from itertools import starmap, repeat
try:
    from itertools import imap
except ImportError:
    imap = map
import numpy as np
import weakref
from ..Qt import QtGui, QtCore, QT_LIB
from ..Point import Point
from .. import functions as fn
from .GraphicsItem import GraphicsItem
from .GraphicsObject import GraphicsObject
from .. import getConfigOption
from ..pgcollections import OrderedDict
from .. import debug
from ..python2_3 import basestring

__all__ = ['ScatterPlotItem', 'SpotItem']


## Build all symbol paths
Symbols = OrderedDict([(name, QtGui.QPainterPath()) for name in ['o', 's', 't', 't1', 't2', 't3','d', '+', 'x', 'p', 'h', 'star']])
Symbols['o'].addEllipse(QtCore.QRectF(-0.5, -0.5, 1, 1))
Symbols['s'].addRect(QtCore.QRectF(-0.5, -0.5, 1, 1))
coords = {
    't': [(-0.5, -0.5), (0, 0.5), (0.5, -0.5)],
    't1': [(-0.5, 0.5), (0, -0.5), (0.5, 0.5)],
    't2': [(-0.5, -0.5), (-0.5, 0.5), (0.5, 0)],
    't3': [(0.5, 0.5), (0.5, -0.5), (-0.5, 0)],
    'd': [(0., -0.5), (-0.4, 0.), (0, 0.5), (0.4, 0)],
    '+': [
        (-0.5, -0.05), (-0.5, 0.05), (-0.05, 0.05), (-0.05, 0.5),
        (0.05, 0.5), (0.05, 0.05), (0.5, 0.05), (0.5, -0.05),
        (0.05, -0.05), (0.05, -0.5), (-0.05, -0.5), (-0.05, -0.05)
    ],
    'p': [(0, -0.5), (-0.4755, -0.1545), (-0.2939, 0.4045),
          (0.2939, 0.4045), (0.4755, -0.1545)],
    'h': [(0.433, 0.25), (0., 0.5), (-0.433, 0.25), (-0.433, -0.25),
          (0, -0.5), (0.433, -0.25)],
    'star': [(0, -0.5), (-0.1123, -0.1545), (-0.4755, -0.1545),
             (-0.1816, 0.059), (-0.2939, 0.4045), (0, 0.1910),
             (0.2939, 0.4045), (0.1816, 0.059), (0.4755, -0.1545),
             (0.1123, -0.1545)]
}
for k, c in coords.items():
    Symbols[k].moveTo(*c[0])
    for x,y in c[1:]:
        Symbols[k].lineTo(x, y)
    Symbols[k].closeSubpath()
tr = QtGui.QTransform()
tr.rotate(45)
Symbols['x'] = tr.map(Symbols['+'])


def drawSymbol(painter, symbol, size, pen, brush):
    if symbol is None:
        return
    painter.scale(size, size)
    painter.setPen(pen)
    painter.setBrush(brush)
    if isinstance(symbol, basestring):
        symbol = Symbols[symbol]
    if np.isscalar(symbol):
        symbol = list(Symbols.values())[symbol % len(Symbols)]
    painter.drawPath(symbol)


def renderSymbol(symbol, size, pen, brush, device=None):
    """
    Render a symbol specification to QImage.
    Symbol may be either a QPainterPath or one of the keys in the Symbols dict.
    If *device* is None, a new QPixmap will be returned. Otherwise,
    the symbol will be rendered into the device specified (See QPainter documentation
    for more information).
    """
    ## Render a spot with the given parameters to a pixmap
    penPxWidth = max(np.ceil(pen.widthF()), 1)
    if device is None:
        device = QtGui.QImage(int(size+penPxWidth), int(size+penPxWidth), QtGui.QImage.Format_ARGB32)
        device.fill(0)
    p = QtGui.QPainter(device)
    try:
        p.setRenderHint(p.Antialiasing)
        p.translate(device.width()*0.5, device.height()*0.5)
        drawSymbol(p, symbol, size, pen, brush)
    finally:
        p.end()
    return device

def makeSymbolPixmap(size, pen, brush, symbol):
    ## deprecated
    img = renderSymbol(symbol, size, pen, brush)
    return QtGui.QPixmap(img)

class SymbolAtlas(object):
    """
    Used to efficiently construct a single QPixmap containing all rendered symbols
    for a ScatterPlotItem. This is required for fragment rendering.

