Arrow Keys and Such

This is a discussion on Arrow Keys and Such within the Game Programming forums, part of the General Programming Boards category; Ok I've noticed this on a number of games over the past few years. The 4 arrows keys are different ...

  1. #1
    & the hat of GPL slaying Thantos's Avatar
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    Arrow Keys and Such

    Ok I've noticed this on a number of games over the past few years.

    The 4 arrows keys are different then the arrow keys on the numpad (when numlock is off), and the number keys over the QWERTYUIOP line is different from the number keys on the numpad (when numlock is on).

    Anyone know how this is done? I'm trying to do it in C. Is C just too old to do that?

    I've tried to see if there were any differences in values between the two sets but I couldn't find any.

    Just wondering. Thanks for any info.

  2. #2
    Has a Masters in B.S.
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    ok heres the deal,

    when NumLock is on the key pad keys = numbers so that key 1 = 1 and ect ect, other wise the = exactly so... well heres a list

    Key = Key Equilivent
    NumLock on:

    1 = 1,
    2 = 2,
    3 = 3,
    4 = 4,
    5 = 5,
    6 = 6,
    7 = 7,
    8 = 8,
    9 = 9,
    0 = 0.

    Key = Function Equilivent

    NumLock off;

    1 = End
    2 = Down Arrow
    3 = Page Down
    4 = Left Arrow
    5 = ?/Nothing
    6 = Right Arrow
    7 = Home
    8 = Up Arrow
    9 = Page Up
    0 = Insert
    ADVISORY: This users posts are rated CP-MA, for Mature Audiences only.

  3. #3
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    They ARE different keys, but the keyboard handler you use will convert them to the same key value.

    The values that you obtain as keypresses are NOT the values sent by the keyboard to the computer -- there's preprocessing by the keyboard handler. If you wrote your own handler, you would find that pressing the 8/Up key on the keypad would have its own scan code, which is not the same as the scan code for the '8' key or the 'up' key.

    In windows, you actually can take the second param to the WM_KEYDOWN message and obtain the actual scancode for the key. The param most people use, the virtual key code, is created by Windows by mapping scancodes to keycodes.

  4. #4
    & the hat of GPL slaying Thantos's Avatar
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    Ok I understand what your saying The V. Now to figure out how to build a keyboard handler

  5. #5
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    That works just fine, buuuut:

    1) You can't run a program that installs its own handler except under true DOS. Windows, if running, will barf if you try to "steal" keyboard handling from it.

    2) Keyboard handlers are highly system-dependant, as are the scancodes of keys.

    So, when you need to do keyboard handling like this, you need to look at targetting this to only one OS.

    Code:
    If you are using           Then use
    --------------------       -------------
    DOS/Win3.1                 Custom keyboard handler
    Win32                      DirectInput or WM_KEYDOWN parameter extraction
    Unix/Linux                 ??? -- almost certainly depends on hardware + software
    Last edited by The V.; 10-25-2001 at 04:51 PM.

  6. #6
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    well, I think that when you press one of the arrow keys two ASCII codes are sent, the first one is 0, the other ones are:

    82: INSERT
    83: DELETE
    71: HOME
    79: END
    73: PAGE UP
    81: PAGE DOWN
    72: UP
    80: DOWN
    75: LEFT
    77: RIGHT
    59 - 68: F1 - F10

    I can't remember which are the F11 and F12 keys, but I don't think that you will need them

    Oskilian

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