from ..Qt import QtCore, QtGui, QtWidgets, QT_LIB

import importlib
import math
import warnings

import numpy as np

from .. import Qt, debug
from .. import functions as fn
from .. import getConfigOption
from ..Qt import OpenGLConstants as GLC
from ..Qt import OpenGLHelpers
from .GraphicsObject import GraphicsObject

if QT_LIB in ["PyQt5", "PySide2"]:
    QtOpenGL = QtGui
else:
    QtOpenGL = importlib.import_module(f'{QT_LIB}.QtOpenGL')

__all__ = ['PlotCurveItem']


class OpenGLState(QtCore.QObject):
    VERT_SRC = """
        attribute vec4 a_position;
        uniform mat4 u_mvp;
        void main() {
            gl_Position = u_mvp * a_position;
        }
    """
    FRAG_SRC = """
        uniform highp vec4 u_color;
        void main() {
            gl_FragColor = u_color;
        }
    """

    def __init__(self, parent):
        super().__init__(parent)
        self.context = None
        self.vbo_nbytes = 0
        self.render_cache = None
        self.m_vao = QtOpenGL.QOpenGLVertexArrayObject(self)
        self.m_vbo = QtOpenGL.QOpenGLBuffer(QtOpenGL.QOpenGLBuffer.Type.VertexBuffer)

    def setup(self, context):
        if self.context is context:
            return

        if self.context is not None:
            self.context.aboutToBeDestroyed.disconnect(self.cleanup)
            self.cleanup()

        self.context = context
        self.context.aboutToBeDestroyed.connect(self.cleanup)

        glwidget = self.parent()
        program = glwidget.retrieveProgram("PlotCurveItem")
        if program is None:
            program = QtOpenGL.QOpenGLShaderProgram()
            program.addShaderFromSourceCode(QtOpenGL.QOpenGLShader.ShaderTypeBit.Vertex, OpenGLState.VERT_SRC)
            program.addShaderFromSourceCode(QtOpenGL.QOpenGLShader.ShaderTypeBit.Fragment, OpenGLState.FRAG_SRC)
            program.bindAttributeLocation("a_position", 0)
            program.link()
            glwidget.storeProgram("PlotCurveItem", program)

        self.m_vao.create()
        self.m_vbo.create()
        self.vbo_nbytes = 0

        self.m_vao.bind()
        self.m_vbo.bind()
        program.enableAttributeArray(0)
        program.setAttributeBuffer(0, GLC.GL_FLOAT, 0, 2)
        self.m_vbo.release()
        self.m_vao.release()

    def cleanup(self):
        # this method should restore the state back to __init__
        glwidget = self.parent()
        glwidget.makeCurrent()

        self.m_vbo.destroy()
        self.m_vao.destroy()

        self.context = None
        self.vbo_nbytes = 0
        self.render_cache = None

        glwidget.doneCurrent()

    def verticesChanged(self, curve):
        self.render_cache = None

def arrayToLineSegments(x, y, connect, finiteCheck, out=None):
    if out is None:
        out = Qt.internals.PrimitiveArray(QtCore.QLineF, 4)

    # analogue of arrayToQPath taking the same parameters
    if len(x) < 2:
        out.resize(0)
        return out

    connect_array = None
    if isinstance(connect, np.ndarray):
        # the last element is not used
        connect_array, connect = np.asarray(connect[:-1], dtype=bool), 'array'

    all_finite = True
    if finiteCheck or connect == 'finite':
        mask = np.isfinite(x) & np.isfinite(y)
        all_finite = np.all(mask)

    if connect == 'all':
        if not all_finite:
            # remove non-finite points, if any
            x = x[mask]
            y = y[mask]

    elif connect == 'finite':
        if all_finite:
            connect = 'all'
        else:
            # each non-finite point affects the segment before and after
            connect_array = mask[:-1] & mask[1:]

    elif connect == 'pairs':
        if not all_finite:
            # ensure that we have an even number of elements
            npairs = len(x) // 2
            mask = mask[:npairs*2]
            # remove pair if at least one point within pair is non-finite
            mask.reshape((-1, 2))[:] = (mask[0::2] & mask[1::2])[:, np.newaxis]
            x = x[:npairs*2][mask]
            y = y[:npairs*2][mask]

    elif connect == 'array':
        if not all_finite:
            # replicate the behavior of arrayToQPath
            backfill_idx = fn._compute_backfill_indices(mask)
            x = x[backfill_idx]
            y = y[backfill_idx]

    if connect == 'all':
        nsegs = len(x) - 1
        out.resize(nsegs)
        if nsegs:
            memory = out.ndarray()
            memory[:, 0] = x[:-1]
            memory[:, 2] = x[1:]
            memory[:, 1] = y[:-1]
            memory[:, 3] = y[1:]

    elif connect == 'pairs':
        nsegs = len(x) // 2
        out.resize(nsegs)
        if nsegs:
            memory = out.ndarray()
            memory = memory.reshape((-1, 2))
            memory[:, 0] = x[:nsegs * 2]
            memory[:, 1] = y[:nsegs * 2]

    elif connect_array is not None:
        # the following are handled here
        # - 'array'
        # - 'finite' with non-finite elements
        nsegs = np.count_nonzero(connect_array)
        out.resize(nsegs)
        if nsegs:
            memory = out.ndarray()
            memory[:, 0] = x[:-1][connect_array]
            memory[:, 2] = x[1:][connect_array]
            memory[:, 1] = y[:-1][connect_array]
            memory[:, 3] = y[1:][connect_array]

    else:
        nsegs = 0
        out.resize(nsegs)

    return out

class PlotCurveItem(GraphicsObject):
    """
    Class representing a single plot curve. Instances of this class are created
    automatically as part of :class:`PlotDataItem <pyqtgraph.PlotDataItem>`; 
    these rarely need to be instantiated directly.

