[英]Separate window message pumps and receiving WM_QUIT
I'm trying to create independent window wrapper classes for my project. 我正在尝试为我的项目创建独立的窗口包装器类。 It's mostly working but cannot figure out how to get WM_QUIT in my main message pump. 它通常可以正常工作,但无法弄清楚如何在我的主消息泵中获取WM_QUIT。 In the interest of learning Windows, I don't want to use other libraries for this. 为了学习Windows,我不想为此使用其他库。
This is a quick example of whats happening. 这是一个正在发生的事的快速示例。
#include <iostream>
#include <Windows.h>
void TestPump()
{
MSG msg = { 0 };
PostQuitMessage(0);
std::cout << "Posted WM_QUIT" << std::endl;
while (true)
{
BOOL result = PeekMessage(&msg, (HWND) -1, 0, 0, PM_REMOVE);
std::cout << "PeekMessage returned " << result << std::endl;
if (result == 0)
break;
if (WM_QUIT == msg.message)
std::cout << "got WM_QUIT" << std::endl;
}
}
void MakeWindow()
{
auto hwnd = CreateWindowEx(0, "Button", "dummy", 0, 0, 0, 32, 32, NULL, NULL, NULL, NULL);
std::cout << std::endl << "Created Window" << std::endl << std::endl;
}
int main()
{
TestPump();
MakeWindow();
TestPump();
std::cin.get();
return EXIT_SUCCESS;
}
The PeekMessage documentation is here: https://msdn.microsoft.com/en-us/library/windows/desktop/ms644943(v=vs.85).aspx PeekMessage文档位于此处: https ://msdn.microsoft.com/zh-cn/library/windows/desktop/ms644943( v= vs.85).aspx
I haven't been able to find any examples of using a -1 HWND filter, but MSDN says that it'll receive thread messages where the HWND is NULL (I've checked that this is true for WM_QUIT), which I believe PostQuitMessage does with WM_QUIT. 我还没有找到使用-1 HWND过滤器的任何示例,但是MSDN说它将接收HWND为NULL的线程消息(我检查过WM_QUIT的确如此),我相信PostQuitMessage与WM_QUIT有关。
The problem only occurs if I create a Window. 仅当我创建一个窗口时才会出现此问题。
Is there anything I'm doing wrong, or are there better methods? 我做错了什么吗,还是有更好的方法?
This seems to be an interesting case so I've created a mcve, though I'm struggling to explain this behavior: 这似乎是一个有趣的案例,所以我创建了一个mcve,尽管我正在努力解释这种行为:
#include <Windows.h>
#include <CommCtrl.h>
#include <iostream>
#include <cassert>
void
Create_ThreadMessagePump(void)
{
::MSG msg;
::PeekMessageW(&msg, NULL, WM_USER, WM_USER, PM_NOREMOVE);
::std::wcout << L"initialized thread message pump" << ::std::endl;
}
void
Create_Window(void)
{
auto const hwnd{::CreateWindowExW(0, WC_STATICW, L"dummy window", 0, 0, 0, 32, 32, NULL, NULL, NULL, NULL)};
(void) hwnd; // not used
assert(NULL != hwnd);
::std::wcout << L"created window" << ::std::endl;
}
void
Test_QuitMessageExtraction(void)
{
::PostQuitMessage(0);
::std::wcout << L"posted WM_QUIT" << ::std::endl;
for(;;)
{
::MSG msg;
auto const result{::PeekMessageW(&msg, (HWND) -1, 0, 0, PM_REMOVE)};
::std::wcout << L"PeekMessageW returned " << result << ::std::endl;
if(0 == result)
{
::std::wcout << L"no more messages to peek" << ::std::endl;
break;
}
if(WM_QUIT == msg.message)
{
::std::wcout << L"got WM_QUIT" << ::std::endl;
}
}
}
int
main()
{
//Create_ThreadMessagePump(); // does not change anything
Test_QuitMessageExtraction();
Create_Window();
Test_QuitMessageExtraction();
system("pause");
return(0);
}
output: 输出:
posted WM_QUIT
PeekMessageW returned 1
got WM_QUIT
PeekMessageW returned 0
no more messages to peek
created window
posted WM_QUIT
PeekMessageW returned 0
no more messages to peek
The problem appears to be with the way WM_QUIT
and PostQuitMessage()
operates. 问题似乎与WM_QUIT
和PostQuitMessage()
操作方式有关。 You can find information here: 您可以在此处找到信息:
Why is there a special PostQuitMessage function? 为什么会有特殊的PostQuitMessage函数? . 。
In short, the WM_QUIT
message will not be received while the queue is non-empty. 简而言之,当队列为非空时,将不会收到WM_QUIT
消息。 Even if you filter out other messages by using a -1 HWND
, the queue is still non-empty, and thus WM_QUIT
is not returned. 即使使用-1 HWND
过滤掉其他消息,该队列仍然是非空的,因此不会返回WM_QUIT
。 Creating of a window results in multiple HWNDs being created. 创建窗口会导致创建多个HWND。
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