# Source code for pyqtgraph.graphicsItems.FillBetweenItem

    from .. import functions as fn
    from ..Qt import QtGui, QtWidgets
    from .PlotCurveItem import PlotCurveItem
    from .PlotDataItem import PlotDataItem

    __all__ = ['FillBetweenItem']

    class FillBetweenItem(QtWidgets.QGraphicsPathItem):
        """
        GraphicsItem filling the space between two PlotDataItems.
        """

        def __init__(self, curve1=None, curve2=None, brush=None, pen=None):
            QtWidgets.QGraphicsPathItem.__init__(self)
            self.curves = None
            if curve1 is not None and curve2 is not None:
                self.setCurves(curve1, curve2)
            elif curve1 is not None or curve2 is not None:
                raise Exception("Must specify two curves to fill between.")

            if brush is not None:
                self.setBrush(brush)
            self.setPen(pen)
            self.updatePath()

        def setBrush(self, *args, **kwds):
            """Change the fill brush. Acceps the same arguments as pg.mkBrush()"""
            QtWidgets.QGraphicsPathItem.setBrush(self, fn.mkBrush(*args, **kwds))

        def setPen(self, *args, **kwds):
            QtWidgets.QGraphicsPathItem.setPen(self, fn.mkPen(*args, **kwds))

        def setCurves(self, curve1, curve2):
            """Set the curves to fill between.

            Arguments must be instances of PlotDataItem or PlotCurveItem.

            Added in version 0.9.9
            """
            if self.curves is not None:
                for c in self.curves:
                    try:
                        c.sigPlotChanged.disconnect(self.curveChanged)
                    except (TypeError, RuntimeError):
                        pass

            curves = [curve1, curve2]
            for c in curves:
                if not isinstance(c, PlotDataItem) and not isinstance(c, PlotCurveItem):
                    raise TypeError("Curves must be PlotDataItem or PlotCurveItem.")
            self.curves = curves
            curve1.sigPlotChanged.connect(self.curveChanged)
            curve2.sigPlotChanged.connect(self.curveChanged)
            self.setZValue(min(curve1.zValue(), curve2.zValue())-1)
            self.curveChanged()

        def curveChanged(self):
            self.updatePath()

        def updatePath(self):
            if self.curves is None:
                self.setPath(QtGui.QPainterPath())
                return
            paths = []
            for c in self.curves:
                if isinstance(c, PlotDataItem):
                    paths.append(c.curve.getPath())
                elif isinstance(c, PlotCurveItem):
                    paths.append(c.getPath())

            path = QtGui.QPainterPath()
            transform = QtGui.QTransform()
            ps1 = paths[0].toSubpathPolygons(transform)
            ps2 = paths[1].toReversed().toSubpathPolygons(transform)
            ps2.reverse()
            if len(ps1) == 0 or len(ps2) == 0:
                self.setPath(QtGui.QPainterPath())
                return

            for p1, p2 in zip(ps1, ps2):
                path.addPolygon(p1 + p2)
            self.setPath(path)