"""
ROI.py -  Interactive graphics items for GraphicsView (ROI widgets)
Copyright 2010  Luke Campagnola
Distributed under MIT/X11 license. See license.txt for more information.

Implements a series of graphics items which display movable/scalable/rotatable shapes
for use as region-of-interest markers. ROI class automatically handles extraction 
of array data from ImageItems.

The ROI class is meant to serve as the base for more specific types; see several examples
of how to build an ROI at the bottom of the file.
"""

import sys
from math import atan2, cos, degrees, hypot, sin

import numpy as np

from .. import functions as fn

#from numpy.linalg import norm
from ..Point import Point
from ..Qt import QtCore, QtGui, QtWidgets
from ..SRTTransform import SRTTransform
from .GraphicsObject import GraphicsObject
from .UIGraphicsItem import UIGraphicsItem

translate = QtCore.QCoreApplication.translate

__all__ = [
    'ROI', 
    'TestROI', 'RectROI', 'EllipseROI', 'CircleROI', 
    'LineROI', 'MultiLineROI', 'MultiRectROI', 'LineSegmentROI', 'PolyLineROI', 
    'CrosshairROI','TriangleROI'
]


def rectStr(r):
    return "[%f, %f] + [%f, %f]" % (r.x(), r.y(), r.width(), r.height())

class ROI(GraphicsObject):
    """
    Generic region-of-interest widget.
    
    Can be used for implementing many types of selection box with 
    rotate/translate/scale handles.
    ROIs can be customized to have a variety of shapes (by subclassing or using
    any of the built-in subclasses) and any combination of draggable handles
    that allow the user to manipulate the ROI.

    Default mouse interaction:

      * Left drag moves the ROI
      * Left drag + Ctrl moves the ROI with position snapping
      * Left drag + Alt rotates the ROI
      * Left drag + Alt + Ctrl rotates the ROI with angle snapping
      * Left drag + Shift scales the ROI
      * Left drag + Shift + Ctrl scales the ROI with size snapping

    In addition to the above interaction modes, it is possible to attach any
    number of handles to the ROI that can be dragged to change the ROI in
    various ways (see the ROI.add____Handle methods).


    ================ ===========================================================
    **Arguments**
    pos              (length-2 sequence) Indicates the position of the ROI's 
                     origin. For most ROIs, this is the lower-left corner of
                     its bounding rectangle.
    size             (length-2 sequence) Indicates the width and height of the 
                     ROI.
    angle            (float) The rotation of the ROI in degrees. Default is 0.
    invertible       (bool) If True, the user may resize the ROI to have 
                     negative width or height (assuming the ROI has scale
                     handles). Default is False.
    maxBounds        (QRect, QRectF, or None) Specifies boundaries that the ROI 
                     cannot be dragged outside of by the user. Default is None.
    snapSize         (float) The spacing of snap positions used when *scaleSnap*
                     or *translateSnap* are enabled. Default is 1.0.
    scaleSnap        (bool) If True, the width and height of the ROI are forced
                     to be integer multiples of *snapSize* when being resized
                     by the user. Default is False.
    translateSnap    (bool) If True, the x and y positions of the ROI are forced
                     to be integer multiples of *snapSize* when being resized
                     by the user. Default is False.
    rotateSnap       (bool) If True, the ROI angle is forced to a multiple of 
                     the ROI's snap angle (default is 15 degrees) when rotated
                     by the user. Default is False.
    parent           (QGraphicsItem) The graphics item parent of this ROI. It
                     is generally not necessary to specify the parent.
    pen              (QPen or argument to pg.mkPen) The pen to use when drawing
                     the shape of the ROI.
    hoverPen         (QPen or argument to mkPen) The pen to use while the
                     mouse is hovering over the ROI shape.
    handlePen        (QPen or argument to mkPen) The pen to use when drawing
                     the ROI handles.
    handleHoverPen   (QPen or argument to mkPen) The pen to use while the mouse
                     is hovering over an ROI handle.
    movable          (bool) If True, the ROI can be moved by dragging anywhere 
                     inside the ROI. Default is True.
    rotatable        (bool) If True, the ROI can be rotated by mouse drag + ALT
    resizable        (bool) If True, the ROI can be resized by mouse drag + 
                     SHIFT
    removable        (bool) If True, the ROI will be given a context menu with
                     an option to remove the ROI. The ROI emits
                     sigRemoveRequested when this menu action is selected.
                     Default is False.
    ================ ===========================================================
    
    
    
    ======================= ====================================================
    **Signals**
    sigRegionChangeFinished Emitted when the user stops dragging the ROI (or
                            one of its handles) or if the ROI is changed
                            programatically.
    sigRegionChangeStarted  Emitted when the user starts dragging the ROI (or
                            one of its handles).
    sigRegionChanged        Emitted any time the position of the ROI changes,
                            including while it is being dragged by the user.
    sigHoverEvent           Emitted when the mouse hovers over the ROI.
    sigClicked              Emitted when the user clicks on the ROI.
                            Note that clicking is disabled by default to prevent
                            stealing clicks from objects behind the ROI. To 
                            enable clicking, call 
                            roi.setAcceptedMouseButtons(QtCore.Qt.MouseButton.LeftButton). 
                            See QtWidgets.QGraphicsItem documentation for more 
                            details.
    sigRemoveRequested      Emitted when the user selects 'remove' from the 
                            ROI's context menu (if available).
    ======================= ====================================================
    """
    
    sigRegionChangeFinished = QtCore.Signal(object)
    sigRegionChangeStarted = QtCore.Signal(object)
    sigRegionChanged = QtCore.Signal(object)
    sigHoverEvent = QtCore.Signal(object)
    sigClicked = QtCore.Signal(object, object)
    sigRemoveRequested = QtCore.Signal(object)
    
    def __init__(self, pos, size=Point(1, 1), angle=0.0, invertible=False,
                 maxBounds=None, snapSize=1.0, scaleSnap=False,
                 translateSnap=False, rotateSnap=False, parent=None, pen=None,
                 hoverPen=None, handlePen=None, handleHoverPen=None,
                 movable=True, rotatable=True, resizable=True, removable=False,
                 aspectLocked=False):
        GraphicsObject.__init__(self, parent)
        self.setAcceptedMouseButtons(QtCore.Qt.MouseButton.NoButton)
        pos = Point(pos)
        size = Point(size)
        self.aspectLocked = aspectLocked
        self.translatable = movable
        self.rotatable = rotatable
        self.resizable = resizable
        self.removable = removable
        self.menu = None
        
        self.freeHandleMoved = False ## keep track of whether free handles have moved since last change signal was emitted.
        self.mouseHovering = False

        if pen is None:
            pen = (255, 255, 255)
        self.setPen(pen)
        if hoverPen is None:
            hoverPen = (255, 255, 0)
        self.hoverPen = fn.mkPen(hoverPen)
        if handlePen is None:
            handlePen = (150, 255, 255)
        self.handlePen = fn.mkPen(handlePen)
        if handleHoverPen is None:
            handleHoverPen = (255, 255, 0)
        self.handleHoverPen = handleHoverPen

        self.handles = []
        self.state = {'pos': Point(0,0), 'size': Point(1,1), 'angle': 0}  ## angle is in degrees for ease of Qt integration
        self.lastState = None
        self.setPos(pos)
        self.setAngle(angle)
        self.setSize(size)
        self.setZValue(10)
        self.isMoving = False
        
        self.handleSize = 5
        self.invertible = invertible
        self.maxBounds = maxBounds
        
        self.snapSize = snapSize
        self.translateSnap = translateSnap
        self.rotateSnap = rotateSnap
        self.rotateSnapAngle = 15.0
        self.scaleSnap = scaleSnap
        self.scaleSnapSize = snapSize

        # Implement mouse handling in a separate class to allow easier customization
        self.mouseDragHandler = MouseDragHandler(self)
    
    def getState(self):
        return self.stateCopy()

    def stateCopy(self):
        sc = {}
        sc['pos'] = Point(self.state['pos'])
        sc['size'] = Point(self.state['size'])
        sc['angle'] = self.state['angle']
        return sc
        
    def saveState(self):
        """Return the state of the widget in a format suitable for storing to 
        disk. (Points are converted to tuple)
        
        Combined with setState(), this allows ROIs to be easily saved and 
        restored."""
        state = {}
        state['pos'] = tuple(self.state['pos'])
        state['size'] = tuple(self.state['size'])
        state['angle'] = self.state['angle']
        return state
    
    def setState(self, state, update=True):
        """
        Set the state of the ROI from a structure generated by saveState() or
        getState().
        """
        self.setPos(state['pos'], update=False)
        self.setSize(state['size'], update=False)
        self.setAngle(state['angle'], update=update)
    
    def setZValue(self, z):
        QtWidgets.QGraphicsItem.setZValue(self, z)
        for h in self.handles:
            h['item'].setZValue(z+1)
        
    def parentBounds(self):
        """
        Return the bounding rectangle of this ROI in the coordinate system
        of its parent.        
        """
        return self.mapToParent(self.boundingRect()).boundingRect()

    def setPen(self, *args, **kwargs):
        """
        Set the pen to use when drawing the ROI shape.
        For arguments, see :func:`mkPen <pyqtgraph.mkPen>`.
        """
        self.pen = fn.mkPen(*args, **kwargs)
        self.currentPen = self.pen
        self.update()
        
    def size(self):
        """Return the size (w,h) of the ROI."""
        return self.getState()['size']
        
    def pos(self):
        """Return the position (x,y) of the ROI's origin. 
        For most ROIs, this will be the lower-left corner."""
        return self.getState()['pos']
        
    def angle(self):
        """Return the angle of the ROI in degrees."""
        return self.getState()['angle']
        
    def setPos(self, pos, y=None, update=True, finish=True):
        """Set the position of the ROI (in the parent's coordinate system).
        
        Accepts either separate (x, y) arguments or a single :class:`Point` or
        ``QPointF`` argument. 
        
        By default, this method causes both ``sigRegionChanged`` and
        ``sigRegionChangeFinished`` to be emitted. If *finish* is False, then
        ``sigRegionChangeFinished`` will not be emitted. You can then use 
        stateChangeFinished() to cause the signal to be emitted after a series
        of state changes.
        
        If *update* is False, the state change will be remembered but not processed and no signals 
        will be emitted. You can then use stateChanged() to complete the state change. This allows
        multiple change functions to be called sequentially while minimizing processing overhead
        and repeated signals. Setting ``update=False`` also forces ``finish=False``.
        """
        if update not in (True, False):
            raise TypeError("update argument must be bool")
        
        if y is None:
            pos = Point(pos)
        else:
            # avoid ambiguity where update is provided as a positional argument
            if isinstance(y, bool):
                raise TypeError("Positional arguments to setPos() must be numerical.")
            pos = Point(pos, y)

        self.state['pos'] = pos
        QtWidgets.QGraphicsItem.setPos(self, pos)
        if update:
            self.stateChanged(finish=finish)
        
    def setSize(self, size, center=None, centerLocal=None, snap=False, update=True, finish=True):
        """
        Set the ROI's size.
        
