Laborejo/qtgui/conductor.py

#! /usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Copyright 2021, Nils Hilbricht, Germany ( https://www.hilbricht.net )

This file is part of the Laborejo Software Suite ( https://www.laborejo.org ),

Laborejo2 is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""

import logging; logger = logging.getLogger(__name__); logger.info("import")

from PyQt5 import QtCore, QtGui, QtSvg, QtWidgets
from .constantsAndConfigs import constantsAndConfigs
from template.qtgui.helper import stringToColor, removeInstancesFromScene, callContextMenu, stretchLine, stretchRect
from template.helper import pairwise
from .submenus import SecondaryTempoChangeMenu, TempoBlockPropertiesEdit
import engine.api as api

_zValuesRelativeToConductor = { #Only use for objects added directly to the Conductor, not their children.
    "line":0,
    "startItem":1,
    "block":2,
    "item":4,
    "handle":5,
}

class Conductor(QtWidgets.QGraphicsItem):
    """The track for tempo items. Some methods have the same name and functionality
    as note-track to be compatible. For example drag and drop of blocks."""

    def __init__(self, parentView):
        super().__init__()
        self.setFlag(QtWidgets.QGraphicsItem.ItemHasNoContents, True) #only child items. Without this we get notImplementedError: QGraphicsItem.paint() is abstract and must be overridden

        self.parentView = parentView
        self.totalHeight = 71

        self.staticPoints = None #Cached backend staticRepresentationList: TempoPoints and interpolated points list
        self.staticBlocks = None #Cached Block Data list
        self.staticMeta = None #Cached track meta data dict.

        self.staffLine = QtWidgets.QGraphicsLineItem(0,0,10,0) #x1, y1, x2, y2
        self.staffLine.setParentItem(self)
        self.staffLine.setPos(0,0)

        #Displays the real time in minutes and seconds. Definition at the end of thils file.
        self.timeLine = TimeLine(self) #registers its own callbacks
        self.timeLine.setParentItem(self)

        api.callbacks.updateTempoTrackBlocks.append(self.updateBlocks)
        api.callbacks.updateTempoTrack.append(self.createGraphicItemsFromData)
        api.callbacks.updateTempoTrackMeta.append(self.updateMetaData)

    def boundingRect(self):
        """The tempo track extends above the real tracks"""
        return QtCore.QRectF(0, -1*self.totalHeight, 20000, 1.2*self.totalHeight) #x,y,w,h

    def blockAt(self, xScenePosition):
        for block in ConductorTransparentBlock.instances:
            start =  block.staticExportItem["position"] / constantsAndConfigs.ticksToPixelRatio
            end = start + block.staticExportItem["duration"] / constantsAndConfigs.ticksToPixelRatio
            if start <= xScenePosition < end:
                return block
        return None #After the last block.

    @property
    def transparentBlockHandles(self):
        return ConductorTransparentBlock.instances

    def updateMetaData(self, trackMetaDictionary):
        """Keep the meta data up to date.
        Meta Data is (absolute) min and max tempo values:
        {'minimumAbsoluteTempoValue': 120, 'maximumAbsoluteTempoValue': 120}
        """
        self.staticMeta = trackMetaDictionary

    def updateBlocks(self, staticRepresentationList):
        """This is called when the blocks itself change, of course.
        But also """
        self.staticBlocks = staticRepresentationList

        removeInstancesFromScene(ConductorTransparentBlock)
        for dictExportItem in staticRepresentationList:
            guiBlock = ConductorTransparentBlock(parent = self, staticExportItem = dictExportItem, x = 0, y = -10, w = dictExportItem["duration"] / constantsAndConfigs.ticksToPixelRatio, h = 20)
            guiBlock.setParentItem(self)
            guiBlock.setPos(dictExportItem["position"] / constantsAndConfigs.ticksToPixelRatio,0)

        rightBorder = (dictExportItem["duration"] + dictExportItem["position"]) / constantsAndConfigs.ticksToPixelRatio
        self.updateStaffLine(rightBorder)

    def blockById(self, backendId):
        for guiblock in ConductorTransparentBlock.instances:
            if guiblock.staticExportItem["id"] == backendId:
                return guiblock
        #else:
        #    raise ValueError(f"{backendId} not found")