    Use example:
        atlas = SymbolAtlas()
        sc1 = atlas.getSymbolCoords('o', 5, QPen(..), QBrush(..))
        sc2 = atlas.getSymbolCoords('t', 10, QPen(..), QBrush(..))
        pm = atlas.getAtlas()

    """
    def __init__(self):
        # symbol key : QRect(...) coordinates where symbol can be found in atlas.
        # note that the coordinate list will always be the same list object as
        # long as the symbol is in the atlas, but the coordinates may
        # change if the atlas is rebuilt.
        # weak value; if all external refs to this list disappear,
        # the symbol will be forgotten.
        self.symbolMap = weakref.WeakValueDictionary()

        self.atlasData = None # numpy array of atlas image
        self.atlas = None     # atlas as QPixmap
        self.atlasValid = False
        self.max_width=0

    def getSymbolCoords(self, opts):
        """
        Given a list of spot records, return an object representing the coordinates of that symbol within the atlas
        """
        sourceRect = np.empty(len(opts), dtype=object)
        keyi = None
        sourceRecti = None
        for i, rec in enumerate(opts):
            key = (id(rec[3]), rec[2], id(rec[4]), id(rec[5]))   # TODO: use string indexes?
            if key == keyi:
                sourceRect[i] = sourceRecti
            else:
                try:
                    sourceRect[i] = self.symbolMap[key]
                except KeyError:
                    newRectSrc = QtCore.QRectF()
                    newRectSrc.pen = rec['pen']
                    newRectSrc.brush = rec['brush']
                    newRectSrc.symbol = rec[3]
                    self.symbolMap[key] = newRectSrc
                    self.atlasValid = False
                    sourceRect[i] = newRectSrc
                    keyi = key
                    sourceRecti = newRectSrc
        return sourceRect

    def buildAtlas(self):
        # get rendered array for all symbols, keep track of avg/max width
        rendered = {}
        avgWidth = 0.0
        maxWidth = 0
        images = []
        for key, sourceRect in self.symbolMap.items():
            if sourceRect.width() == 0:
                img = renderSymbol(sourceRect.symbol, key[1], sourceRect.pen, sourceRect.brush)
                images.append(img)  ## we only need this to prevent the images being garbage collected immediately
                arr = fn.imageToArray(img, copy=False, transpose=False)
            else:
                (y,x,h,w) = sourceRect.getRect()
                arr = self.atlasData[int(x):int(x+w), int(y):int(y+w)]
            rendered[key] = arr
            w = arr.shape[0]
            avgWidth += w
            maxWidth = max(maxWidth, w)

        nSymbols = len(rendered)
        if nSymbols > 0:
            avgWidth /= nSymbols
            width = max(maxWidth, avgWidth * (nSymbols**0.5))
        else:
            avgWidth = 0
            width = 0

        # sort symbols by height
        symbols = sorted(rendered.keys(), key=lambda x: rendered[x].shape[1], reverse=True)

        self.atlasRows = []

        x = width
        y = 0
        rowheight = 0
        for key in symbols:
            arr = rendered[key]
            w,h = arr.shape[:2]
            if x+w > width:
                y += rowheight
                x = 0
                rowheight = h
                self.atlasRows.append([y, rowheight, 0])
            self.symbolMap[key].setRect(y, x, h, w)
            x += w
            self.atlasRows[-1][2] = x
        height = y + rowheight

        self.atlasData = np.zeros((int(width), int(height), 4), dtype=np.ubyte)
        for key in symbols:
            y, x, h, w = self.symbolMap[key].getRect()
            self.atlasData[int(x):int(x+w), int(y):int(y+h)] = rendered[key]
        self.atlas = None
        self.atlasValid = True
        self.max_width = maxWidth

    def getAtlas(self):
        if not self.atlasValid:
            self.buildAtlas()
        if self.atlas is None:
            if len(self.atlasData) == 0:
                return QtGui.QPixmap(0,0)
            img = fn.makeQImage(self.atlasData, copy=False, transpose=False)
            self.atlas = QtGui.QPixmap(img)
        return self.atlas




class ScatterPlotItem(GraphicsObject):
    """
    Displays a set of x/y points. Instances of this class are created
    automatically as part of PlotDataItem; these rarely need to be instantiated
    directly.