        =============== ==========================================================================
        **Arguments**
        size            (Point | QPointF | sequence) The final size of the ROI
        center          (None | Point) Optional center point around which the ROI is scaled,
                        expressed as [0-1, 0-1] over the size of the ROI.
        centerLocal     (None | Point) Same as *center*, but the position is expressed in the
                        local coordinate system of the ROI
        snap            (bool) If True, the final size is snapped to the nearest increment (see
                        ROI.scaleSnapSize)
        update          (bool) See setPos()
        finish          (bool) See setPos()
        =============== ==========================================================================
        """
        if update not in (True, False):
            raise TypeError("update argument must be bool")
        size = Point(size)
        if snap:
            size[0] = round(size[0] / self.scaleSnapSize) * self.scaleSnapSize
            size[1] = round(size[1] / self.scaleSnapSize) * self.scaleSnapSize

        if centerLocal is not None:
            oldSize = Point(self.state['size'])
            oldSize[0] = 1 if oldSize[0] == 0 else oldSize[0]
            oldSize[1] = 1 if oldSize[1] == 0 else oldSize[1]
            center = Point(centerLocal) / oldSize

        if center is not None:
            center = Point(center)
            c = self.mapToParent(Point(center) * self.state['size'])
            c1 = self.mapToParent(Point(center) * size)
            newPos = self.state['pos'] + c - c1
            self.setPos(newPos, update=False, finish=False)
        
        self.prepareGeometryChange()
        self.state['size'] = size
        if update:
            self.stateChanged(finish=finish)

    def setAngle(self, angle, center=None, centerLocal=None, snap=False, update=True, finish=True):
        """
        Set the ROI's rotation angle.
        
        =============== ==========================================================================
        **Arguments**
        angle           (float) The final ROI angle in degrees
        center          (None | Point) Optional center point around which the ROI is rotated,
                        expressed as [0-1, 0-1] over the size of the ROI.
        centerLocal     (None | Point) Same as *center*, but the position is expressed in the
                        local coordinate system of the ROI
        snap            (bool) If True, the final ROI angle is snapped to the nearest increment
                        (default is 15 degrees; see ROI.rotateSnapAngle)
        update          (bool) See setPos()
        finish          (bool) See setPos()
        =============== ==========================================================================
        """
        if update not in (True, False):
            raise TypeError("update argument must be bool")

        if snap is True:
            angle = round(angle / self.rotateSnapAngle) * self.rotateSnapAngle
        
        self.state['angle'] = angle
        tr = QtGui.QTransform()  # note: only rotation is contained in the transform
        tr.rotate(angle)
        if center is not None:
            centerLocal = Point(center) * self.state['size']
        if centerLocal is not None:
            centerLocal = Point(centerLocal)
            # rotate to new angle, keeping a specific point anchored as the center of rotation
            cc = self.mapToParent(centerLocal) - (tr.map(centerLocal) + self.state['pos'])
            self.translate(cc, update=False)

        self.setTransform(tr)
        if update:
            self.stateChanged(finish=finish)
        
    def scale(self, s, center=None, centerLocal=None, snap=False, update=True, finish=True):
        """
        Resize the ROI by scaling relative to *center*.
        See setPos() for an explanation of the *update* and *finish* arguments.
        """
        newSize = self.state['size'] * s
        self.setSize(newSize, center=center, centerLocal=centerLocal, snap=snap, update=update, finish=finish)
   
    def translate(self, *args, **kargs):
        """
        Move the ROI to a new position.
        Accepts either (x, y, snap) or ([x,y], snap) as arguments
        If the ROI is bounded and the move would exceed boundaries, then the ROI
        is moved to the nearest acceptable position instead.
        
        *snap* can be:
        
        =============== ==========================================================================
        None (default)  use self.translateSnap and self.snapSize to determine whether/how to snap
        False           do not snap
        Point(w,h)      snap to rectangular grid with spacing (w,h)
        True            snap using self.snapSize (and ignoring self.translateSnap)
        =============== ==========================================================================
           
        Also accepts *update* and *finish* arguments (see setPos() for a description of these).
        """

        if len(args) == 1:
            pt = args[0]
        else:
            pt = args
            
        newState = self.stateCopy()
        newState['pos'] = newState['pos'] + pt
        
        snap = kargs.get('snap', None)
        if snap is None:
            snap = self.translateSnap
        if snap is not False:
            newState['pos'] = self.getSnapPosition(newState['pos'], snap=snap)
        
        if self.maxBounds is not None:
            r = self.stateRect(newState)
            d = Point(0,0)
            if self.maxBounds.left() > r.left():
                d[0] = self.maxBounds.left() - r.left()
            elif self.maxBounds.right() < r.right():
                d[0] = self.maxBounds.right() - r.right()
            if self.maxBounds.top() > r.top():
                d[1] = self.maxBounds.top() - r.top()
            elif self.maxBounds.bottom() < r.bottom():
                d[1] = self.maxBounds.bottom() - r.bottom()
            newState['pos'] += d
        
        update = kargs.get('update', True)
        finish = kargs.get('finish', True)
        self.setPos(newState['pos'], update=update, finish=finish)

    def rotate(self, angle, center=None, snap=False, update=True, finish=True):
        """
        Rotate the ROI by *angle* degrees. 
        
        =============== ==========================================================================
        **Arguments**
        angle           (float) The angle in degrees to rotate
        center          (None | Point) Optional center point around which the ROI is rotated, in
                        the local coordinate system of the ROI
        snap            (bool) If True, the final ROI angle is snapped to the nearest increment
                        (default is 15 degrees; see ROI.rotateSnapAngle)
        update          (bool) See setPos()
        finish          (bool) See setPos()
        =============== ==========================================================================
        """
        self.setAngle(self.angle()+angle, center=center, snap=snap, update=update, finish=finish)

    def handleMoveStarted(self):
        self.preMoveState = self.getState()
        self.sigRegionChangeStarted.emit(self)
    
    def addTranslateHandle(self, pos, axes=None, item=None, name=None, index=None):
        """
        Add a new translation handle to the ROI. Dragging the handle will move 
        the entire ROI without changing its angle or shape. 
        
        Note that, by default, ROIs may be moved by dragging anywhere inside the
        ROI. However, for larger ROIs it may be desirable to disable this and
        instead provide one or more translation handles.
        
        =================== ====================================================
        **Arguments**
        pos                 (length-2 sequence) The position of the handle 
                            relative to the shape of the ROI. A value of (0,0)
                            indicates the origin, whereas (1, 1) indicates the
                            upper-right corner, regardless of the ROI's size.
        item                The Handle instance to add. If None, a new handle
                            will be created.
        name                The name of this handle (optional). Handles are 
                            identified by name when calling 
                            getLocalHandlePositions and getSceneHandlePositions.
        =================== ====================================================
        """
        pos = Point(pos)
        return self.addHandle({'name': name, 'type': 't', 'pos': pos, 'item': item}, index=index)
    
    def addFreeHandle(self, pos=None, axes=None, item=None, name=None, index=None):
        """
        Add a new free handle to the ROI. Dragging free handles has no effect
        on the position or shape of the ROI. 
        
        =================== ====================================================
        **Arguments**
        pos                 (length-2 sequence) The position of the handle 
                            relative to the shape of the ROI. A value of (0,0)
                            indicates the origin, whereas (1, 1) indicates the
                            upper-right corner, regardless of the ROI's size.
        item                The Handle instance to add. If None, a new handle
                            will be created.
        name                The name of this handle (optional). Handles are 
                            identified by name when calling 
                            getLocalHandlePositions and getSceneHandlePositions.
        =================== ====================================================
        """
        if pos is not None:
            pos = Point(pos)
        return self.addHandle({'name': name, 'type': 'f', 'pos': pos, 'item': item}, index=index)
    
    def addScaleHandle(self, pos, center, axes=None, item=None, name=None, lockAspect=False, index=None):
        """
        Add a new scale handle to the ROI. Dragging a scale handle allows the
        user to change the height and/or width of the ROI.
        
        =================== ====================================================
        **Arguments**
        pos                 (length-2 sequence) The position of the handle 
                            relative to the shape of the ROI. A value of (0,0)
                            indicates the origin, whereas (1, 1) indicates the
                            upper-right corner, regardless of the ROI's size.
        center              (length-2 sequence) The center point around which 
                            scaling takes place. If the center point has the
                            same x or y value as the handle position, then 
                            scaling will be disabled for that axis.
        item                The Handle instance to add. If None, a new handle
                            will be created.
        name                The name of this handle (optional). Handles are 
                            identified by name when calling 
                            getLocalHandlePositions and getSceneHandlePositions.
        =================== ====================================================
        """
        pos = Point(pos)
        center = Point(center)
        info = {'name': name, 'type': 's', 'center': center, 'pos': pos, 'item': item, 'lockAspect': lockAspect}
        if pos.x() == center.x():
            info['xoff'] = True
        if pos.y() == center.y():
            info['yoff'] = True
        return self.addHandle(info, index=index)
    
    def addRotateHandle(self, pos, center, item=None, name=None, index=None):
        """
        Add a new rotation handle to the ROI. Dragging a rotation handle allows 
        the user to change the angle of the ROI.
        
        =================== ====================================================
        **Arguments**
        pos                 (length-2 sequence) The position of the handle 
                            relative to the shape of the ROI. A value of (0,0)
                            indicates the origin, whereas (1, 1) indicates the
                            upper-right corner, regardless of the ROI's size.
        center              (length-2 sequence) The center point around which 
                            rotation takes place.
        item                The Handle instance to add. If None, a new handle
                            will be created.
        name                The name of this handle (optional). Handles are 
                            identified by name when calling 
                            getLocalHandlePositions and getSceneHandlePositions.
        =================== ====================================================
        """
        pos = Point(pos)
        center = Point(center)
        return self.addHandle({'name': name, 'type': 'r', 'center': center, 'pos': pos, 'item': item}, index=index)
    
    def addScaleRotateHandle(self, pos, center, item=None, name=None, index=None):
        """
        Add a new scale+rotation handle to the ROI. When dragging a handle of 
        this type, the user can simultaneously rotate the ROI around an 
        arbitrary center point as well as scale the ROI by dragging the handle
        toward or away from the center point.
        