    Features:

      - Fast data update
      - Fill under curve
      - Mouse interaction

    =====================  ===============================================
    **Signals:**
    sigPlotChanged(self)   Emitted when the data being plotted has changed
    sigClicked(self, ev)   Emitted when the curve is clicked
    =====================  ===============================================
    """

    sigPlotChanged = QtCore.Signal(object)
    sigClicked = QtCore.Signal(object, object)

    def __init__(self, *args, **kargs):
        """
        Forwards all arguments to :func:`setData <pyqtgraph.PlotCurveItem.setData>`.

        Some extra arguments are accepted as well:

        ==============  =======================================================
        **Arguments:**
        parent          The parent GraphicsObject (optional)
        clickable       If `True`, the item will emit ``sigClicked`` when it is
                        clicked on. Defaults to `False`.
        ==============  =======================================================
        """
        GraphicsObject.__init__(self, kargs.get('parent', None))
        self.clear()

        ## this is disastrous for performance.
        #self.setCacheMode(QtWidgets.QGraphicsItem.CacheMode.DeviceCoordinateCache)

        self.metaData = {}
        self.opts = {
            'shadowPen': None,
            'fillLevel': None,
            'fillOutline': False,
            'brush': None,
            'stepMode': None,
            'name': None,
            'antialias': getConfigOption('antialias'),
            'connect': 'all',
            'mouseWidth': 8, # width of shape responding to mouse click
            'compositionMode': None,
            'skipFiniteCheck': False,
            'segmentedLineMode': getConfigOption('segmentedLineMode'),
        }
        if 'pen' not in kargs:
            self.opts['pen'] = fn.mkPen('w')
        self.setClickable(kargs.get('clickable', False))
        self.setData(*args, **kargs)
        self.glstate = None

    def implements(self, interface=None):
        ints = ['plotData']
        if interface is None:
            return ints
        return interface in ints

    def name(self):
        return self.opts.get('name', None)

    def setClickable(self, s, width=None):
        """Sets whether the item responds to mouse clicks.

        The `width` argument specifies the width in pixels orthogonal to the
        curve that will respond to a mouse click.
        """
        self.clickable = s
        if width is not None:
            self.opts['mouseWidth'] = width
            self._mouseShape = None
            self._boundingRect = None

    def setCompositionMode(self, mode):
        """
        Change the composition mode of the item. This is useful when overlaying
        multiple items.
        
        Parameters
        ----------
        mode : ``QtGui.QPainter.CompositionMode``
            Composition of the item, often used when overlaying items.  Common
            options include:

            ``QPainter.CompositionMode.CompositionMode_SourceOver`` (Default)
            Image replaces the background if it is opaque. Otherwise, it uses
            the alpha channel to blend the image with the background.

            ``QPainter.CompositionMode.CompositionMode_Overlay`` Image color is
            mixed with the background color to reflect the lightness or
            darkness of the background

            ``QPainter.CompositionMode.CompositionMode_Plus`` Both the alpha
            and color of the image and background pixels are added together.

            ``QPainter.CompositionMode.CompositionMode_Plus`` The output is the
            image color multiplied by the background.

            See ``QPainter::CompositionMode`` in the Qt Documentation for more
            options and details
        """
        self.opts['compositionMode'] = mode
        self.update()

    def getData(self):
        return self.xData, self.yData

    def dataBounds(self, ax, frac=1.0, orthoRange=None):
        ## Need this to run as fast as possible.
        ## check cache first:
        cache = self._boundsCache[ax]
        if cache is not None and cache[0] == (frac, orthoRange):
            return cache[1]

        (x, y) = self.getData()
        if x is None or len(x) == 0:
            return (None, None)

        if ax == 0:
            d = x
            d2 = y
        elif ax == 1:
            d = y
            d2 = x
        else:
            raise ValueError("Invalid axis value")

        ## If an orthogonal range is specified, mask the data now
        if orthoRange is not None:
            mask = (d2 >= orthoRange[0]) * (d2 <= orthoRange[1])
            if self.opts.get("stepMode", None) == "center":
                mask = mask[:-1]  # len(y) == len(x) - 1 when stepMode is center
            d = d[mask]
            #d2 = d2[mask]

        if len(d) == 0:
            return (None, None)

        ## Get min/max (or percentiles) of the requested data range
        if frac >= 1.0:
            # include complete data range
            # first try faster nanmin/max function, then cut out infs if needed.
            with warnings.catch_warnings(): 
                # All-NaN data is acceptable; Explicit numpy warning is not needed.
                warnings.simplefilter("ignore")
                b = ( float(np.nanmin(d)), float(np.nanmax(d)) ) # enforce float format for bounds, even if data format is different
            if math.isinf(b[0]) or math.isinf(b[1]):
                mask = np.isfinite(d)
                d = d[mask]
                if len(d) == 0:
                    return (None, None)
                b = ( float(d.min()), float(d.max()) ) # enforce float format for bounds, even if data format is different

        elif frac <= 0.0:
            raise Exception("Value for parameter 'frac' must be > 0. (got %s)" % str(frac))
        else:
            # include a percentile of data range
            mask = np.isfinite(d)
            d = d[mask]
            if len(d) == 0:
                return (None, None)
            b = np.percentile(d, [50 * (1 - frac), 50 * (1 + frac)]) # percentile result is always float64 or larger

