Qt 6.9: Build succeeds but crashes on run

[wslyw]

Here's my code:

CMainUI::CMainUI():
   ui(new Ui::CMainUI)
{
    m_pWindwoBar = new QWK::WindowBar;

    QWK::WidgetWindowAgent* agent = new QWK::WidgetWindowAgent(this);
    agent->setup(this);

    agent->setTitleBar(m_pWindwoBar);

    agent->setSystemButton(QWK::WindowAgentBase::WindowIcon, m_pWindwoBar->iconButton());
    agent->setSystemButton(QWK::WindowAgentBase::Minimize, m_pWindwoBar->minButton());
    agent->setSystemButton(QWK::WindowAgentBase::Maximize, m_pWindwoBar->maxButton());
    agent->setSystemButton(QWK::WindowAgentBase::Close, m_pWindwoBar->closeButton());

    agent->setHitTestVisible(m_pWindwoBar->menuBar(), true);

    ui->setupUi(this);
}

The code crashes at this line:
QWK::WidgetWindowAgent* agent = new QWK::WidgetWindowAgent(this);

The crash occurs in a thread checking function inside QObject

// check the constructor's parent thread argument
static bool check_parent_thread(QObject *parent,
                                QThreadData *parentThreadData,
                                QThreadData *currentThreadData)
{
    if (parent && parentThreadData != currentThreadData) {
        QThread *parentThread = parentThreadData->thread.loadAcquire();
        QThread *currentThread = currentThreadData->thread.loadAcquire();
        qWarning("QObject: Cannot create children for a parent that is in a different thread.\n"
                 "(Parent is %s(%p), parent's thread is %s(%p), current thread is %s(%p)",
                 parent->metaObject()->className(),
                 parent,
                 parentThread ? parentThread->metaObject()->className() : "QThread",
                 parentThread,
                 currentThread ? currentThread->metaObject()->className() : "QThread",
                 currentThread);
        return false;
    }
    return true;
}

this is my main.cpp

int main(int argc, char *argv[])
{
    QGuiApplication::setAttribute(Qt::AA_DontCreateNativeWidgetSiblings);

    QApplication a(argc, argv);
    CMainUI w;
    w.show();

    return a.exec();
}

The command I used when building/compiling QWindowKit is:
cmake -B build -S .
cmake --build build --config Release
cmake --install install .

If I remove the this pointer in the constructor, it doesn't crash, but then the frameless window feature doesn't work.
I cannot get the specific stack trace. My environment is Qt 6.9 + MSVC2022 + Win11, CMake version 3.29.

[wangwenx190]

这应该不是你的全部代码。
qt这个报错是你窗口的线程和QWK的线程不是同一个，跨线程的父子关系本来也是不允许的。
这肯定你是自己的代码有问题。而且我这项目已经不少人用了，但从没人遇到过这个问题。
我建议你仔细看看你自己代码哪里出问题了，尤其涉及线程的地方。如果检查不出来，那么你需要把一个最小的复现工程发上来。

[wslyw]

CMainUI is created in the main function. This project only has a CMainUI class and the windowbar and the windowbutton source code from examples.

Here is the full code.

CMainUI.h

#ifndef CMAINUI_H
#define CMAINUI_H

#include "windowbar.h"
#include <QMainWindow>

#include <QWKWidgets/widgetwindowagent.h>

QT_BEGIN_NAMESPACE
namespace Ui {
class CMainUI;
}
QT_END_NAMESPACE

class CMainUI : public QMainWindow
{
    Q_OBJECT

public:
    CMainUI();
    ~CMainUI();

private:
    Ui::CMainUI *ui;

    QWK::WindowBar*     m_pWindwoBar = nullptr;
};
#endif // CMAINUI_H

CMainUI.cpp

#include "cmainui.h"
#include "ui_cmainui.h"

#include <QWKWidgets/widgetwindowagent.h>
#include <QThread>

CMainUI::CMainUI():
   ui(new Ui::CMainUI)
{
    qDebug() << "CMainUI.cpp: " << QThread::currentThread();

    m_pWindwoBar = new QWK::WindowBar;