        =================== ====================================================
        **Arguments**
        pos                 (length-2 sequence) The position of the handle 
                            relative to the shape of the ROI. A value of (0,0)
                            indicates the origin, whereas (1, 1) indicates the
                            upper-right corner, regardless of the ROI's size.
        center              (length-2 sequence) The center point around which 
                            scaling and rotation take place.
        item                The Handle instance to add. If None, a new handle
                            will be created.
        name                The name of this handle (optional). Handles are 
                            identified by name when calling 
                            getLocalHandlePositions and getSceneHandlePositions.
        =================== ====================================================
        """
        pos = Point(pos)
        center = Point(center)
        if pos[0] == center[0] and pos[1] == center[1]:
            raise Exception("Scale/rotate handles cannot be at their center point.")
        return self.addHandle({'name': name, 'type': 'sr', 'center': center, 'pos': pos, 'item': item}, index=index)
    
    def addRotateFreeHandle(self, pos, center, axes=None, item=None, name=None, index=None):
        """
        Add a new rotation+free handle to the ROI. When dragging a handle of 
        this type, the user can rotate the ROI around an 
        arbitrary center point, while moving toward or away from the center 
        point has no effect on the shape of the ROI.
        
        =================== ====================================================
        **Arguments**
        pos                 (length-2 sequence) The position of the handle 
                            relative to the shape of the ROI. A value of (0,0)
                            indicates the origin, whereas (1, 1) indicates the
                            upper-right corner, regardless of the ROI's size.
        center              (length-2 sequence) The center point around which 
                            rotation takes place.
        item                The Handle instance to add. If None, a new handle
                            will be created.
        name                The name of this handle (optional). Handles are 
                            identified by name when calling 
                            getLocalHandlePositions and getSceneHandlePositions.
        =================== ====================================================
        """
        pos = Point(pos)
        center = Point(center)
        return self.addHandle({'name': name, 'type': 'rf', 'center': center, 'pos': pos, 'item': item}, index=index)
    
    def addHandle(self, info, index=None):
        ## If a Handle was not supplied, create it now
        if 'item' not in info or info['item'] is None:
            h = Handle(self.handleSize, typ=info['type'], pen=self.handlePen,
                       hoverPen=self.handleHoverPen, parent=self)
            info['item'] = h
        else:
            h = info['item']
            if info['pos'] is None:
                info['pos'] = h.pos()
        h.setPos(info['pos'] * self.state['size'])

        ## connect the handle to this ROI
        #iid = len(self.handles)
        h.connectROI(self)
        if index is None:
            self.handles.append(info)
        else:
            self.handles.insert(index, info)
        
        h.setZValue(self.zValue()+1)
        self.stateChanged()
        return h
    
    def indexOfHandle(self, handle):
        """
        Return the index of *handle* in the list of this ROI's handles.
        """
        if isinstance(handle, Handle):
            index = [i for i, info in enumerate(self.handles) if info['item'] is handle]    
            if len(index) == 0:
                raise Exception("Cannot return handle index; not attached to this ROI")
            return index[0]
        else:
            return handle
        
    def removeHandle(self, handle):
        """Remove a handle from this ROI. Argument may be either a Handle 
        instance or the integer index of the handle."""
        index = self.indexOfHandle(handle)
            
        handle = self.handles[index]['item']
        self.handles.pop(index)
        handle.disconnectROI(self)
        if len(handle.rois) == 0 and self.scene() is not None:
            self.scene().removeItem(handle)
        self.stateChanged()
    
    def replaceHandle(self, oldHandle, newHandle):
        """Replace one handle in the ROI for another. This is useful when 
        connecting multiple ROIs together.
        
        *oldHandle* may be a Handle instance or the index of a handle to be
        replaced."""
        index = self.indexOfHandle(oldHandle)
        info = self.handles[index]
        self.removeHandle(index)
        info['item'] = newHandle
        info['pos'] = newHandle.pos()
        self.addHandle(info, index=index)
        
    def checkRemoveHandle(self, handle):
        ## This is used when displaying a Handle's context menu to determine
        ## whether removing is allowed. 
        ## Subclasses may wish to override this to disable the menu entry.
        ## Note: by default, handles are not user-removable even if this method returns True.
        return True
        
    def getLocalHandlePositions(self, index=None):
        """Returns the position of handles in the ROI's coordinate system.
        
        The format returned is a list of (name, pos) tuples.
        """
        if index is None:
            positions = []
            for h in self.handles:
                positions.append((h['name'], h['pos']))
            return positions
        else:
            return (self.handles[index]['name'], self.handles[index]['pos'])
            
    def getSceneHandlePositions(self, index=None):
        """Returns the position of handles in the scene coordinate system.
        
        The format returned is a list of (name, pos) tuples.
        """
        if index is None:
            positions = []
            for h in self.handles:
                positions.append((h['name'], h['item'].scenePos()))
            return positions
        else:
            return (self.handles[index]['name'], self.handles[index]['item'].scenePos())
        
    def getHandles(self):
        """
        Return a list of this ROI's Handles.
        """
        return [h['item'] for h in self.handles]
    
    def mapSceneToParent(self, pt):
        return self.mapToParent(self.mapFromScene(pt))

    def setSelected(self, s):
        QtWidgets.QGraphicsItem.setSelected(self, s)
        #print "select", self, s
        if s:
            for h in self.handles:
                h['item'].show()
        else:
            for h in self.handles:
                h['item'].hide()

    def hoverEvent(self, ev):
        hover = False
        if not ev.isExit():
            if self.translatable and ev.acceptDrags(QtCore.Qt.MouseButton.LeftButton):
                hover=True
                
            for btn in [QtCore.Qt.MouseButton.LeftButton, QtCore.Qt.MouseButton.RightButton, QtCore.Qt.MouseButton.MiddleButton]:
                if (self.acceptedMouseButtons() & btn) and ev.acceptClicks(btn):
                    hover=True
            if self.contextMenuEnabled():
                ev.acceptClicks(QtCore.Qt.MouseButton.RightButton)
                
        if hover:
            self.setMouseHover(True)
            ev.acceptClicks(QtCore.Qt.MouseButton.LeftButton)  ## If the ROI is hilighted, we should accept all clicks to avoid confusion.
            ev.acceptClicks(QtCore.Qt.MouseButton.RightButton)
            ev.acceptClicks(QtCore.Qt.MouseButton.MiddleButton)
            self.sigHoverEvent.emit(self)
        else:
            self.setMouseHover(False)

    def setMouseHover(self, hover):
        ## Inform the ROI that the mouse is(not) hovering over it
        if self.mouseHovering == hover:
            return
        self.mouseHovering = hover
        self._updateHoverColor()
        
    def _updateHoverColor(self):
        pen = self._makePen()
        if self.currentPen != pen:
            self.currentPen = pen
            self.update()
        
    def _makePen(self):
        # Generate the pen color for this ROI based on its current state.
        if self.mouseHovering:
            return self.hoverPen
        else:
            return self.pen

    def contextMenuEnabled(self):
        return self.removable
    
    def raiseContextMenu(self, ev):
        if not self.contextMenuEnabled():
            return
        menu = self.getMenu()
        menu = self.scene().addParentContextMenus(self, menu, ev)
        pos = ev.screenPos()
        menu.popup(QtCore.QPoint(int(pos.x()), int(pos.y())))

    def getMenu(self):
        if self.menu is None:
            self.menu = QtWidgets.QMenu()
            self.menu.setTitle(translate("ROI", "ROI"))
            remAct = QtGui.QAction(translate("ROI", "Remove ROI"), self.menu)
            remAct.triggered.connect(self.removeClicked)
            self.menu.addAction(remAct)
            self.menu.remAct = remAct
        # ROI menu may be requested when showing the handle context menu, so
        # return the menu but disable it if the ROI isn't removable
        self.menu.setEnabled(self.contextMenuEnabled())
        return self.menu

    def removeClicked(self):
        ## Send remove event only after we have exited the menu event handler
        QtCore.QTimer.singleShot(0, self._emitRemoveRequest)

    def _emitRemoveRequest(self):
        self.sigRemoveRequested.emit(self)

    def mouseDragEvent(self, ev):
        self.mouseDragHandler.mouseDragEvent(ev)

    def mouseClickEvent(self, ev):
        if ev.button() == QtCore.Qt.MouseButton.RightButton and self.isMoving:
            ev.accept()
            self.cancelMove()
        if ev.button() == QtCore.Qt.MouseButton.RightButton and self.contextMenuEnabled():
            self.raiseContextMenu(ev)
            ev.accept()
        elif self.acceptedMouseButtons() & ev.button():
            ev.accept()
            self.sigClicked.emit(self, ev)
        else:
            ev.ignore()

    def _moveStarted(self):
        self.isMoving = True
        self.preMoveState = self.getState()
        self.sigRegionChangeStarted.emit(self)

    def _moveFinished(self):
        if self.isMoving:
            self.stateChangeFinished()
        self.isMoving = False

    def cancelMove(self):
        self.isMoving = False
        self.setState(self.preMoveState)

    def checkPointMove(self, handle, pos, modifiers):
        """When handles move, they must ask the ROI if the move is acceptable.
        By default, this always returns True. Subclasses may wish override.
        """
        return True

    def movePoint(self, handle, pos, modifiers=None, finish=True, coords='parent'):
        ## called by Handles when they are moved. 
        ## pos is the new position of the handle in scene coords, as requested by the handle.
        if modifiers is None:
            modifiers = QtCore.Qt.KeyboardModifier.NoModifier
        newState = self.stateCopy()
        index = self.indexOfHandle(handle)
        h = self.handles[index]
        p0 = self.mapToParent(h['pos'] * self.state['size'])
        p1 = Point(pos)
        
        if coords == 'parent':
            pass
        elif coords == 'scene':
            p1 = self.mapSceneToParent(p1)
        else:
            raise Exception("New point location must be given in either 'parent' or 'scene' coordinates.")

