add isFixedSize implementation

Yuhang Zhao

2023-12-05 d02f3b0bc32f711bf33a7fd288185963e9e96189

 src/widgets/widgetitemdelegate.cpp

@@ -31,6 +31,31 @@
        return {originPoint, size};
    }

    QWindow *WidgetItemDelegate::hostWindow(QObject *host) const {
        return static_cast<QWidget *>(host)->windowHandle();
    }

    bool WidgetItemDelegate::isHostSizeFixed(QObject *host) const {
        const auto widget = static_cast<QWidget *>(host);
        // "Qt::MSWindowsFixedSizeDialogHint" is used cross-platform actually.
        if (widget->windowFlags() & Qt::MSWindowsFixedSizeDialogHint) {
            return true;
        }
        // Caused by setFixedWidth/Height/Size().
        const QSize minSize = widget->minimumSize();
        const QSize maxSize = widget->maximumSize();
        if (!minSize.isEmpty() && !maxSize.isEmpty() && (minSize == maxSize)) {
            return true;
        }
        // Usually set by the user.
        const QSizePolicy sizePolicy = widget->sizePolicy();
        if ((sizePolicy.horizontalPolicy() == QSizePolicy::Fixed)
            && (sizePolicy.verticalPolicy() == QSizePolicy::Fixed)) {
            return true;
        }
        return false;
    }

    bool WidgetItemDelegate::resetQtGrabbedControl() const {
        if (qt_button_down) {
            static constexpr const auto invalidPos = QPoint{-99999, -99999};