        ## adjust for fill level
        if ax == 1 and self.opts['fillLevel'] not in [None, 'enclosed']:
            b = ( 
                float( min(b[0], self.opts['fillLevel']) ), 
                float( max(b[1], self.opts['fillLevel']) )
            ) # enforce float format for bounds, even if data format is different

        ## Add pen width only if it is non-cosmetic.
        pen = self.opts['pen']
        spen = self.opts['shadowPen']
        if pen is not None and not pen.isCosmetic() and pen.style() != QtCore.Qt.PenStyle.NoPen:
            b = (b[0] - pen.widthF()*0.7072, b[1] + pen.widthF()*0.7072)
        if spen is not None and not spen.isCosmetic() and spen.style() != QtCore.Qt.PenStyle.NoPen:
            b = (b[0] - spen.widthF()*0.7072, b[1] + spen.widthF()*0.7072)

        self._boundsCache[ax] = [(frac, orthoRange), b]
        return b

    def pixelPadding(self):
        pen = self.opts['pen']
        spen = self.opts['shadowPen']
        w = 0
        if  pen is not None and pen.isCosmetic() and pen.style() != QtCore.Qt.PenStyle.NoPen:
            w += pen.widthF()*0.7072
        if spen is not None and spen.isCosmetic() and spen.style() != QtCore.Qt.PenStyle.NoPen:
            w = max(w, spen.widthF()*0.7072)
        if self.clickable:
            w = max(w, self.opts['mouseWidth']//2 + 1)
        return w

    def boundingRect(self):
        if self._boundingRect is None:
            (xmn, xmx) = self.dataBounds(ax=0)
            if xmn is None or xmx is None:
                return QtCore.QRectF()
            (ymn, ymx) = self.dataBounds(ax=1)
            if ymn is None or ymx is None:
                return QtCore.QRectF()

            px = py = 0.0
            pxPad = self.pixelPadding()
            if pxPad > 0:
                # determine length of pixel in local x, y directions
                px, py = self.pixelVectors()
                try:
                    px = 0 if px is None else px.length()
                except OverflowError:
                    px = 0
                try:
                    py = 0 if py is None else py.length()
                except OverflowError:
                    py = 0

                # return bounds expanded by pixel size
                px *= pxPad
                py *= pxPad
            #px += self._maxSpotWidth * 0.5
            #py += self._maxSpotWidth * 0.5
            self._boundingRect = QtCore.QRectF(xmn-px, ymn-py, (2*px)+xmx-xmn, (2*py)+ymx-ymn)

        return self._boundingRect

    def viewTransformChanged(self):
        self.invalidateBounds()
        self.prepareGeometryChange()

    #def boundingRect(self):
        #if self._boundingRect is None:
            #(x, y) = self.getData()
            #if x is None or y is None or len(x) == 0 or len(y) == 0:
                #return QtCore.QRectF()


            #if self.opts['shadowPen'] is not None:
                #lineWidth = (max(self.opts['pen'].width(), self.opts['shadowPen'].width()) + 1)
            #else:
                #lineWidth = (self.opts['pen'].width()+1)


            #pixels = self.pixelVectors()
            #if pixels == (None, None):
                #pixels = [Point(0,0), Point(0,0)]

            #xmin = x.min()
            #xmax = x.max()
            #ymin = y.min()
            #ymax = y.max()

            #if self.opts['fillLevel'] is not None:
                #ymin = min(ymin, self.opts['fillLevel'])
                #ymax = max(ymax, self.opts['fillLevel'])

            #xmin -= pixels[0].x() * lineWidth
            #xmax += pixels[0].x() * lineWidth
            #ymin -= abs(pixels[1].y()) * lineWidth
            #ymax += abs(pixels[1].y()) * lineWidth

            #self._boundingRect = QtCore.QRectF(xmin, ymin, xmax-xmin, ymax-ymin)
        #return self._boundingRect


    def invalidateBounds(self):
        self._boundingRect = None
        self._boundsCache = [None, None]

    def setPen(self, *args, **kargs):
        """Set the pen used to draw the curve."""
        if args and args[0] is None:
            self.opts['pen'] = None
        else:
            self.opts['pen'] = fn.mkPen(*args, **kargs)
        self.invalidateBounds()
        self.update()

    def setShadowPen(self, *args, **kargs):
        """
        Set the shadow pen used to draw behind the primary pen.
        This pen must have a larger width than the primary
        pen to be visible. Arguments are passed to 
        :func:`mkPen <pyqtgraph.mkPen>`
        """
        if args and args[0] is None:
            self.opts['shadowPen'] = None
        else:
            self.opts['shadowPen'] = fn.mkPen(*args, **kargs)
        self.invalidateBounds()
        self.update()

    def setBrush(self, *args, **kargs):
        """
        Sets the brush used when filling the area under the curve. All 
        arguments are passed to :func:`mkBrush <pyqtgraph.mkBrush>`.
        """
        if args and args[0] is None:
            self.opts['brush'] = None
        else:
            self.opts['brush'] = fn.mkBrush(*args, **kargs)
        self.invalidateBounds()
        self.update()

    def setFillLevel(self, level):
        """Sets the level filled to when filling under the curve"""
        self.opts['fillLevel'] = level
        self.fillPath = None
        self._fillPathList = None
        self.invalidateBounds()
        self.update()
        
    def setSkipFiniteCheck(self, skipFiniteCheck):
        """
        When it is known that the plot data passed to ``PlotCurveItem`` contains only finite numerical values,
        the `skipFiniteCheck` property can help speed up plotting. If this flag is set and the data contains 
        any non-finite values (such as `NaN` or `Inf`), unpredictable behavior will occur. The data might not
        be plotted, or there migth be significant performance impact.
        """
        self.opts['skipFiniteCheck']  = bool(skipFiniteCheck)

