import math
import sys
import weakref
from copy import deepcopy

import numpy as np

from ... import debug as debug
from ... import functions as fn
from ... import getConfigOption
from ...Point import Point
from ...Qt import QtCore, QtGui, QtWidgets, isQObjectAlive
from ..GraphicsWidget import GraphicsWidget
from ..ItemGroup import ItemGroup

__all__ = ['ViewBox']


class WeakList(object):

    def __init__(self):
        self._items = []

    def append(self, obj):
        #Add backwards to iterate backwards (to make iterating more efficient on removal).
        self._items.insert(0, weakref.ref(obj))

    def __iter__(self):
        i = len(self._items)-1
        while i >= 0:
            ref = self._items[i]
            d = ref()
            if d is None:
                del self._items[i]
            else:
                yield d
            i -= 1


class ChildGroup(ItemGroup):

    def __init__(self, parent):
        ItemGroup.__init__(self, parent)

        # Used as callback to inform ViewBox when items are added/removed from
        # the group.
        # Note 1: We would prefer to override itemChange directly on the
        #         ViewBox, but this causes crashes on PySide.
        # Note 2: We might also like to use a signal rather than this callback
        #         mechanism, but this causes a different PySide crash.
        self.itemsChangedListeners = WeakList()

        # exempt from telling view when transform changes
        self._GraphicsObject__inform_view_on_change = False

    def itemChange(self, change, value):
        ret = ItemGroup.itemChange(self, change, value)
        if change in [
            self.GraphicsItemChange.ItemChildAddedChange,
            self.GraphicsItemChange.ItemChildRemovedChange,
        ]:
            try:
                itemsChangedListeners = self.itemsChangedListeners
            except AttributeError:
                # It's possible that the attribute was already collected when the itemChange happened
                # (if it was triggered during the gc of the object).
                pass
            else:
                for listener in itemsChangedListeners:
                    listener.itemsChanged()
        return ret


class ViewBox(GraphicsWidget):
    """
    **Bases:** :class:`GraphicsWidget <pyqtgraph.GraphicsWidget>`

    Box that allows internal scaling/panning of children by mouse drag.
    This class is usually created automatically as part of a :class:`PlotItem <pyqtgraph.PlotItem>` or :class:`Canvas <pyqtgraph.canvas.Canvas>` or with :func:`GraphicsLayout.addViewBox() <pyqtgraph.GraphicsLayout.addViewBox>`.

    Features:

      * Scaling contents by mouse or auto-scale when contents change
      * View linking--multiple views display the same data ranges
      * Configurable by context menu
      * Item coordinate mapping methods

    """

    sigYRangeChanged = QtCore.Signal(object, object)
    sigXRangeChanged = QtCore.Signal(object, object)
    sigRangeChangedManually = QtCore.Signal(object)
    sigRangeChanged = QtCore.Signal(object, object, object)
    sigStateChanged = QtCore.Signal(object)
    sigTransformChanged = QtCore.Signal(object)
    sigResized = QtCore.Signal(object)

    ## mouse modes
    PanMode = 3
    RectMode = 1

    ## axes
    XAxis = 0
    YAxis = 1
    XYAxes = 2

    ## for linking views together
    NamedViews = weakref.WeakValueDictionary()   # name: ViewBox
    AllViews = weakref.WeakKeyDictionary()       # ViewBox: None

    def __init__(self, parent=None, border=None, lockAspect=False, enableMouse=True, invertY=False, enableMenu=True, name=None, invertX=False, defaultPadding=0.02):
        """
        =================  =============================================================
        **Arguments:**
        *parent*           (QGraphicsWidget) Optional parent widget
        *border*           (QPen) Do draw a border around the view, give any
                           single argument accepted by :func:`mkPen <pyqtgraph.mkPen>`
        *lockAspect*       (False or float) The aspect ratio to lock the view
                           coorinates to. (or False to allow the ratio to change)
        *enableMouse*      (bool) Whether mouse can be used to scale/pan the view
        *invertY*          (bool) See :func:`invertY <pyqtgraph.ViewBox.invertY>`
        *invertX*          (bool) See :func:`invertX <pyqtgraph.ViewBox.invertX>`
        *enableMenu*       (bool) Whether to display a context menu when
                           right-clicking on the ViewBox background.
        *name*             (str) Used to register this ViewBox so that it appears
                           in the "Link axis" dropdown inside other ViewBox
                           context menus. This allows the user to manually link
                           the axes of any other view to this one.
        *defaultPadding*   (float) fraction of the data range that will be added
                           as padding by default
        =================  =============================================================
        """

        GraphicsWidget.__init__(self, parent)
        self.name = None
        self.linksBlocked = False
        self.addedItems = []
        self._matrixNeedsUpdate = True  ## indicates that range has changed, but matrix update was deferred
        self._autoRangeNeedsUpdate = True ## indicates auto-range needs to be recomputed.

        self._lastScene = None  ## stores reference to the last known scene this view was a part of.

        self.state = {

            ## separating targetRange and viewRange allows the view to be resized
            ## while keeping all previously viewed contents visible
            'targetRange': [[0,1], [0,1]],   ## child coord. range visible [[xmin, xmax], [ymin, ymax]]
            'viewRange': [[0,1], [0,1]],     ## actual range viewed

            'yInverted': invertY,
            'xInverted': invertX,
            'aspectLocked': False,    ## False if aspect is unlocked, otherwise float specifies the locked ratio.
            'autoRange': [True, True],  ## False if auto range is disabled,
                                        ## otherwise float gives the fraction of data that is visible
            'autoPan': [False, False],         ## whether to only pan (do not change scaling) when auto-range is enabled
            'autoVisibleOnly': [False, False], ## whether to auto-range only to the visible portion of a plot
            'linkedViews': [None, None],  ## may be None, "viewName", or weakref.ref(view)
                                          ## a name string indicates that the view *should* link to another, but no view with that name exists yet.
            'defaultPadding': defaultPadding,

            'mouseEnabled': [enableMouse, enableMouse],
            'mouseMode': ViewBox.PanMode if getConfigOption('leftButtonPan') else ViewBox.RectMode,
            'enableMenu': enableMenu,
            'wheelScaleFactor': -1.0 / 8.0,

            'background': None,
            
            'logMode': [False, False],

            # Limits
            # maximum value of double float is 1.7E+308, but internal caluclations exceed this limit before the range reaches it.
            'limits': { 
                'xLimits': [-1E307, +1E307],   # Maximum and minimum visible X values
                'yLimits': [-1E307, +1E307],   # Maximum and minimum visible Y values
                'xRange': [None, None],   # Maximum and minimum X range
                'yRange': [None, None],   # Maximum and minimum Y range
                }

        }
        self._updatingRange = False  ## Used to break recursive loops. See updateAutoRange.
        self._itemBoundsCache = weakref.WeakKeyDictionary()

        self.locateGroup = None  ## items displayed when using ViewBox.locate(item)

        self.setFlag(self.GraphicsItemFlag.ItemClipsChildrenToShape)
        self.setFlag(self.GraphicsItemFlag.ItemIsFocusable, True)  ## so we can receive key presses

        ## childGroup is required so that ViewBox has local coordinates similar to device coordinates.
        ## this is a workaround for a Qt + OpenGL bug that causes improper clipping
        ## https://bugreports.qt.nokia.com/browse/QTBUG-23723
        self.childGroup = ChildGroup(self)
        self.childGroup.itemsChangedListeners.append(self)

        self.background = QtWidgets.QGraphicsRectItem(self.rect())
        self.background.setParentItem(self)
        self.background.setZValue(-1e6)
        self.background.setPen(fn.mkPen(None))
        self.updateBackground()

        self.border = fn.mkPen(border)

        self.borderRect = QtWidgets.QGraphicsRectItem(self.rect())
        self.borderRect.setParentItem(self)
        self.borderRect.setZValue(1e3)
        self.borderRect.setPen(self.border)

