# Source code for pyqtgraph.graphicsItems.ScaleBar

    from .. import functions as fn
    from .. import getConfigOption
    from ..Point import Point
    from ..Qt import QtCore, QtWidgets
    from .GraphicsObject import *
    from .GraphicsWidgetAnchor import *
    from .TextItem import TextItem

    __all__ = ['ScaleBar']

    class ScaleBar(GraphicsObject, GraphicsWidgetAnchor):
        """
        Displays a rectangular bar to indicate the relative scale of objects on the view.
        """
        def __init__(self, size, width=5, brush=None, pen=None, suffix='m', offset=None):
            GraphicsObject.__init__(self)
            GraphicsWidgetAnchor.__init__(self)
            self.setFlag(self.GraphicsItemFlag.ItemHasNoContents)
            self.setAcceptedMouseButtons(QtCore.Qt.MouseButton.NoButton)

            if brush is None:
                brush = getConfigOption('foreground')
            self.brush = fn.mkBrush(brush)
            self.pen = fn.mkPen(pen)
            self._width = width
            self.size = size
            if offset is None:
                offset = (0,0)
            self.offset = offset

            self.bar = QtWidgets.QGraphicsRectItem()
            self.bar.setPen(self.pen)
            self.bar.setBrush(self.brush)
            self.bar.setParentItem(self)

            self.text = TextItem(text=fn.siFormat(size, suffix=suffix), anchor=(0.5,1))
            self.text.setParentItem(self)

        def parentChanged(self):
            view = self.parentItem()
            if view is None:
                return
            view.sigRangeChanged.connect(self.updateBar)
            self.updateBar()

        def updateBar(self):
            view = self.parentItem()
            if view is None:
                return
            p1 = view.mapFromViewToItem(self, QtCore.QPointF(0,0))
            p2 = view.mapFromViewToItem(self, QtCore.QPointF(self.size,0))
            w = (p2-p1).x()
            self.bar.setRect(QtCore.QRectF(-w, 0, w, self._width))
            self.text.setPos(-w/2., 0)

        def boundingRect(self):
            return QtCore.QRectF()

        def setParentItem(self, p):
            ret = GraphicsObject.setParentItem(self, p)
            if self.offset is not None:
                offset = Point(self.offset)
                anchorx = 1 if offset[0] <= 0 else 0
                anchory = 1 if offset[1] <= 0 else 0
                anchor = (anchorx, anchory)
                self.anchor(itemPos=anchor, parentPos=anchor, offset=offset)
            return ret