    def updateStaffLine(self, x):
        assert not self.staffLine.line().isNull()
        line = self.staffLine.line()
        line.setLength(x)
        self.staffLine.setLine(line)
        self.staffLine.setZValue(_zValuesRelativeToConductor["line"])

    def createGraphicItemsFromData(self, staticRepresentationList):

        self.staticPoints = staticRepresentationList

        removeInstancesFromScene(TempoPoint)
        y = -35 #The Y Value adjusts for the offset the text-item creates

        for point in staticRepresentationList:
            if not point["type"] == "interpolated": #a real user point or lastInBlock or lastInTrack
                x = point["position"] / constantsAndConfigs.ticksToPixelRatio
                p = TempoPoint(self, point, self.blockById(point["blockId"]))
                p.setParentItem(self)
                p.setPos(x, y)


    def stretchXCoordinates(self, factor):
        """Reposition the items on the X axis.
        Call goes through all parents/children, starting from ScoreView._stretchXCoordinates.
        Docstring there."""

        positionalItems = (TempoPoint.instances + ConductorTransparentBlock.instances)

        for tempoPoint in positionalItems:
            tempoPoint.setX(tempoPoint.pos().x() * factor)

        for block in ConductorTransparentBlock.instances:
            block.stretchXCoordinates(factor)

        stretchLine(self.staffLine, factor)
        self.timeLine.stretchXCoordinates(factor)


    def mousePressEvent(self, event):
        """It is possible that this has coordinates outside of the Conductor instance. When the
        mousePressEvent is inside and the mouse moves outside for the release event it still counts
        as event of this instance"""

        if self.parentView.mode() in ("notation", "cc") and event.button() == QtCore.Qt.LeftButton and 0 <= event.scenePos().x() < self.staffLine.line().x2(): #within the conductor line.
            event.accept()
            self.add(event.scenePos()) #create a new tempo point by telling the api a position and then reacting to "delete all, recreate" from the callback.
        else:
            super().mousePressEvent(event) #call default implementation from QGraphicsRectItem

    def add(self, scenePos):
        """Use a scenePos (from self.mousePressEvent) to instruct the backend
        to create a new tempo point.

        Uses the values from the item left of it
        """

        sp = scenePos.x() * constantsAndConfigs.ticksToPixelRatio
        if constantsAndConfigs.snapToGrid:
            sp = round(sp / constantsAndConfigs.gridRhythm) * constantsAndConfigs.gridRhythm

        unitsPerMinute, referenceTicks = api.tempoAtTickPosition(sp)
        api.insertTempoItemAtAbsolutePosition(sp, unitsPerMinute, referenceTicks, graphType = "standalone")

class ConductorTransparentBlock(QtWidgets.QGraphicsRectItem):
    """A simplified version of a Block. Since we don't use blocks in the GUI, only in the backend
    we still need them sometimes as macro strutures, where we don't care about the content.

    The block handle is at the END of a block. """


    class ConductorBlockName(QtWidgets.QGraphicsSimpleTextItem):

        instances = []

        def __init__(self, parent, positionInSeconds):
            self.__class__.instances.append(self)
            m, s = divmod(positionInSeconds, 60)
            text = "{}:{} min".format(str(int(m)).zfill(2), str(int(s)).zfill(2))
            super().__init__(text)

            marker = QtWidgets.QGraphicsLineItem(0, 0, 0, -10) #vertical marker to connect to the conductor line
            marker.setParentItem(self)

    instances = []

    def __init__(self, parent, staticExportItem, x, y, w, h):
        self.__class__.instances.append(self)
        super().__init__(x, y, w, h)
        self.setFlags(QtWidgets.QGraphicsItem.ItemDoesntPropagateOpacityToChildren|QtWidgets.QGraphicsItem.ItemIsMovable) #no mouseReleaseEvent without selection or movable.
        self.setAcceptHoverEvents(True)
        self.parent = parent #Conductor instance
        self.parentGuiTrack = parent  #redundant, but specifically for block movement. see ScoreScene
        self.color = stringToColor(staticExportItem["name"])
        self.trans = QtGui.QColor("transparent")
        self.setPen(self.trans)
        self.setBrush(self.color)
        self.setOpacity(0.5) #mimic background behaviour
        self.staticExportItem = staticExportItem
        self.posBeforeMove = None
        self.cursorPosOnMoveStart = None