        ## Make scale box that is shown when dragging on the view
        self.rbScaleBox = QtWidgets.QGraphicsRectItem(0, 0, 1, 1)
        self.rbScaleBox.setPen(fn.mkPen((255,255,100), width=1))
        self.rbScaleBox.setBrush(fn.mkBrush(255,255,0,100))
        self.rbScaleBox.setZValue(1e9)
        self.rbScaleBox.hide()
        self.addItem(self.rbScaleBox, ignoreBounds=True)

        ## show target rect for debugging
        self.target = QtWidgets.QGraphicsRectItem(0, 0, 1, 1)
        self.target.setPen(fn.mkPen('r'))
        self.target.setParentItem(self)
        self.target.hide()

        self.axHistory = [] # maintain a history of zoom locations
        self.axHistoryPointer = -1 # pointer into the history. Allows forward/backward movement, not just "undo"

        self.setZValue(-100)
        self.setSizePolicy(QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Policy.Expanding, QtWidgets.QSizePolicy.Policy.Expanding))

        self.setAspectLocked(lockAspect)

        if enableMenu:
            self.menu = ViewBoxMenu(self)
        else:
            self.menu = None

        self.register(name)
        if name is None:
            self.updateViewLists()

        self._viewPixelSizeCache  = None

    def getAspectRatio(self):
        '''return the current aspect ratio'''
        rect = self.rect()
        vr = self.viewRect()
        if rect.height() == 0 or vr.width() == 0 or vr.height() == 0:
            currentRatio = 1.0
        else:
            currentRatio = (rect.width()/float(rect.height())) / (
                                                vr.width()/vr.height())
        return currentRatio

    def register(self, name):
        """
        Add this ViewBox to the registered list of views.

        This allows users to manually link the axes of any other ViewBox to
        this one. The specified *name* will appear in the drop-down lists for
        axis linking in the context menus of all other views.

        The same can be accomplished by initializing the ViewBox with the *name* attribute.
        """
        ViewBox.AllViews[self] = None
        if self.name is not None:
            del ViewBox.NamedViews[self.name]
        self.name = name
        if name is not None:
            ViewBox.NamedViews[name] = self
            ViewBox.updateAllViewLists()
            sid = id(self)
            self.destroyed.connect(lambda: ViewBox.forgetView(sid, name) if (ViewBox is not None and 'sid' in locals() and 'name' in locals()) else None)

    def unregister(self):
        """
        Remove this ViewBox from the list of linkable views. (see :func:`register() <pyqtgraph.ViewBox.register>`)
        """
        del ViewBox.AllViews[self]
        if self.name is not None:
            del ViewBox.NamedViews[self.name]

    def close(self):
        self.clear()
        self.unregister()

    def implements(self, interface):
        return interface == 'ViewBox'

    def itemChange(self, change, value):
        ret = super().itemChange(change, value)
        if change == self.GraphicsItemChange.ItemSceneChange:
            scene = self.scene()
            if scene is not None and hasattr(scene, 'sigPrepareForPaint'):
                scene.sigPrepareForPaint.disconnect(self.prepareForPaint)
        elif change == self.GraphicsItemChange.ItemSceneHasChanged:
            scene = self.scene()
            if scene is not None and hasattr(scene, 'sigPrepareForPaint'):
                scene.sigPrepareForPaint.connect(self.prepareForPaint)
        return ret

    def prepareForPaint(self):
        #autoRangeEnabled = (self.state['autoRange'][0] is not False) or (self.state['autoRange'][1] is not False)
        # don't check whether auto range is enabled here--only check when setting dirty flag.
        if self._autoRangeNeedsUpdate: # and autoRangeEnabled:
            self.updateAutoRange()
        self.updateMatrix()

    def getState(self, copy=True):
        """Return the current state of the ViewBox.
        Linked views are always converted to view names in the returned state."""
        state = self.state.copy()
        views = []
        for v in state['linkedViews']:
            if isinstance(v, weakref.ref):
                v = v()
            if v is None or isinstance(v, str):
                views.append(v)
            else:
                views.append(v.name)
        state['linkedViews'] = views
        if copy:
            return deepcopy(state)
        else:
            return state

    def setState(self, state):
        """Restore the state of this ViewBox.
        (see also getState)"""
        state = state.copy()
        self.setXLink(state['linkedViews'][0])
        self.setYLink(state['linkedViews'][1])
        del state['linkedViews']

        self.state.update(state)

        self._applyMenuEnabled()
        self.updateViewRange()
        self.sigStateChanged.emit(self)

    def setBackgroundColor(self, color):
        """
        Set the background color of the ViewBox.

        If color is None, then no background will be drawn.

        Added in version 0.9.9
        """
        self.background.setVisible(color is not None)
        self.state['background'] = color
        self.updateBackground()

    def setMouseMode(self, mode):
        """
        Set the mouse interaction mode. *mode* must be either ViewBox.PanMode or ViewBox.RectMode.
        In PanMode, the left mouse button pans the view and the right button scales.
        In RectMode, the left button draws a rectangle which updates the visible region (this mode is more suitable for single-button mice)
        """
        if mode not in [ViewBox.PanMode, ViewBox.RectMode]:
            raise Exception("Mode must be ViewBox.PanMode or ViewBox.RectMode")
        self.state['mouseMode'] = mode
        self.sigStateChanged.emit(self)

    def setLeftButtonAction(self, mode='rect'):  ## for backward compatibility
        if mode.lower() == 'rect':
            self.setMouseMode(ViewBox.RectMode)
        elif mode.lower() == 'pan':
            self.setMouseMode(ViewBox.PanMode)
        else:
            raise Exception('graphicsItems:ViewBox:setLeftButtonAction: unknown mode = %s (Options are "pan" and "rect")' % mode)

    def innerSceneItem(self):
        return self.childGroup

    def setMouseEnabled(self, x=None, y=None):
        """
        Set whether each axis is enabled for mouse interaction. *x*, *y* arguments must be True or False.
        This allows the user to pan/scale one axis of the view while leaving the other axis unchanged.
        """
        if x is not None:
            self.state['mouseEnabled'][0] = x
        if y is not None:
            self.state['mouseEnabled'][1] = y
        self.sigStateChanged.emit(self)

    def mouseEnabled(self):
        return self.state['mouseEnabled'][:]

    def setMenuEnabled(self, enableMenu=True):
        self.state['enableMenu'] = enableMenu
        self._applyMenuEnabled()
        self.sigStateChanged.emit(self)

    def menuEnabled(self):
        return self.state.get('enableMenu', True)

    def _applyMenuEnabled(self):
        enableMenu = self.state.get("enableMenu", True)
        if enableMenu and self.menu is None:
            self.menu = ViewBoxMenu(self)
            self.updateViewLists()
        elif not enableMenu and self.menu is not None:
            self.menu.setParent(None)
            self.menu = None

    def addItem(self, item, ignoreBounds=False):
        """
        Add a QGraphicsItem to this view. The view will include this item when determining how to set its range
        automatically unless *ignoreBounds* is True.
        """
        if item.zValue() < self.zValue():
            item.setZValue(self.zValue()+1)

        scene = self.scene()
        if scene is not None and scene is not item.scene():
            scene.addItem(item)  ## Necessary due to Qt bug: https://bugreports.qt-project.org/browse/QTBUG-18616
        item.setParentItem(self.childGroup)

        if not ignoreBounds:
            self.addedItems.append(item)
        self.updateAutoRange()

    def removeItem(self, item):
        """Remove an item from this view."""
        try:
            self.addedItems.remove(item)
        except:
            pass

        scene = self.scene()
        if scene is not None:
            scene.removeItem(item)
        item.setParentItem(None)
        self.updateAutoRange()

    def clear(self):
        for i in self.addedItems[:]:
            self.removeItem(i)
        for ch in self.childGroup.childItems():
            ch.setParentItem(None)

    def resizeEvent(self, ev):
        if ev.oldSize() != ev.newSize():
            self._viewPixelSizeCache  = None
            self._matrixNeedsUpdate = True

            self.linkedXChanged()
            self.linkedYChanged()

            self.updateAutoRange()
            self.updateViewRange()

