How to use the enaml.qt.QtCore.QSize function in enaml

def minimumSize(self):
        """ Get the minimum size for the layout.

        """
        widget = self.currentWidget()
        if widget is not None:
            return widget.minimumSizeHint()
        return QSize(256, 192)

self._is_editable = False
        self._force_hidden = False
        self._last_visible = True
        self._line_edit = None

        title_icon = self._title_icon = QIconWidget(self)
        title_icon.setVisible(False)

        title_label = self._title_label = QTextLabel(self)

        spacer = self._spacer = QWidget(self)
        policy = spacer.sizePolicy()
        policy.setHorizontalPolicy(QSizePolicy.Expanding)
        spacer.setSizePolicy(policy)

        btn_size = QSize(14, 13)

        max_button = self._max_button = QBitmapButton(self)
        max_button.setObjectName('docktitlebar-maximize-button')
        max_button.setBitmap(MAXIMIZE_BUTTON.toBitmap())
        max_button.setIconSize(btn_size)
        max_button.setVisible(self._buttons & self.MaximizeButton)
        max_button.setToolTip('Maximize')

        restore_button = self._restore_button = QBitmapButton(self)
        restore_button.setObjectName('docktitlebar-restore-button')
        restore_button.setBitmap(RESTORE_BUTTON.toBitmap())
        restore_button.setIconSize(btn_size)
        restore_button.setVisible(self._buttons & self.RestoreButton)
        restore_button.setToolTip('Restore Down')

        close_button = self._close_button = QBitmapButton(self)

result : QSize
            A (potentially invalid) QSize which is the maximum size
            allowable while still satisfying all constraints.

        """
        d = self.declaration
        expanding = ('ignore', 'weak')
        if d.hug_width in expanding and d.hug_height in expanding:
            return QSize(16777215, 16777215)
        if self._owns_layout and self._layout_manager is not None:
            w, h = self._layout_manager.get_max_size(d.width, d.height)
            if w < 0 or d.hug_width in expanding:
                w = 16777215
            if h < 0 or d.hug_height in expanding:
                h = 16777215
            return QSize(w, h)
        return QSize(16777215, 16777215)

def _targetGlobalPos(self):
        """ Get the global position of the parent anchor.

        Returns
        -------
        result : QPoint
            The global coordinates of the target parent anchor.

        """
        state = self._state
        if state.anchor_mode == QPopupView.AnchorCursor:
            origin = QCursor.pos()
            size = QSize()
        else:
            parent = self.parent()
            if parent is None:
                # FIXME expose something other than the primary screen.
                desktop = QApplication.desktop()
                geo = desktop.availableGeometry()
                origin = geo.topLeft()
                size = geo.size()
            else:
                origin = parent.mapToGlobal(QPoint(0, 0))
                size = parent.size()
        anchor = state.parent_anchor
        px = int(anchor.x() * size.width())
        py = int(anchor.y() * size.height())
        return origin + QPoint(px, py)

def setSizeHint(self, hint):
        """ Sets the size hint to use for this widget.

        """
        self._size_hint = QSize(hint)

def __init__(self, widget, data):
        """ Initialize a QFlowWidgetItem.

        Parameters
        ----------
        widget : QWidget
            The widget to manage with this item.

        data : FlowLayoutData
            The layout data struct associated with this item.

        """
        super(QFlowWidgetItem, self).__init__(widget)
        self.data = data
        self._cached_hint = QSize()
        self._cached_max = QSize()
        self._cached_min = QSize()

Resizing is disabled if an animation is running.

        """
        animation = self._animation
        if animation and animation.state() == animation.Running:
            return
        p = self.position()
        if p == QDockBar.North:
            delta = QSize(0, delta.y())
        elif p == QDockBar.East:
            delta = QSize(-delta.x(), 0)
        elif p == QDockBar.South:
            delta = QSize(0, -delta.y())
        else:
            delta = QSize(delta.x(), 0)
        user_size = self.size() + delta
        user_size = user_size.expandedTo(self.minimumSize())
        parent = self.parent()
        if parent is not None:
            user_size = user_size.boundedTo(parent.size())
        self._user_size = user_size
        if p == QDockBar.East or p == QDockBar.South:
            d = user_size - self.size()
            p = self.pos() - QPoint(d.width(), d.height())
            self.setGeometry(QRect(p, user_size))
        else:
            self.resize(user_size)

def sizeHint(self):
        """ Get the size hint for the text label.

        """
        base = self._text_size
        if not base.isValid():
            metrics = self.fontMetrics()
            base = QSize(metrics.width(self._text), metrics.height())
            self._text_size = base
        left, top, right, bottom = self.getContentsMargins()
        return base + QSize(left + right, top + bottom)

def setMaximumSize(self, size):
        """ Set the maximum size for the QWindow.

        This is an overridden parent class method which stores the
        provided size as the explictly set QSize. The explicit
        size can be reset by passing a QSize equal to the maximum
        widget size of QSize(16777215, 16777215).

        Parameters
        ----------
        size : QSize
            The maximum size for the QWindow.

        """
        super(QWindowBase, self).setMaximumSize(size)
        if size == QSize(16777215, 16777215):
            self._expl_max_size = QSize()
        else:
            self._expl_max_size = size
        self.layout().update()

def invalidate(self):
        """ Invalidate the internal cached data for this widget item.

        The invalidation will only have an effect if the layout data
        associate with this item is marked as dirty.

        """
        if self.data.dirty:
            self._cached_hint = QSize()
            self._cached_min = QSize()
            self.data.dirty = False