# Source code for pyqtgraph.GraphicsScene.GraphicsScene

    import warnings
    import weakref
    from time import perf_counter, perf_counter_ns

    from .. import debug as debug
    from .. import getConfigOption
    from ..Point import Point
    from ..Qt import QtCore, QtGui, QtWidgets, isQObjectAlive
    from .mouseEvents import HoverEvent, MouseClickEvent, MouseDragEvent

    getMillis = lambda: perf_counter_ns() // 10 ** 6

    __all__ = ['GraphicsScene']

    class GraphicsScene(QtWidgets.QGraphicsScene):
        """
        Extension of QGraphicsScene that implements a complete, parallel mouse event system.
        (It would have been preferred to just alter the way QGraphicsScene creates and delivers
        events, but this turned out to be impossible because the constructor for QGraphicsMouseEvent
        is private)

          *  Generates MouseClicked events in addition to the usual press/move/release events.
             (This works around a problem where it is impossible to have one item respond to a
             drag if another is watching for a click.)
          *  Adjustable radius around click that will catch objects so you don't have to click *exactly* over small/thin objects
          *  Global context menu--if an item implements a context menu, then its parent(s) may also add items to the menu.
          *  Allows items to decide _before_ a mouse click which item will be the recipient of mouse events.
             This lets us indicate unambiguously to the user which item they are about to click/drag on
          *  Eats mouseMove events that occur too soon after a mouse press.
          *  Reimplements items() and itemAt() to circumvent PyQt bug

        ====================== ====================================================================
        **Signals**
        sigMouseClicked(event) Emitted when the mouse is clicked over the scene. Use ev.pos() to
                               get the click position relative to the item that was clicked on,
                               or ev.scenePos() to get the click position in scene coordinates.
                               See :class:`pyqtgraph.GraphicsScene.mouseEvents.MouseClickEvent`.
        sigMouseMoved(pos)     Emitted when the mouse cursor moves over the scene. The position
                               is given in scene coordinates.
        sigMouseHover(items)   Emitted when the mouse is moved over the scene. Items is a list
                               of items under the cursor.
        sigItemAdded(item)     Emitted when an item is added via addItem(). The item is given.
        sigItemRemoved(item)   Emitted when an item is removed via removeItem(). The item is given.
        ====================== ====================================================================

        Mouse interaction is as follows:

        1) Every time the mouse moves, the scene delivers both the standard hoverEnter/Move/LeaveEvents
           as well as custom HoverEvents.
        2) Items are sent HoverEvents in Z-order and each item may optionally call event.acceptClicks(button),
           acceptDrags(button) or both. If this method call returns True, this informs the item that _if_
           the user clicks/drags the specified mouse button, the item is guaranteed to be the
           recipient of click/drag events (the item may wish to change its appearance to indicate this).
           If the call to acceptClicks/Drags returns False, then the item is guaranteed to *not* receive
           the requested event (because another item has already accepted it).
        3) If the mouse is clicked, a mousePressEvent is generated as usual. If any items accept this press event, then
           No click/drag events will be generated and mouse interaction proceeds as defined by Qt. This allows
           items to function properly if they are expecting the usual press/move/release sequence of events.
           (It is recommended that items do NOT accept press events, and instead use click/drag events)
           Note: The default implementation of QGraphicsItem.mousePressEvent will *accept* the event if the
           item is has its Selectable or Movable flags enabled. You may need to override this behavior.
        4) If no item accepts the mousePressEvent, then the scene will begin delivering mouseDrag and/or mouseClick events.
           If the mouse is moved a sufficient distance (or moved slowly enough) before the button is released,
           then a mouseDragEvent is generated.
           If no drag events are generated before the button is released, then a mouseClickEvent is generated.
        5) Click/drag events are delivered to the item that called acceptClicks/acceptDrags on the HoverEvent
           in step 1. If no such items exist, then the scene attempts to deliver the events to items near the event.
           ClickEvents may be delivered in this way even if no
           item originally claimed it could accept the click. DragEvents may only be delivered this way if it is the initial
           move in a drag.
        """

        sigMouseHover = QtCore.Signal(object)   ## emits a list of objects hovered over
        sigMouseMoved = QtCore.Signal(object)   ## emits position of mouse on every move
        sigMouseClicked = QtCore.Signal(object)   ## emitted when mouse is clicked. Check for event.isAccepted() to see whether the event has already been acted on.