            # self._matrixNeedsUpdate = True

            self.background.setRect(self.rect())
            self.borderRect.setRect(self.rect())
        
            self.sigStateChanged.emit(self)
            self.sigResized.emit(self)

    def viewRange(self):
        """Return a the view's visible range as a list: [[xmin, xmax], [ymin, ymax]]"""
        return [x[:] for x in self.state['viewRange']]  ## return copy

    def viewRect(self):
        """Return a QRectF bounding the region visible within the ViewBox"""
        try:
            vr0 = self.state['viewRange'][0]
            vr1 = self.state['viewRange'][1]
            return QtCore.QRectF(vr0[0], vr1[0], vr0[1]-vr0[0], vr1[1] - vr1[0])
        except:
            print("make qrectf failed:", self.state['viewRange'])
            raise

    def targetRange(self):
        return [x[:] for x in self.state['targetRange']]  ## return copy

    def targetRect(self):
        """
        Return the region which has been requested to be visible.
        (this is not necessarily the same as the region that is *actually* visible--
        resizing and aspect ratio constraints can cause targetRect() and viewRect() to differ)
        """
        try:
            tr0 = self.state['targetRange'][0]
            tr1 = self.state['targetRange'][1]
            return QtCore.QRectF(tr0[0], tr1[0], tr0[1]-tr0[0], tr1[1] - tr1[0])
        except:
            print("make qrectf failed:", self.state['targetRange'])
            raise

    def _resetTarget(self):
        # Reset target range to exactly match current view range.
        # This is used during mouse interaction to prevent unpredictable
        # behavior (because the user is unaware of targetRange).
        if self.state['aspectLocked'] is False: # (interferes with aspect locking)
            self.state['targetRange'] = [self.state['viewRange'][0][:], self.state['viewRange'][1][:]]
            
    def _effectiveLimits(self):
        # Determines restricted effective scaling range when in log mapping mode
        if self.state['logMode'][0]:
            xlimits = (# constrain to the +1.7E308 to 2.2E-308 range of double float values
                max( self.state['limits']['xLimits'][0], -307.6 ),
                min( self.state['limits']['xLimits'][1], +308.2 )
            )
        else:
            xlimits = self.state['limits']['xLimits']
        
        if self.state['logMode'][1]: 
            ylimits = (# constrain to the +1.7E308 to 2.2E-308 range of double float values
                max( self.state['limits']['yLimits'][0], -307.6 ),
                min( self.state['limits']['yLimits'][1], +308.2 )
            )
        else:
            ylimits = self.state['limits']['yLimits']
        # print('limits ', xlimits, ylimits) # diagnostic output should reflect additional limit in log mode
        return (xlimits, ylimits)

    def setRange(self, rect=None, xRange=None, yRange=None, padding=None, update=True, disableAutoRange=True):
        """
        Set the visible range of the ViewBox.
        Must specify at least one of *rect*, *xRange*, or *yRange*.

        ================== =====================================================================
        **Arguments:**
        *rect*             (QRectF) The full range that should be visible in the view box.
        *xRange*           (min,max) The range that should be visible along the x-axis.
        *yRange*           (min,max) The range that should be visible along the y-axis.
        *padding*          (float) Expand the view by a fraction of the requested range.
                           By default, this value is set between the default padding value
                           and 0.1 depending on the size of the ViewBox.
        *update*           (bool) If True, update the range of the ViewBox immediately.
                           Otherwise, the update is deferred until before the next render.
        *disableAutoRange* (bool) If True, auto-ranging is diabled. Otherwise, it is left
                           unchanged.
        ================== =====================================================================

        """
        self._viewPixelSizeCache  = None

        changes = {}   # axes
        setRequested = [False, False]

        if rect is not None:
            changes = {0: [rect.left(), rect.right()], 1: [rect.top(), rect.bottom()]}
            setRequested = [True, True]
        if xRange is not None:
            changes[0] = xRange
            setRequested[0] = True
        if yRange is not None:
            changes[1] = yRange
            setRequested[1] = True

        if len(changes) == 0:
            raise Exception("Must specify at least one of rect, xRange, or yRange. (gave rect=%s)" % str(type(rect)))

        # Update axes one at a time
        changed = [False, False]

        # Disable auto-range for each axis that was requested to be set
        if disableAutoRange:
            xOff = False if setRequested[0] else None
            yOff = False if setRequested[1] else None
            self.enableAutoRange(x=xOff, y=yOff)
            changed.append(True)
            
        limits = self._effectiveLimits()
        # print('rng:limits ', limits) # diagnostic output should reflect additional limit in log mode
        # limits = (self.state['limits']['xLimits'], self.state['limits']['yLimits'])
        minRng = [self.state['limits']['xRange'][0], self.state['limits']['yRange'][0]]
        maxRng = [self.state['limits']['xRange'][1], self.state['limits']['yRange'][1]]

        for ax, range in changes.items():
            mn = min(range)
            mx = max(range)

            # If we requested 0 range, try to preserve previous scale.
            # Otherwise just pick an arbitrary scale.
            if mn == mx:
                dy = self.state['viewRange'][ax][1] - self.state['viewRange'][ax][0]
                if dy == 0:
                    dy = 1
                mn -= dy*0.5
                mx += dy*0.5
            # Make sure that the range includes a usable number of quantization steps:
            #    approx. eps  : 3e-16
            #    * min. steps : 10
            #    * mean value : (mn+mx)*0.5 
            quantization_limit = (mn+mx) * 1.5e-15 # +/-10 discrete steps of double resolution
            if mx-mn < 2*quantization_limit:
                mn -= quantization_limit
                mx += quantization_limit

            # Make sure no nan/inf get through
            if not math.isfinite(mn) or not math.isfinite(mx):
                raise Exception("Cannot set range [%s, %s]" % (str(mn), str(mx)))

            # Apply padding
            if padding is None:
                xpad = self.suggestPadding(ax)
            else:
                xpad = padding
            p = (mx-mn) * xpad
            mn -= p
            mx += p

            # max range cannot be larger than bounds, if they are given
            if limits[ax][0] is not None and limits[ax][1] is not None:
                if maxRng[ax] is not None:
                    maxRng[ax] = min(maxRng[ax], limits[ax][1] - limits[ax][0])
                else:
                    maxRng[ax] = limits[ax][1] - limits[ax][0]

            # If we have limits, we will have at least a max range as well
            if maxRng[ax] is not None or minRng[ax] is not None:
                diff = mx - mn
                if maxRng[ax] is not None and diff > maxRng[ax]:
                    delta = maxRng[ax] - diff
                elif minRng[ax] is not None and diff < minRng[ax]:
                    delta = minRng[ax] - diff
                else:
                    delta = 0

                mn -= delta / 2.
                mx += delta / 2.

            # Make sure our requested area is within limits, if any
            if limits[ax][0] is not None or limits[ax][1] is not None:
                lmn, lmx = limits[ax]
                if lmn is not None and mn < lmn:
                    delta = lmn - mn  # Shift the requested view to match our lower limit
                    mn = lmn
                    mx += delta
                elif lmx is not None and mx > lmx:
                    delta = lmx - mx
                    mx = lmx
                    mn += delta

            # Set target range
            if self.state['targetRange'][ax] != [mn, mx]:
                self.state['targetRange'][ax] = [mn, mx]
                changed[ax] = True

        # Update viewRange to match targetRange as closely as possible while
        # accounting for aspect ratio constraint
        lockX, lockY = setRequested
        if lockX and lockY:
            lockX = False
            lockY = False
        self.updateViewRange(lockX, lockY)

        # If nothing has changed, we are done.
        if any(changed):
            # Update target rect for debugging
            if self.target.isVisible():
                self.target.setRect(self.mapRectFromItem(self.childGroup, self.targetRect()))

            # If ortho axes have auto-visible-only, update them now
            # Note that aspect ratio constraints and auto-visible probably do not work together..
            if changed[0] and self.state['autoVisibleOnly'][1] and (self.state['autoRange'][0] is not False):
                self._autoRangeNeedsUpdate = True
            elif changed[1] and self.state['autoVisibleOnly'][0] and (self.state['autoRange'][1] is not False):
                self._autoRangeNeedsUpdate = True
            self.sigStateChanged.emit(self)

    def setYRange(self, min, max, padding=None, update=True):
        """
        Set the visible Y range of the view to [*min*, *max*].
        The *padding* argument causes the range to be set larger by the fraction specified.
        (by default, this value is between the default padding and 0.1 depending on the size of the ViewBox)
        """
        self.setRange(yRange=[min, max], update=update, padding=padding)

    def setXRange(self, min, max, padding=None, update=True):
        """
        Set the visible X range of the view to [*min*, *max*].
        The *padding* argument causes the range to be set larger by the fraction specified.
        (by default, this value is between the default padding and 0.1 depending on the size of the ViewBox)
        """
        self.setRange(xRange=[min, max], update=update, padding=padding)

    def autoRange(self, padding=None, items=None, item=None):
        """
        Set the range of the view box to make all children visible.
        Note that this is not the same as enableAutoRange, which causes the view to
        automatically auto-range whenever its contents are changed.