        #Display Block ID
        #self.idText = QtWidgets.QGraphicsSimpleTextItem(str(self.staticExportItem["id"]))
        #self.idText.setParentItem(self)
        #self.idText.setPos(0, -30)

        if self.staticExportItem["duration"] >= 8*api.D1: #cosmetics
            self.startLabel = QtWidgets.QGraphicsSimpleTextItem(self.staticExportItem["name"] + " start")
            self.startLabel.setParentItem(self)
            self.startLabel.setPos(15, -2*constantsAndConfigs.stafflineGap)
            self.startLabel.setFlags(QtWidgets.QGraphicsItem.ItemIgnoresParentOpacity)

            self.endLabel = QtWidgets.QGraphicsSimpleTextItem(self.staticExportItem["name"] + " end ")
            self.endLabel.setParentItem(self)
            self.endLabel.setPos(self.rect().width() - self.endLabel.boundingRect().width(), -2*constantsAndConfigs.stafflineGap)
            self.endLabel.setFlags(QtWidgets.QGraphicsItem.ItemIgnoresParentOpacity)
        else:
            self.startLabel = QtWidgets.QGraphicsSimpleTextItem("")
            self.endLabel = QtWidgets.QGraphicsSimpleTextItem("")

        #Add Resizing Handle at the end
        self.marker = ConductorBlockHandle(parent = self)
        self.marker.setParentItem(self)
        self.marker.setPos(staticExportItem["duration"] / constantsAndConfigs.ticksToPixelRatio, -1/2* self.rect().height()+2)

        #self.setZValue(_zValuesRelativeToConductor["handle"]) #includes the handle

    def stretchXCoordinates(self, factor):
        """Reposition the items on the X axis.
        Call goes through all parents/children, starting from ScoreView._stretchXCoordinates.
        Docstring there."""
        stretchRect(self, factor)
        self.marker.setX(self.marker.pos().x() * factor)

    def mousePressEvent(self, event):
        """Just reroute to the parent score so that mousePressEventCustom can get triggered"""
        self.parent.mousePressEvent(event)

    def mousePressEventCustom(self, event):
        """Custom gets called by the scene mouse press event"""
        self.posBeforeMove = self.pos()
        self.cursorPosOnMoveStart = QtGui.QCursor.pos()
        #self.setBrush(self.color)
        super().mousePressEvent(event)

    def mouseReleaseEventCustom(self, event):
        #self.setBrush(self.trans)
        self.setPos(self.posBeforeMove) #In case the block was moved to a position where no track is (below the tracks) we just reset the graphics. If the moving was correct then the new position will be set by redrawing the whole Conductor.
        self.posBeforeMove = None
        self.cursorPosOnMoveStart = None
        super().mouseReleaseEvent(event)

    def splitHere(self, event):
        posRelativeToBlockStart = event.scenePos().x() * constantsAndConfigs.ticksToPixelRatio - self.x() * constantsAndConfigs.ticksToPixelRatio
        if constantsAndConfigs.snapToGrid:
            posRelativeToBlockStart = round(posRelativeToBlockStart / constantsAndConfigs.gridRhythm) * constantsAndConfigs.gridRhythm

        if posRelativeToBlockStart > 0:
            api.splitTempoBlock(self.staticExportItem["id"], int(posRelativeToBlockStart))

