The utility I am writing requires use of the SetWindowsHookEx
function to capture key presses with the LowLevelKeyboardProc
callback.
I have implemented the code found on this MSDN blog.
The correct keycode is being captured, however I appear to be unable to get the correct value of the 30th bit when using the bitmask taken from the answer to this StackOverflow question: Get 30th bit of the lParam param in WM_KEYDOWN message
private const int LAST_KEY_STATE_BITMASK = 0x40000000;
This bit should allow me to detect if the key is being held down, according to the Microsoft documentation.
I only want to act upon a keydown event when the key is first pressed and is not being held; keyup won't suffice.
The code I am using to try and get the value of the 30th bit is:
int vkCode = Marshal.ReadInt32(lParam);
int lastKeyState = (vkCode & LAST_KEY_STATE_BITMASK);
Which, from my understanding, should return 0 when the key isn't being held down and 1 when it is.
I have also tried using lParam.ToInt32()
and (int)lParam
in place of vkCode
but to no avail.
Please help!
Here's the full program as it is in its current state:
using System;
using System.Diagnostics;
using System.Windows.Forms;
using System.Runtime.InteropServices;
public class KeyCapture
{
private const int WH_KEYBOARD_LL = 13;
private const int WM_KEYDOWN = 0x0100;
private const int LAST_KEY_STATE_BITMASK = 0x40000000;
private static LowLevelKeyboardProc _proc = HookCallback;
private static IntPtr _hookID = IntPtr.Zero;
public static void Main()
{
_hookID = SetHook(_proc);
Application.Run();
UnhookWindowsHookEx(_hookID);
}
private static IntPtr SetHook(LowLevelKeyboardProc proc)
{
using (Process curProcess = Process.GetCurrentProcess())
using (ProcessModule curModule = curProcess.MainModule)
{
return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
GetModuleHandle(curModule.ModuleName), 0);
}
}
private delegate IntPtr LowLevelKeyboardProc(
int nCode, IntPtr wParam, IntPtr lParam);
private static IntPtr HookCallback(
int nCode, IntPtr wParam, IntPtr lParam)
{
if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
{
int vkCode = Marshal.ReadInt32(lParam);
int lastKeyState = (vkCode & LAST_KEY_STATE_BITMASK);
Console.WriteLine((Keys)vkCode + "|" + vkCode + "|" + lastKeyState);
}
return CallNextHookEx(_hookID, nCode, wParam, lParam);
}
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr SetWindowsHookEx(int idHook,
LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool UnhookWindowsHookEx(IntPtr hhk);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
IntPtr wParam, IntPtr lParam);
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr GetModuleHandle(string lpModuleName);
}