    The size, shape, pen, and fill brush may be set for each point individually
    or for all points.


    ========================  ===============================================
    **Signals:**
    sigPlotChanged(self)      Emitted when the data being plotted has changed
    sigClicked(self, points)  Emitted when the curve is clicked. Sends a list
                              of all the points under the mouse pointer.
    ========================  ===============================================

    """
    #sigPointClicked = QtCore.Signal(object, object)
    sigClicked = QtCore.Signal(object, object)  ## self, points
    sigPlotChanged = QtCore.Signal(object)
    def __init__(self, *args, **kargs):
        """
        Accepts the same arguments as setData()
        """
        profiler = debug.Profiler()
        GraphicsObject.__init__(self)

        self.picture = None   # QPicture used for rendering when pxmode==False
        self.fragmentAtlas = SymbolAtlas()

        self.data = np.empty(0, dtype=[('x', float), ('y', float), ('size', float), ('symbol', object), ('pen', object), ('brush', object), ('data', object), ('item', object), ('sourceRect', object), ('targetRect', object), ('width', float)])
        self.bounds = [None, None]  ## caches data bounds
        self._maxSpotWidth = 0      ## maximum size of the scale-variant portion of all spots
        self._maxSpotPxWidth = 0    ## maximum size of the scale-invariant portion of all spots
        self.opts = {
            'pxMode': True,
            'useCache': True,  ## If useCache is False, symbols are re-drawn on every paint.
            'antialias': getConfigOption('antialias'),
            'compositionMode': None,
            'name': None,
        }

        self.setPen(fn.mkPen(getConfigOption('foreground')), update=False)
        self.setBrush(fn.mkBrush(100,100,150), update=False)
        self.setSymbol('o', update=False)
        self.setSize(7, update=False)
        profiler()
        self.setData(*args, **kargs)
        profiler('setData')

        #self.setCacheMode(self.DeviceCoordinateCache)

    def setData(self, *args, **kargs):
        """
        **Ordered Arguments:**

        * If there is only one unnamed argument, it will be interpreted like the 'spots' argument.
        * If there are two unnamed arguments, they will be interpreted as sequences of x and y values.

        ====================== ===============================================================================================
        **Keyword Arguments:**
        *spots*                Optional list of dicts. Each dict specifies parameters for a single spot:
                               {'pos': (x,y), 'size', 'pen', 'brush', 'symbol'}. This is just an alternate method
                               of passing in data for the corresponding arguments.
        *x*,*y*                1D arrays of x,y values.
        *pos*                  2D structure of x,y pairs (such as Nx2 array or list of tuples)
        *pxMode*               If True, spots are always the same size regardless of scaling, and size is given in px.
                               Otherwise, size is in scene coordinates and the spots scale with the view.
                               Default is True
        *symbol*               can be one (or a list) of:
                               * 'o'  circle (default)
                               * 's'  square
                               * 't'  triangle
                               * 'd'  diamond
                               * '+'  plus
                               * any QPainterPath to specify custom symbol shapes. To properly obey the position and size,
                               custom symbols should be centered at (0,0) and width and height of 1.0. Note that it is also
                               possible to 'install' custom shapes by setting ScatterPlotItem.Symbols[key] = shape.
        *pen*                  The pen (or list of pens) to use for drawing spot outlines.
        *brush*                The brush (or list of brushes) to use for filling spots.
        *size*                 The size (or list of sizes) of spots. If *pxMode* is True, this value is in pixels. Otherwise,
                               it is in the item's local coordinate system.
        *data*                 a list of python objects used to uniquely identify each spot.
        *identical*            *Deprecated*. This functionality is handled automatically now.
        *antialias*            Whether to draw symbols with antialiasing. Note that if pxMode is True, symbols are
                               always rendered with antialiasing (since the rendered symbols can be cached, this
                               incurs very little performance cost)
        *compositionMode*      If specified, this sets the composition mode used when drawing the
                               scatter plot (see QPainter::CompositionMode in the Qt documentation).
        *name*                 The name of this item. Names are used for automatically
                               generating LegendItem entries and by some exporters.
        ====================== ===============================================================================================
        """
        oldData = self.data  ## this causes cached pixmaps to be preserved while new data is registered.
        self.clear()  ## clear out all old data
        self.addPoints(*args, **kargs)

    def addPoints(self, *args, **kargs):
        """
        Add new points to the scatter plot.
        Arguments are the same as setData()
        """