        sigPrepareForPaint = QtCore.Signal()  ## emitted immediately before the scene is about to be rendered

        sigItemAdded = QtCore.Signal(object)  ## emits the item object just added
        sigItemRemoved = QtCore.Signal(object)  ## emits the item object just removed

        _addressCache = weakref.WeakValueDictionary()

        ExportDirectory = None

        def __init__(self, clickRadius: int = 2, moveDistance=5, parent=None):
            QtWidgets.QGraphicsScene.__init__(self, parent)
            self.setClickRadius(clickRadius)
            self.setMoveDistance(moveDistance)
            self.exportDirectory = None

            self.clickEvents = []
            self.dragButtons = []
            self.mouseGrabber = None
            self.dragItem = None
            self.lastDrag = None
            self.hoverItems = weakref.WeakKeyDictionary()
            self.lastHoverEvent = None
            self.minDragTime = 0.5  # drags shorter than 0.5 sec are interpreted as clicks

            self.contextMenu = [QtGui.QAction(QtCore.QCoreApplication.translate("GraphicsScene", "Export..."), self)]
            self.contextMenu[0].triggered.connect(self.showExportDialog)

            self.exportDialog = None
            self._lastMoveEventTime = 0

        def render(self, *args):
            self.prepareForPaint()
            return QtWidgets.QGraphicsScene.render(self, *args)

        def prepareForPaint(self):
            """Called before every render. This method will inform items that the scene is about to
            be rendered by emitting sigPrepareForPaint.

            This allows items to delay expensive processing until they know a paint will be required."""
            self.sigPrepareForPaint.emit()

        def setClickRadius(self, r: int):
            """
            Set the distance away from mouse clicks to search for interacting items.
            When clicking, the scene searches first for items that directly intersect the click position
            followed by any other items that are within a rectangle that extends r pixels away from the
            click position.
            """
            self._clickRadius = int(r)

        def setMoveDistance(self, d):
            """
            Set the distance the mouse must move after a press before mouseMoveEvents will be delivered.
            This ensures that clicks with a small amount of movement are recognized as clicks instead of
            drags.
            """
            self._moveDistance = d

        def mousePressEvent(self, ev):
            super().mousePressEvent(ev)
            if self.mouseGrabberItem() is None:  ## nobody claimed press; we are free to generate drag/click events
                if self.lastHoverEvent is not None:
                    # If the mouse has moved since the last hover event, send a new one.
                    # This can happen if a context menu is open while the mouse is moving.
                    if ev.scenePos() != self.lastHoverEvent.scenePos():
                        self.sendHoverEvents(ev)

                self.clickEvents.append(MouseClickEvent(ev))

                ## set focus on the topmost focusable item under this click
                items = self.items(ev.scenePos())
                for i in items:
                    if i.isEnabled() and i.isVisible() and (i.flags() & i.GraphicsItemFlag.ItemIsFocusable):
                        i.setFocus(QtCore.Qt.FocusReason.MouseFocusReason)
                        break

        def _moveEventIsAllowed(self):
            # For ignoring events that are too close together

            # Max number of events per second
            rateLimit = getConfigOption('mouseRateLimit')
            if rateLimit <= 0:
                return True

            # Delay between events (in milliseconds)
            delay = 1000.0 / rateLimit
            if getMillis() - self._lastMoveEventTime >= delay:
                return True
            return False

        def mouseMoveEvent(self, ev):
            # ignore high frequency events
            if self._moveEventIsAllowed():
                self._lastMoveEventTime = getMillis()
                self.sigMouseMoved.emit(ev.scenePos())

