question about lParam

This is a discussion on question about lParam within the Windows Programming forums, part of the Platform Specific Boards category; lParam [in] Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag. For more ...

  1. #1
    Registered User
    Join Date
    Oct 2004
    Posts
    16

    question about lParam

    lParam
    [in] Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag. For more information about the lParam parameter, see Keystroke Message Flags. This parameter can be one or more of the following values.
    0-15
    Specifies the repeat count. The value is the number of times the keystroke is repeated as a result of the user's holding down the key.
    16-23
    Specifies the scan code. The value depends on the OEM.
    24
    Specifies whether the key is an extended key, such as a function key or a key on the numeric keypad. The value is 1 if the key is an extended key; otherwise, it is 0.
    25-28
    Reserved.
    29
    Specifies the context code. The value is 1 if the ALT key is down; otherwise, it is 0.
    30
    Specifies the previous key state. The value is 1 if the key is down before the message is sent; it is 0 if the key is up.
    31
    Specifies the transition state. The value is 0 if the key is being pressed and 1 if it is being released.


    in this description of what lParam will contain, how do i check to see what the transition state is?

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    Location
    The edge of the known universe
    Posts
    32,821
    Well the description is a list of bit fields.

    So in unsigned arithmetic, it would be
    Code:
    lParam & ( 1u << 31 )

  3. #3
    Yes, my avatar is stolen anonytmouse's Avatar
    Join Date
    Dec 2002
    Posts
    2,544
    You can also use the pre-defined flags.
    Code:
    bIsUp      = (HIWORD(lParam) & KF_UP);
    bAltIsDown = (HIWORD(lParam) & KF_ALTDOWN);
    bExtended  = (HIWORD(lParam) & KF_EXTENDED);
    This is the list of flags:
    Quote Originally Posted by MSDN About Keyboard Input
    KF_ALTDOWN Manipulates the ALT key flag, which indicated if the ALT key is pressed.
    KF_DLGMODE Manipulates the dialog mode flag, which indicates whether a dialog box is active.
    KF_EXTENDED Manipulates the extended key flag.
    KF_MENUMODE Manipulates the menu mode flag, which indicates whether a menu is active.
    KF_REPEAT Manipulates the repeat count.
    KF_UP Manipulates the transition state flag.

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. another do while question
    By kbpsu in forum C++ Programming
    Replies: 3
    Last Post: 03-23-2009, 01:14 PM
  2. Cancel Button not working
    By Xzyx987X in forum Windows Programming
    Replies: 3
    Last Post: 10-27-2004, 01:41 AM
  3. Question...
    By TechWins in forum A Brief History of Cprogramming.com
    Replies: 16
    Last Post: 07-28-2003, 10:47 PM
  4. opengl program as win API menu item
    By SAMSAM in forum Game Programming
    Replies: 1
    Last Post: 03-03-2003, 07:48 PM
  5. opengl DC question
    By SAMSAM in forum Game Programming
    Replies: 6
    Last Post: 02-26-2003, 09:22 PM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21