        ## Handles with a 'center' need to know their local position relative to the center point (lp0, lp1)
        if 'center' in h:
            c = h['center']
            cs = c * self.state['size']
            lp0 = self.mapFromParent(p0) - cs
            lp1 = self.mapFromParent(p1) - cs
        
        if h['type'] == 't':
            snap = True if (modifiers & QtCore.Qt.KeyboardModifier.ControlModifier) else None
            self.translate(p1-p0, snap=snap, update=False)
        
        elif h['type'] == 'f':
            newPos = self.mapFromParent(p1)
            h['item'].setPos(newPos)
            h['pos'] = newPos
            self.freeHandleMoved = True
            
        elif h['type'] == 's':
            ## If a handle and its center have the same x or y value, we can't scale across that axis.
            if h['center'][0] == h['pos'][0]:
                lp1[0] = 0
            if h['center'][1] == h['pos'][1]:
                lp1[1] = 0
            
            ## snap 
            if self.scaleSnap or (modifiers & QtCore.Qt.KeyboardModifier.ControlModifier):
                lp1[0] = round(lp1[0] / self.scaleSnapSize) * self.scaleSnapSize
                lp1[1] = round(lp1[1] / self.scaleSnapSize) * self.scaleSnapSize
                
            ## preserve aspect ratio (this can override snapping)
            if h['lockAspect'] or (modifiers & QtCore.Qt.KeyboardModifier.AltModifier):
                #arv = Point(self.preMoveState['size']) - 
                lp1 = lp1.proj(lp0)
            
            ## determine scale factors and new size of ROI
            hs = h['pos'] - c
            if hs[0] == 0:
                hs[0] = 1
            if hs[1] == 0:
                hs[1] = 1
            newSize = lp1 / hs
            
            ## Perform some corrections and limit checks
            if newSize[0] == 0:
                newSize[0] = newState['size'][0]
            if newSize[1] == 0:
                newSize[1] = newState['size'][1]
            if not self.invertible:
                if newSize[0] < 0:
                    newSize[0] = newState['size'][0]
                if newSize[1] < 0:
                    newSize[1] = newState['size'][1]
            if self.aspectLocked:
                newSize[0] = newSize[1]
            
            ## Move ROI so the center point occupies the same scene location after the scale
            s0 = c * self.state['size']
            s1 = c * newSize
            cc = self.mapToParent(s0 - s1) - self.mapToParent(Point(0, 0))
            
            ## update state, do more boundary checks
            newState['size'] = newSize
            newState['pos'] = newState['pos'] + cc
            if self.maxBounds is not None:
                r = self.stateRect(newState)
                if not self.maxBounds.contains(r):
                    return
            
            self.setPos(newState['pos'], update=False)
            self.setSize(newState['size'], update=False)
        
        elif h['type'] in ['r', 'rf']:
            if h['type'] == 'rf':
                self.freeHandleMoved = True
            
            if not self.rotatable:
                return
            ## If the handle is directly over its center point, we can't compute an angle.
            try:
                if lp1.length() == 0 or lp0.length() == 0:
                    return
            except OverflowError:
                return
            
            ## determine new rotation angle, constrained if necessary
            ang = newState['angle'] - lp0.angle(lp1)
            if ang is None:  ## this should never happen..
                return
            if self.rotateSnap or (modifiers & QtCore.Qt.KeyboardModifier.ControlModifier):
                ang = round(ang / self.rotateSnapAngle) * self.rotateSnapAngle
            
            ## create rotation transform
            tr = QtGui.QTransform()
            tr.rotate(ang)
            
            ## move ROI so that center point remains stationary after rotate
            cc = self.mapToParent(cs) - (tr.map(cs) + self.state['pos'])
            newState['angle'] = ang
            newState['pos'] = newState['pos'] + cc
            
            ## check boundaries, update
            if self.maxBounds is not None:
                r = self.stateRect(newState)
                if not self.maxBounds.contains(r):
                    return
            self.setPos(newState['pos'], update=False)
            self.setAngle(ang, update=False)
            
            ## If this is a free-rotate handle, its distance from the center may change.
            
            if h['type'] == 'rf':
                h['item'].setPos(self.mapFromScene(p1))  ## changes ROI coordinates of handle
                h['pos'] = self.mapFromParent(p1)
                
        elif h['type'] == 'sr':
            try:
                if lp1.length() == 0 or lp0.length() == 0:
                    return
            except OverflowError:
                return
            
            ang = newState['angle'] - lp0.angle(lp1)
            if ang is None:
                return
            if self.rotateSnap or (modifiers & QtCore.Qt.KeyboardModifier.ControlModifier):
                ang = round(ang / self.rotateSnapAngle) * self.rotateSnapAngle

            if self.aspectLocked or h['center'][0] != h['pos'][0]:
                newState['size'][0] = self.state['size'][0] * lp1.length() / lp0.length()
                if self.scaleSnap:  # use CTRL only for angular snap here.
                    newState['size'][0] = round(newState['size'][0] / self.snapSize) * self.snapSize

            if self.aspectLocked or h['center'][1] != h['pos'][1]:
                newState['size'][1] = self.state['size'][1] * lp1.length() / lp0.length()
                if self.scaleSnap:  # use CTRL only for angular snap here.
                    newState['size'][1] = round(newState['size'][1] / self.snapSize) * self.snapSize

            if newState['size'][0] == 0:
                newState['size'][0] = 1
            if newState['size'][1] == 0:
                newState['size'][1] = 1

            c1 = c * newState['size']
            tr = QtGui.QTransform()
            tr.rotate(ang)
            
            cc = self.mapToParent(cs) - (tr.map(c1) + self.state['pos'])
            newState['angle'] = ang
            newState['pos'] = newState['pos'] + cc
            if self.maxBounds is not None:
                r = self.stateRect(newState)
                if not self.maxBounds.contains(r):
                    return
            
            self.setState(newState, update=False)
        
        self.stateChanged(finish=finish)
    
    def stateChanged(self, finish=True):
        """Process changes to the state of the ROI.
        If there are any changes, then the positions of handles are updated accordingly
        and sigRegionChanged is emitted. If finish is True, then 
        sigRegionChangeFinished will also be emitted."""
        
        changed = False
        if self.lastState is None:
            changed = True
        else:
            state = self.getState()
            for k in list(state.keys()):
                if state[k] != self.lastState[k]:
                    changed = True
        
        self.prepareGeometryChange()
        if changed:
            ## Move all handles to match the current configuration of the ROI
            for h in self.handles:
                if h['item'] in self.childItems():
                    h['item'].setPos(h['pos'] * self.state['size'])
                    
            self.update()
            self.sigRegionChanged.emit(self)
        elif self.freeHandleMoved:
            self.sigRegionChanged.emit(self)
            
        self.freeHandleMoved = False
        self.lastState = self.getState()
            
        if finish:
            self.stateChangeFinished()
            self.informViewBoundsChanged()
    
    def stateChangeFinished(self):
        self.sigRegionChangeFinished.emit(self)
    
    def stateRect(self, state):
        r = QtCore.QRectF(0, 0, state['size'][0], state['size'][1])
        tr = QtGui.QTransform()
        tr.rotate(-state['angle'])
        r = tr.mapRect(r)
        return r.adjusted(state['pos'][0], state['pos'][1], state['pos'][0], state['pos'][1])
    
    def getSnapPosition(self, pos, snap=None):
        ## Given that pos has been requested, return the nearest snap-to position
        ## optionally, snap may be passed in to specify a rectangular snap grid.
        ## override this function for more interesting snap functionality..
        
        if snap is None or snap is True:
            if self.snapSize is None:
                return pos
            snap = Point(self.snapSize, self.snapSize)
        
        return Point(
            round(pos[0] / snap[0]) * snap[0],
            round(pos[1] / snap[1]) * snap[1]
        )
    
    def boundingRect(self):
        return QtCore.QRectF(0, 0, self.state['size'][0], self.state['size'][1]).normalized()

    def paint(self, p, opt, widget):
        # Note: don't use self.boundingRect here, because subclasses may need to redefine it.
        r = QtCore.QRectF(0, 0, self.state['size'][0], self.state['size'][1]).normalized()
        
        p.setRenderHint(QtGui.QPainter.RenderHint.Antialiasing)
        p.setPen(self.currentPen)
        p.translate(r.left(), r.top())
        p.scale(r.width(), r.height())
        p.drawRect(0, 0, 1, 1)

    def getArraySlice(self, data, img, axes=(0,1), returnSlice=True):
        """Return a tuple of slice objects that can be used to slice the region
        from *data* that is covered by the bounding rectangle of this ROI.
        Also returns the transform that maps the ROI into data coordinates.
        
        If returnSlice is set to False, the function returns a pair of tuples with the values that would have 
        been used to generate the slice objects. ((ax0Start, ax0Stop), (ax1Start, ax1Stop))
        
        If the slice cannot be computed (usually because the scene/transforms are not properly
        constructed yet), then the method returns None.
        """
        ## Determine shape of array along ROI axes
        dShape = (data.shape[axes[0]], data.shape[axes[1]])
        
        ## Determine transform that maps ROI bounding box to image coordinates
        try:
            tr = self.sceneTransform() * fn.invertQTransform(img.sceneTransform())
        except np.linalg.linalg.LinAlgError:
            return None
            
        ## Modify transform to scale from image coords to data coords
        axisOrder = img.axisOrder
        if axisOrder == 'row-major':
            tr.scale(float(dShape[1]) / img.width(), float(dShape[0]) / img.height())
        else:
            tr.scale(float(dShape[0]) / img.width(), float(dShape[1]) / img.height())
        
        ## Transform ROI bounds into data bounds
        dataBounds = tr.mapRect(self.boundingRect())
        
        ## Intersect transformed ROI bounds with data bounds
        if axisOrder == 'row-major':
            intBounds = dataBounds.intersected(QtCore.QRectF(0, 0, dShape[1], dShape[0]))
        else:
            intBounds = dataBounds.intersected(QtCore.QRectF(0, 0, dShape[0], dShape[1]))
        
        ## Determine index values to use when referencing the array. 
        bounds = (
            (int(min(intBounds.left(), intBounds.right())), int(1+max(intBounds.left(), intBounds.right()))),
            (int(min(intBounds.bottom(), intBounds.top())), int(1+max(intBounds.bottom(), intBounds.top())))
        )
        if axisOrder == 'row-major':
            bounds = bounds[::-1]
        
        if returnSlice:
            ## Create slice objects
            sl = [slice(None)] * data.ndim
            sl[axes[0]] = slice(*bounds[0])
            sl[axes[1]] = slice(*bounds[1])
            return tuple(sl), tr
        else:
            return bounds, tr

    def getArrayRegion(self, data, img, axes=(0,1), returnMappedCoords=False, **kwds):
        r"""Use the position and orientation of this ROI relative to an imageItem
        to pull a slice from an array.

        =================== ====================================================
        **Arguments**
        data                The array to slice from. Note that this array does
                            *not* have to be the same data that is represented
                            in *img*.
        img                 (ImageItem or other suitable QGraphicsItem)
                            Used to determine the relationship between the 
                            ROI and the boundaries of *data*.
        axes                (length-2 tuple) Specifies the axes in *data* that
                            correspond to the (x, y) axes of *img*. If the
                            image's axis order is set to
                            'row-major', then the axes are instead specified in
                            (y, x) order.
        returnMappedCoords  (bool) If True, the array slice is returned along
                            with a corresponding array of coordinates that were
                            used to extract data from the original array.
        \**kwds             All keyword arguments are passed to 
                            :func:`affineSlice <pyqtgraph.affineSlice>`.
        =================== ====================================================
        
        This method uses :func:`affineSlice <pyqtgraph.affineSlice>` to generate
        the slice from *data* and uses :func:`getAffineSliceParams <pyqtgraph.ROI.getAffineSliceParams>`
        to determine the parameters to pass to :func:`affineSlice <pyqtgraph.affineSlice>`.
        