    def setData(self, *args, **kargs):
        """
        =============== =================================================================
        **Arguments:**
        x, y            (numpy arrays) Data to display
        pen             Pen to use when drawing. Any single argument accepted by
                        :func:`mkPen <pyqtgraph.mkPen>` is allowed.
        shadowPen       Pen for drawing behind the primary pen. Usually this
                        is used to emphasize the curve by providing a
                        high-contrast border. Any single argument accepted by
                        :func:`mkPen <pyqtgraph.mkPen>` is allowed.
        fillLevel       (float or None) Fill the area under the curve to
                        the specified value.
        fillOutline     (bool) If True, an outline surrounding the `fillLevel`
                        area is drawn.
        brush           Brush to use when filling. Any single argument accepted
                        by :func:`mkBrush <pyqtgraph.mkBrush>` is allowed.
        antialias       (bool) Whether to use antialiasing when drawing. This
                        is disabled by default because it decreases performance.
        stepMode        (str or None) If 'center', a step is drawn using the `x`
                        values as boundaries and the given `y` values are
                        associated to the mid-points between the boundaries of
                        each step. This is commonly used when drawing
                        histograms. Note that in this case, ``len(x) == len(y) + 1``
                        
                        If 'left' or 'right', the step is drawn assuming that
                        the `y` value is associated to the left or right boundary,
                        respectively. In this case ``len(x) == len(y)``
                        If not passed or an empty string or `None` is passed, the
                        step mode is not enabled.
        connect         Argument specifying how vertexes should be connected
                        by line segments. 
                        
                            | 'all' (default) indicates full connection. 
                            | 'pairs' draws one separate line segment for each two points given.
                            | 'finite' omits segments attached to `NaN` or `Inf` values. 
                            | For any other connectivity, specify an array of boolean values.
        compositionMode See :func:`setCompositionMode
                        <pyqtgraph.PlotCurveItem.setCompositionMode>`.
        skipFiniteCheck (bool, defaults to `False`) Optimization flag that can
                        speed up plotting by not checking and compensating for
                        `NaN` values.  If set to `True`, and `NaN` values exist, the
                        data may not be displayed or the plot may take a
                        significant performance hit.
        =============== =================================================================

        If non-keyword arguments are used, they will be interpreted as
        ``setData(y)`` for a single argument and ``setData(x, y)`` for two
        arguments.
        
        **Notes on performance:**
        
        Line widths greater than 1 pixel affect the performance as discussed in 
        the documentation of :class:`PlotDataItem <pyqtgraph.PlotDataItem>`.
        """
        self.updateData(*args, **kargs)

    def updateData(self, *args, **kargs):
        profiler = debug.Profiler()

        if 'compositionMode' in kargs:
            self.setCompositionMode(kargs['compositionMode'])

        if len(args) == 1:
            kargs['y'] = args[0]
        elif len(args) == 2:
            kargs['x'] = args[0]
            kargs['y'] = args[1]

        if 'y' not in kargs or kargs['y'] is None:
            kargs['y'] = np.array([])
        if 'x' not in kargs or kargs['x'] is None:
            kargs['x'] = np.arange(len(kargs['y']))

        for k in ['x', 'y']:
            data = kargs[k]
            if isinstance(data, list):
                data = np.array(data)
                kargs[k] = data
            if not isinstance(data, np.ndarray) or data.ndim > 1:
                raise Exception("Plot data must be 1D ndarray.")
            if data.dtype.kind == 'c':
                raise Exception("Can not plot complex data types.")


        profiler("data checks")

        #self.setCacheMode(QtWidgets.QGraphicsItem.CacheMode.NoCache)  ## Disabling and re-enabling the cache works around a bug in Qt 4.6 causing the cached results to display incorrectly
                                                        ##    Test this bug with test_PlotWidget and zoom in on the animated plot
        self.yData = kargs['y'].view(np.ndarray)
        self.xData = kargs['x'].view(np.ndarray)
        
        self.invalidateBounds()
        self.prepareGeometryChange()
        self.informViewBoundsChanged()

        profiler('copy')

        if 'stepMode' in kargs:
            self.opts['stepMode'] = kargs['stepMode']

        if self.opts['stepMode'] in ("center", True):  ## check against True for backwards compatibility
            if self.opts['stepMode'] is True:
                warnings.warn(
                    'stepMode=True is deprecated and will result in an error after October 2022. Use stepMode="center" instead.',
                    DeprecationWarning, stacklevel=3
                )
            if len(self.xData) != len(self.yData)+1:  ## allow difference of 1 for step mode plots
                raise Exception("len(X) must be len(Y)+1 since stepMode=True (got %s and %s)" % (self.xData.shape, self.yData.shape))
        else:
            if self.xData.shape != self.yData.shape:  ## allow difference of 1 for step mode plots
                raise Exception("X and Y arrays must be the same shape--got %s and %s." % (self.xData.shape, self.yData.shape))

        self.path = None
        self.fillPath = None
        self._fillPathList = None
        self._mouseShape = None
        self._lineSegmentsRendered = False

        if 'name' in kargs:
            self.opts['name'] = kargs['name']
        if 'connect' in kargs:
            self.opts['connect'] = kargs['connect']
        if 'pen' in kargs:
            self.setPen(kargs['pen'])
        if 'shadowPen' in kargs:
            self.setShadowPen(kargs['shadowPen'])
        if 'fillLevel' in kargs:
            self.setFillLevel(kargs['fillLevel'])
        if 'fillOutline' in kargs:
            self.opts['fillOutline'] = kargs['fillOutline']
        if 'brush' in kargs:
            self.setBrush(kargs['brush'])
        if 'antialias' in kargs:
            self.opts['antialias'] = kargs['antialias']
        if 'skipFiniteCheck' in kargs:
            self.opts['skipFiniteCheck'] = kargs['skipFiniteCheck']

        profiler('set')
        self.update()
        profiler('update')
        self.sigPlotChanged.emit(self)
        profiler('emit')

