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c++ - 在 Node.js C++ 插件中，永远不会调用 SetWindowsHookEx 的回调

问题描述

这是一个简单的 Windows C++ 键盘记录器示例

当我在 Visual Studio 中运行它时，HookCallback它被正确调用。

我想node-addon-api在 Node.js 中做同样的事情，但我不想在文件中记录按键，我想使用回调将键码值发送到 JavaScript 世界。

这是我的存储库。这就是我正在做的...

JavaScript

const addon = require("bindings")("push_to_talk");

addon.start((keyCode) => {
  console.log("key is pressed:", keyCode);
});

console.log("testing...");

本国的

#include <Windows.h>
#include <napi.h>
#include <time.h>
#include <cstdio>
#include <fstream>
#include <iostream>
#include <sstream>

// Declare the TSFN
Napi::ThreadSafeFunction tsfn;

// Create a native callback function to be invoked by the TSFN
auto callback = [](Napi::Env env, Napi::Function jsCallback, int* value) {
    // Call the JS callback
    jsCallback.Call({Napi::Number::New(env, *value)});

    // We're finished with the data.
    delete value;
};

// variable to store the HANDLE to the hook. Don't declare it anywhere else then globally
// or you will get problems since every function uses this variable.
HHOOK _hook;

// This struct contains the data received by the hook callback. As you see in the callback function
// it contains the thing you will need: vkCode = virtual key code.
KBDLLHOOKSTRUCT kbdStruct;

// Trigger the JS callback when a key is pressed
void Start(const Napi::CallbackInfo& info) {
    std::cout << "Start is called" << std::endl;

    Napi::Env env = info.Env();

    // Create a ThreadSafeFunction
    tsfn = Napi::ThreadSafeFunction::New(
      env,
      info[0].As<Napi::Function>(),  // JavaScript function called asynchronously
      "Keyboard Events",             // Name
      0,                             // Unlimited queue
      1                              // Only one thread will use this initially
    );
}

// This is the callback function. Consider it the event that is raised when, in this case,
// a key is pressed.
LRESULT __stdcall HookCallback(int nCode, WPARAM wParam, LPARAM lParam) {
    std::cout << "HookCallback is called" << std::endl;

    if (nCode >= 0) {
        // the action is valid: HC_ACTION.
        if (wParam == WM_KEYDOWN) {
            // lParam is the pointer to the struct containing the data needed, so cast and assign it
            // to kdbStruct.
            kbdStruct = *((KBDLLHOOKSTRUCT*)lParam);

            // Send (kbdStruct.vkCode) to JS world via "start" function callback parameter
            int* value = new int(kbdStruct.vkCode);
            napi_status status = tsfn.BlockingCall(value, callback);
            if (status != napi_ok) {
                std::cout << "BlockingCall is not ok" << std::endl;
            }
        }
    }

    // call the next hook in the hook chain. This is nessecary or your hook chain will break and the
    // hook stops
    return CallNextHookEx(_hook, nCode, wParam, lParam);
}

void SetHook() {
    std::cout << "SetHook is called" << std::endl;

    // Set the hook and set it to use the callback function above
    // WH_KEYBOARD_LL means it will set a low level keyboard hook. More information about it at
    // MSDN. The last 2 parameters are NULL, 0 because the callback function is in the same thread
    // and window as the function that sets and releases the hook.
    if (!(_hook = SetWindowsHookEx(WH_KEYBOARD_LL, HookCallback, NULL, 0))) {
        LPCSTR a = "Failed to install hook!";
        LPCSTR b = "Error";
        MessageBox(NULL, a, b, MB_ICONERROR);
    }
}

Napi::Object Init(Napi::Env env, Napi::Object exports) {
    exports.Set(Napi::String::New(env, "start"), Napi::Function::New(env, Start));

    // set the hook
    SetHook();

    return exports;
}

NODE_API_MODULE(push_to_talk, Init)

但是，在我的情况下HookCallback，永远不会调用（HookCallback is called永远不会打印消息），当我点击键盘时，点击速度会减慢，并且由于某种原因我遭受了非常明显的滞后。

