Dragging Window handling WM_NCCALCSIZE and WM_NCHITTEST squishes contents

#include <QApplication>
#include <QHBoxLayout>
#include <QLabel>
#include <QPainter>
#include <QWidget>
#include <Windows.h>
#include <windowsx.h>

class Draggy : public QWidget
{
    bool nativeEvent(const QByteArray &eventType, void *message,
                     qintptr *result) override
    {
        MSG *msg = reinterpret_cast<MSG *>(message);
        switch (msg->message)
        {
            case WM_NCCALCSIZE: {
                *result = 0;
                return true;
            }
            break;
            case WM_NCHITTEST: {
                const LONG borderWidth = 8;
                RECT winrect;
                GetWindowRect(HWND(winId()), &winrect);

                long x = GET_X_LPARAM(msg->lParam);
                long y = GET_Y_LPARAM(msg->lParam);

                QPoint point(x - winrect.left, y - winrect.top);

                *result = 0;

                bool resizeWidth = minimumWidth() != maximumWidth();
                bool resizeHeight = minimumHeight() != maximumHeight();

                if (resizeWidth)
                {
                    // left border
                    if (x < winrect.left + borderWidth)
                    {
                        *result = HTLEFT;
                    }
                    // right border
                    else if (x >= winrect.right - borderWidth)
                    {
                        *result = HTRIGHT;
                    }
                }
                if (resizeHeight)
                {
                    // bottom border
                    if (y >= winrect.bottom - borderWidth)
                    {
                        *result = HTBOTTOM;
                    }
                    // top border
                    else if (y < winrect.top + borderWidth)
                    {
                        *result = HTTOP;
                    }
                }
                if (resizeWidth && resizeHeight)
                {
                    // bottom left corner
                    if (x >= winrect.left && x < winrect.left + borderWidth &&
                        y < winrect.bottom && y >= winrect.bottom - borderWidth)
                    {
                        *result = HTBOTTOMLEFT;
                    }
                    // bottom right corner
                    else if (x < winrect.right &&
                             x >= winrect.right - borderWidth &&
                             y < winrect.bottom &&
                             y >= winrect.bottom - borderWidth)
                    {
                        *result = HTBOTTOMRIGHT;
                    }
                    // top left corner
                    else if (x >= winrect.left &&
                             x < winrect.left + borderWidth &&
                             y >= winrect.top && y < winrect.top + borderWidth)
                    {
                        *result = HTTOPLEFT;
                    }
                    // top right corner
                    else if (x < winrect.right &&
                             x >= winrect.right - borderWidth &&
                             y >= winrect.top && y < winrect.top + borderWidth)
                    {
                        *result = HTTOPRIGHT;
                    }
                }

                if (*result == 0)
                {
                    *result = HTCAPTION;
                }

                return true;
            }
            break;
            default:
                return false;
        }
    }

    void paintEvent(QPaintEvent *event) override
    {
        QPainter painter(this);
        painter.setRenderHint(QPainter::Antialiasing);
        painter.setBrush(Qt::black);
        auto rect = this->rect();
        painter.drawLine(rect.bottomLeft(), rect.topRight());
        painter.drawLine(rect.topLeft(), rect.bottomRight());
    }
};

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    Draggy wrap;
    QHBoxLayout layout(&wrap);
    QLabel foo("Foo");
    layout.addWidget(&foo, 0, Qt::AlignCenter);
    wrap.show();

    return app.exec();
}