        ==============  =============================================================
        **Arguments:**
        padding         The fraction of the total data range to add on to the final
                        visible range. By default, this value is set between the 
                        default padding and 0.1 depending on the size of the ViewBox.
        items           If specified, this is a list of items to consider when
                        determining the visible range.
        ==============  =============================================================
        """
        if item is None:
            bounds = self.childrenBoundingRect(items=items)
        else:
            bounds = self.mapFromItemToView(item, item.boundingRect()).boundingRect()

        if bounds is not None:
            self.setRange(bounds, padding=padding)

    def suggestPadding(self, axis):
        l = self.width() if axis==0 else self.height()
        def_pad = self.state['defaultPadding']
        if def_pad == 0.: 
            return def_pad # respect requested zero padding
        max_pad = max(0.1, def_pad) # don't shrink a large default padding
        if l > 0:
            padding = fn.clip_scalar( 50*def_pad / (l**0.5), def_pad, max_pad)
        else:
            padding = def_pad
        return padding

    def setLimits(self, **kwds):
        """
        Set limits that constrain the possible view ranges.

        **Panning limits**. The following arguments define the region within the
        viewbox coordinate system that may be accessed by panning the view.

        =========== ============================================================
        xMin        Minimum allowed x-axis value
        xMax        Maximum allowed x-axis value
        yMin        Minimum allowed y-axis value
        yMax        Maximum allowed y-axis value
        =========== ============================================================

        **Scaling limits**. These arguments prevent the view being zoomed in or
        out too far.

        =========== ============================================================
        minXRange   Minimum allowed left-to-right span across the view.
        maxXRange   Maximum allowed left-to-right span across the view.
        minYRange   Minimum allowed top-to-bottom span across the view.
        maxYRange   Maximum allowed top-to-bottom span across the view.
        =========== ============================================================

        Added in version 0.9.9
        """
        update = False
        allowed = ['xMin', 'xMax', 'yMin', 'yMax', 'minXRange', 'maxXRange', 'minYRange', 'maxYRange']
        for kwd in kwds:
            if kwd not in allowed:
                raise ValueError("Invalid keyword argument '%s'." % kwd)
        for axis in [0,1]:
            for mnmx in [0,1]:
                kwd = [['xMin', 'xMax'], ['yMin', 'yMax']][axis][mnmx]
                lname = ['xLimits', 'yLimits'][axis]
                if kwd in kwds and self.state['limits'][lname][mnmx] != kwds[kwd]:
                    self.state['limits'][lname][mnmx] = kwds[kwd]
                    update = True
                kwd = [['minXRange', 'maxXRange'], ['minYRange', 'maxYRange']][axis][mnmx]
                lname = ['xRange', 'yRange'][axis]
                if kwd in kwds and self.state['limits'][lname][mnmx] != kwds[kwd]:
                    self.state['limits'][lname][mnmx] = kwds[kwd]
                    update = True

        if update:
            self.updateViewRange()

    def scaleBy(self, s=None, center=None, x=None, y=None):
        """
        Scale by *s* around given center point (or center of view).
        *s* may be a Point or tuple (x, y).

        Optionally, x or y may be specified individually. This allows the other
        axis to be left unaffected (note that using a scale factor of 1.0 may
        cause slight changes due to floating-point error).
        """
        if s is not None:
            x, y = s[0], s[1]

        affect = [x is not None, y is not None]
        if not any(affect):
            return

        scale = Point([1.0 if x is None else x, 1.0 if y is None else y])

        if self.state['aspectLocked'] is not False:
            scale[0] = scale[1]

        vr = self.targetRect()
        if center is None:
            center = Point(vr.center())
        else:
            center = Point(center)

        tl = center + (vr.topLeft()-center) * scale
        br = center + (vr.bottomRight()-center) * scale

        if not affect[0]:
            self.setYRange(tl.y(), br.y(), padding=0)
        elif not affect[1]:
            self.setXRange(tl.x(), br.x(), padding=0)
        else:
            self.setRange(QtCore.QRectF(tl, br), padding=0)

    def translateBy(self, t=None, x=None, y=None):
        """
        Translate the view by *t*, which may be a Point or tuple (x, y).

        Alternately, x or y may be specified independently, leaving the other
        axis unchanged (note that using a translation of 0 may still cause
        small changes due to floating-point error).
        """
        vr = self.targetRect()
        if t is not None:
            t = Point(t)
            self.setRange(vr.translated(t), padding=0)
        else:
            if x is not None:
                x = vr.left()+x, vr.right()+x
            if y is not None:
                y = vr.top()+y, vr.bottom()+y
            if x is not None or y is not None:
                self.setRange(xRange=x, yRange=y, padding=0)

    def enableAutoRange(self, axis=None, enable=True, x=None, y=None):
        """
        Enable (or disable) auto-range for *axis*, which may be ViewBox.XAxis, ViewBox.YAxis, or ViewBox.XYAxes for both
        (if *axis* is omitted, both axes will be changed).
        When enabled, the axis will automatically rescale when items are added/removed or change their shape.
        The argument *enable* may optionally be a float (0.0-1.0) which indicates the fraction of the data that should
        be visible (this only works with items implementing a dataRange method, such as PlotDataItem).
        """
        # support simpler interface:
        if x is not None or y is not None:
            if x is not None:
                self.enableAutoRange(ViewBox.XAxis, x)
            if y is not None:
                self.enableAutoRange(ViewBox.YAxis, y)
            return

        if enable is True:
            enable = 1.0

        if axis is None:
            axis = ViewBox.XYAxes

        needAutoRangeUpdate = False

        if axis == ViewBox.XYAxes or axis == 'xy':
            axes = [0, 1]
        elif axis == ViewBox.XAxis or axis == 'x':
            axes = [0]
        elif axis == ViewBox.YAxis or axis == 'y':
            axes = [1]
        else:
            raise Exception('axis argument must be ViewBox.XAxis, ViewBox.YAxis, or ViewBox.XYAxes.')

        for ax in axes:
            if self.state['autoRange'][ax] != enable:
                # If we are disabling, do one last auto-range to make sure that
                # previously scheduled auto-range changes are enacted
                if enable is False and self._autoRangeNeedsUpdate:
                    self.updateAutoRange()

                self.state['autoRange'][ax] = enable
                self._autoRangeNeedsUpdate |= (enable is not False)
                self.update()

        self.sigStateChanged.emit(self)

    def disableAutoRange(self, axis=None):
        """Disables auto-range. (See enableAutoRange)"""
        self.enableAutoRange(axis, enable=False)

    def autoRangeEnabled(self):
        return self.state['autoRange'][:]

    def setAutoPan(self, x=None, y=None):
        """Set whether automatic range will only pan (not scale) the view.
        """
        if x is not None:
            self.state['autoPan'][0] = x
        if y is not None:
            self.state['autoPan'][1] = y
        if None not in [x,y]:
            self.updateAutoRange()

    def setAutoVisible(self, x=None, y=None):
        """Set whether automatic range uses only visible data when determining
        the range to show.
        """
        if x is not None:
            self.state['autoVisibleOnly'][0] = x
            if x is True:
                self.state['autoVisibleOnly'][1] = False
        if y is not None:
            self.state['autoVisibleOnly'][1] = y
            if y is True:
                self.state['autoVisibleOnly'][0] = False