    def contextMenuEventCustom(self, event):
        listOfLabelsAndFunctions = [
            ("edit properties", lambda: TempoBlockPropertiesEdit(self.scene().parentView.mainWindow, staticExportItem = self.staticExportItem)),
            ("separator", None),
            ("split here", lambda: self.splitHere(event)),
            ("duplicate", lambda: api.duplicateTempoBlock(self.staticExportItem["id"])),
            ("create content link", lambda: api.duplicateContentLinkTempoBlock(self.staticExportItem["id"])),
            ("unlink", lambda: api.unlinkTempoBlock(self.staticExportItem["id"])),
            ("separator", None),
            ("join with next block", lambda: api.mergeWithNextTempoBlock(self.staticExportItem["id"])),
            ("delete block", lambda: api.deleteTempoBlock(self.staticExportItem["id"])),
            ("separator", None),
            ("append block at the end", api.appendTempoBlock),
            ]
        callContextMenu(listOfLabelsAndFunctions)

class ConductorBlockHandle(QtWidgets.QGraphicsRectItem):
    """Provides user interaction so the temp block can be resized by moving this handle with the
    mouse left and right.
    When user interaction happens this handle acts upon its parent transparent block to resize it
    and finally sends a message to the backend, to ask for a data change."""

    def __init__(self, parent):
        self.parentTransparentBlock = parent
        #Line item super().__init__(0,-1, 0, parent.rect().height()-4) #x1, y1, x2, y2
        super().__init__(-3, -2, 3,  parent.rect().height()) #x, y, w, h
        self.setFlags(QtWidgets.QGraphicsItem.ItemIsMovable|QtWidgets.QGraphicsItem.ItemSendsGeometryChanges|QtWidgets.QGraphicsItem.ItemIsFocusable|QtWidgets.QGraphicsItem.ItemIgnoresParentOpacity)  #QtWidgets.QGraphicsItem.ItemClipsToShape puts the item behind the parent rect and only receives event inside its own shape.
        self.setAcceptHoverEvents(True)
        self.setZValue(_zValuesRelativeToConductor["handle"]) #The handle does not compete with the transparent block but with its contents! Therefore the startItem is set to have a custom lower priority than the handle
        self.setBrush(QtGui.QColor("black"))

        self.minimalSize = api.D1 / constantsAndConfigs.ticksToPixelRatio

        pen = QtGui.QPen()  # creates a default pen
        #if not self.parentTransparentBlock.staticExportItem["exportsAllItems"]:
        #    pen.setStyle(QtCore.Qt.DotLine)
        pen.setWidth(0)
        self.setPen(pen)

        self.inactivePen = pen
        self.inactivePen.setColor(QtGui.QColor("black"))

        self.activePen = QtGui.QPen(pen)
        self.activePen.setColor(QtGui.QColor("cyan"))

    def shape(self):
        """Return a more accurate shape for this item so that
        mouse hovering is more accurate"""
        path = QtGui.QPainterPath()
        path.addRect(QtCore.QRectF(-2, -2, 5, self.parentTransparentBlock.rect().height()+2 )) #this is directly related to inits parameter x, y, w, h
        return path

    def hoverEnterEvent(self, event):
        if self.parentTransparentBlock.parent.parentView.mode() in ("notation", "cc"):  #Blockmode is for moving around. not resizing.
            self.setCursor(QtCore.Qt.SizeHorCursor)
            self.setPen(self.activePen)
            #self.parentTransparentBlock.setBrush(self.parentTransparentBlock.color)
            self.setBrush(QtGui.QColor("cyan"))

    def hoverLeaveEvent(self, event):
        if self.parentTransparentBlock.parent.parentView.mode() in ("notation", "cc"):  #Blockmode is for moving around. not resizing.
            self.unsetCursor()
            self.setPen(self.inactivePen)
            #self.parentTransparentBlock.setBrush(self.parentTransparentBlock.trans)
            self.setBrush(QtGui.QColor("black"))

    def mousePressEvent(self, event):
        if self.parentTransparentBlock.parent.parentView.mode() in ("notation", "cc"):  #Blockmode is for moving around. not resizing.
            self.posBeforeMove = self.pos()
            self.cursorPosOnMoveStart = QtGui.QCursor.pos()
            super().mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if self.parentTransparentBlock.parent.parentView.mode() in ("notation", "cc"):  #Blockmode is for moving around. not resizing.
            if not self.cursorPosOnMoveStart:
                super().mouseMoveEvent(event)
                return None

            delta = QtGui.QCursor.pos() - self.cursorPosOnMoveStart
            new = self.posBeforeMove + delta

            if not new.x() < self.minimalSize:
                self.setPos(new.x(), self.posBeforeMove.y())
                pRect = self.parentTransparentBlock.rect()
                pRect.setRight(new.x())
                self.parentTransparentBlock.setRect(pRect)

            event.accept() #this blocks the qt movable object since we already move the object on our own.
            #Don't call the super mouseMoveEvent!