        If *returnMappedCoords* is True, then the method returns a tuple (result, coords) 
        such that coords is the set of coordinates used to interpolate values from the original
        data, mapped into the parent coordinate system of the image. This is useful, when slicing
        data from images that have been transformed, for determining the location of each value
        in the sliced data.
        
        All extra keyword arguments are passed to :func:`affineSlice <pyqtgraph.affineSlice>`.
        """
        # this is a hidden argument for internal use
        fromBR = kwds.pop('fromBoundingRect', False)
        
        # Automaticaly compute missing parameters
        _shape, _vectors, _origin = self.getAffineSliceParams(data, img, axes, fromBoundingRect=fromBR)
        
        # Replace them with user defined parameters if defined
        shape = kwds.pop('shape', _shape)
        vectors = kwds.pop('vectors', _vectors)
        origin = kwds.pop('origin', _origin)
        
        if not returnMappedCoords:
            rgn = fn.affineSlice(data, shape=shape, vectors=vectors, origin=origin, axes=axes, **kwds)
            return rgn
        else:
            kwds['returnCoords'] = True
            result, coords = fn.affineSlice(data, shape=shape, vectors=vectors, origin=origin, axes=axes, **kwds)
            
            ### map coordinates and return
            mapped = fn.transformCoordinates(img.transform(), coords)
            return result, mapped

    def _getArrayRegionForArbitraryShape(self, data, img, axes=(0,1), returnMappedCoords=False, **kwds):
        """
        Return the result of :meth:`~pyqtgraph.ROI.getArrayRegion`, masked by
        the shape of the ROI. Values outside the ROI shape are set to 0.

        See :meth:`~pyqtgraph.ROI.getArrayRegion` for a description of the
        arguments.
        """
        if returnMappedCoords:
            sliced, mappedCoords = ROI.getArrayRegion(
                self, data, img, axes, returnMappedCoords, fromBoundingRect=True, **kwds)
        else:
            sliced = ROI.getArrayRegion(
                self, data, img, axes, returnMappedCoords, fromBoundingRect=True, **kwds)

        if img.axisOrder == 'col-major':
            mask = self.renderShapeMask(sliced.shape[axes[0]], sliced.shape[axes[1]])
        else:
            mask = self.renderShapeMask(sliced.shape[axes[1]], sliced.shape[axes[0]])
            mask = mask.T

        # reshape mask to ensure it is applied to the correct data axes
        shape = [1] * data.ndim
        shape[axes[0]] = sliced.shape[axes[0]]
        shape[axes[1]] = sliced.shape[axes[1]]
        mask = mask.reshape(shape)

        if returnMappedCoords:
            return sliced * mask, mappedCoords
        else:
            return sliced * mask

    def getAffineSliceParams(self, data, img, axes=(0,1), fromBoundingRect=False):
        """
        Returns the parameters needed to use :func:`affineSlice <pyqtgraph.affineSlice>`
        (shape, vectors, origin) to extract a subset of *data* using this ROI 
        and *img* to specify the subset.
        
        If *fromBoundingRect* is True, then the ROI's bounding rectangle is used
        rather than the shape of the ROI.
        
        See :func:`getArrayRegion <pyqtgraph.ROI.getArrayRegion>` for more information.
        """
        if self.scene() is not img.scene():
            raise Exception("ROI and target item must be members of the same scene.")
        
        origin = img.mapToData(self.mapToItem(img, QtCore.QPointF(0, 0)))
        
        ## vx and vy point in the directions of the slice axes, but must be scaled properly
        vx = img.mapToData(self.mapToItem(img, QtCore.QPointF(1, 0))) - origin
        vy = img.mapToData(self.mapToItem(img, QtCore.QPointF(0, 1))) - origin
        
        lvx = hypot(vx.x(), vx.y())  # length
        lvy = hypot(vy.x(), vy.y())  # length
        ##img.width is number of pixels, not width of item.
        ##need pxWidth and pxHeight instead of pxLen ?
        sx = 1.0 / lvx
        sy = 1.0 / lvy
        
        vectors = ((vx.x()*sx, vx.y()*sx), (vy.x()*sy, vy.y()*sy))
        if fromBoundingRect is True:
            shape = self.boundingRect().width(), self.boundingRect().height()
            origin = img.mapToData(self.mapToItem(img, self.boundingRect().topLeft()))
            origin = (origin.x(), origin.y())
        else:
            shape = self.state['size']
            origin = (origin.x(), origin.y())
        
        shape = [abs(shape[0]/sx), abs(shape[1]/sy)]
        
        if img.axisOrder == 'row-major':
            # transpose output
            vectors = vectors[::-1]
            shape = shape[::-1]

        return shape, vectors, origin

    def renderShapeMask(self, width, height):
        """Return an array of 0.0-1.0 into which the shape of the item has been drawn.
        
        This can be used to mask array selections.
        """
        if width == 0 or height == 0:
            return np.empty((width, height), dtype=float)
        
        im = QtGui.QImage(width, height, QtGui.QImage.Format.Format_ARGB32)
        im.fill(QtCore.Qt.GlobalColor.transparent)
        p = QtGui.QPainter(im)
        p.setPen(fn.mkPen(None))
        p.setBrush(fn.mkBrush('w'))
        shape = self.shape()
        bounds = shape.boundingRect()
        p.scale(im.width() / bounds.width(), im.height() / bounds.height())
        p.translate(-bounds.topLeft())
        p.drawPath(shape)
        p.end()
        cidx = 0 if sys.byteorder == 'little' else 3
        mask = fn.ndarray_from_qimage(im)[...,cidx].T
        return mask.astype(float) / 255
        
    def getGlobalTransform(self, relativeTo=None):
        """Return global transformation (rotation angle+translation) required to move 
        from relative state to current state. If relative state isn't specified,
        then we use the state of the ROI when mouse is pressed."""
        if relativeTo is None:
            relativeTo = self.preMoveState
        st = self.getState()
        
        ## this is only allowed because we will be comparing the two 
        relativeTo['scale'] = relativeTo['size']
        st['scale'] = st['size']
        
        t1 = SRTTransform(relativeTo)
        t2 = SRTTransform(st)
        return t2/t1

    def applyGlobalTransform(self, tr):
        st = self.getState()
        
        st['scale'] = st['size']
        st = SRTTransform(st)
        st = (st * tr).saveState()
        st['size'] = st['scale']
        self.setState(st)


class Handle(UIGraphicsItem):
    """
    Handle represents a single user-interactable point attached to an ROI. They
    are usually created by a call to one of the ROI.add___Handle() methods.
    
    Handles are represented as a square, diamond, or circle, and are drawn with 
    fixed pixel size regardless of the scaling of the view they are displayed in.
    
    Handles may be dragged to change the position, size, orientation, or other
    properties of the ROI they are attached to.
    """
    types = {   ## defines number of sides, start angle for each handle type
        't': (4, np.pi/4),
        'f': (4, np.pi/4), 
        's': (4, 0),
        'r': (12, 0),
        'sr': (12, 0),
        'rf': (12, 0),
    }

    sigClicked = QtCore.Signal(object, object)   # self, event
    sigRemoveRequested = QtCore.Signal(object)   # self
    
    def __init__(self, radius, typ=None, pen=(200, 200, 220),
                 hoverPen=(255, 255, 0), parent=None, deletable=False):
        self.rois = []
        self.radius = radius
        self.typ = typ
        self.pen = fn.mkPen(pen)
        self.hoverPen = fn.mkPen(hoverPen)
        self.currentPen = self.pen
        self.pen.setWidth(0)
        self.pen.setCosmetic(True)
        self.isMoving = False
        self.sides, self.startAng = self.types[typ]
        self.buildPath()
        self._shape = None
        self.menu = self.buildMenu()
        
        UIGraphicsItem.__init__(self, parent=parent)
        self.setAcceptedMouseButtons(QtCore.Qt.MouseButton.NoButton)
        self.deletable = deletable
        if deletable:
            self.setAcceptedMouseButtons(QtCore.Qt.MouseButton.RightButton)        
        self.setZValue(11)
            
    def connectROI(self, roi):
        ### roi is the "parent" roi, i is the index of the handle in roi.handles
        self.rois.append(roi)
        
    def disconnectROI(self, roi):
        self.rois.remove(roi)
            
    def setDeletable(self, b):
        self.deletable = b
        if b:
            self.setAcceptedMouseButtons(self.acceptedMouseButtons() | QtCore.Qt.MouseButton.RightButton)
        else:
            self.setAcceptedMouseButtons(self.acceptedMouseButtons() & ~QtCore.Qt.MouseButton.RightButton)

    def removeClicked(self):
        self.sigRemoveRequested.emit(self)

    def hoverEvent(self, ev):
        hover = False
        if not ev.isExit():
            if ev.acceptDrags(QtCore.Qt.MouseButton.LeftButton):
                hover=True
            for btn in [QtCore.Qt.MouseButton.LeftButton, QtCore.Qt.MouseButton.RightButton, QtCore.Qt.MouseButton.MiddleButton]:
                if (self.acceptedMouseButtons() & btn) and ev.acceptClicks(btn):
                    hover=True
                    
        if hover:
            self.currentPen = self.hoverPen
        else:
            self.currentPen = self.pen
        self.update()

    def mouseClickEvent(self, ev):
        ## right-click cancels drag
        if ev.button() == QtCore.Qt.MouseButton.RightButton and self.isMoving:
            self.isMoving = False  ## prevents any further motion
            self.movePoint(self.startPos, finish=True)
            ev.accept()
        elif self.acceptedMouseButtons() & ev.button():
            ev.accept()
            if ev.button() == QtCore.Qt.MouseButton.RightButton and self.deletable:
                self.raiseContextMenu(ev)
            self.sigClicked.emit(self, ev)
        else:
            ev.ignore()
                
    def buildMenu(self):
        menu = QtWidgets.QMenu()
        menu.setTitle(translate("ROI", "Handle"))
        self.removeAction = menu.addAction(translate("ROI", "Remove handle"), self.removeClicked) 
        return menu
        
    def getMenu(self):
        return self.menu

    def raiseContextMenu(self, ev):
        menu = self.scene().addParentContextMenus(self, self.getMenu(), ev)
        
        ## Make sure it is still ok to remove this handle
        removeAllowed = all(r.checkRemoveHandle(self) for r in self.rois)
        self.removeAction.setEnabled(removeAllowed)
        pos = ev.screenPos()
        menu.popup(QtCore.QPoint(int(pos.x()), int(pos.y())))    

    def mouseDragEvent(self, ev):
        if ev.button() != QtCore.Qt.MouseButton.LeftButton:
            return
        ev.accept()
        
