如何在 Windows composer 中集成 Qt frameless window？ （系统快捷方式不起作用）

How to integrate the Qt frameless window in Windows composer? (system shortcut doesnt works)

我在 Windows 平台上工作。 如果我使用原生无框 window 标志，例如：

::SetWindowLongPtr((HWND)winId(), GWL_STYLE, WS_POPUP | WS_SYSMENU | WS_THICKFRAME | WS_MAXIMIZEBOX | WS_MINIMIZEBOX);

我收到无框 window，它可以与默认的 Windows windows 作曲家一起正常工作 - 当我按下 "WIN" 键 + 箭头时，它会正确地改变状态。

当我尝试使用具有以下无框架 window 标志的 Qt 库时：

setWindowFlags(Qt::Popup | Qt::FramelessWindowHint | Qt::WindowSystemMenuHint | Qt::WindowMinMaxButtonsHint | Qt::CustomizeWindowHint);

我收到 window 对 "WIN" 键 + 箭头没有反应。所以它不适用于默认 Windows window composer.

Qt window 标志的哪些组合具有与上述本机标志类似的行为？

看来，这确实与Qt关系不大。在 Windows window 上只有全帧似乎禁用了 "snap" 快捷方式，即使 window 仍然可以调整大小或使用键盘箭头移动（从 Alt+ Space系统菜单）。

解决方法实际上非常简单。基本上实现 QWidget::nativeEvent() 虚拟方法并忽略 WM_NCCALCSIZE 消息。

我 运行 在从一个屏幕捕捉到另一个屏幕时遇到了一些绘画问题，但使用遮罩解决了这个问题（代码注释中的注释）。很高兴找到一个更干净的解决方案（实际上它可能符合 Qt 错误）。

作为奖励，这还允许圆角。 painting/styling基于我为another answer制作的圆形消息框，绘画代码在那边有更完整的记录。

系统菜单和所有与按键 (move/resize/snap/etc) 的交互都有效。可以通过在 nativeEvent() 中实现 WM_NCHITTEST 消息来添加鼠标处理（请参阅下面的参考资料）。

只在Win7上测试过，想知道它在Win10上的表现如何。

FramelessWidget

#include <QPainter>
#include <QPalette>
#include <QStyle>
#include <QStyleOption>
#include <QWidget>
#include <qt_windows.h>

class FramelessWidget : public QWidget
{
    Q_OBJECT
  public:
    explicit FramelessWidget(QWidget *p = nullptr, Qt::WindowFlags f = Qt::Window) :
      // the flags set here should "match" the GWL_STYLE flags set below
      QWidget(p, f | Qt::WindowMinMaxButtonsHint | Qt::WindowSystemMenuHint | Qt::WindowCloseButtonHint | Qt::FramelessWindowHint)
    {
      setAttribute(Qt::WA_TranslucentBackground);  // for rounded corners
      // set flags which will override what Qt does, especially with the Qt::FramelessWindowHint which essentially disables WS_SIZEBOX/WS_THICKFRAME
      SetWindowLongPtr(HWND(winId()), GWL_STYLE, WS_POPUPWINDOW | WS_CAPTION | WS_SIZEBOX | WS_MAXIMIZEBOX | WS_MINIMIZEBOX | WS_CLIPCHILDREN);
    }

    // these settings are only used when no styleSheet is set
    qreal radius = 0.0;        // desired radius in absolute pixels
    qreal borderWidth = -1.0;  // -1: use style hint frame width; 0: no border; > 0: use this width.

  protected:
    bool nativeEvent(const QByteArray &eventType, void *message, long *result) override
    {
      MSG *msg = static_cast<MSG*>(message);
      if (msg && msg->message == WM_NCCALCSIZE) {
        // Just return 0 and mark event as handled. This will draw the widget contents
        // into the full size of the frame, instead of leaving room for it.
        *result = 0;
        return true;
      }
      return QWidget::nativeEvent(eventType, message, result);
    }

    // Override paint event because of transparent background. 
    // Can be styled using CSS or QPalette with backgroundRole()/foregroundRole().
    void paintEvent(QPaintEvent *) override
    {
      QPainter p(this);
      p.setRenderHints(QPainter::Antialiasing);
      QStyleOption opt;
      opt.initFrom(this);
      // be sure to use the full frame size, not the default rect() which is inside frame.
      opt.rect.setSize(frameSize());  

      if (testAttribute(Qt::WA_StyleSheetTarget)) {
        style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
        setMask(QRegion(opt.rect));  // see notes below
        return;
      }

      QRectF rect(opt.rect);
      qreal penWidth = borderWidth;
      if (penWidth < 0.0)
        penWidth = style()->pixelMetric(QStyle::PM_DefaultFrameWidth, &opt, this);
      if (penWidth > 0.0) {
        p.setPen(QPen(palette().brush(foregroundRole()), penWidth));
        const qreal dlta = (penWidth * 0.5);
        rect.adjust(dlta, dlta, -dlta, -dlta);
      }
      else {
        p.setPen(Qt::NoPen);
      }
      p.setBrush(palette().brush(backgroundRole()));
      if (radius > 0.0)
        p.drawRoundedRect(rect, radius, radius, Qt::AbsoluteSize);
      else
        p.drawRect(rect);

      // Setting a mask works around an issue with artifacts when switching screens with Win+arrow
      // keys. I don't think it's the actual mask which does it, rather it triggers the region 
      // around the widget to be polished but I'm not sure. As support for my theory, the mask 
      // doesn't even have to follow the border radius.
      setMask(QRegion(opt.rect));
    }

};  // FramelessWidget

测试实施


int main(int argc, char *argv[])
{
  QApplication a(argc, argv);
  //QLoggingCategory::setFilterRules(QStringLiteral("qt.qpa.windows = true\n"));
  FramelessWidget msgBox;
  msgBox.setWindowTitle("Frameless window test");
  msgBox.setLayout(new QVBoxLayout);
  msgBox.layout()->addWidget(new QLabel(QStringLiteral("<h3>Frameless rounded widget.</h3>"), &msgBox));
  QLabel *lbl = new QLabel(QStringLiteral(
    "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean fermentum erat rhoncus, "
    "scelerisque eros ac, hendrerit metus. Nunc ac lorem id tortor porttitor mollis. Nunc "
    "tristique orci vel risus convallis, non hendrerit sapien condimentum. Phasellus lorem tortor, "
    "mollis luctus efficitur id, consequat eget nulla. Nam ac magna quis elit tristique hendrerit id "
    "at erat. Integer id tortor elementum, dictum urna sed, tincidunt metus. Proin ultrices tempus "
    "lacinia. Integer sit amet fringilla nunc."
  ), &msgBox);
  lbl->setWordWrap(true);
  msgBox.layout()->addWidget(lbl);
  QPushButton *pb = new QPushButton(QStringLiteral("Close"), &msgBox);
  QObject::connect(pb, &QPushButton::clicked, qApp, &QApplication::quit);
  msgBox.layout()->addItem(new QSpacerItem(1,1, QSizePolicy::Expanding, QSizePolicy::Expanding));
  msgBox.layout()->addWidget(pb);

  msgBox.setStyleSheet(QStringLiteral(
    "FramelessWidget { "
      "border-radius: 12px; "
      "border: 3px solid palette(shadow); "
      "background: qlineargradient(x1: 0, y1: 0, x2: 1, y2: 1, stop: 0 #ffeb7f, stop: 1 #d09d1e); "
    "}"
  ));

  msgBox.show();
  return a.exec();
}

参考文献：