    def mouseReleaseEvent(self, event):
        if self.cursorPosOnMoveStart and self.parentTransparentBlock.parent.parentView.mode() in ("notation", "cc"):

            endingRelativeToBlockStart = self.x() * constantsAndConfigs.ticksToPixelRatio - self.parentTransparentBlock.x()
            if constantsAndConfigs.snapToGrid:
                endingRelativeToBlockStart = round(endingRelativeToBlockStart / constantsAndConfigs.gridRhythm) * constantsAndConfigs.gridRhythm
            assert endingRelativeToBlockStart > 0

            self.setPos(self.posBeforeMove) #In case the handle was moved to a position where it wasn't allowed no backend action will happen. Just in case we reset the graphics for a smoother user experience.
            self.posBeforeMove = None
            self.cursorPosOnMoveStart = None

            api.changeTempoBlockDuration(self.parentTransparentBlock.staticExportItem["id"], endingRelativeToBlockStart)

        super().mouseReleaseEvent(event)

class TempoPoint(QtWidgets.QGraphicsItem):
    """A point where the values can be edited by the user.
    Only in notation and cc mode. Blockmode is for moving the blocks itself.

    The first TempoPoint cannot be hovered. It is instead attached to a block handle.
    """

    instances = []

    def __init__(self, parentTempoTrack, staticExportItem, parentBlock):
        self.__class__.instances.append(self)
        super().__init__()
        self.staticExportItem = staticExportItem
        self.parentTempoTrack = parentTempoTrack
        self.parentBlock = parentBlock
        self.setZValue(_zValuesRelativeToConductor["item"])
        self.setAcceptHoverEvents(True)

        if not self.staticExportItem["positionInBlock"] == 0:
            self.setFlags(QtWidgets.QGraphicsItem.ItemIsMovable|QtWidgets.QGraphicsItem.ItemIsFocusable)
            #Too irritating. And confuses with handle movement. self.setCursor(QtCore.Qt.SizeHorCursor) #this sets the cursor while the mouse is over the item. It is independent of AcceptHoverEvents
        else:
            self.setZValue(0) #avoid hovering conflict with block handle
            self.ungrabMouse = api.nothing #to surpress a warning from the context menu

        #Set this flag after setFlags above
        self.setFlag(QtWidgets.QGraphicsItem.ItemHasNoContents, True) #only child items. Without this we get notImplementedError: QGraphicsItem.paint() is abstract and must be overridden

        self.note = QtWidgets.QGraphicsTextItem("")
        self.note.setParentItem(self)
        self.note.setFont(constantsAndConfigs.musicFont)
        s = constantsAndConfigs.realNoteDisplay[staticExportItem["referenceTicks"]]
        self.note.setHtml(f"<font size='6'>{s}</font>")
        self.note.setPos(-6,0) #adjust items font x offsset.

        self.number = QtWidgets.QGraphicsTextItem("")
        self.number.setParentItem(self)
        #self.number.setHtml("<font color='black' size='2'>{}</font>".format(str(int(staticExportItem["unitsPerMinute"]))))
        self.number.setHtml("<font size='2'>{}</font>".format(str(int(staticExportItem["unitsPerMinute"]))))
        self.number.setPos(-6,0) #adjust items font x offsset.

        if not self.staticExportItem["graphType"] == "standalone":
            self.arrow = QtWidgets.QGraphicsTextItem("⟶") #unicode long arrow right #http://xahlee.info/comp/unicode_arrows.html
            self.arrow.setParentItem(self)
            self.arrow.setPos(7,30)
        else:
            self.arrow = None

        for n in (self.note, self.number, self.arrow):
            if n: n.setDefaultTextColor(QtGui.QColor("black"))

        self.wheelEventChangedValue = 0 #resetted in hoverEnterEvent. But we still need it for new items that appear directly under the mouse cursor

    def boundingRect(self):
        """We could return self.childrenBoundingRect() but we want the clickable area to be bigger"""
        return QtCore.QRectF(0,0,25,50) #x, y, w, h

    def mouseMoveEvent(self, event):
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            if self.staticExportItem["positionInBlock"] == 0:
                #First in block can't be moved
                event.accept()
                return