        ## deal with non-keyword arguments
        if len(args) == 1:
            kargs['spots'] = args[0]
        elif len(args) == 2:
            kargs['x'] = args[0]
            kargs['y'] = args[1]
        elif len(args) > 2:
            raise Exception('Only accepts up to two non-keyword arguments.')

        ## convert 'pos' argument to 'x' and 'y'
        if 'pos' in kargs:
            pos = kargs['pos']
            if isinstance(pos, np.ndarray):
                kargs['x'] = pos[:,0]
                kargs['y'] = pos[:,1]
            else:
                x = []
                y = []
                for p in pos:
                    if isinstance(p, QtCore.QPointF):
                        x.append(p.x())
                        y.append(p.y())
                    else:
                        x.append(p[0])
                        y.append(p[1])
                kargs['x'] = x
                kargs['y'] = y

        ## determine how many spots we have
        if 'spots' in kargs:
            numPts = len(kargs['spots'])
        elif 'y' in kargs and kargs['y'] is not None:
            numPts = len(kargs['y'])
        else:
            kargs['x'] = []
            kargs['y'] = []
            numPts = 0

        ## Extend record array
        oldData = self.data
        self.data = np.empty(len(oldData)+numPts, dtype=self.data.dtype)
        ## note that np.empty initializes object fields to None and string fields to ''

        self.data[:len(oldData)] = oldData
        #for i in range(len(oldData)):
            #oldData[i]['item']._data = self.data[i]  ## Make sure items have proper reference to new array

        newData = self.data[len(oldData):]
        newData['size'] = -1  ## indicates to use default size

        if 'spots' in kargs:
            spots = kargs['spots']
            for i in range(len(spots)):
                spot = spots[i]
                for k in spot:
                    if k == 'pos':
                        pos = spot[k]
                        if isinstance(pos, QtCore.QPointF):
                            x,y = pos.x(), pos.y()
                        else:
                            x,y = pos[0], pos[1]
                        newData[i]['x'] = x
                        newData[i]['y'] = y
                    elif k == 'pen':
                        newData[i][k] = fn.mkPen(spot[k])
                    elif k == 'brush':
                        newData[i][k] = fn.mkBrush(spot[k])
                    elif k in ['x', 'y', 'size', 'symbol', 'brush', 'data']:
                        newData[i][k] = spot[k]
                    else:
                        raise Exception("Unknown spot parameter: %s" % k)
        elif 'y' in kargs:
            newData['x'] = kargs['x']
            newData['y'] = kargs['y']

        if 'pxMode' in kargs:
            self.setPxMode(kargs['pxMode'])
        if 'antialias' in kargs:
            self.opts['antialias'] = kargs['antialias']

        ## Set any extra parameters provided in keyword arguments
        for k in ['pen', 'brush', 'symbol', 'size']:
            if k in kargs:
                setMethod = getattr(self, 'set' + k[0].upper() + k[1:])
                setMethod(kargs[k], update=False, dataSet=newData, mask=kargs.get('mask', None))

        if 'data' in kargs:
            self.setPointData(kargs['data'], dataSet=newData)

        self.prepareGeometryChange()
        self.informViewBoundsChanged()
        self.bounds = [None, None]
        self.invalidate()
        self.updateSpots(newData)
        self.sigPlotChanged.emit(self)

    def invalidate(self):
        ## clear any cached drawing state
        self.picture = None
        self.update()

    def getData(self):
        return self.data['x'], self.data['y']

    def setPoints(self, *args, **kargs):
        ##Deprecated; use setData
        return self.setData(*args, **kargs)