                # First allow QGraphicsScene to eliver hoverEvent/Move/Exit Events
                super().mouseMoveEvent(ev)
                # Next Deliver our own Hover Events
                self.sendHoverEvents(ev)
                if ev.buttons():
                    # button is pressed' send mouseMoveEvents and mouseDragEvents
                    super().mouseMoveEvent(ev)
                    if self.mouseGrabberItem() is None:
                        now = perf_counter()
                        init = False
                        ## keep track of which buttons are involved in dragging
                        for btn in [QtCore.Qt.MouseButton.LeftButton, QtCore.Qt.MouseButton.MiddleButton, QtCore.Qt.MouseButton.RightButton]:
                            if not (ev.buttons() & btn):
                                continue
                            if btn not in self.dragButtons:  ## see if we've dragged far enough yet
                                cev = [e for e in self.clickEvents if e.button() == btn]
                                if cev:
                                    cev = cev[0]
                                    dist = Point(ev.scenePos() - cev.scenePos()).length()
                                    if dist == 0 or (dist < self._moveDistance and now - cev.time() < self.minDragTime):
                                        continue
                                    init = init or (len(self.dragButtons) == 0)  ## If this is the first button to be dragged, then init=True
                                    self.dragButtons.append(btn)
                        ## if we have dragged buttons, deliver a drag event
                        if len(self.dragButtons) > 0:
                            if self.sendDragEvent(ev, init=init):
                                ev.accept()

            else:
                super().mouseMoveEvent(ev)
                # if you do not accept event (which is ignored) then cursor will disappear
                ev.accept()

        def leaveEvent(self, ev):  ## inform items that mouse is gone
            if len(self.dragButtons) == 0:
                self.sendHoverEvents(ev, exitOnly=True)

        def mouseReleaseEvent(self, ev):
            if self.mouseGrabberItem() is None:
                if ev.button() in self.dragButtons:
                    if self.sendDragEvent(ev, final=True):
                        #print "sent drag event"
                        ev.accept()
                    self.dragButtons.remove(ev.button())
                else:
                    cev = [e for e in self.clickEvents if e.button() == ev.button()]
                    if cev:
                        if self.sendClickEvent(cev[0]):
                            ev.accept()
                        try:
                            self.clickEvents.remove(cev[0])
                        except ValueError:
                            warnings.warn(
                                ("A ValueError can occur here with errant "
                                 "QApplication.processEvent() calls, see "
                                "https://github.com/pyqtgraph/pyqtgraph/pull/2580 "
                                "for more information."),
                                RuntimeWarning,
                                stacklevel=2
                            )
            if not ev.buttons():
                self.dragItem = None
                self.dragButtons = []
                self.clickEvents = []
                self.lastDrag = None
            super().mouseReleaseEvent(ev)

            self.sendHoverEvents(ev)  ## let items prepare for next click/drag

        def mouseDoubleClickEvent(self, ev):
            super().mouseDoubleClickEvent(ev)
            if self.mouseGrabberItem() is None:  ## nobody claimed press; we are free to generate drag/click events
                self.clickEvents.append(MouseClickEvent(ev, double=True))

        def sendHoverEvents(self, ev, exitOnly=False):
            ## if exitOnly, then just inform all previously hovered items that the mouse has left.

            if exitOnly:
                acceptable=False
                items = []
                event = HoverEvent(None, acceptable)
            else:
                acceptable = not ev.buttons()  ## if we are in mid-drag, do not allow items to accept the hover event.
                event = HoverEvent(ev, acceptable)
                items = self.itemsNearEvent(event, hoverable=True)
                self.sigMouseHover.emit(items)

            prevItems = list(self.hoverItems.keys())

            for item in items:
                if hasattr(item, 'hoverEvent'):
                    event.currentItem = item
                    if item not in self.hoverItems:
                        self.hoverItems[item] = None
                        event.enter = True
                    else:
                        prevItems.remove(item)
                        event.enter = False

                    try:
                        item.hoverEvent(event)
                    except:
                        debug.printExc("Error sending hover event:")

            event.enter = False
            event.exit = True
            #print "hover exit items:", prevItems
            for item in prevItems:
                event.currentItem = item
                try:
                    # NOTE: isQObjectAlive(item) was added for PySide6 where
                    #       verlet_chain_demo.py triggers a RuntimeError.
                    if isQObjectAlive(item) and item.scene() is self:
                        item.hoverEvent(event)
                except:
                    debug.printExc("Error sending hover exit event:")
                finally:
                    del self.hoverItems[item]

            # Update last hover event unless:
            #   - mouse is dragging (move+buttons); in this case we want the dragged
            #     item to continue receiving events until the drag is over
            #   - event is not a mouse event (QEvent.Type.Leave sometimes appears here)
            if (ev.type() == ev.Type.GraphicsSceneMousePress or
                (ev.type() == ev.Type.GraphicsSceneMouseMove and not ev.buttons())):
                self.lastHoverEvent = event  ## save this so we can ask about accepted events later.

