110 lines
3 KiB
C#
110 lines
3 KiB
C#
/*
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* Copyright (c) 2019 ETH Zürich, Educational Development and Technology (LET)
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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using System;
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using System.Runtime.InteropServices;
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using System.Threading;
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using SafeExamBrowser.Contracts.Logging;
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using SafeExamBrowser.Contracts.UserInterface.Shell;
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using SafeExamBrowser.Contracts.UserInterface.Shell.Events;
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using SafeExamBrowser.WindowsApi.Constants;
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using SafeExamBrowser.WindowsApi.Delegates;
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using SafeExamBrowser.WindowsApi.Types;
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namespace SafeExamBrowser.WindowsApi
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{
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public class KeyboardActivator : IActionCenterActivator
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{
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private bool A, LeftWindows;
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private IntPtr handle;
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private HookDelegate hookDelegate;
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private ILogger logger;
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public event ActivatorEventHandler Activate { add { } remove { } }
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public event ActivatorEventHandler Deactivate { add { } remove { } }
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public event ActivatorEventHandler Toggle;
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public KeyboardActivator(ILogger logger)
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{
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this.logger = logger;
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}
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public void Start()
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{
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var hookReadyEvent = new AutoResetEvent(false);
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var hookThread = new Thread(() =>
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{
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var sleepEvent = new AutoResetEvent(false);
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var process = System.Diagnostics.Process.GetCurrentProcess();
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var module = process.MainModule;
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var moduleHandle = Kernel32.GetModuleHandle(module.ModuleName);
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// IMPORTANT:
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// Ensures that the hook delegate does not get garbage collected prematurely, as it will be passed to unmanaged code.
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// Not doing so will result in a <c>CallbackOnCollectedDelegate</c> error and subsequent application crash!
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hookDelegate = new HookDelegate(LowLevelKeyboardProc);
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handle = User32.SetWindowsHookEx(HookType.WH_KEYBOARD_LL, hookDelegate, moduleHandle, 0);
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hookReadyEvent.Set();
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while (true)
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{
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sleepEvent.WaitOne();
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}
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});
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hookThread.SetApartmentState(ApartmentState.STA);
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hookThread.IsBackground = true;
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hookThread.Start();
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hookReadyEvent.WaitOne();
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}
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public void Stop()
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{
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User32.UnhookWindowsHookEx(handle);
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}
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private IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam)
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{
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if (nCode >= 0)
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{
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var changed = false;
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var keyData = (KBDLLHOOKSTRUCT) Marshal.PtrToStructure(lParam, typeof(KBDLLHOOKSTRUCT));
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var pressed = IsPressed(wParam.ToInt32());
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switch (keyData.KeyCode)
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{
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case (uint) VirtualKeyCode.A:
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changed = A != pressed;
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A = pressed;
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break;
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case (uint) VirtualKeyCode.LeftWindows:
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changed = LeftWindows != pressed;
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LeftWindows = pressed;
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break;
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}
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if (A && LeftWindows && changed)
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{
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logger.Debug("Detected toggle sequence for action center.");
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Toggle?.Invoke();
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return (IntPtr) 1;
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}
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}
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return User32.CallNextHookEx(handle, nCode, wParam, lParam);
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}
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private bool IsPressed(int wParam)
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{
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return wParam == Constant.WM_KEYDOWN || wParam == Constant.WM_SYSKEYDOWN;
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}
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}
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}
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