    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 setPen(self, *args, **kargs):
        """Set the pen(s) used to draw the outline around each spot.
        If a list or array is provided, then the pen for each spot will be set separately.
        Otherwise, the arguments are passed to pg.mkPen and used as the default pen for
        all spots which do not have a pen explicitly set."""
        update = kargs.pop('update', True)
        dataSet = kargs.pop('dataSet', self.data)

        if len(args) == 1 and (isinstance(args[0], np.ndarray) or isinstance(args[0], list)):
            pens = args[0]
            if 'mask' in kargs and kargs['mask'] is not None:
                pens = pens[kargs['mask']]
            if len(pens) != len(dataSet):
                raise Exception("Number of pens does not match number of points (%d != %d)" % (len(pens), len(dataSet)))
            dataSet['pen'] = pens
        else:
            self.opts['pen'] = fn.mkPen(*args, **kargs)

        dataSet['sourceRect'] = None
        if update:
            self.updateSpots(dataSet)

    def setBrush(self, *args, **kargs):
        """Set the brush(es) used to fill the interior of each spot.
        If a list or array is provided, then the brush for each spot will be set separately.
        Otherwise, the arguments are passed to pg.mkBrush and used as the default brush for
        all spots which do not have a brush explicitly set."""
        update = kargs.pop('update', True)
        dataSet = kargs.pop('dataSet', self.data)

        if len(args) == 1 and (isinstance(args[0], np.ndarray) or isinstance(args[0], list)):
            brushes = args[0]
            if 'mask' in kargs and kargs['mask'] is not None:
                brushes = brushes[kargs['mask']]
            if len(brushes) != len(dataSet):
                raise Exception("Number of brushes does not match number of points (%d != %d)" % (len(brushes), len(dataSet)))
            dataSet['brush'] = brushes
        else:
            self.opts['brush'] = fn.mkBrush(*args, **kargs)
            #self._spotPixmap = None

        dataSet['sourceRect'] = None
        if update:
            self.updateSpots(dataSet)

    def setSymbol(self, symbol, update=True, dataSet=None, mask=None):
        """Set the symbol(s) used to draw each spot.
        If a list or array is provided, then the symbol for each spot will be set separately.
        Otherwise, the argument will be used as the default symbol for
        all spots which do not have a symbol explicitly set."""
        if dataSet is None:
            dataSet = self.data

        if isinstance(symbol, np.ndarray) or isinstance(symbol, list):
            symbols = symbol
            if mask is not None:
                symbols = symbols[mask]
            if len(symbols) != len(dataSet):
                raise Exception("Number of symbols does not match number of points (%d != %d)" % (len(symbols), len(dataSet)))
            dataSet['symbol'] = symbols
        else:
            self.opts['symbol'] = symbol
            self._spotPixmap = None

        dataSet['sourceRect'] = None
        if update:
            self.updateSpots(dataSet)

    def setSize(self, size, update=True, dataSet=None, mask=None):
        """Set the size(s) used to draw each spot.
        If a list or array is provided, then the size for each spot will be set separately.
        Otherwise, the argument will be used as the default size for
        all spots which do not have a size explicitly set."""
        if dataSet is None:
            dataSet = self.data

        if isinstance(size, np.ndarray) or isinstance(size, list):
            sizes = size
            if mask is not None:
                sizes = sizes[mask]
            if len(sizes) != len(dataSet):
                raise Exception("Number of sizes does not match number of points (%d != %d)" % (len(sizes), len(dataSet)))
            dataSet['size'] = sizes
        else:
            self.opts['size'] = size
            self._spotPixmap = None

        dataSet['sourceRect'] = None
        if update:
            self.updateSpots(dataSet)

    def setPointData(self, data, dataSet=None, mask=None):
        if dataSet is None:
            dataSet = self.data

        if isinstance(data, np.ndarray) or isinstance(data, list):
            if mask is not None:
                data = data[mask]
            if len(data) != len(dataSet):
                raise Exception("Length of meta data does not match number of points (%d != %d)" % (len(data), len(dataSet)))