        def sendDragEvent(self, ev, init=False, final=False):
            ## Send a MouseDragEvent to the current dragItem or to
            ## items near the beginning of the drag
            event = MouseDragEvent(ev, self.clickEvents[0], self.lastDrag, start=init, finish=final)
            #print "dragEvent: init=", init, 'final=', final, 'self.dragItem=', self.dragItem
            if init and self.dragItem is None:
                if self.lastHoverEvent is not None:
                    acceptedItem = self.lastHoverEvent.dragItems().get(event.button(), None)
                else:
                    acceptedItem = None

                if acceptedItem is not None and acceptedItem.scene() is self:
                    #print "Drag -> pre-selected item:", acceptedItem
                    self.dragItem = acceptedItem
                    event.currentItem = self.dragItem
                    try:
                        self.dragItem.mouseDragEvent(event)
                    except:
                        debug.printExc("Error sending drag event:")

                else:
                    #print "drag -> new item"
                    for item in self.itemsNearEvent(event):
                        #print "check item:", item
                        if not item.isVisible() or not item.isEnabled():
                            continue
                        if hasattr(item, 'mouseDragEvent'):
                            event.currentItem = item
                            try:
                                item.mouseDragEvent(event)
                            except:
                                debug.printExc("Error sending drag event:")
                            if event.isAccepted():
                                #print "   --> accepted"
                                self.dragItem = item
                                if item.flags() & item.GraphicsItemFlag.ItemIsFocusable:
                                    item.setFocus(QtCore.Qt.FocusReason.MouseFocusReason)
                                break
            elif self.dragItem is not None:
                event.currentItem = self.dragItem
                try:
                    self.dragItem.mouseDragEvent(event)
                except:
                    debug.printExc("Error sending hover exit event:")

            self.lastDrag = event

            return event.isAccepted()

        def sendClickEvent(self, ev):
            ## if we are in mid-drag, click events may only go to the dragged item.
            if self.dragItem is not None and hasattr(self.dragItem, 'mouseClickEvent'):
                ev.currentItem = self.dragItem
                self.dragItem.mouseClickEvent(ev)

            ## otherwise, search near the cursor
            else:
                if self.lastHoverEvent is not None:
                    acceptedItem = self.lastHoverEvent.clickItems().get(ev.button(), None)
                else:
                    acceptedItem = None
                if acceptedItem is not None:
                    ev.currentItem = acceptedItem
                    try:
                        acceptedItem.mouseClickEvent(ev)
                    except:
                        debug.printExc("Error sending click event:")
                else:
                    for item in self.itemsNearEvent(ev):
                        if not item.isVisible() or not item.isEnabled():
                            continue
                        if hasattr(item, 'mouseClickEvent'):
                            ev.currentItem = item
                            try:
                                item.mouseClickEvent(ev)
                            except:
                                debug.printExc("Error sending click event:")

                            if ev.isAccepted():
                                if item.flags() & item.GraphicsItemFlag.ItemIsFocusable:
                                    item.setFocus(QtCore.Qt.FocusReason.MouseFocusReason)
                                break
            self.sigMouseClicked.emit(ev)
            return ev.isAccepted()

        def addItem(self, item):
            # extend QGraphicsScene.addItem to emit a sigItemAdded signal
            ret = QtWidgets.QGraphicsScene.addItem(self, item)
            self.sigItemAdded.emit(item)
            return ret

        def removeItem(self, item):
            # extend QGraphicsScene.removeItem to emit a sigItemRemoved signal
            ret = QtWidgets.QGraphicsScene.removeItem(self, item)
            self.sigItemRemoved.emit(item)
            return ret

        def itemsNearEvent(
            self,
            event,
            selMode=QtCore.Qt.ItemSelectionMode.IntersectsItemShape,
            sortOrder=QtCore.Qt.SortOrder.DescendingOrder,
            hoverable=False,
        ):
            """
            Return an iterator that iterates first through the items that directly intersect point (in Z order)
            followed by any other items that are within the scene's click radius.
            """
            view = self.views()[0]
            tr = view.viewportTransform()

            if hasattr(event, "buttonDownScenePos"):
                point = event.buttonDownScenePos()
            else:
                point = event.scenePos()