    @staticmethod
    def _generateStepModeData(stepMode, x, y, baseline):
        ## each value in the x/y arrays generates 2 points.
        if stepMode == "right":
            x2 = np.empty((len(x) + 1, 2), dtype=x.dtype)
            x2[:-1] = x[:, np.newaxis]
            x2[-1] = x2[-2]
        elif stepMode == "left":
            x2 = np.empty((len(x) + 1, 2), dtype=x.dtype)
            x2[1:] = x[:, np.newaxis]
            x2[0] = x2[1]
        elif stepMode in ("center", True):  ## support True for back-compat
            x2 = np.empty((len(x),2), dtype=x.dtype)
            x2[:] = x[:, np.newaxis]
        else:
            raise ValueError("Unsupported stepMode %s" % stepMode)
        if baseline is None:
            x = x2.reshape(x2.size)[1:-1]
            y2 = np.empty((len(y),2), dtype=y.dtype)
            y2[:] = y[:,np.newaxis]
            y = y2.reshape(y2.size)
        else:
            # if baseline is provided, add vertical lines to left/right ends
            x = x2.reshape(x2.size)
            y2 = np.empty((len(y)+2,2), dtype=y.dtype)
            y2[1:-1] = y[:,np.newaxis]
            y = y2.reshape(y2.size)[1:-1]
            y[[0, -1]] = baseline
        return x, y

    def generatePath(self, x, y):
        if self.opts['stepMode']:
            x, y = self._generateStepModeData(
                self.opts['stepMode'],
                x,
                y,
                baseline=self.opts['fillLevel']
            )

        return fn.arrayToQPath(
            x,
            y,
            connect=self.opts['connect'],
            finiteCheck=not self.opts['skipFiniteCheck']
        )

    def getPath(self):
        if self.path is None:
            x,y = self.getData()
            if x is None or len(x) == 0 or y is None or len(y) == 0:
                self.path = QtGui.QPainterPath()
            else:
                self.path = self.generatePath(*self.getData())
            self.fillPath = None
            self._fillPathList = None
            self._mouseShape = None

        return self.path

    def setSegmentedLineMode(self, mode):
        """
        Sets the mode that decides whether or not lines are drawn as segmented lines. Drawing lines
        as segmented lines is more performant than the standard drawing method with continuous
        lines.

        Parameters
        ----------
        mode : str
               ``'auto'`` (default) segmented lines are drawn if the pen's width > 1, pen style is a
               solid line, the pen color is opaque and anti-aliasing is not enabled.

               ``'on'`` lines are always drawn as segmented lines

               ``'off'`` lines are never drawn as segmented lines, i.e. the drawing
               method with continuous lines is used
        """
        if mode not in ('auto', 'on', 'off'):
            raise ValueError(f'segmentedLineMode must be "auto", "on" or "off", got {mode} instead')
        self.opts['segmentedLineMode'] = mode
        self.invalidateBounds()
        self.update()

    def _shouldUseDrawLineSegments(self, pen):
        mode = self.opts['segmentedLineMode']
        if mode in ('on',):
            return True
        if mode in ('off',):
            return False
        return (
            pen.widthF() > 1.0
            # non-solid pen styles need single polyline to be effective
            and pen.style() == QtCore.Qt.PenStyle.SolidLine
            # segmenting the curve slows gradient brushes, and is expected
            # to do the same for other patterns
            and pen.isSolid()   # pen.brush().style() == Qt.BrushStyle.SolidPattern
            # ends of adjacent line segments overlapping is visible when not opaque
            and pen.color().alphaF() == 1.0
            # anti-aliasing introduces transparent pixels and therefore also causes visible overlaps
            # for adjacent line segments
            and not self.opts['antialias']
        )

    def _getLineSegments(self):
        if not self._lineSegmentsRendered:
            x, y = self.getData()
            if self.opts['stepMode']:
                x, y = self._generateStepModeData(
                    self.opts['stepMode'],
                    x,
                    y,
                    baseline=self.opts['fillLevel']
                )

            self._lineSegments = arrayToLineSegments(
                x,
                y,
                connect=self.opts['connect'],
                finiteCheck=not self.opts['skipFiniteCheck'],
                out=self._lineSegments
            )

            self._lineSegmentsRendered = True

        return self._lineSegments.drawargs()

    def _getClosingSegments(self):
        # this is only used for fillOutline
        # no point caching with so few elements generated
        segments = []
        if self.opts['fillLevel'] == 'enclosed':
            return segments

        baseline = self.opts['fillLevel']
        x, y = self.getData()
        lx, rx = x[[0, -1]]
        ly, ry = y[[0, -1]]

        if ry != baseline:
            segments.append(QtCore.QLineF(rx, ry, rx, baseline))
        segments.append(QtCore.QLineF(rx, baseline, lx, baseline))
        if ly != baseline:
            segments.append(QtCore.QLineF(lx, baseline, lx, ly))

        return segments

    def _getFillPath(self):
        if self.fillPath is not None:
            return self.fillPath

        path = QtGui.QPainterPath(self.getPath())
        self.fillPath = path
        if self.opts['fillLevel'] == 'enclosed':
            return path

        baseline = self.opts['fillLevel']
        x, y = self.getData()
        lx, rx = x[[0, -1]]
        ly, ry = y[[0, -1]]

        if ry != baseline:
            path.lineTo(rx, baseline)
        path.lineTo(lx, baseline)
        if ly != baseline:
            path.lineTo(lx, ly)

        return path

    def _shouldUseFillPathList(self):
        connect = self.opts['connect']
        return (
            # not meaningful to fill disjoint lines
            isinstance(connect, str) and connect in ['all', 'finite']
            # guard against odd-ball argument 'enclosed'
            and isinstance(self.opts['fillLevel'], (int, float))
        )

    def _getFillPathList(self, widget):
        if self._fillPathList is not None:
            return self._fillPathList

        x, y = self.getData()
        if self.opts['stepMode']:
            x, y = self._generateStepModeData(
                self.opts['stepMode'],
                x,
                y,
                # note that left/right vertical lines can be omitted here
                baseline=None
            )