        if x is not None or y is not None:
            self.updateAutoRange()

    def updateAutoRange(self):
        ## Break recursive loops when auto-ranging.
        ## This is needed because some items change their size in response
        ## to a view change.
        if self._updatingRange:
            return
        self._updatingRange = True
        try:
            if not any(self.state['autoRange']):
                return

            targetRect = self.viewRange()

            fractionVisible = self.state['autoRange'][:]
            for i in [0,1]:
                if type(fractionVisible[i]) is bool:
                    fractionVisible[i] = 1.0

            childRange = None

            order = [0,1]
            if self.state['autoVisibleOnly'][0] is True:
                order = [1,0]

            args = {}
            for ax in order:
                if self.state['autoRange'][ax] is False:
                    continue
                if self.state['autoVisibleOnly'][ax]:
                    oRange = [None, None]
                    oRange[ax] = targetRect[1-ax]
                    childRange = self.childrenBounds(frac=fractionVisible, orthoRange=oRange)
                else:
                    if childRange is None:
                        childRange = self.childrenBounds(frac=fractionVisible)
                ## Make corrections to range
                xr = childRange[ax]
                if xr is not None:
                    if self.state['autoPan'][ax]:
                        x = sum(xr) * 0.5
                        w2 = (targetRect[ax][1]-targetRect[ax][0]) / 2.
                        childRange[ax] = [x-w2, x+w2]
                    else:
                        padding = self.suggestPadding(ax)
                        wp = (xr[1] - xr[0]) * padding
                        childRange[ax][0] -= wp
                        childRange[ax][1] += wp
                    targetRect[ax] = childRange[ax]
                    args['xRange' if ax == 0 else 'yRange'] = targetRect[ax]

            # check for and ignore bad ranges
            for k in ['xRange', 'yRange']:
                if k in args:
                    if not math.isfinite(args[k][0]) or not math.isfinite(args[k][1]):
                        _ = args.pop(k)
                        #print("Warning: %s is invalid: %s" % (k, str(r))

            if len(args) == 0:
                return
            args['padding'] = 0.0
            args['disableAutoRange'] = False
            self.setRange(**args)
        finally:
            self._autoRangeNeedsUpdate = False
            self._updatingRange = False

    def setXLink(self, view):
        """Link this view's X axis to another view. (see LinkView)"""
        self.linkView(self.XAxis, view)

    def setYLink(self, view):
        """Link this view's Y axis to another view. (see LinkView)"""
        self.linkView(self.YAxis, view)
        
    def setLogMode(self, axis, logMode):
        """Informs ViewBox that log mode is active for the specified axis, so that the view range cen be restricted"""
        if axis == 'x':
            self.state['logMode'][0] = bool(logMode)
            # print('x log mode', self.state['logMode'][0] )
        elif axis == 'y':
            self.state['logMode'][1] = bool(logMode)
            # print('x log mode', self.state['logMode'][0] )

    def linkView(self, axis, view):
        """
        Link X or Y axes of two views and unlink any previously connected axes. *axis* must be ViewBox.XAxis or ViewBox.YAxis.
        If view is None, the axis is left unlinked.
        """
        if isinstance(view, str):
            if view == '':
                view = None
            else:
                view = ViewBox.NamedViews.get(view, view)  ## convert view name to ViewBox if possible

        if hasattr(view, 'implements') and view.implements('ViewBoxWrapper'):
            view = view.getViewBox()

        ## used to connect/disconnect signals between a pair of views
        if axis == ViewBox.XAxis:
            signal = 'sigXRangeChanged'
            slot = self.linkedXChanged
        else:
            signal = 'sigYRangeChanged'
            slot = self.linkedYChanged


        oldLink = self.linkedView(axis)
        if oldLink is not None:
            try:
                getattr(oldLink, signal).disconnect(slot)
                oldLink.sigResized.disconnect(slot)
            except (TypeError, RuntimeError):
                ## This can occur if the view has been deleted already
                pass


        if view is None or isinstance(view, str):
            self.state['linkedViews'][axis] = view
        else:
            self.state['linkedViews'][axis] = weakref.ref(view)
            getattr(view, signal).connect(slot)
            view.sigResized.connect(slot)
            if view.autoRangeEnabled()[axis] is not False:
                self.enableAutoRange(axis, False)
                slot()
            else:
                if self.autoRangeEnabled()[axis] is False:
                    slot()


        self.sigStateChanged.emit(self)

    def blockLink(self, b):
        self.linksBlocked = b  ## prevents recursive plot-change propagation

    def linkedXChanged(self):
        ## called when x range of linked view has changed
        view = self.linkedView(0)
        self.linkedViewChanged(view, ViewBox.XAxis)

    def linkedYChanged(self):
        ## called when y range of linked view has changed
        view = self.linkedView(1)
        self.linkedViewChanged(view, ViewBox.YAxis)

    def linkedView(self, ax):
        ## Return the linked view for axis *ax*.
        ## this method _always_ returns either a ViewBox or None.
        v = self.state['linkedViews'][ax]
        if v is None or isinstance(v, str):
            return None
        else:
            return v()  ## dereference weakref pointer. If the reference is dead, this returns None

    def linkedViewChanged(self, view, axis):
        if self.linksBlocked or view is None:
            return

        #print self.name, "ViewBox.linkedViewChanged", axis, view.viewRange()[axis]
        vr = view.viewRect()
        vg = view.screenGeometry()
        sg = self.screenGeometry()
        if vg is None or sg is None:
            return

        view.blockLink(True)
        try:
            if axis == ViewBox.XAxis:
                overlap = min(sg.right(), vg.right()) - max(sg.left(), vg.left())
                if overlap < min(vg.width()/3, sg.width()/3):  ## if less than 1/3 of views overlap,
                                                               ## then just replicate the view
                    x1 = vr.left()
                    x2 = vr.right()
                else:  ## views overlap; line them up
                    upp = float(vr.width()) / vg.width()
                    if self.xInverted():
                        x1 = vr.left()   + (sg.right()-vg.right()) * upp
                    else:
                        x1 = vr.left()   + (sg.x()-vg.x()) * upp
                    x2 = x1 + sg.width() * upp
                self.enableAutoRange(ViewBox.XAxis, False)
                self.setXRange(x1, x2, padding=0)
            else:
                overlap = min(sg.bottom(), vg.bottom()) - max(sg.top(), vg.top())
                if overlap < min(vg.height()/3, sg.height()/3):  ## if less than 1/3 of views overlap,
                                                                 ## then just replicate the view
                    y1 = vr.top()
                    y2 = vr.bottom()
                else:  ## views overlap; line them up
                    upp = float(vr.height()) / vg.height()
                    if self.yInverted():
                        y2 = vr.bottom() + (sg.bottom()-vg.bottom()) * upp
                    else:
                        y2 = vr.bottom() + (sg.top()-vg.top()) * upp
                    y1 = y2 - sg.height() * upp
                self.enableAutoRange(ViewBox.YAxis, False)
                self.setYRange(y1, y2, padding=0)
        finally:
            view.blockLink(False)

    def screenGeometry(self):
        """return the screen geometry of the viewbox"""
        v = self.getViewWidget()
        if v is None:
            return None
        b = self.sceneBoundingRect()
        wr = v.mapFromScene(b).boundingRect()
        pos = v.mapToGlobal(v.pos())
        wr.adjust(pos.x(), pos.y(), pos.x(), pos.y())
        return wr

    def itemsChanged(self):
        ## called when items are added/removed from self.childGroup
        self.updateAutoRange()

    def itemBoundsChanged(self, item):
        self._itemBoundsCache.pop(item, None)
        if (self.state['autoRange'][0] is not False) or (self.state['autoRange'][1] is not False):
            self._autoRangeNeedsUpdate = True
            self.update()

    def _invertAxis(self, ax, inv):
        key = 'xy'[ax] + 'Inverted'
        if self.state[key] == inv:
            return

        self.state[key] = inv
        self._matrixNeedsUpdate = True # updateViewRange won't detect this for us
        self.updateViewRange()
        self.update()
        self.sigStateChanged.emit(self)
        if ax:
            self.sigYRangeChanged.emit(self, tuple(self.state['viewRange'][ax]))
        else:
            self.sigXRangeChanged.emit(self, tuple(self.state['viewRange'][ax]))

    def invertY(self, b=True):
        """
        By default, the positive y-axis points upward on the screen. Use invertY(True) to reverse the y-axis.
        """
        self._invertAxis(1, b)

    def yInverted(self):
        return self.state['yInverted']

    def invertX(self, b=True):
        """
        By default, the positive x-axis points rightward on the screen. Use invertX(True) to reverse the x-axis.
        """
        self._invertAxis(0, b)

    def xInverted(self):
        return self.state['xInverted']

    def setBorder(self, *args, **kwds):
        """
        Set the pen used to draw border around the view

        If border is None, then no border will be drawn.