        ## Inform ROIs that a drag is happening 
        ##  note: the ROI is informed that the handle has moved using ROI.movePoint
        ##  this is for other (more nefarious) purposes.
        #for r in self.roi:
            #r[0].pointDragEvent(r[1], ev)
            
        if ev.isFinish():
            if self.isMoving:
                for r in self.rois:
                    r.stateChangeFinished()
            self.isMoving = False
            self.currentPen = self.pen
            self.update()
        elif ev.isStart():
            for r in self.rois:
                r.handleMoveStarted()
            self.isMoving = True
            self.startPos = self.scenePos()
            self.cursorOffset = self.scenePos() - ev.buttonDownScenePos()
            self.currentPen = self.hoverPen
            
        if self.isMoving:  ## note: isMoving may become False in mid-drag due to right-click.
            pos = ev.scenePos() + self.cursorOffset
            self.currentPen = self.hoverPen
            self.movePoint(pos, ev.modifiers(), finish=False)

    def movePoint(self, pos, modifiers=None, finish=True):
        if modifiers is None:
            modifiers = QtCore.Qt.KeyboardModifier.NoModifier
        for r in self.rois:
            if not r.checkPointMove(self, pos, modifiers):
                return
        #print "point moved; inform %d ROIs" % len(self.roi)
        # A handle can be used by multiple ROIs; tell each to update its handle position
        for r in self.rois:
            r.movePoint(self, pos, modifiers, finish=finish, coords='scene')
        
    def buildPath(self):
        size = self.radius
        self.path = QtGui.QPainterPath()
        ang = self.startAng
        dt = 2 * np.pi / self.sides
        for i in range(0, self.sides+1):
            x = size * cos(ang)
            y = size * sin(ang)
            ang += dt
            if i == 0:
                self.path.moveTo(x, y)
            else:
                self.path.lineTo(x, y)            
            
    def paint(self, p, opt, widget):
        p.setRenderHints(p.RenderHint.Antialiasing, True)
        p.setPen(self.currentPen)
        
        p.drawPath(self.shape())
            
    def shape(self):
        if self._shape is None:
            s = self.generateShape()
            if s is None:
                return self.path
            self._shape = s
            self.prepareGeometryChange()  ## beware--this can cause the view to adjust, which would immediately invalidate the shape.
        return self._shape
    
    def boundingRect(self):
        s1 = self.shape()  # noqa: avoid problems with shape invalidation
        return self.shape().boundingRect()
            
    def generateShape(self):
        dt = self.deviceTransform()
        
        if dt is None:
            self._shape = self.path
            return None
        
        v = dt.map(QtCore.QPointF(1, 0)) - dt.map(QtCore.QPointF(0, 0))
        va = atan2(v.y(), v.x())
        
        dti = fn.invertQTransform(dt)
        devPos = dt.map(QtCore.QPointF(0,0))
        tr = QtGui.QTransform()
        tr.translate(devPos.x(), devPos.y())
        tr.rotateRadians(va)
        
        return dti.map(tr.map(self.path))
        
    def viewTransformChanged(self):
        GraphicsObject.viewTransformChanged(self)
        self._shape = None  ## invalidate shape, recompute later if requested.
        self.update()


class MouseDragHandler(object):
    """Implements default mouse drag behavior for ROI (not for ROI handles).
    """
    def __init__(self, roi):
        self.roi = roi
        self.dragMode = None
        self.startState = None
        self.snapModifier = QtCore.Qt.KeyboardModifier.ControlModifier
        self.translateModifier = QtCore.Qt.KeyboardModifier.NoModifier
        self.rotateModifier = QtCore.Qt.KeyboardModifier.AltModifier
        self.scaleModifier = QtCore.Qt.KeyboardModifier.ShiftModifier
        self.rotateSpeed = 0.5
        self.scaleSpeed = 1.01

    def mouseDragEvent(self, ev):
        roi = self.roi

        if ev.isStart():
            if ev.button() == QtCore.Qt.MouseButton.LeftButton:
                roi.setSelected(True)
                mods = ev.modifiers() & ~self.snapModifier
                if roi.translatable and mods == self.translateModifier:
                    self.dragMode = 'translate'
                elif roi.rotatable and mods == self.rotateModifier:
                    self.dragMode = 'rotate'
                elif roi.resizable and mods == self.scaleModifier:
                    self.dragMode = 'scale'
                else:
                    self.dragMode = None
                
                if self.dragMode is not None:
                    roi._moveStarted()
                    self.startPos = roi.mapToParent(ev.buttonDownPos())
                    self.startState = roi.saveState()
                    self.cursorOffset = roi.pos() - self.startPos
                    ev.accept()
                else:
                    ev.ignore()
            else:
                self.dragMode = None
                ev.ignore()


        if ev.isFinish() and self.dragMode is not None:
            roi._moveFinished()
            return

        # roi.isMoving becomes False if the move was cancelled by right-click
        if not roi.isMoving or self.dragMode is None:
            return

        snap = True if (ev.modifiers() & self.snapModifier) else None
        pos = roi.mapToParent(ev.pos())
        if self.dragMode == 'translate':
            newPos = pos + self.cursorOffset
            roi.translate(newPos - roi.pos(), snap=snap, finish=False)
        elif self.dragMode == 'rotate':
            diff = self.rotateSpeed * (ev.scenePos() - ev.buttonDownScenePos()).x()
            angle = self.startState['angle'] - diff
            roi.setAngle(angle, centerLocal=ev.buttonDownPos(), snap=snap, finish=False)
        elif self.dragMode == 'scale':
            diff = self.scaleSpeed ** -(ev.scenePos() - ev.buttonDownScenePos()).y()
            roi.setSize(Point(self.startState['size']) * diff, centerLocal=ev.buttonDownPos(), snap=snap, finish=False)


class TestROI(ROI):
    def __init__(self, pos, size, **args):
        ROI.__init__(self, pos, size, **args)
        self.addTranslateHandle([0.5, 0.5])
        self.addScaleHandle([1, 1], [0, 0])
        self.addScaleHandle([0, 0], [1, 1])
        self.addScaleRotateHandle([1, 0.5], [0.5, 0.5])
        self.addScaleHandle([0.5, 1], [0.5, 0.5])
        self.addRotateHandle([1, 0], [0, 0])
        self.addRotateHandle([0, 1], [1, 1])


class RectROI(ROI):
    r"""
    Rectangular ROI subclass with a single scale handle at the top-right corner.

    ============== =============================================================
    **Arguments**
    pos            (length-2 sequence) The position of the ROI origin.
                   See ROI().
    size           (length-2 sequence) The size of the ROI. See ROI().
    centered       (bool) If True, scale handles affect the ROI relative to its
                   center, rather than its origin.
    sideScalers    (bool) If True, extra scale handles are added at the top and 
                   right edges.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    
    """
    def __init__(self, pos, size, centered=False, sideScalers=False, **args):
        ROI.__init__(self, pos, size, **args)
        if centered:
            center = [0.5, 0.5]
        else:
            center = [0, 0]
            
        self.addScaleHandle([1, 1], center)
        if sideScalers:
            self.addScaleHandle([1, 0.5], [center[0], 0.5])
            self.addScaleHandle([0.5, 1], [0.5, center[1]])

class LineROI(ROI):
    r"""
    Rectangular ROI subclass with scale-rotate handles on either side. This
    allows the ROI to be positioned as if moving the ends of a line segment.
    A third handle controls the width of the ROI orthogonal to its "line" axis.
    
    ============== =============================================================
    **Arguments**
    pos1           (length-2 sequence) The position of the center of the ROI's
                   left edge.
    pos2           (length-2 sequence) The position of the center of the ROI's
                   right edge.
    width          (float) The width of the ROI.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    
    """
    def __init__(self, pos1, pos2, width, **args):
        pos1 = Point(pos1)
        pos2 = Point(pos2)
        d = pos2-pos1
        l = d.length()
        ra = d.angle(Point(1, 0), units="radians")
        c = Point(width/2. * sin(ra), -width/2. * cos(ra))
        pos1 = pos1 + c
        
        ROI.__init__(self, pos1, size=Point(l, width), angle=degrees(ra), **args)
        self.addScaleRotateHandle([0, 0.5], [1, 0.5])
        self.addScaleRotateHandle([1, 0.5], [0, 0.5])
        self.addScaleHandle([0.5, 1], [0.5, 0.5])


class MultiRectROI(QtWidgets.QGraphicsObject):
    r"""
    Chain of rectangular ROIs connected by handles.

    This is generally used to mark a curved path through
    an image similarly to PolyLineROI. It differs in that each segment
    of the chain is rectangular instead of linear and thus has width.
    
    ============== =============================================================
    **Arguments**
    points         (list of length-2 sequences) The list of points in the path.
    width          (float) The width of the ROIs orthogonal to the path.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    """
    sigRegionChangeFinished = QtCore.Signal(object)
    sigRegionChangeStarted = QtCore.Signal(object)
    sigRegionChanged = QtCore.Signal(object)
    
    def __init__(self, points, width, pen=None, **args):
        QtWidgets.QGraphicsObject.__init__(self)
        self.pen = pen
        self.roiArgs = args
        self.lines = []
        if len(points) < 2:
            raise Exception("Must start with at least 2 points")
        
        ## create first segment
        self.addSegment(points[1], connectTo=points[0], scaleHandle=True)
        
        ## create remaining segments
        for p in points[2:]:
            self.addSegment(p)
        
        
    def paint(self, *args):
        pass
    
    def boundingRect(self):
        return QtCore.QRectF()
        
    def roiChangedEvent(self):
        w = self.lines[0].state['size'][1]
        for l in self.lines[1:]:
            w0 = l.state['size'][1]
            if w == w0:
                continue
            l.scale([1.0, w/w0], center=[0.5,0.5])
        self.sigRegionChanged.emit(self)
            
    def roiChangeStartedEvent(self):
        self.sigRegionChangeStarted.emit(self)
        
    def roiChangeFinishedEvent(self):
        self.sigRegionChangeFinished.emit(self)
        
    def getHandlePositions(self):
        """Return the positions of all handles in local coordinates."""
        pos = [self.mapFromScene(self.lines[0].getHandles()[0].scenePos())]
        for l in self.lines:
            pos.append(self.mapFromScene(l.getHandles()[1].scenePos()))
        return pos
        
    def getArrayRegion(self, arr, img=None, axes=(0,1), **kwds):
        """
        Return the result of :meth:`~pyqtgraph.ROI.getArrayRegion` for each rect
        in the chain concatenated into a single ndarray.

        See :meth:`~pyqtgraph.ROI.getArrayRegion` for a description of the
        arguments.