            ## Sort by descending Z-order (don't trust scene.itms() to do this either)
            ## use 'absolute' z value, which is the sum of all item/parent ZValues
            def absZValue(item):
                if item is None:
                    return 0
                return item.zValue() + absZValue(item.parentItem())

            ## Get items, which directly are at the given point (sorted by z-value)
            items_at_point = self.items(point, selMode, sortOrder, tr)
            items_at_point.sort(key=absZValue, reverse=True)

            ## Get items, which are within the click radius around the given point (sorted by z-value)
            r = self._clickRadius
            items_within_radius = []
            rgn = None
            if r > 0:
                rect = view.mapToScene(QtCore.QRect(0, 0, 2 * r, 2 * r)).boundingRect()
                w = rect.width()
                h = rect.height()
                rgn = QtCore.QRectF(point.x() - w / 2, point.y() - h / 2, w, h)
                items_within_radius = self.items(rgn, selMode, sortOrder, tr)
                items_within_radius.sort(key=absZValue, reverse=True)
                # Remove items, which are already in the other list
                for item in items_at_point:
                    if item in items_within_radius:
                        items_within_radius.remove(item)

            ## Put both groups of items together, but in the correct order
            ## The items directly at the given point shall have higher priority
            all_items = items_at_point + items_within_radius

            ## Remove items, which we don't want, due to several reasons
            selected_items = []
            for item in all_items:
                if hoverable and not hasattr(item, "hoverEvent"):
                    continue
                if item.scene() is not self:
                    continue
                shape = item.shape()  # Note: default shape() returns boundingRect()
                if shape is None:
                    continue
                # Remove items whose shape does not contain point or region
                # (scene.items() apparently sucks at this)
                if (
                    rgn is not None
                    and shape.intersects(item.mapFromScene(rgn).boundingRect())
                ) or shape.contains(item.mapFromScene(point)):
                    selected_items.append(item)

            return selected_items

        def getViewWidget(self):
            return self.views()[0]

        def addParentContextMenus(self, item, menu, event):
            """
            Can be called by any item in the scene to expand its context menu to include parent context menus.
            Parents may implement getContextMenus to add new menus / actions to the existing menu.
            getContextMenus must accept 1 argument (the event that generated the original menu) and
            return a single QMenu or a list of QMenus.

            The final menu will look like:

                |    Original Item 1
                |    Original Item 2
                |    ...
                |    Original Item N
                |    ------------------
                |    Parent Item 1
                |    Parent Item 2
                |    ...
                |    Grandparent Item 1
                |    ...

            ==============  ==================================================
            **Arguments:**
            item            The item that initially created the context menu
                            (This is probably the item making the call to this function)
            menu            The context menu being shown by the item
            event           The original event that triggered the menu to appear.
            ==============  ==================================================
            """

            menusToAdd = []
            while item is not self:
                item = item.parentItem()
                if item is None:
                    item = self
                if not hasattr(item, "getContextMenus"):
                    continue
                subMenus = item.getContextMenus(event) or []
                if isinstance(subMenus, list): ## so that some items (like FlowchartViewBox) can return multiple menus
                    menusToAdd.extend(subMenus)
                else:
                    menusToAdd.append(subMenus)
            # Filter out options that were previously added
            existingActions = menu.actions()
            actsToAdd = []
            for menuOrAct in menusToAdd:
                if isinstance(menuOrAct, QtWidgets.QMenu):
                    menuOrAct = menuOrAct.menuAction()
                elif not isinstance(menuOrAct, QtGui.QAction):
                    raise Exception(
                        f"Cannot add object {menuOrAct} (type={type(menuOrAct)}) to QMenu."
                    )
                if menuOrAct not in existingActions:
                    actsToAdd.append(menuOrAct)

            if actsToAdd:
                menu.addSeparator()

            menu.addActions(actsToAdd)
            return menu

        def getContextMenus(self, event):
            self.contextMenuItem = event.acceptedItem
            return self.contextMenu

        def showExportDialog(self):
            if self.exportDialog is None:
                from . import exportDialog
                self.exportDialog = exportDialog.ExportDialog(self)
            self.exportDialog.show(self.contextMenuItem)