更新：根据LowLevelKeyboardProc文档：“这个钩子是在安装它的线程的上下文中调用的。调用是通过向安装钩子的线程发送消息来进行的。因此，安装钩子的线程必须有一个消息循环。 ”

我试图GetMessage像这样调用循环

Napi::Object Init(Napi::Env env, Napi::Object exports) {
    exports.Set(Napi::String::New(env, "start"), Napi::Function::New(env, Start));

    // set the hook
    SetHook();

    MSG msg;
    BOOL bRet;
    while ((bRet = GetMessage(&msg, NULL, 0, 0)) != 0) {
        if (bRet == -1) {
            // handle the error and possibly exit
        } else {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    return exports;
}

但这会阻塞 JavaScript 线程。此外，当现在按下键盘按钮时，HookCallback is called实际上会打印调试消息，但随后在这一行发生崩溃while ((bRet = GetMessage(&msg, NULL, 0, 0)) != 0)......

$ node .
SetHook is called
HookCallback is called
C:\Windows\SYSTEM32\cmd.exe - node  .[10888]: c:\ws\src\node_api.cc:1078: Assertion `(func) != nullptr' failed.
 1: 77201783 RegisterLogonProcess+3427
 2: 77DC537D KiUserCallbackDispatcher+77
 3: 607007B9 Init+521 [c:\users\aabuhijleh\desktop\projects\testing\push-to-talk\src\push-to-talk.cc]:L93

标签： c++node.jswinapinativenode-addon-api

解决方案

通过在一个单独的线程中创建一个消息循环，我能够让它像这里看到的那样工作

// Trigger the JS callback when a key is pressed
void Start(const Napi::CallbackInfo& info) {
    std::cout << "Start is called" << std::endl;

    Napi::Env env = info.Env();

    // Create a ThreadSafeFunction
    tsfn = Napi::ThreadSafeFunction::New(
      env,
      info[0].As<Napi::Function>(),  // JavaScript function called asynchronously
      "Keyboard Events",             // Name
      0,                             // Unlimited queue
      1,                             // Only one thread will use this initially
      [](Napi::Env) {                // Finalizer used to clean threads up
          nativeThread.join();
      });

    nativeThread = std::thread([] {
        // This is the callback function. Consider it the event that is raised when, in this case,
        // a key is pressed.
        static auto HookCallback = [](int nCode, WPARAM wParam, LPARAM lParam) -> LRESULT {
            if (nCode >= 0) {
                // the action is valid: HC_ACTION.
                if (wParam == WM_KEYDOWN) {
                    // lParam is the pointer to the struct containing the data needed, so cast and
                    // assign it to kdbStruct.
                    kbdStruct = *((KBDLLHOOKSTRUCT*)lParam);

                    // Send (kbdStruct.vkCode) to JS world via "start" function callback parameter
                    int* value = new int(kbdStruct.vkCode);
                    napi_status status = tsfn.BlockingCall(value, callback);
                    if (status != napi_ok) {
                        std::cout << "BlockingCall is not ok" << std::endl;
                    }
                }
            }

            // call the next hook in the hook chain. This is nessecary or your hook chain will
            // break and the hook stops
            return CallNextHookEx(_hook, nCode, wParam, lParam);
        };

        // Set the hook and set it to use the callback function above
        // WH_KEYBOARD_LL means it will set a low level keyboard hook. More information about it at
        // MSDN. The last 2 parameters are NULL, 0 because the callback function is in the same
        // thread and window as the function that sets and releases the hook.
        if (!(_hook = SetWindowsHookEx(WH_KEYBOARD_LL, HookCallback, NULL, 0))) {
            LPCSTR a = "Failed to install hook!";
            LPCSTR b = "Error";
            MessageBox(NULL, a, b, MB_ICONERROR);
        }

        // Create a message loop
        MSG msg;
        BOOL bRet;
        while ((bRet = GetMessage(&msg, NULL, 0, 0)) != 0) {
            if (bRet == -1) {
                // handle the error and possibly exit
            } else {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
        }
    });
}

现在，当按下键盘时正确调用 JavaScript 回调。

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