        # Set suitable chunk size for current configuration:
        #   * Without OpenGL split in small chunks
        #   * With OpenGL split in rather big chunks
        #     Note, the present code is used only if config option 'enableExperimental' is False,
        #     otherwise the 'paintGL' method is used.
        # Values were found using 'PlotSpeedTest.py' example, see #2257.
        chunksize = 50 if not isinstance(widget, QtWidgets.QOpenGLWidget) else 5000

        connect_kind = self.opts['connect']
        if isinstance(connect_kind, np.ndarray):
            connect_kind = "array"

        fillLevel = self.opts['fillLevel']
        self._fillPathList = []
        sidx = []
        slen = []

        if connect_kind == "all":
            mask = np.isfinite(x) & np.isfinite(y)
            if not mask.all():
                # remove non-finite values
                x = x[mask]
                y = y[mask]
            sidx = [0]
            slen = [len(x)]

        elif connect_kind == "finite":
            isfinite = np.isfinite(x) & np.isfinite(y)
            nonfinite_locs = np.nonzero(~isfinite)[0]
            # pretend that there's a nonfinite before and after the array
            nonfinite_locs = np.concatenate(([-1], nonfinite_locs, [len(x)]))
            sidx = nonfinite_locs[:-1] + 1      # start index of segment
            slen = np.diff(nonfinite_locs) - 1  # length of segment

        for s, l in zip(sidx, slen):
            if l < 2:
                continue
            xchunk = x[s:s+l]
            ychunk = y[s:s+l]
            pathlist = self._construct_finite_segment_FillPathList(xchunk, ychunk, fillLevel, chunksize)
            self._fillPathList.extend(pathlist)

        return self._fillPathList

    def _construct_finite_segment_FillPathList(self, x, y, baseline, chunksize):
        paths = []
        offset = 0
        xybuf = np.empty((chunksize+3, 2))

        while offset < len(x) - 1:
            subx = x[offset:offset + chunksize]
            suby = y[offset:offset + chunksize]
            size = len(subx)
            xyview = xybuf[:size+3]
            xyview[:-3, 0] = subx
            xyview[:-3, 1] = suby
            xyview[-3:, 0] = subx[[-1, 0, 0]]
            xyview[-3:, 1] = [baseline, baseline, suby[0]]
            offset += size - 1  # last point is re-used for next chunk
            # data was either declared to be all-finite OR was sanitized
            path = fn._arrayToQPath_all(xyview[:, 0], xyview[:, 1], finiteCheck=False)
            paths.append(path)

        return paths

    @debug.warnOnException  ## raising an exception here causes crash
    def paint(self, p, opt, widget):
        profiler = debug.Profiler()
        if self.xData is None or len(self.xData) == 0:
            return

        # opengl fill mode supports filling to a fillLevel
        # for connect="all" and connect="finite" only.
        opengl_supported_fill = (
            self.opts['fillLevel'] is None  # not filling is always supported
            or (
                isinstance(self.opts['fillLevel'], (int, float))
                and isinstance(self.opts['connect'], str)
                and self.opts['connect'] in ['all', 'finite']
                and not self.opts['fillOutline']
            )
        )

        if (
            getConfigOption('enableExperimental')
            and isinstance(widget, OpenGLHelpers.GraphicsViewGLWidget)
            and opengl_supported_fill
            and not self.opts['stepMode']
        ):
            if self.glstate is None:
                self.glstate = OpenGLState(widget)
                self.sigPlotChanged.connect(self.glstate.verticesChanged)
            p.beginNativePainting()
            try:
                self.paintGL(widget)
            finally:
                p.endNativePainting()
            return

        if self._exportOpts is not False:
            aa = self._exportOpts.get('antialias', True)
        else:
            aa = self.opts['antialias']

        p.setRenderHint(p.RenderHint.Antialiasing, aa)

        cmode = self.opts['compositionMode']
        if cmode is not None:
            p.setCompositionMode(cmode)

        brush = self.opts['brush']
        do_fill = (
            self.opts['fillLevel'] is not None
            and not (brush is None or brush.style() == QtCore.Qt.BrushStyle.NoBrush)
        )
        do_fill_outline = do_fill and self.opts['fillOutline']

        if do_fill:
            if self._shouldUseFillPathList():
                paths = self._getFillPathList(widget)
            else:
                paths = [self._getFillPath()]

            profiler('generate fill path')
            for path in paths:
                p.fillPath(path, brush)
            profiler('draw fill path')

        for pen_kind in ['shadowPen', 'pen']:
            pen = self.opts[pen_kind]
            if pen is None or pen.style() == QtCore.Qt.PenStyle.NoPen:
                continue
            p.setPen(pen)

            if self._shouldUseDrawLineSegments(pen):
                p.drawLines(*self._getLineSegments())
                if do_fill_outline:
                    p.drawLines(self._getClosingSegments())
            else:
                if do_fill_outline:
                    p.drawPath(self._getFillPath())
                else:
                    p.drawPath(self.getPath())

        profiler('drawPath')

    def paintGL(self, widget):
        if (view := self.getViewBox()) is None:
            return

        x, y = self.getData()
        num_pts = len(x)
        valid_pts = num_pts

        # minimum 2 pts to draw anything
        if num_pts < 2:
            return

        glstate = self.glstate
        glstate.setup(widget.context())
        glf = widget.getFunctions()
        program = widget.retrieveProgram("PlotCurveItem")

