Winapi - SetWindowLongPtr in ShutdownBlockReasonCreate/Destroy implementation of JNI native code

Winapi - SetWindowLongPtr in ShutdownBlockReasonCreate / Destroy implementation of JNI native code(Winapi - SetWindowLongPtr in ShutdownBlockReasonCreate/Destroy implementation of JNI native code)

问题描述

我目前正在处理一个涉及使用 SWT 的 Eclipse RCP 的 Java 项目，并试图通过在保存时向 Windows 环境中的用户提供有意义的消息来处理正常关闭.我应该使用 ShutdownBlockReasonCreate 和 ShutdownBLockReasonDestroy API 来实现这一点，但经过一些研究后，我不得不在我非常陌生的 C++ 本机代码中实现它们.因为它们在 JNA 中不可用，并且 Eclipse SWT 不提供这种现成的功能(很想知道)

I'm currently working on a Java project involving Eclipse RCP using SWT and was trying to handle graceful shutdown by providing meaningful messages to user in Windows environment when saving. I was supposed to use ShutdownBlockReasonCreate and ShutdownBLockReasonDestroy APIs to achieve this but after some research I had to implement them in C++ native code which I'm very new to. As they are not available in JNA and Eclipse SWT does not provide such capability off-the-shelf (would love to know otherwise)

经过所有努力后，我能够将一个有效的 C++ 代码(如下)放在一起来控制 SWT 窗口(通过引用另一个实现 https://github.com/seraphy/JavaGracefulShutdownForWin7).但是我偶然发现了一个与 WindowProc CALLBACK 相关的问题.来自 Java 背景，这些语法花了我一段时间才理解.但我有点明白它想要做什么.因为这是我们需要处理 WM_QUERYENDSESSION 和 WM_ENDSESSION 消息的地方.

After going through all the effort I was able to pull together a working C++ code (as follows) to get control of the SWT window (by referencing another implementation https://github.com/seraphy/JavaGracefulShutdownForWin7). However I stumble upon an issue which relates to WindowProc CALLBACK. Coming from Java background these syntax took me a while to understand. But I sort of get what it's trying to do. Because this is where we need to handle WM_QUERYENDSESSION and WM_ENDSESSION messages.

但在此之前，我想在这篇文章中讨论的问题与 Windows API SetWindowLongPtr 相关，您可以在 Java_com_app_project_winapi_WindowsAPI_shutdownBlockReasonCreate(JNIEnv *env, jclasscls, jstring title) 函数.如您所见，我将其注释掉了，只是因为在 ShutdownBlockReasonCreate(hWnd, SHUTDOWN_REASON) 之后调用此方法时，我的窗口往往表现得非常奇怪.例如，

#include <jni.h>

#include <iostream>
#include "com_app_project_winapi_WindowsAPI.h"
#include <windows.h>

using namespace std;

namespace {

    LPCWSTR SHUTDOWN_REASON = L"Application is still saving ...";

    LRESULT CALLBACK AppWndProc(
        _In_ HWND hWnd,
        _In_ UINT message,
        _In_ WPARAM wParam,
        _In_ LPARAM lParam
    ) {


        switch (message) {
            // Not doing anything yet
        }

        return DefWindowProc(hWnd, message, wParam, lParam);
    }
}


JNIEXPORT void JNICALL Java_com_app_project_winapi_WindowsAPI_shutdownBlockReasonCreate(JNIEnv *env, jclass cls, jstring title) {
    cout << "shutdownblockreason create" << endl;

    const char *str = NULL;

    str = (env)->GetStringUTFChars(title, 0);
    HWND hWnd = FindWindow(NULL, str);
    (env)->ReleaseStringUTFChars(title, str);
    if (hWnd == NULL) {
        return;
    }

    ShutdownBlockReasonCreate(hWnd, SHUTDOWN_REASON);


    //SetWindowLongPtr(hWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(AppWndProc));

    return;
}

JNIEXPORT void JNICALL Java_com_app_project_winapi_WindowsAPI_shutdownBlockReasonDestroy(JNIEnv *env, jclass cls, jstring title) {
    cout << "shutdownblockreason destroy" << endl;

    const char *str = NULL;

    str = (env)->GetStringUTFChars(title, 0);
    HWND hWnd = FindWindow(NULL, str);
    (env)->ReleaseStringUTFChars(title, str);
    if (hWnd == NULL) {
        return;
    }

    ShutdownBlockReasonDestroy(hWnd);

    return;
}

第三，你应该使用 <代码>SetWindowSubclass() 而不是 SetWindowLongPtr().请参阅 缺点旧子类化方法和更安全的子类化.

Third, you should be using SetWindowSubclass() instead of SetWindowLongPtr(). See Disadvantages of the Old Subclassing Approach and Safer subclassing.

话虽如此，请尝试更多类似的东西:

With that said, try something more like this instead:

#include <jni.h>
#include <iostream>
#include "com_app_project_winapi_WindowsAPI.h"
#include <windows.h>
#include <commctrl.h>

namespace {
    LPCWSTR SHUTDOWN_REASON = L"Application is still saving ...";

    /*
    WNDPROC PrevWndProc = NULL;
    LRESULT CALLBACK AppWndProc(
        _In_ HWND hWnd,
        _In_ UINT message,
        _In_ WPARAM wParam,
        _In_ LPARAM lParam
    ) {
    */
    LRESULT CALLBACK AppWndProc(
        _In_ HWND hWnd,
        _In_ UINT message,
        _In_ WPARAM wParam,
        _In_ LPARAM lParam,
        _In_ UINT_PTR uIdSubclass,
        _In_ DWORD_PTR dwRefData
    ) {
        switch (message) {
            case WM_NCDESTROY:
                RemoveWindowSubclass(hWnd, AppWndProc, uIdSubclass);
                break;

            //...
        }

        //return CallWindowProc(PrevWndProc, hWnd, message, wParam, lParam);
        return DefSubclassProc(hWnd, message, wParam, lParam);
    }
}

JNIEXPORT void JNICALL Java_com_app_project_winapi_WindowsAPI_shutdownBlockReasonCreate(JNIEnv *env, jclass cls, jstring title) {
    std::cout << "shutdownblockreason create" << std::endl;

    const jchar *str = env->GetStringChars(title, NULL);
    HWND hWnd = FindWindowW(NULL, (LPCWSTR) str);
    env->ReleaseStringChars(title, str);
    if (!hWnd) {
        return;
    }

    ShutdownBlockReasonCreate(hWnd, SHUTDOWN_REASON);

    //PrevWndProc = (WNDPROC) SetWindowLongPtr(hWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(AppWndProc)); 
    SetWindowSubclass(hWnd, &AppWndProc, 1, 0);
}

JNIEXPORT void JNICALL Java_com_app_project_winapi_WindowsAPI_shutdownBlockReasonDestroy(JNIEnv *env, jclass cls, jstring title) {
    std::cout << "shutdownblockreason destroy" << std::endl;

    const jchar *str = env->GetStringChars(title, NULL);
    HWND hWnd = FindWindowW(NULL, (LPCWSTR) str);
    env->ReleaseStringChars(title, str);
    if (!hWnd) {
        return;
    }

    //SetWindowLongPtr(hWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(PrevWndProc));
    RemoveWindowSubclass(hWnd, &AppWndProc, 1);

    ShutdownBlockReasonDestroy(hWnd);
}

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