        ## Bug: If data is a numpy record array, then items from that array must be copied to dataSet one at a time.
        ## (otherwise they are converted to tuples and thus lose their field names.
        if isinstance(data, np.ndarray) and (data.dtype.fields is not None)and len(data.dtype.fields) > 1:
            for i, rec in enumerate(data):
                dataSet['data'][i] = rec
        else:
            dataSet['data'] = data

    def setPxMode(self, mode):
        if self.opts['pxMode'] == mode:
            return

        self.opts['pxMode'] = mode
        self.invalidate()

    def updateSpots(self, dataSet=None):
        if dataSet is None:
            dataSet = self.data

        invalidate = False
        if self.opts['pxMode']:
            mask = np.equal(dataSet['sourceRect'], None)
            if np.any(mask):
                invalidate = True
                opts = self.getSpotOpts(dataSet[mask])
                sourceRect = self.fragmentAtlas.getSymbolCoords(opts)
                dataSet['sourceRect'][mask] = sourceRect

            self.fragmentAtlas.getAtlas() # generate atlas so source widths are available.

            dataSet['width'] = np.array(list(imap(QtCore.QRectF.width, dataSet['sourceRect'])))/2
            dataSet['targetRect'] = None
            self._maxSpotPxWidth = self.fragmentAtlas.max_width
        else:
            self._maxSpotWidth = 0
            self._maxSpotPxWidth = 0
            self.measureSpotSizes(dataSet)

        if invalidate:
            self.invalidate()

    def getSpotOpts(self, recs, scale=1.0):
        if recs.ndim == 0:
            rec = recs
            symbol = rec['symbol']
            if symbol is None:
                symbol = self.opts['symbol']
            size = rec['size']
            if size < 0:
                size = self.opts['size']
            pen = rec['pen']
            if pen is None:
                pen = self.opts['pen']
            brush = rec['brush']
            if brush is None:
                brush = self.opts['brush']
            return (symbol, size*scale, fn.mkPen(pen), fn.mkBrush(brush))
        else:
            recs = recs.copy()
            recs['symbol'][np.equal(recs['symbol'], None)] = self.opts['symbol']
            recs['size'][np.equal(recs['size'], -1)] = self.opts['size']
            recs['size'] *= scale
            recs['pen'][np.equal(recs['pen'], None)] = fn.mkPen(self.opts['pen'])
            recs['brush'][np.equal(recs['brush'], None)] = fn.mkBrush(self.opts['brush'])
            return recs



    def measureSpotSizes(self, dataSet):
        for rec in dataSet:
            ## keep track of the maximum spot size and pixel size
            symbol, size, pen, brush = self.getSpotOpts(rec)
            width = 0
            pxWidth = 0
            if self.opts['pxMode']:
                pxWidth = size + pen.widthF()
            else:
                width = size
                if pen.isCosmetic():
                    pxWidth += pen.widthF()
                else:
                    width += pen.widthF()
            self._maxSpotWidth = max(self._maxSpotWidth, width)
            self._maxSpotPxWidth = max(self._maxSpotPxWidth, pxWidth)
        self.bounds = [None, None]


    def clear(self):
        """Remove all spots from the scatter plot"""
        #self.clearItems()
        self.data = np.empty(0, dtype=self.data.dtype)
        self.bounds = [None, None]
        self.invalidate()

    def dataBounds(self, ax, frac=1.0, orthoRange=None):
        if frac >= 1.0 and orthoRange is None and self.bounds[ax] is not None:
            return self.bounds[ax]

        #self.prepareGeometryChange()
        if self.data is None or len(self.data) == 0:
            return (None, None)

        if ax == 0:
            d = self.data['x']
            d2 = self.data['y']
        elif ax == 1:
            d = self.data['y']
            d2 = self.data['x']

        if orthoRange is not None:
            mask = (d2 >= orthoRange[0]) * (d2 <= orthoRange[1])
            d = d[mask]
            d2 = d2[mask]

            if d.size == 0:
                return (None, None)

        if frac >= 1.0:
            self.bounds[ax] = (np.nanmin(d) - self._maxSpotWidth*0.7072, np.nanmax(d) + self._maxSpotWidth*0.7072)
            return self.bounds[ax]
        elif frac <= 0.0:
            raise Exception("Value for parameter 'frac' must be > 0. (got %s)" % str(frac))
        else:
            mask = np.isfinite(d)
            d = d[mask]
            return np.percentile(d, [50 * (1 - frac), 50 * (1 + frac)])

    def pixelPadding(self):
        return self._maxSpotPxWidth*0.7072

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

        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
        return QtCore.QRectF(xmn-px, ymn-py, (2*px)+xmx-xmn, (2*py)+ymx-ymn)

    def viewTransformChanged(self):
        self.prepareGeometryChange()
        GraphicsObject.viewTransformChanged(self)
        self.bounds = [None, None]
        self.data['targetRect'] = None

    def setExportMode(self, *args, **kwds):
        GraphicsObject.setExportMode(self, *args, **kwds)
        self.invalidate()

    def mapPointsToDevice(self, pts):
        # Map point locations to device
        tr = self.deviceTransform()
        if tr is None:
            return None

        pts = fn.transformCoordinates(tr, pts)
        pts -= self.data['width']
        pts = np.clip(pts, -2**30, 2**30) ## prevent Qt segmentation fault.