        Added in version 0.9.10

        See :func:`mkPen <pyqtgraph.mkPen>` for arguments.
        """
        self.border = fn.mkPen(*args, **kwds)
        self.borderRect.setPen(self.border)
    
    def setDefaultPadding(self, padding=0.02):
        """
        Sets the fraction of the data range that is used to pad the view range in when auto-ranging.
        By default, this fraction is 0.02.
        """
        self.state['defaultPadding'] = padding

    def setAspectLocked(self, lock=True, ratio=1):
        """
        If the aspect ratio is locked, view scaling must always preserve the aspect ratio.
        By default, the ratio is set to 1; x and y both have the same scaling.
        This ratio can be overridden (xScale/yScale), or use None to lock in the current ratio.
        """

        if not lock:
            if self.state['aspectLocked'] == False:
                return
            self.state['aspectLocked'] = False
        else:
            currentRatio = self.getAspectRatio()
            if ratio is None:
                ratio = currentRatio
            if self.state['aspectLocked'] == ratio: # nothing to change
                return
            self.state['aspectLocked'] = ratio
            if ratio != currentRatio:  ## If this would change the current range, do that now
                self.updateViewRange()

        self.updateAutoRange()
        self.updateViewRange()
        self.sigStateChanged.emit(self)

    def childTransform(self):
        """
        Return the transform that maps from child(item in the childGroup) coordinates to local coordinates.
        (This maps from inside the viewbox to outside)
        """
        self.updateMatrix()
        m = self.childGroup.transform()
        return m

    def mapToView(self, obj):
        """Maps from the local coordinates of the ViewBox to the coordinate system displayed inside the ViewBox"""
        self.updateMatrix()
        m = fn.invertQTransform(self.childTransform())
        return m.map(obj)

    def mapFromView(self, obj):
        """Maps from the coordinate system displayed inside the ViewBox to the local coordinates of the ViewBox"""
        self.updateMatrix()
        m = self.childTransform()
        return m.map(obj)

    def mapSceneToView(self, obj):
        """Maps from scene coordinates to the coordinate system displayed inside the ViewBox"""
        self.updateMatrix()
        return self.mapToView(self.mapFromScene(obj))

    def mapViewToScene(self, obj):
        """Maps from the coordinate system displayed inside the ViewBox to scene coordinates"""
        self.updateMatrix()
        return self.mapToScene(self.mapFromView(obj))

    def mapFromItemToView(self, item, obj):
        """Maps *obj* from the local coordinate system of *item* to the view coordinates"""
        self.updateMatrix()
        return self.childGroup.mapFromItem(item, obj)

    def mapFromViewToItem(self, item, obj):
        """Maps *obj* from view coordinates to the local coordinate system of *item*."""
        self.updateMatrix()
        return self.childGroup.mapToItem(item, obj)

    def mapViewToDevice(self, obj):
        self.updateMatrix()
        return self.mapToDevice(self.mapFromView(obj))

    def mapDeviceToView(self, obj):
        self.updateMatrix()
        return self.mapToView(self.mapFromDevice(obj))

    def viewPixelSize(self):
        """Return the (width, height) of a screen pixel in view coordinates."""
        if self._viewPixelSizeCache  is None:

            o = self.mapToView(Point(0, 0))
            px, py = [Point(self.mapToView(v) - o) for v in self.pixelVectors()]
            self._viewPixelSizeCache  = (px.length(), py.length())

        return self._viewPixelSizeCache 

    def itemBoundingRect(self, item):
        """Return the bounding rect of the item in view coordinates"""
        return self.mapSceneToView(item.sceneBoundingRect()).boundingRect()

    def wheelEvent(self, ev, axis=None):
        if axis in (0, 1):
            mask = [False, False]
            mask[axis] = self.state['mouseEnabled'][axis]
        else:
            mask = self.state['mouseEnabled'][:]
        s = 1.02 ** (ev.delta() * self.state['wheelScaleFactor']) # actual scaling factor
        s = [(None if m is False else s) for m in mask]
        center = Point(fn.invertQTransform(self.childGroup.transform()).map(ev.pos()))

        self._resetTarget()
        self.scaleBy(s, center)
        ev.accept()
        self.sigRangeChangedManually.emit(mask)

    def mouseClickEvent(self, ev):
        if ev.button() == QtCore.Qt.MouseButton.RightButton and self.menuEnabled():
            ev.accept()
            self.raiseContextMenu(ev)

    def raiseContextMenu(self, ev):
        menu = self.getMenu(ev)
        if menu is not None:
            self.scene().addParentContextMenus(self, menu, ev)
            menu.popup(ev.screenPos().toPoint())

    def getMenu(self, ev):
        return self.menu

    def getContextMenus(self, event):
        return self.menu.actions() if self.menuEnabled() else []

    def mouseDragEvent(self, ev, axis=None):
        ## if axis is specified, event will only affect that axis.
        ev.accept()  ## we accept all buttons

        pos = ev.scenePos()
        dif = pos - ev.lastScenePos()
        dif = dif * -1

        ## Ignore axes if mouse is disabled
        mouseEnabled = np.array(self.state['mouseEnabled'], dtype=np.float64)
        mask = mouseEnabled.copy()
        if axis is not None:
            mask[1-axis] = 0.0

        ## Scale or translate based on mouse button
        if ev.button() in [QtCore.Qt.MouseButton.LeftButton, QtCore.Qt.MouseButton.MiddleButton]:
            if self.state['mouseMode'] == ViewBox.RectMode and axis is None:
                if ev.isFinish():  ## This is the final move in the drag; change the view scale now
                    #print "finish"
                    self.rbScaleBox.hide()
                    ax = QtCore.QRectF(Point(ev.buttonDownScenePos(ev.button())), Point(pos))
                    ax = self.childGroup.mapRectFromScene(ax)
                    self.showAxRect(ax)
                    self.axHistoryPointer += 1
                    self.axHistory = self.axHistory[:self.axHistoryPointer] + [ax]
                else:
                    ## update shape of scale box
                    self.updateScaleBox(ev.buttonDownScenePos(), ev.scenePos())
            else:
                tr = self.childGroup.transform()
                tr = fn.invertQTransform(tr)
                tr = tr.map(dif*mask) - tr.map(Point(0,0))

                x = tr.x() if mask[0] == 1 else None
                y = tr.y() if mask[1] == 1 else None

                self._resetTarget()
                if x is not None or y is not None:
                    self.translateBy(x=x, y=y)
                self.sigRangeChangedManually.emit(self.state['mouseEnabled'])
        elif ev.button() & QtCore.Qt.MouseButton.RightButton:
            #print "vb.rightDrag"
            if self.state['aspectLocked'] is not False:
                mask[0] = 0

            dif = ev.screenPos() - ev.lastScreenPos()
            dif = np.array([dif.x(), dif.y()])
            dif[0] *= -1
            s = ((mask * 0.02) + 1) ** dif

            tr = self.childGroup.transform()
            tr = fn.invertQTransform(tr)

            x = s[0] if mouseEnabled[0] == 1 else None
            y = s[1] if mouseEnabled[1] == 1 else None

            center = Point(tr.map(ev.buttonDownPos(QtCore.Qt.MouseButton.RightButton)))
            self._resetTarget()
            self.scaleBy(x=x, y=y, center=center)
            self.sigRangeChangedManually.emit(self.state['mouseEnabled'])

    def keyPressEvent(self, ev):
        """
        This routine should capture key presses in the current view box.
        Key presses are used only when mouse mode is RectMode
        The following events are implemented:
        ctrl-A : zooms out to the default "full" view of the plot
        ctrl-+ : moves forward in the zooming stack (if it exists)
        ctrl-- : moves backward in the zooming stack (if it exists)

