#KEYPAD

[mbozzi]

If you're going to argue with the manual, we cannot help you.

Post a complete program that exhibits the problem.

[helios]

Tduck: In that example you found in the how-to, what's the type of 'ch'? It's the first declaration in main().
See also the example in http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html#KEYS

The problem with this:

char ch1 = getch();

is that getch() may return information in its return value that doesn't fit into a char. For example, the value of KEY_LEFT could easily be 1026 (I don't know its actual value and it's not important). On a desktop platform, if you try to assign 1026 to a char variable, the variable will hold the value 2 instead. You will get other, similar problems with other values. E.g. (char)384 == (char)-128 (again, this is true on typical desktop platforms, but not necessarily elsewhere).
Your compiler should have issued a warning about loss of information when assigning an int to a char. Did you ignore that warning?

[Tduck]

I think I know where the confusion came in. It seems that on the website that the variable ch, I misinterpreted it as a character, not an integer. Thank you helios and mbozzi.

int intPut;
while(intPut != 'q')
{
    intPut = getch();
    if(intPut == KEY_LEFT) { printw("You pressed left.\n"); }
    else if(intPut == KEY_RIGHT) { printw("You pressed right.\n"); }
    else if(intPut == KEY_UP) { printw("You pressed up.\n"); }
    else if (intPut == KEY_DOWN) { printw("You pressed down.\n"); }
    else { printw("You didn't press an arrow key.\n"); }
}

[jonnin]

characters ARE integers. input should probably have been char or unsigned char, depending on how your constants KEY_RIGHT etc are defined. However, int works, its just a little confusing to use int here. You will frequently see it the other way around (code that uses char as an integer) in older, pre 'auto everything' code.