        return pts

    def getViewMask(self, pts):
        # Return bool mask indicating all points that are within viewbox
        # pts is expressed in *device coordiantes*
        vb = self.getViewBox()
        if vb is None:
            return None
        viewBounds = vb.mapRectToDevice(vb.boundingRect())
        w = self.data['width']
        mask = ((pts[0] + w > viewBounds.left()) &
                (pts[0] - w < viewBounds.right()) &
                (pts[1] + w > viewBounds.top()) &
                (pts[1] - w < viewBounds.bottom())) ## remove out of view points
        return mask

    @debug.warnOnException  ## raising an exception here causes crash
    def paint(self, p, *args):
        cmode = self.opts.get('compositionMode', None)
        if cmode is not None:
            p.setCompositionMode(cmode)
        #p.setPen(fn.mkPen('r'))
        #p.drawRect(self.boundingRect())

        if self._exportOpts is not False:
            aa = self._exportOpts.get('antialias', True)
            scale = self._exportOpts.get('resolutionScale', 1.0)  ## exporting to image; pixel resolution may have changed
        else:
            aa = self.opts['antialias']
            scale = 1.0

        if self.opts['pxMode'] is True:
            p.resetTransform()

            # Map point coordinates to device
            pts = np.vstack([self.data['x'], self.data['y']])
            pts = self.mapPointsToDevice(pts)
            if pts is None:
                return

            # Cull points that are outside view
            viewMask = self.getViewMask(pts)

            if self.opts['useCache'] and self._exportOpts is False:
                # Draw symbols from pre-rendered atlas
                atlas = self.fragmentAtlas.getAtlas()

                # Update targetRects if necessary
                updateMask = viewMask & np.equal(self.data['targetRect'], None)
                if np.any(updateMask):
                    updatePts = pts[:,updateMask]
                    width = self.data[updateMask]['width']*2
                    self.data['targetRect'][updateMask] = list(imap(QtCore.QRectF, updatePts[0,:], updatePts[1,:], width, width))

                data = self.data[viewMask]
                if QT_LIB == 'PyQt4':
                    p.drawPixmapFragments(data['targetRect'].tolist(), data['sourceRect'].tolist(), atlas)
                else:
                    list(imap(p.drawPixmap, data['targetRect'], repeat(atlas), data['sourceRect']))
            else:
                # render each symbol individually
                p.setRenderHint(p.Antialiasing, aa)

                data = self.data[viewMask]
                pts = pts[:,viewMask]
                for i, rec in enumerate(data):
                    p.resetTransform()
                    p.translate(pts[0,i] + rec['width']/2, pts[1,i] + rec['width']/2)
                    drawSymbol(p, *self.getSpotOpts(rec, scale))
        else:
            if self.picture is None:
                self.picture = QtGui.QPicture()
                p2 = QtGui.QPainter(self.picture)
                for rec in self.data:
                    if scale != 1.0:
                        rec = rec.copy()
                        rec['size'] *= scale
                    p2.resetTransform()
                    p2.translate(rec['x'], rec['y'])
                    drawSymbol(p2, *self.getSpotOpts(rec, scale))
                p2.end()

            p.setRenderHint(p.Antialiasing, aa)
            self.picture.play(p)

    def points(self):
        for i,rec in enumerate(self.data):
            if rec['item'] is None:
                rec['item'] = SpotItem(rec, self, i)
        return self.data['item']