    QWK::WidgetWindowAgent* agent = new QWK::WidgetWindowAgent(this);
    agent->setup(this);

    agent->setTitleBar(m_pWindwoBar);

    agent->setSystemButton(QWK::WindowAgentBase::WindowIcon, m_pWindwoBar->iconButton());
    agent->setSystemButton(QWK::WindowAgentBase::Minimize, m_pWindwoBar->minButton());
    agent->setSystemButton(QWK::WindowAgentBase::Maximize, m_pWindwoBar->maxButton());
    agent->setSystemButton(QWK::WindowAgentBase::Close, m_pWindwoBar->closeButton());

    agent->setHitTestVisible(m_pWindwoBar->menuBar(), true);

    ui->setupUi(this);
}

CMainUI::~CMainUI()
{
    delete ui;
}

"ui_cmainui.h" is the UI header file automatically generated by Qt, it's a default UI that was created.

main.cpp

#include "cmainui.h"

#include <QApplication>
#include <QThread>
#include <QWKWidgets/widgetwindowagent.h>

int main(int argc, char *argv[])
{
    QGuiApplication::setAttribute(Qt::AA_DontCreateNativeWidgetSiblings);

    QApplication a(argc, argv);

    qDebug() << "main.cpp: " << QThread::currentThread();

    CMainUI w;
    w.show();

    return a.exec();
}

I added qDebug statements in both main.cpp and CMainUI.cpp to print the thread information. The output shows that both are on the main thread.
main.cpp: QThread(0x228efe39f20, name = "Qt mainThread")
CMainUI.cpp: QThread(0x228efe39f20, name = "Qt mainThread")

Here is my CMakeLists.txt

cmake_minimum_required(VERSION 3.19)
project(daemonitor LANGUAGES CXX)

find_package(Qt6 6.5 REQUIRED COMPONENTS Core Widgets)

qt_standard_project_setup()

qt_add_executable(daemonitor
    WIN32 MACOSX_BUNDLE
    main.cpp
    cmainui.cpp
    cmainui.h
    cmainui.ui
    windowbar.cpp
    windowbar.h
    windowbar_p.h
    windowbutton.cpp
    windowbutton.h
    windowbutton_p.h
)

target_include_directories(${PROJECT_NAME} PRIVATE
    ${CMAKE_CURRENT_SOURCE_DIR}/qwindowkit/include
)

find_library(QWindowKitCore
    NAMES QWKCore
    PATHS ${CMAKE_CURRENT_SOURCE_DIR}/qwindowkit/lib
    NO_DEFAULT_PATH
)

find_library(QWindowKitWidgets
    NAMES QWKWidgets
    PATHS ${CMAKE_CURRENT_SOURCE_DIR}/qwindowkit/lib
    NO_DEFAULT_PATH
)

target_link_libraries(${PROJECT_NAME} PRIVATE
    Qt::Core
    Qt::Widgets
    Qt::Gui
    ${QWindowKitCore}
    ${QWindowKitWidgets}
)

include(GNUInstallDirs)
install(TARGETS daemonitor
    BUNDLE  DESTINATION .
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
)

qt_generate_deploy_app_script(
    TARGET daemonitor
    OUTPUT_SCRIPT deploy_script
    NO_UNSUPPORTED_PLATFORM_ERROR
)
install(SCRIPT ${deploy_script})

[SineStriker]

CMainUI::CMainUI():
ui(new Ui::CMainUI)
{
qDebug() << "CMainUI.cpp: " << QThread::currentThread();

m_pWindwoBar = new QWK::WindowBar;

QWK::WidgetWindowAgent* agent = new QWK::WidgetWindowAgent(this);
agent->setup(this);

agent->setTitleBar(m_pWindwoBar);

agent->setSystemButton(QWK::WindowAgentBase::WindowIcon, m_pWindwoBar->iconButton());
agent->setSystemButton(QWK::WindowAgentBase::Minimize, m_pWindwoBar->minButton());
agent->setSystemButton(QWK::WindowAgentBase::Maximize, m_pWindwoBar->maxButton());
agent->setSystemButton(QWK::WindowAgentBase::Close, m_pWindwoBar->closeButton());

agent->setHitTestVisible(m_pWindwoBar->menuBar(), true);

我搭了一下你这个例子，你这里没有给 windowBar 设置 menuBar，然后给 agent->setHitTestVisible 传了 menuBar 相当于传了个空，会在 setHitTestVisible 这里直接 ASSERT false 崩掉。

ui->setupUi(this);

}

我把 agent->setHitTestVisible 注释掉以后就能正常运行了，你再检查下吧。

[wangwenx190]

如果这真的就是你全部的代码，那么不可能触发什么线程问题的。我只能怀疑你用了魔改版的Qt。