圣诞节到了！！你的桌面下雪了吗？？ - Qt趣味开发之让你的桌面下雪

import QtQuick 2.12
import QtQuick.Controls 2.12
import QtQuick.Particles 2.12

Rectangle {
    id: rootRect
    objectName: "rootRect"
    color: Qt.rgba(0, 0, 0, 0.01);

    ParticleSystem{
        id: particleSystem
        objectName: "particleSystem"
    }

    Emitter {
        id: particleEmitter
        objectName: "particleEmitter"
        system: particleSystem
        anchors.top: parent.top
        anchors.horizontalCenter: parent.horizontalCenter
        width: parent.width
        height: 1

        emitRate: 10
        lifeSpan: 10000
        lifeSpanVariation: 100

        size: 25
        sizeVariation: 5
        endSize: 20

        velocity: CumulativeDirection {
            AngleDirection {
                objectName: "sonwVelocity"
                angle: 90
                angleVariation: 10
                magnitude: 200
                magnitudeVariation: 20
            }
        }
        acceleration: AngleDirection{
            angle: 90
            magnitude: 25
        }
    }

    ImageParticle {
        system: particleSystem
        source: "file:///D:/Image/star.png"
//        alpha: 0
//        colorVariation: 0.2

        rotation: 0
        rotationVariation: 10
        rotationVelocity: 90
        rotationVelocityVariation: 10
        entryEffect: ImageParticle.Scale
    }

    Turbulence {
        system: particleSystem
        anchors.left: parent.left
        anchors.verticalCenter: parent.verticalCenter
        width: parent.width
        height: parent.height / 2
        strength: 100
    }
}

代码比较简单，就是一个创建了一个粒子发射器，发射粒子就可以了。
其中控制是否下雪、速度等是通过C++的代码控制的，这里以控制下雪的速度为例，简要进行说明：

// 下雪的速度
int ParticleWidget::getSnowSpeed(void)
{
    QQuickItem* pRootItem = m_pQuickWidget->rootObject();
    QObject* object = pRootItem->findChild<QObject*>("sonwVelocity");
//    object->dumpObjectTree();
    if (object == nullptr)
        return false;

    int value = (int)object->property("magnitude").toDouble();
    return value;
}

void ParticleWidget::setSnowSpeed(int speed)
{
    QQuickItem* pRootItem = m_pQuickWidget->rootObject();
    QObject* object = pRootItem->findChild<QObject*>("sonwVelocity");
//    object->dumpObjectTree();
    if (object == nullptr)
        return;

    object->setProperty("magnitude", speed);
}

在粒子发射器（ Emitter ）中的属性 velocity ，我们创建了一个objectName 为 sonwVelocity ，该对象的属性 magnitude 就是控制速度的属性。C++代码通过设置和获取该属性的值，从而获取和控制速度。这里使用 findChild 函数，查找子元素。

2. 托盘

Qt中的托盘也比较简单，使用类 QSystemTrayIcon 即可实现。

void ParticleConfig::initSystemTrayIcon(void)
{
    m_pSystemTrayIcon = new QSystemTrayIcon(this);
    m_pSystemTrayIcon->setIcon(QIcon("./images/icon.png"));

    // 初始化菜单
    QMenu* pMenu = new QMenu;

    // 设置
    QAction* pConfigAction = new QAction(tr("Setting"));
    QObject::connect(pConfigAction, &QAction::triggered, this, &ParticleConfig::onClickedConfigAction);
    pMenu->addAction(pConfigAction);

    // 关于我
    QAction* pAboutMeAction = new QAction(tr("About Me"));
    QObject::connect(pAboutMeAction, &QAction::triggered, this, &ParticleConfig::onClickedAboutMe);
    pMenu->addAction(pAboutMeAction);

    pMenu->addSeparator();

    // 退出
    QAction* pExitAction = new QAction(tr("Exit"));
    QObject::connect(pExitAction, &QAction::triggered, this, &ParticleConfig::onClickedExit);
    pMenu->addAction(pExitAction);

    m_pSystemTrayIcon->setContextMenu(pMenu);

    QObject::connect(m_pSystemTrayIcon, &QSystemTrayIcon::activated, \
        this, &ParticleConfig::onActivated);

    m_pSystemTrayIcon->show();
}

函数 setContextMenu() 可以为托盘设置菜单。信号 activated 则可以响应双击等事件。

void ParticleConfig::onActivated(QSystemTrayIcon::ActivationReason reason)
{
    if (reason == QSystemTrayIcon::DoubleClick)
        onClickedConfigAction();
}

2. 窗口透明

实现代码如下：

m_pQuickWidget = new QQuickWidget;
mainLayout->addWidget(m_pQuickWidget);
m_pQuickWidget->setSource(QUrl("qrc:/main.qml"));
m_pQuickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView);
m_pQuickWidget->setClearColor(Qt::transparent);

this->setWindowFlags(this->windowFlags() | Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint | Qt::Dialog);
this->setAttribute(Qt::WA_TranslucentBackground);

QTimer::singleShot(100, [&]()->void{
   SetWindowLong((HWND)winId(), GWL_EXSTYLE, GetWindowLong((HWND)winId(), GWL_EXSTYLE) |
        WS_EX_TRANSPARENT//忽略一切消息（WM_PAINT除外）
        | WS_EX_LAYERED);
                  });