    def pointsAt(self, pos):
        x = pos.x()
        y = pos.y()
        pw = self.pixelWidth()
        ph = self.pixelHeight()
        pts = []
        for s in self.points():
            sp = s.pos()
            ss = s.size()
            sx = sp.x()
            sy = sp.y()
            s2x = s2y = ss * 0.5
            if self.opts['pxMode']:
                s2x *= pw
                s2y *= ph
            if x > sx-s2x and x < sx+s2x and y > sy-s2y and y < sy+s2y:
                pts.append(s)
                #print "HIT:", x, y, sx, sy, s2x, s2y
            #else:
                #print "No hit:", (x, y), (sx, sy)
                #print "       ", (sx-s2x, sy-s2y), (sx+s2x, sy+s2y)
        return pts[::-1]


    def mouseClickEvent(self, ev):
        if ev.button() == QtCore.Qt.LeftButton:
            pts = self.pointsAt(ev.pos())
            if len(pts) > 0:
                self.ptsClicked = pts
                ev.accept()
                self.sigClicked.emit(self, self.ptsClicked)
            else:
                #print "no spots"
                ev.ignore()
        else:
            ev.ignore()


class SpotItem(object):
    """
    Class referring to individual spots in a scatter plot.
    These can be retrieved by calling ScatterPlotItem.points() or
    by connecting to the ScatterPlotItem's click signals.
    """

    def __init__(self, data, plot, index):
        self._data = data
        self._index = index
        # SpotItems are kept in plot.data["items"] numpy object array which
        # does not support cyclic garbage collection (numpy issue 6581).
        # Keeping a strong ref to plot here would leak the cycle
        self.__plot_ref = weakref.ref(plot)

    @property
    def _plot(self):
        return self.__plot_ref()

    def data(self):
        """Return the user data associated with this spot."""
        return self._data['data']

    def index(self):
        """Return the index of this point as given in the scatter plot data."""
        return self._index

    def size(self):
        """Return the size of this spot.
        If the spot has no explicit size set, then return the ScatterPlotItem's default size instead."""
        if self._data['size'] == -1:
            return self._plot.opts['size']
        else:
            return self._data['size']

    def pos(self):
        return Point(self._data['x'], self._data['y'])

    def viewPos(self):
        return self._plot.mapToView(self.pos())

    def setSize(self, size):
        """Set the size of this spot.
        If the size is set to -1, then the ScatterPlotItem's default size
        will be used instead."""
        self._data['size'] = size
        self.updateItem()

    def symbol(self):
        """Return the symbol of this spot.
        If the spot has no explicit symbol set, then return the ScatterPlotItem's default symbol instead.
        """
        symbol = self._data['symbol']
        if symbol is None:
            symbol = self._plot.opts['symbol']
        try:
            n = int(symbol)
            symbol = list(Symbols.keys())[n % len(Symbols)]
        except:
            pass
        return symbol

    def setSymbol(self, symbol):
        """Set the symbol for this spot.
        If the symbol is set to '', then the ScatterPlotItem's default symbol will be used instead."""
        self._data['symbol'] = symbol
        self.updateItem()

    def pen(self):
        pen = self._data['pen']
        if pen is None:
            pen = self._plot.opts['pen']
        return fn.mkPen(pen)

    def setPen(self, *args, **kargs):
        """Set the outline pen for this spot"""
        pen = fn.mkPen(*args, **kargs)
        self._data['pen'] = pen
        self.updateItem()

    def resetPen(self):
        """Remove the pen set for this spot; the scatter plot's default pen will be used instead."""
        self._data['pen'] = None  ## Note this is NOT the same as calling setPen(None)
        self.updateItem()

    def brush(self):
        brush = self._data['brush']
        if brush is None:
            brush = self._plot.opts['brush']
        return fn.mkBrush(brush)

    def setBrush(self, *args, **kargs):
        """Set the fill brush for this spot"""
        brush = fn.mkBrush(*args, **kargs)
        self._data['brush'] = brush
        self.updateItem()

    def resetBrush(self):
        """Remove the brush set for this spot; the scatter plot's default brush will be used instead."""
        self._data['brush'] = None  ## Note this is NOT the same as calling setBrush(None)
        self.updateItem()

    def setData(self, data):
        """Set the user-data associated with this spot"""
        self._data['data'] = data

    def updateItem(self):
        self._data['sourceRect'] = None
        self._plot.updateSpots(self._data.reshape(1))
        self._plot.invalidate()