        """
        ev.accept()
        if ev.text() == '-':
            self.scaleHistory(-1)
        elif ev.text() in ['+', '=']:
            self.scaleHistory(1)
        elif ev.key() == QtCore.Qt.Key.Key_Backspace:
            self.scaleHistory(len(self.axHistory))
        else:
            ev.ignore()

    def scaleHistory(self, d):
        if len(self.axHistory) == 0:
            return
        ptr = max(0, min(len(self.axHistory)-1, self.axHistoryPointer+d))
        if ptr != self.axHistoryPointer:
            self.axHistoryPointer = ptr
            self.showAxRect(self.axHistory[ptr])

    def updateScaleBox(self, p1, p2):
        r = QtCore.QRectF(p1, p2)
        r = self.childGroup.mapRectFromScene(r)
        self.rbScaleBox.setPos(r.topLeft())
        tr = QtGui.QTransform.fromScale(r.width(), r.height())
        self.rbScaleBox.setTransform(tr)
        self.rbScaleBox.show()

    def showAxRect(self, ax, **kwargs):
        """Set the visible range to the given rectangle
        Passes keyword arguments to setRange
        """
        self.setRange(ax.normalized(), **kwargs) # be sure w, h are correct coordinates
        self.sigRangeChangedManually.emit(self.state['mouseEnabled'])

    def allChildren(self, item=None):
        """Return a list of all children and grandchildren of this ViewBox"""
        if item is None:
            item = self.childGroup

        children = [item]
        for ch in item.childItems():
            children.extend(self.allChildren(ch))
        return children

    def childrenBounds(self, frac=None, orthoRange=(None,None), items=None):
        """Return the bounding range of all children.
        [[xmin, xmax], [ymin, ymax]]
        Values may be None if there are no specific bounds for an axis.
        """
        profiler = debug.Profiler()
        if items is None:
            items = self.addedItems

        ## measure pixel dimensions in view box
        px, py = [v.length() if v is not None else 0 for v in self.childGroup.pixelVectors()]

        ## First collect all boundary information
        itemBounds = []
        for item in items:
            if not item.isVisible() or not item.scene() is self.scene():
                continue

            useX = True
            useY = True

            if hasattr(item, 'dataBounds'):
                if frac is None:
                    frac = (1.0, 1.0)
                xr = item.dataBounds(0, frac=frac[0], orthoRange=orthoRange[0])
                yr = item.dataBounds(1, frac=frac[1], orthoRange=orthoRange[1])
                pxPad = 0 if not hasattr(item, 'pixelPadding') else item.pixelPadding()
                if (
                    xr is None or
                    (xr[0] is None and xr[1] is None) or
                    not math.isfinite(xr[0]) or
                    not math.isfinite(xr[1])
                ):
                    useX = False
                    xr = (0,0)
                if (
                    yr is None or
                    (yr[0] is None and yr[1] is None) or
                    not math.isfinite(yr[0]) or
                    not math.isfinite(yr[1])
                ):
                    useY = False
                    yr = (0,0)

                bounds = QtCore.QRectF(xr[0], yr[0], xr[1]-xr[0], yr[1]-yr[0])
                bounds = self.mapFromItemToView(item, bounds).boundingRect()

                if not any([useX, useY]):
                    continue

                ## If we are ignoring only one axis, we need to check for rotations
                if useX != useY:  ##   !=  means  xor
                    ang = round(item.transformAngle())
                    if ang == 0 or ang == 180:
                        pass
                    elif ang == 90 or ang == 270:
                        useX, useY = useY, useX
                    else:
                        ## Item is rotated at non-orthogonal angle, ignore bounds entirely.
                        ## Not really sure what is the expected behavior in this case.
                        continue  ## need to check for item rotations and decide how best to apply this boundary.


                itemBounds.append((bounds, useX, useY, pxPad))
            else:
                if item.flags() & item.GraphicsItemFlag.ItemHasNoContents:
                    continue
                bounds = self.mapFromItemToView(item, item.boundingRect()).boundingRect()
                itemBounds.append((bounds, True, True, 0))

        ## determine tentative new range
        range = [None, None]
        for bounds, useX, useY, px in itemBounds:
            if useY:
                if range[1] is not None:
                    range[1] = [min(bounds.top(), range[1][0]), max(bounds.bottom(), range[1][1])]
                else:
                    range[1] = [bounds.top(), bounds.bottom()]
            if useX:
                if range[0] is not None:
                    range[0] = [min(bounds.left(), range[0][0]), max(bounds.right(), range[0][1])]
                else:
                    range[0] = [bounds.left(), bounds.right()]
            profiler()

        ## Now expand any bounds that have a pixel margin
        ## This must be done _after_ we have a good estimate of the new range
        ## to ensure that the pixel size is roughly accurate.
        w = self.width()
        h = self.height()
        if w > 0 and range[0] is not None:
            pxSize = (range[0][1] - range[0][0]) / w
            for bounds, useX, useY, px in itemBounds:
                if px == 0 or not useX:
                    continue
                range[0][0] = min(range[0][0], bounds.left() - px*pxSize)
                range[0][1] = max(range[0][1], bounds.right() + px*pxSize)
        if h > 0 and range[1] is not None:
            pxSize = (range[1][1] - range[1][0]) / h
            for bounds, useX, useY, px in itemBounds:
                if px == 0 or not useY:
                    continue
                range[1][0] = min(range[1][0], bounds.top() - px*pxSize)
                range[1][1] = max(range[1][1], bounds.bottom() + px*pxSize)
        return range

    def childrenBoundingRect(self, *args, **kwds):
        range = self.childrenBounds(*args, **kwds)
        tr = self.targetRange()
        if range[0] is None:
            range[0] = tr[0]
        if range[1] is None:
            range[1] = tr[1]

        bounds = QtCore.QRectF(range[0][0], range[1][0], range[0][1]-range[0][0], range[1][1]-range[1][0])
        return bounds

    # Including a prepareForPaint call is part of the Qt strategy to
    # defer expensive redraw opertions until requested by a 'sigPrepareForPaint' signal
    # 
    # However, as currently implemented, a call to prepareForPaint as part of the regular 
    # 'update' call results in an undesired reset of pan/zoom:
    # https://github.com/pyqtgraph/pyqtgraph/issues/2029
    #
    # def update(self, *args, **kwargs):
    #     self.prepareForPaint()
    #     GraphicsWidget.update(self, *args, **kwargs)

    def updateViewRange(self, forceX=False, forceY=False):
        ## Update viewRange to match targetRange as closely as possible, given
        ## aspect ratio constraints. The *force* arguments are used to indicate
        ## which axis (if any) should be unchanged when applying constraints.
        viewRange = [self.state['targetRange'][0][:], self.state['targetRange'][1][:]]
        changed = [False, False]

        #-------- Make correction for aspect ratio constraint ----------

        # aspect is (widget w/h) / (view range w/h)
        aspect = self.state['aspectLocked']  # size ratio / view ratio
        tr = self.targetRect()
        bounds = self.rect()
        
        limits = self._effectiveLimits()
        # print('upd:limits ', limits) # diagnostic output should reflect additional limit in log mode
        minRng = [self.state['limits']['xRange'][0], self.state['limits']['yRange'][0]]
        maxRng = [self.state['limits']['xRange'][1], self.state['limits']['yRange'][1]]

        for axis in [0, 1]:
            if limits[axis][0] is None and limits[axis][1] is None and minRng[axis] is None and maxRng[axis] is None:
                continue
            # max range cannot be larger than bounds, if they are given
            if limits[axis][0] is not None and limits[axis][1] is not None:
                if maxRng[axis] is not None:
                    maxRng[axis] = min(maxRng[axis], limits[axis][1] - limits[axis][0])
                else:
                    maxRng[axis] = limits[axis][1] - limits[axis][0]

        if aspect is not False and 0 not in [aspect, tr.height(), bounds.height(), bounds.width()]:

            ## This is the view range aspect ratio we have requested
            targetRatio = tr.width() / tr.height() if tr.height() != 0 else 1
            ## This is the view range aspect ratio we need to obey aspect constraint
            viewRatio = (bounds.width() / bounds.height() if bounds.height() != 0 else 1) / aspect
            viewRatio = 1 if viewRatio == 0 else viewRatio

            # Calculate both the x and y ranges that would be needed to obtain the desired aspect ratio
            dy = 0.5 * (tr.width() / viewRatio - tr.height())
            dx = 0.5 * (tr.height() * viewRatio - tr.width())

            rangeY = [self.state['targetRange'][1][0] - dy, self.state['targetRange'][1][1] + dy]
            rangeX = [self.state['targetRange'][0][0] - dx, self.state['targetRange'][0][1] + dx]

            canidateRange = [rangeX, rangeY]

            # Decide which range to try to keep unchanged
            #print self.name, "aspect:", aspect, "changed:", changed, "auto:", self.state['autoRange']
            if forceX:
                ax = 0
            elif forceY:
                ax = 1
            else:
                # if we are not required to keep a particular axis unchanged,
                # then try to make the entire target range visible
                ax = 0 if targetRatio > viewRatio else 1
                target = 0 if ax == 1 else 1
                # See if this choice would cause out-of-range issues
                if maxRng is not None or minRng is not None:
                    diff = canidateRange[target][1] - canidateRange[target][0]
                    if maxRng[target] is not None and diff > maxRng[target] or \
                       minRng[target] is not None and diff < minRng[target]:
                        # tweak the target range down so we can still pan properly
                        self.state['targetRange'][ax] = canidateRange[ax]
                        ax = target  # Switch the "fixed" axes

            if ax == 0:
                ## view range needs to be taller than target
                if dy != 0:
                    changed[1] = True
                viewRange[1] = rangeY
            else:
                ## view range needs to be wider than target
                if dx != 0:
                    changed[0] = True
                viewRange[0] = rangeX


        changed = [(viewRange[i][0] != self.state['viewRange'][i][0]) or (viewRange[i][1] != self.state['viewRange'][i][1]) for i in (0,1)]
        self.state['viewRange'] = viewRange

        if any(changed):
            self._matrixNeedsUpdate = True
            self.update()

            # Inform linked views that the range has changed
            for ax in [0, 1]:
                if not changed[ax]:
                    continue
                link = self.linkedView(ax)
                if link is not None:
                    link.linkedViewChanged(self, ax)

            # emit range change signals
            # print('announcing view range changes:',self.state['viewRange'] )
            if changed[0]:
                self.sigXRangeChanged.emit(self, tuple(self.state['viewRange'][0]))
            if changed[1]:
                self.sigYRangeChanged.emit(self, tuple(self.state['viewRange'][1]))
            self.sigRangeChanged.emit(self, self.state['viewRange'], changed)

    def updateMatrix(self, changed=None):
        if not self._matrixNeedsUpdate:
            return
        ## Make the childGroup's transform match the requested viewRange.
        bounds = self.rect()

        vr = self.viewRect()
        if vr.height() == 0 or vr.width() == 0:
            return
        scale = Point(bounds.width()/vr.width(), bounds.height()/vr.height())
        if not self.state['yInverted']:
            scale = scale * Point(1, -1)
        if self.state['xInverted']:
            scale = scale * Point(-1, 1)
        m = QtGui.QTransform()

        ## First center the viewport at 0
        center = bounds.center()
        m.translate(center.x(), center.y())

        ## Now scale and translate properly
        m.scale(scale[0], scale[1])
        st = Point(vr.center())
        m.translate(-st[0], -st[1])

        self.childGroup.setTransform(m)
        self._matrixNeedsUpdate = False

        self.sigTransformChanged.emit(self)  ## segfaults here: 1

    def paint(self, p, opt, widget):
        if self.border is not None:
            bounds = self.shape()
            p.setPen(self.border)
            #p.fillRect(bounds, QtGui.QColor(0, 0, 0))
            p.drawPath(bounds)

        #p.setPen(fn.mkPen('r'))
        #path = QtGui.QPainterPath()
        #path.addRect(self.targetRect())
        #tr = self.mapFromView(path)
        #p.drawPath(tr)

    def updateBackground(self):
        bg = self.state['background']
        if bg is None:
            self.background.hide()
        else:
            self.background.show()
            self.background.setBrush(fn.mkBrush(bg))

    def updateViewLists(self):
        try:
            self.window()
        except RuntimeError:  ## this view has already been deleted; it will probably be collected shortly.
            return

        def view_key(view):
            return (view.window() is self.window(), view.name)

        ## make a sorted list of all named views
        nv = sorted(ViewBox.NamedViews.values(), key=view_key)

        if self in nv:
            nv.remove(self)

        if self.menu is not None:
            self.menu.setViewList(nv)

        for ax in [0,1]:
            link = self.state['linkedViews'][ax]
            if isinstance(link, str):     ## axis has not been linked yet; see if it's possible now
                for v in nv:
                    if link == v.name:
                        self.linkView(ax, v)

    @staticmethod
    def updateAllViewLists():
        for v in ViewBox.AllViews:
            v.updateViewLists()

    @staticmethod
    def forgetView(vid, name):
        if ViewBox is None:     ## can happen as python is shutting down
            return
        if QtWidgets.QApplication.instance() is None:
            return
        ## Called with ID and name of view (the view itself is no longer available)
        for v in list(ViewBox.AllViews.keys()):
            if id(v) == vid:
                ViewBox.AllViews.pop(v)
                break
        ViewBox.NamedViews.pop(name, None)
        ViewBox.updateAllViewLists()

    @staticmethod
    def quit():
        ## called when the application is about to exit.
        ## this disables all callbacks, which might otherwise generate errors if invoked during exit.
        for k in ViewBox.AllViews:
            if isQObjectAlive(k) and getConfigOption('crashWarning'):
                sys.stderr.write('Warning: ViewBox should be closed before application exit.\n')

            try:
                k.destroyed.disconnect()
            except RuntimeError:  ## signal is already disconnected.
                pass
            except TypeError:  ## view has already been deleted (?)
                pass
            except AttributeError:  # PySide has deleted signal
                pass

    def locate(self, item, timeout=3.0, children=False):
        """
        Temporarily display the bounding rect of an item and lines connecting to the center of the view.
        This is useful for determining the location of items that may be out of the range of the ViewBox.
        if allChildren is True, then the bounding rect of all item's children will be shown instead.
        """
        self.clearLocate()

        if item.scene() is not self.scene():
            raise Exception("Item does not share a scene with this ViewBox.")

        c = self.viewRect().center()
        if children:
            br = self.mapFromItemToView(item, item.childrenBoundingRect()).boundingRect()
        else:
            br = self.mapFromItemToView(item, item.boundingRect()).boundingRect()

        g = ItemGroup()
        g.setParentItem(self.childGroup)
        self.locateGroup = g
        g.box = QtWidgets.QGraphicsRectItem(br)
        g.box.setParentItem(g)
        g.lines = []
        for p in (br.topLeft(), br.bottomLeft(), br.bottomRight(), br.topRight()):
            line = QtWidgets.QGraphicsLineItem(c.x(), c.y(), p.x(), p.y())
            line.setParentItem(g)
            g.lines.append(line)

        for item in g.childItems():
            item.setPen(fn.mkPen(color='y', width=3))
        g.setZValue(1000000)

        if children:
            g.path = QtWidgets.QGraphicsPathItem(g.childrenShape())
        else:
            g.path = QtWidgets.QGraphicsPathItem(g.shape())
        g.path.setParentItem(g)
        g.path.setPen(fn.mkPen('g'))
        g.path.setZValue(100)

        QtCore.QTimer.singleShot(timeout*1000, self.clearLocate)

    def clearLocate(self):
        if self.locateGroup is None:
            return
        self.scene().removeItem(self.locateGroup)
        self.locateGroup = None


from .ViewBoxMenu import ViewBoxMenu