        Note: ``returnMappedCoords`` is not yet supported for this ROI type.
        """
        rgns = []
        for l in self.lines:
            rgn = l.getArrayRegion(arr, img, axes=axes, **kwds)
            if rgn is None:
                continue
            rgns.append(rgn)
            #print l.state['size']
            
        ## make sure orthogonal axis is the same size
        ## (sometimes fp errors cause differences)
        if img.axisOrder == 'row-major':
            axes = axes[::-1]
        ms = min([r.shape[axes[1]] for r in rgns])
        sl = [slice(None)] * rgns[0].ndim
        sl[axes[1]] = slice(0,ms)
        rgns = [r[tuple(sl)] for r in rgns]
        #print [r.shape for r in rgns], axes
        
        return np.concatenate(rgns, axis=axes[0])
        
    def addSegment(self, pos=(0,0), scaleHandle=False, connectTo=None):
        """
        Add a new segment to the ROI connecting from the previous endpoint to *pos*.
        (pos is specified in the parent coordinate system of the MultiRectROI)
        """
        
        ## by default, connect to the previous endpoint
        if connectTo is None:
            connectTo = self.lines[-1].getHandles()[1]
            
        ## create new ROI
        newRoi = ROI((0,0), [1, 5], parent=self, pen=self.pen, **self.roiArgs)
        self.lines.append(newRoi)
        
        ## Add first SR handle
        if isinstance(connectTo, Handle):
            self.lines[-1].addScaleRotateHandle([0, 0.5], [1, 0.5], item=connectTo)
            newRoi.movePoint(connectTo, connectTo.scenePos(), coords='scene')
        else:
            h = self.lines[-1].addScaleRotateHandle([0, 0.5], [1, 0.5])
            newRoi.movePoint(h, connectTo, coords='scene')
            
        ## add second SR handle
        h = self.lines[-1].addScaleRotateHandle([1, 0.5], [0, 0.5]) 
        newRoi.movePoint(h, pos)
        
        ## optionally add scale handle (this MUST come after the two SR handles)
        if scaleHandle:
            newRoi.addScaleHandle([0.5, 1], [0.5, 0.5])
            
        newRoi.translatable = False 
        newRoi.sigRegionChanged.connect(self.roiChangedEvent) 
        newRoi.sigRegionChangeStarted.connect(self.roiChangeStartedEvent) 
        newRoi.sigRegionChangeFinished.connect(self.roiChangeFinishedEvent)
        self.sigRegionChanged.emit(self) 
    

    def removeSegment(self, index=-1): 
        """Remove a segment from the ROI."""
        roi = self.lines[index]
        self.lines.pop(index)
        self.scene().removeItem(roi)
        roi.sigRegionChanged.disconnect(self.roiChangedEvent) 
        roi.sigRegionChangeStarted.disconnect(self.roiChangeStartedEvent) 
        roi.sigRegionChangeFinished.disconnect(self.roiChangeFinishedEvent)
        
        self.sigRegionChanged.emit(self)
        
        
class MultiLineROI(MultiRectROI):
    def __init__(self, *args, **kwds):
        MultiRectROI.__init__(self, *args, **kwds)
        print("Warning: MultiLineROI has been renamed to MultiRectROI. (and MultiLineROI may be redefined in the future)")


class EllipseROI(ROI):
    r"""
    Elliptical ROI subclass with one scale handle and one rotation handle.


    ============== =============================================================
    **Arguments**
    pos            (length-2 sequence) The position of the ROI's origin.
    size           (length-2 sequence) The size of the ROI's bounding rectangle.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    
    """
    def __init__(self, pos, size, **args):
        self.path = None
        ROI.__init__(self, pos, size, **args)
        self.sigRegionChanged.connect(self._clearPath)
        self._addHandles()
        
    def _addHandles(self):
        self.addRotateHandle([1.0, 0.5], [0.5, 0.5])
        self.addScaleHandle([0.5*2.**-0.5 + 0.5, 0.5*2.**-0.5 + 0.5], [0.5, 0.5])
            
    def _clearPath(self):
        self.path = None
        
    def paint(self, p, opt, widget):
        r = self.boundingRect()
        p.setRenderHint(QtGui.QPainter.RenderHint.Antialiasing)
        p.setPen(self.currentPen)
        
        p.scale(r.width(), r.height())## workaround for GL bug
        r = QtCore.QRectF(r.x()/r.width(), r.y()/r.height(), 1,1)
        
        p.drawEllipse(r)
        
    def getArrayRegion(self, arr, img=None, axes=(0, 1), returnMappedCoords=False, **kwds):
        """
        Return the result of :meth:`~pyqtgraph.ROI.getArrayRegion` masked by the
        elliptical shape of the ROI. Regions outside the ellipse are set to 0.

        See :meth:`~pyqtgraph.ROI.getArrayRegion` for a description of the
        arguments.

        Note: ``returnMappedCoords`` is not yet supported for this ROI type.
        """
        # Note: we could use the same method as used by PolyLineROI, but this
        # implementation produces a nicer mask.
        if returnMappedCoords:
           arr, mappedCoords = ROI.getArrayRegion(self, arr, img, axes,
                                                  returnMappedCoords, **kwds)
        else:
           arr = ROI.getArrayRegion(self, arr, img, axes,
                                    returnMappedCoords, **kwds)
        if arr is None or arr.shape[axes[0]] == 0 or arr.shape[axes[1]] == 0:
            if returnMappedCoords:
                return arr, mappedCoords
            else:
                return arr
        w = arr.shape[axes[0]]
        h = arr.shape[axes[1]]

        ## generate an ellipsoidal mask
        mask = np.fromfunction(lambda x,y: np.hypot(((x+0.5)/(w/2.)-1), ((y+0.5)/(h/2.)-1)) < 1, (w, h))
        
        # reshape to match array axes
        if axes[0] > axes[1]:
            mask = mask.T
        shape = [(n if i in axes else 1) for i,n in enumerate(arr.shape)]
        mask = mask.reshape(shape)
        
        if returnMappedCoords:
            return arr * mask, mappedCoords
        else:
            return arr * mask
    
    def shape(self):
        if self.path is None:
            path = QtGui.QPainterPath()
            
            # Note: Qt has a bug where very small ellipses (radius <0.001) do
            # not correctly intersect with mouse position (upper-left and 
            # lower-right quadrants are not clickable).
            #path.addEllipse(self.boundingRect())
            
            # Workaround: manually draw the path.
            br = self.boundingRect()
            center = br.center()
            r1 = br.width() / 2.
            r2 = br.height() / 2.
            theta = np.linspace(0, 2 * np.pi, 24)
            x = center.x() + r1 * np.cos(theta)
            y = center.y() + r2 * np.sin(theta)
            path.moveTo(x[0], y[0])
            for i in range(1, len(x)):
                path.lineTo(x[i], y[i])
            self.path = path
        
        return self.path
        
        

class CircleROI(EllipseROI):
    r"""
    Circular ROI subclass. Behaves exactly as EllipseROI, but may only be scaled
    proportionally to maintain its aspect ratio.
    
    ============== =============================================================
    **Arguments**
    pos            (length-2 sequence) The position of the ROI's origin.
    size           (length-2 sequence) The size of the ROI's bounding rectangle.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    
    """
    def __init__(self, pos, size=None, radius=None, **args):
        if size is None:
            if radius is None:
                raise TypeError("Must provide either size or radius.")
            size = (radius*2, radius*2)
        EllipseROI.__init__(self, pos, size, aspectLocked=True, **args)
        
    def _addHandles(self):
        self.addScaleHandle([0.5*2.**-0.5 + 0.5, 0.5*2.**-0.5 + 0.5], [0.5, 0.5])


class PolyLineROI(ROI):
    r"""
    Container class for multiple connected LineSegmentROIs.

    This class allows the user to draw paths of multiple line segments.

    ============== =============================================================
    **Arguments**
    positions      (list of length-2 sequences) The list of points in the path.
                   Note that, unlike the handle positions specified in other
                   ROIs, these positions must be expressed in the normal
                   coordinate system of the ROI, rather than (0 to 1) relative
                   to the size of the ROI.
    closed         (bool) if True, an extra LineSegmentROI is added connecting 
                   the beginning and end points.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    
    """
    def __init__(self, positions, closed=False, pos=None, **args):
        
        if pos is None:
            pos = [0,0]
            
        self.closed = closed
        self.segments = []
        ROI.__init__(self, pos, size=[1,1], **args)
        
        self.setPoints(positions)

    def setPoints(self, points, closed=None):
        """
        Set the complete sequence of points displayed by this ROI.
        
        ============= =========================================================
        **Arguments**
        points        List of (x,y) tuples specifying handle locations to set.
        closed        If bool, then this will set whether the ROI is closed 
                      (the last point is connected to the first point). If
                      None, then the closed mode is left unchanged.
        ============= =========================================================
        
        """
        if closed is not None:
            self.closed = closed
        
        self.clearPoints()
        
        for p in points:
            self.addFreeHandle(p)
        
        start = -1 if self.closed else 0
        for i in range(start, len(self.handles)-1):
            self.addSegment(self.handles[i]['item'], self.handles[i+1]['item'])
        
    def clearPoints(self):
        """
        Remove all handles and segments.
        """
        while len(self.handles) > 0:
            self.removeHandle(self.handles[0]['item'])
    
    def getState(self):
        state = ROI.getState(self)
        state['closed'] = self.closed
        state['points'] = [Point(h.pos()) for h in self.getHandles()]
        return state

    def saveState(self):
        state = ROI.saveState(self)
        state['closed'] = self.closed
        state['points'] = [tuple(h.pos()) for h in self.getHandles()]
        return state

    def setState(self, state):
        ROI.setState(self, state)
        self.setPoints(state['points'], closed=state['closed'])
        
    def addSegment(self, h1, h2, index=None):
        seg = _PolyLineSegment(handles=(h1, h2), pen=self.pen, hoverPen=self.hoverPen,
                               parent=self, movable=False)
        if index is None:
            self.segments.append(seg)
        else:
            self.segments.insert(index, seg)
        seg.sigClicked.connect(self.segmentClicked)
        seg.setAcceptedMouseButtons(QtCore.Qt.MouseButton.LeftButton)
        seg.setZValue(self.zValue()+1)
        for h in seg.handles:
            h['item'].setDeletable(True)
            h['item'].setAcceptedMouseButtons(h['item'].acceptedMouseButtons() | QtCore.Qt.MouseButton.LeftButton) ## have these handles take left clicks too, so that handles cannot be added on top of other handles
        
    def setMouseHover(self, hover):
        ## Inform all the ROI's segments that the mouse is(not) hovering over it
        ROI.setMouseHover(self, hover)
        for s in self.segments:
            s.setParentHover(hover)
          
    def addHandle(self, info, index=None):
        h = ROI.addHandle(self, info, index=index)
        h.sigRemoveRequested.connect(self.removeHandle)
        self.stateChanged(finish=True)
        return h
        