        # OpenGL only sees the float32 version of our data, and this may cause
        # precision issues. To mitigate this, we shift the origin of our data
        # to the center of its bounds.
        # Note that xc, yc are double precision Python floats. Subtracting them
        # from the x, y ndarrays will automatically upcast the latter to double
        # precision.
        if glstate.render_cache is None:
            # the origin point is calculated once per data change.
            # once the data is uploaded, the origin point is fixed.
            center = self.boundingRect().center()
            xc, yc = center.x(), center.y()
        else:
            xc, yc, *_ = glstate.render_cache

        proj = QtGui.QMatrix4x4()
        proj.ortho(widget.rect())
        tr = self.sceneTransform()
        tr.translate(xc, yc)
        mvp = proj * QtGui.QMatrix4x4(tr)

        vbo_nbytes_needed = num_pts * 2 * 4

        connect_kind = self.opts["connect"]
        if isinstance(connect_kind, np.ndarray):
            connect_kind = "array"
            vbo_nbytes_needed = ((num_pts-1) * 2) * 2 * 4

        # filling is only supported for 'all' and 'finite'.
        # it requires an additional 2 * num_pts of storage
        # to create the triangle strip to be filled.
        fillLevel = None
        if connect_kind in ['all', 'finite']:
            if isinstance(self.opts['fillLevel'], (int, float)):
                fillLevel = float(self.opts['fillLevel'])
                vbo_nbytes_needed += (2 * num_pts) * 2 * 4

        # resize (and invalidate) gpu buffers if needed.
        # a reallocation can only occur together with a change in data.
        # i.e. reallocation ==> change in data (render_cache is None)
        if vbo_nbytes_needed != glstate.vbo_nbytes:
            glstate.m_vbo.bind()
            glstate.m_vbo.allocate(vbo_nbytes_needed)
            glstate.m_vbo.release()
            glstate.vbo_nbytes = vbo_nbytes_needed

        if glstate.render_cache is None:
            buf = None

            if connect_kind == "pairs":
                glstate.render_cache = (xc, yc, valid_pts,)

                buf = np.empty((valid_pts, 2), dtype=np.float32)
                pos = buf
                pos[:, 0] = x - xc
                pos[:, 1] = y - yc

            elif connect_kind == "all":
                if not self.opts["skipFiniteCheck"]:
                    isfinite = np.isfinite(y)
                    if x.dtype.kind == 'f':
                        isfinite &= np.isfinite(x)
                    valid_pts = np.sum(isfinite)
                glstate.render_cache = (xc, yc, valid_pts,)

                fill_pts = 0 if fillLevel is None else 2 * valid_pts
                buf = np.empty((valid_pts + fill_pts, 2), dtype=np.float32)
                pos = buf[:valid_pts, :]
                if valid_pts == num_pts:
                    pos[:, 0] = x - xc
                    pos[:, 1] = y - yc
                else:
                    pos[:, 0] = x[isfinite] - xc
                    pos[:, 1] = y[isfinite] - yc

                if fill_pts:
                    fillpos = buf[valid_pts:, :]
                    fillpos[0::2, 0] = pos[:, 0]
                    fillpos[0::2, 1] = pos[:, 1]
                    fillpos[1::2, 0] = pos[:, 0]
                    fillpos[1::2, 1] = fillLevel - yc

            elif connect_kind == "finite":
                isfinite = np.isfinite(y)
                if x.dtype.kind == 'f':
                    isfinite &= np.isfinite(x)
                nonfinite_locs = np.nonzero(~isfinite)[0]
                # pretend that there's a nonfinite before and after the array
                nonfinite_locs = np.concatenate(([-1], nonfinite_locs, [num_pts]))
                sidx = nonfinite_locs[:-1] + 1      # start index of segment
                slen = np.diff(nonfinite_locs) - 1  # length of segment
                mask = slen >= 2
                sidx = sidx[mask].tolist()
                slen = slen[mask].tolist()
                glstate.render_cache = (xc, yc, valid_pts, sidx, slen)

                fill_pts = 0 if fillLevel is None else 2 * valid_pts
                buf = np.empty((valid_pts + fill_pts, 2), dtype=np.float32)
                pos = buf[:valid_pts, :]
                pos[:, 0] = x - xc
                pos[:, 1] = y - yc

                if fill_pts:
                    fillpos = buf[valid_pts:, :]
                    fillpos[0::2, 0] = pos[:, 0]
                    fillpos[0::2, 1] = pos[:, 1]
                    fillpos[1::2, 0] = pos[:, 0]
                    fillpos[1::2, 1] = fillLevel - yc

            elif connect_kind == "array":
                mask = np.asarray(self.opts["connect"], dtype=bool)[:num_pts-1]
                valid_pts = 2 * np.sum(mask)
                glstate.render_cache = (xc, yc, valid_pts,)

                buf = np.empty((valid_pts, 2), dtype=np.float32)
                pos = buf
                xshift = x - xc
                yshift = y - yc
                pos[0::2, 0] = xshift[:-1][mask]
                pos[1::2, 0] = xshift[1:][mask]
                pos[0::2, 1] = yshift[:-1][mask]
                pos[1::2, 1] = yshift[1:][mask]

            if buf is not None:
                glstate.m_vbo.bind()
                glstate.m_vbo.write(0, buf, buf.nbytes)
                glstate.m_vbo.release()


        widget.drawStencil(view)

        glstate.m_vao.bind()
        program.bind()
        OpenGLHelpers.setUniformValue(program, "u_mvp", mvp)

