En fait, différenciez L / R Ctrl / Alt lorsque vous attrapez WM_KEYDOWN / WM_KEYUP, vous le pouvez. Facile, ce n'est pas le cas, mais le code que j'utilise, ici vous pouvez l'avoir, hmm hmm.
J'espère que cela fonctionne toujours, je le fais.
// Receives a WM_KEYDOWN, WM_KEYUP, WM_SYSKEYDOWN or WM_SYSKEYUP message and 
// returns a virtual key of the key that triggered the message.
// 
// If the key has a common virtual key code, that code is returned. 
// For Alt's and Ctrl's, the values from the KeyCodes enumeration are used.
int translateKeyMessage (MSG& Msg);
// Virtual key codes for keys that aren't defined in the windows headers.
enum KeyCodes
{
    VK_LEFTCTRL = 162,
    VK_RIGHTCTRL = 163,
    VK_LEFTALT = 164,
    VK_RIGHTALT = 165
};
// ======================================================================================
int translateKeyMessage (MSG& Msg)
{
    // Determine the virtual key code.
    int VirtualKeyCode = Msg.wParam;
    // Determine whether the key is an extended key, e.g. a right 
    // hand Alt or Ctrl.
    bool Extended = (Msg.lParam & (1 << 24)) != 0;
    // If this is a system message, is the Alt bit of the message on?
    bool AltBit = false;    
    if (Msg.message == WM_SYSKEYDOWN || Msg.message == WM_SYSKEYUP)
        AltBit = (Msg.lParam & (1 << 29)) != 0;
    if ((Msg.message == WM_SYSKEYUP || Msg.message == WM_KEYUP) && !Extended && !AltBit && VirtualKeyCode == 18)
    {
        // Left Alt
        return KeyCodes::VK_LEFTALT;
    }
    // Left Ctrl
    if (!Extended && !AltBit && VirtualKeyCode == 17)
    {
        // Peek for the next message.
        MSG nextMsg;
        BOOL nextMessageFound = PeekMessage(&nextMsg, NULL, 0, 0, PM_NOREMOVE);
        // If the next message is for the right Alt:
        if (nextMessageFound && nextMsg.message == Msg.message && nextMsg.wParam == 18)
        {
            //
            bool nextExtended = (nextMsg.lParam & (1 << 24)) != 0;
            //
            bool nextAltBit = false;    
            if (nextMsg.message == WM_SYSKEYDOWN || nextMsg.message == WM_SYSKEYUP)
                nextAltBit = (nextMsg.lParam & (1 << 29)) != 0;
            // If it is really for the right Alt
            if (nextExtended && !nextAltBit)
            {
                // Remove the next message
                PeekMessage(&nextMsg, NULL, 0, 0, PM_REMOVE);
                // Right Alt
                return KeyCodes::VK_RIGHTALT;
            }
        }
        // Left Ctrl
        return KeyCodes::VK_LEFTCTRL;
    }
    if (Msg.message == WM_SYSKEYUP && !Extended && AltBit && VirtualKeyCode == 17)
    {
        // Peek for the next message.
        MSG nextMsg;
        BOOL nextMessageFound = PeekMessage(&nextMsg, NULL, 0, 0, PM_NOREMOVE);
        // If the next message is for the right Alt:
        if (nextMessageFound && nextMsg.message == WM_KEYUP && nextMsg.wParam == 18)
        {
            //
            bool nextExtended = (nextMsg.lParam & (1 << 24)) != 0;
            //
            bool nextAltBit = false;    
            if (nextMsg.message == WM_SYSKEYDOWN || nextMsg.message == WM_SYSKEYUP)
                nextAltBit = (nextMsg.lParam & (1 << 29)) != 0;
            // If it is really for the right Alt
            if (nextExtended && !nextAltBit)
            {
                // Remove the next message
                PeekMessage(&nextMsg, NULL, 0, 0, PM_REMOVE);
                // Right Alt
                return KeyCodes::VK_RIGHTALT;
            }
        }
    }
    // Right Ctrl
    if (Extended && !AltBit && VirtualKeyCode == 17)
        return KeyCodes::VK_RIGHTCTRL;
    // Left Alt
    if (!Extended && AltBit && VirtualKeyCode == 18)
        return KeyCodes::VK_LEFTALT;
    // Default
    return VirtualKeyCode;
}