    def segmentClicked(self, segment, ev=None, pos=None): ## pos should be in this item's coordinate system
        if ev is not None:
            pos = segment.mapToParent(ev.pos())
        elif pos is None:
            raise Exception("Either an event or a position must be given.")
        h2 = segment.handles[1]['item']
        
        i = self.segments.index(segment)
        h3 = self.addFreeHandle(pos, index=self.indexOfHandle(h2))
        self.addSegment(h3, h2, index=i+1)
        segment.replaceHandle(h2, h3)
        
    def removeHandle(self, handle, updateSegments=True):
        ROI.removeHandle(self, handle)
        handle.sigRemoveRequested.disconnect(self.removeHandle)
        
        if not updateSegments:
            return
        segments = handle.rois[:]
        
        if len(segments) == 1:
            self.removeSegment(segments[0])
        elif len(segments) > 1:
            handles = [h['item'] for h in segments[1].handles]
            handles.remove(handle)
            segments[0].replaceHandle(handle, handles[0])
            self.removeSegment(segments[1])
        self.stateChanged(finish=True)
        
    def removeSegment(self, seg):
        for handle in seg.handles[:]:
            seg.removeHandle(handle['item'])
        self.segments.remove(seg)
        seg.sigClicked.disconnect(self.segmentClicked)
        self.scene().removeItem(seg)
        
    def checkRemoveHandle(self, h):
        ## called when a handle is about to display its context menu
        if self.closed:
            return len(self.handles) > 3
        else:
            return len(self.handles) > 2
        
    def paint(self, p, *args):
        pass
    
    def boundingRect(self):
        return self.shape().boundingRect()

    def shape(self):
        p = QtGui.QPainterPath()
        if len(self.handles) == 0:
            return p
        p.moveTo(self.handles[0]['item'].pos())
        for i in range(len(self.handles)):
            p.lineTo(self.handles[i]['item'].pos())
        p.lineTo(self.handles[0]['item'].pos())
        return p

    def getArrayRegion(self, *args, **kwds):
        return self._getArrayRegionForArbitraryShape(*args, **kwds)

    def setPen(self, *args, **kwds):
        ROI.setPen(self, *args, **kwds)
        for seg in self.segments:
            seg.setPen(*args, **kwds)



class LineSegmentROI(ROI):
    r"""
    ROI subclass with two freely-moving handles defining a line.

    ============== =============================================================
    **Arguments**
    positions      (list of two length-2 sequences) The endpoints of the line 
                   segment. Note that, unlike the handle positions specified in 
                   other ROIs, these positions must be expressed in the normal
                   coordinate system of the ROI, rather than (0 to 1) relative
                   to the size of the ROI.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    """
    
    def __init__(self, positions=(None, None), pos=None, handles=(None,None), **args):
        if pos is None:
            pos = [0,0]
            
        ROI.__init__(self, pos, [1,1], **args)
        if len(positions) > 2:
            raise Exception("LineSegmentROI must be defined by exactly 2 positions. For more points, use PolyLineROI.")
        
        for i, p in enumerate(positions):
            self.addFreeHandle(p, item=handles[i])
            
    @property
    def endpoints(self):
        # must not be cached because self.handles may change.
        return [h['item'] for h in self.handles]
        
    def listPoints(self):
        return [p['item'].pos() for p in self.handles]

    def getState(self):
        state = ROI.getState(self)
        state['points'] = [Point(h.pos()) for h in self.getHandles()]
        return state

    def saveState(self):
        state = ROI.saveState(self)
        state['points'] = [tuple(h.pos()) for h in self.getHandles()]
        return state

    def setState(self, state):
        ROI.setState(self, state)
        p1 = [state['points'][0][0]+state['pos'][0], state['points'][0][1]+state['pos'][1]]
        p2 = [state['points'][1][0]+state['pos'][0], state['points'][1][1]+state['pos'][1]]
        self.movePoint(self.getHandles()[0], p1, finish=False)
        self.movePoint(self.getHandles()[1], p2)
            
    def paint(self, p, *args):
        p.setRenderHint(QtGui.QPainter.RenderHint.Antialiasing)
        p.setPen(self.currentPen)
        h1 = self.endpoints[0].pos()
        h2 = self.endpoints[1].pos()
        p.drawLine(h1, h2)
        
    def boundingRect(self):
        return self.shape().boundingRect()
    
    def shape(self):
        p = QtGui.QPainterPath()
    
        h1 = self.endpoints[0].pos()
        h2 = self.endpoints[1].pos()
        dh = h2-h1
        if dh.length() == 0:
            return p
        pxv = self.pixelVectors(dh)[1]
        if pxv is None:
            return p
            
        pxv *= 4
        
        p.moveTo(h1+pxv)
        p.lineTo(h2+pxv)
        p.lineTo(h2-pxv)
        p.lineTo(h1-pxv)
        p.lineTo(h1+pxv)
      
        return p
    
    def getArrayRegion(self, data, img, axes=(0,1), order=1, returnMappedCoords=False, **kwds):
        """
        Use the position of this ROI relative to an imageItem to pull a slice 
        from an array.
        
        Since this pulls 1D data from a 2D coordinate system, the return value 
        will have ndim = data.ndim-1
        
        See :meth:`~pyqtgraph.ROI.getArrayRegion` for a description of the
        arguments.
        """
        imgPts = [self.mapToItem(img, h.pos()) for h in self.endpoints]

        d = Point(imgPts[1] - imgPts[0])
        o = Point(imgPts[0])
        rgn = fn.affineSlice(data, shape=(int(d.length()),), vectors=[Point(d.norm())], origin=o, axes=axes, order=order, returnCoords=returnMappedCoords, **kwds)

        return rgn
        

class _PolyLineSegment(LineSegmentROI):
    # Used internally by PolyLineROI
    def __init__(self, *args, **kwds):
        self._parentHovering = False
        LineSegmentROI.__init__(self, *args, **kwds)
        
    def setParentHover(self, hover):
        # set independently of own hover state
        if self._parentHovering != hover:
            self._parentHovering = hover
            self._updateHoverColor()
        
    def _makePen(self):
        if self.mouseHovering or self._parentHovering:
            return self.hoverPen
        else:
            return self.pen
        
    def hoverEvent(self, ev):
        # accept drags even though we discard them to prevent competition with parent ROI
        # (unless parent ROI is not movable)
        if self.parentItem().translatable:
            ev.acceptDrags(QtCore.Qt.MouseButton.LeftButton)
        return LineSegmentROI.hoverEvent(self, ev)


class CrosshairROI(ROI):
    """A crosshair ROI whose position is at the center of the crosshairs. By default, it is scalable, rotatable and translatable."""
    
    def __init__(self, pos=None, size=None, **kargs):
        if size is None:
            size=[1,1]
        if pos is None:
            pos = [0,0]
        self._shape = None
        ROI.__init__(self, pos, size, aspectLocked=True, **kargs)
        
        self.sigRegionChanged.connect(self.invalidate)
        self.addScaleRotateHandle(Point(1, 0), Point(0, 0))

    def invalidate(self):
        self._shape = None
        self.prepareGeometryChange()
        
    def boundingRect(self):
        return self.shape().boundingRect()
    
    def shape(self):
        if self._shape is None:
            radius = self.getState()['size'][1]
            p = QtGui.QPainterPath()
            p.moveTo(Point(0, -radius))
            p.lineTo(Point(0, radius))
            p.moveTo(Point(-radius, 0))
            p.lineTo(Point(radius, 0))
            p = self.mapToDevice(p)
            stroker = QtGui.QPainterPathStroker()
            stroker.setWidth(10)
            outline = stroker.createStroke(p)
            self._shape = self.mapFromDevice(outline)
        
        return self._shape
    
    def paint(self, p, *args):
        radius = self.getState()['size'][1]
        p.setRenderHint(QtGui.QPainter.RenderHint.Antialiasing)
        p.setPen(self.currentPen)
        
        p.drawLine(Point(0, -radius), Point(0, radius))
        p.drawLine(Point(-radius, 0), Point(radius, 0))
        
        
class RulerROI(LineSegmentROI):
    def paint(self, p, *args):
        LineSegmentROI.paint(self, p, *args)
        h1 = self.handles[0]['item'].pos()
        h2 = self.handles[1]['item'].pos()
        p1 = p.transform().map(h1)
        p2 = p.transform().map(h2)

        vec = Point(h2) - Point(h1)
        length = vec.length()
        angle = vec.angle(Point(1, 0))

        pvec = p2 - p1
        pvecT = Point(pvec.y(), -pvec.x())
        pos = 0.5 * (p1 + p2) + pvecT * 40 / pvecT.length()

        p.resetTransform()

        txt = fn.siFormat(length, suffix='m') + '\n%0.1f deg' % angle
        p.drawText(QtCore.QRectF(pos.x()-50, pos.y()-50, 100, 100), QtCore.Qt.AlignmentFlag.AlignCenter, txt)

    def boundingRect(self):
        r = LineSegmentROI.boundingRect(self)
        pxl = self.pixelLength(Point([1, 0]))
        if pxl is None:
            return r
        pxw = 50 * pxl
        return r.adjusted(-50, -50, 50, 50)


class TriangleROI(ROI):
    r"""
    Equilateral triangle ROI subclass with one scale handle and one rotation handle.
    Arguments
    pos            (length-2 sequence) The position of the ROI's origin.
    size           (float) The length of an edge of the triangle.
    \**args        All extra keyword arguments are passed to ROI()
    ============== =============================================================
    """

    def __init__(self, pos, size, **args):
        ROI.__init__(self, pos, [size, size], aspectLocked=True, **args)
        angles = np.linspace(0, np.pi * 4 / 3, 3)
        verticies = (np.array((np.sin(angles), np.cos(angles))).T + 1.0) / 2.0
        self.poly = QtGui.QPolygonF()
        for pt in verticies:
            self.poly.append(QtCore.QPointF(*pt))
        self.addRotateHandle(verticies[0], [0.5, 0.5])
        self.addScaleHandle(verticies[1], [0.5, 0.5])

    def paint(self, p, *args):
        r = self.boundingRect()
        p.setRenderHint(QtGui.QPainter.RenderHint.Antialiasing)
        p.scale(r.width(), r.height())
        p.setPen(self.currentPen)
        p.drawPolygon(self.poly)

    def shape(self):
        self.path = QtGui.QPainterPath()
        r = self.boundingRect()
        # scale the path to match whats on the screen
        t = QtGui.QTransform()
        t.scale(r.width(), r.height())
        self.path.addPolygon(self.poly)
        return t.map(self.path)

    def getArrayRegion(self, *args, **kwds):
        return self._getArrayRegionForArbitraryShape(*args, **kwds)