        # filling occurs first so that the curve outline gets painted over it.
        for brush in [self.opts["brush"]]:
            if fillLevel is None:
                continue
            if brush is None or brush.style() == QtCore.Qt.BrushStyle.NoBrush:
                continue
            OpenGLHelpers.setUniformValue(program, "u_color", brush.color())

            glf.glEnable(GLC.GL_BLEND)
            glf.glBlendFuncSeparate(GLC.GL_SRC_ALPHA, GLC.GL_ONE_MINUS_SRC_ALPHA, 1, GLC.GL_ONE_MINUS_SRC_ALPHA)

            if connect_kind == 'all':
                *_, valid_pts = glstate.render_cache
                glf.glDrawArrays(GLC.GL_TRIANGLE_STRIP, valid_pts, 2 * valid_pts)
            elif connect_kind == 'finite':
                *_, valid_pts, sidx, slen = glstate.render_cache
                for s, l in zip(sidx, slen):
                    glf.glDrawArrays(GLC.GL_TRIANGLE_STRIP, valid_pts + 2 * s, 2 * l)

            glf.glDisable(GLC.GL_BLEND)

        # enable antialiasing if requested
        if self._exportOpts is not False:
            aa = self._exportOpts.get('antialias', True)
        else:
            aa = self.opts['antialias']
        if aa:
            glf.glEnable(GLC.GL_LINE_SMOOTH)
            glf.glEnable(GLC.GL_BLEND)
            glf.glBlendFunc(GLC.GL_SRC_ALPHA, GLC.GL_ONE_MINUS_SRC_ALPHA)
            glf.glHint(GLC.GL_LINE_SMOOTH_HINT, GLC.GL_NICEST)
        else:
            glf.glDisable(GLC.GL_LINE_SMOOTH)

        for pen_kind in ["shadowPen", "pen"]:
            pen = self.opts[pen_kind]
            if pen is None or pen.style() == QtCore.Qt.PenStyle.NoPen:
                continue
            width = pen.widthF()
            if pen.isCosmetic() and width < 1:
                width = 1

            glf.glLineWidth(width)
            OpenGLHelpers.setUniformValue(program, "u_color", pen.color())

            match connect_kind:
                case "pairs" | "array":
                    *_, valid_pts = glstate.render_cache
                    glf.glDrawArrays(GLC.GL_LINES, 0, valid_pts)
                case "all":
                    *_, valid_pts = glstate.render_cache
                    glf.glDrawArrays(GLC.GL_LINE_STRIP, 0, valid_pts)
                case "finite":
                    *_, sidx, slen = glstate.render_cache
                    if hasattr(glf, "glMultiDrawArrays") and not glstate.context.isOpenGLES():
                        glf.glMultiDrawArrays(GLC.GL_LINE_STRIP, sidx, slen, len(sidx))
                    else:
                        # PyQt{5,6} didn't include glMultiDrawArrays
                        for s, l in zip(sidx, slen):
                            glf.glDrawArrays(GLC.GL_LINE_STRIP, s, l)

        glstate.m_vao.release()

    def clear(self):
        self.xData = None  ## raw values
        self.yData = None
        self._lineSegments = None
        self._lineSegmentsRendered = False
        self.path = None
        self.fillPath = None
        self._fillPathList = None
        self._mouseShape = None
        self._mouseBounds = None
        self._boundsCache = [None, None]
        #del self.xData, self.yData, self.xDisp, self.yDisp, self.path

    def mouseShape(self):
        """
        Return a QPainterPath representing the clickable shape of the curve

        """
        if self._mouseShape is None:
            view = self.getViewBox()
            if view is None:
                return QtGui.QPainterPath()
            stroker = QtGui.QPainterPathStroker()
            path = self.getPath()
            path = self.mapToItem(view, path)
            stroker.setWidth(self.opts['mouseWidth'])
            mousePath = stroker.createStroke(path)
            self._mouseShape = self.mapFromItem(view, mousePath)
        return self._mouseShape

    def mouseClickEvent(self, ev):
        if not self.clickable or ev.button() != QtCore.Qt.MouseButton.LeftButton:
            return
        if self.mouseShape().contains(ev.pos()):
            ev.accept()
            self.sigClicked.emit(self, ev)



class ROIPlotItem(PlotCurveItem):
    """Plot curve that monitors an ROI and image for changes to automatically replot."""
    def __init__(self, roi, data, img, axes=(0,1), xVals=None, color=None):
        self.roi = roi
        self.roiData = data
        self.roiImg = img
        self.axes = axes
        self.xVals = xVals
        PlotCurveItem.__init__(self, self.getRoiData(), x=self.xVals, color=color)
        #roi.connect(roi, QtCore.SIGNAL('regionChanged'), self.roiChangedEvent)
        roi.sigRegionChanged.connect(self.roiChangedEvent)
        #self.roiChangedEvent()

    def getRoiData(self):
        d = self.roi.getArrayRegion(self.roiData, self.roiImg, axes=self.axes)
        if d is None:
            return
        while d.ndim > 1:
            d = d.mean(axis=1)
        return d

    def roiChangedEvent(self):
        d = self.getRoiData()
        self.updateData(d, self.xVals)