            #toTheRight = True if event.scenePos().x() - event.lastScenePos().x()) > 0 else False

            delta = event.scenePos().x() - event.lastScenePos().x()
            newPos = self.x() + delta

            if 0 <= newPos < self.parentTempoTrack.staffLine.line().x2(): #within the conductor line
                self.setX(newPos)
            event.accept()
        else:
            event.accept()

    def mousePressEvent(self, event):
        """Override the mousePressEvent to deactivate it.
        Otherwise the event will be sent to the parent block and create a new TempoItem
        at this point even if there is already one. Effectively replacing a custom item with
        default value"""
        #if self.staticExportItem["positionInBlock"] == 0:
        #    print ("no")
        #    #super().mousePressEvent(event)
        event.accept() #

    def mouseReleaseEvent(self, event):
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            if self.staticExportItem["positionInBlock"] == 0:
                #First in block can't be moved
                event.accept()
                return

            tickPositionAbsolute = self.scenePos().x() * constantsAndConfigs.ticksToPixelRatio

            if constantsAndConfigs.snapToGrid:
                tickPositionAbsolute = round(tickPositionAbsolute / constantsAndConfigs.gridRhythm) * constantsAndConfigs.gridRhythm

            api.moveTempoItem(self.staticExportItem["id"], tickPositionAbsolute)
            event.accept()
        else:
            event.accept()

    def hoverEnterEvent(self, event):
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            self.parentTempoTrack.parentView.mainWindow.ui.actionDelete.setEnabled(False) #Delete key collides with our hover-delete.
            self.grabKeyboard()
            self.wheelEventChangedValue = 0
            for n in (self.note, self.number, self.arrow):
                if n: n.setDefaultTextColor(QtGui.QColor("cyan"))
        else:
            event.accept()

    def hoverLeaveEvent(self, event):
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            self.parentTempoTrack.parentView.mainWindow.ui.actionDelete.setEnabled(True) #Delete key collides with our hover-delete.
            self.ungrabKeyboard()
            for n in (self.note, self.number, self.arrow):
                if n: n.setDefaultTextColor(QtGui.QColor("black"))
            if self.wheelEventChangedValue:
                api.insertTempoItemAtAbsolutePosition(self.staticExportItem["position"], self.staticExportItem["unitsPerMinute"] + self.wheelEventChangedValue, self.staticExportItem["referenceTicks"], self.staticExportItem["graphType"])
        else:
            event.accept()

    def wheelEvent(self, event):
        """This buffers until hoverLeaveEvent and then the new value is sent in self.hoverLeaveEvent"""
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            if event.delta() > 0:
                self.wheelEventChangedValue += 1
            else:
                self.wheelEventChangedValue -= 1
            self.number.setHtml("<font size='2'>{}</font>".format(str(int(self.staticExportItem["unitsPerMinute"] + self.wheelEventChangedValue))))
            event.accept()
        else:
            event.accept()

    def keyPressEvent(self, event):
        """Handle the delete item key.
        Needs grabKeyboard, but NOT setFocus

        The event will not be sent if it is blocked by a global shortcut.
        """
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            key = event.key()
            if key == 16777223:
                #after delete the item and tempo tracks gets recreated so we need to reactivate the shortcut now. It will work without these two lines, but that is only implicit behaviour.
                self.parentTempoTrack.parentView.mainWindow.ui.actionDelete.setEnabled(True) #Delete key collides with our hover-delete.
                self.ungrabKeyboard()
                api.removeTempoItem(self.staticExportItem["id"])
            else:
                return super().keyPressEvent(event)
        else:
            event.accept()

    def contextMenuEvent(self, event):
        if self.parentTempoTrack.parentView.mode() in ("notation", "cc"):
            listOfLabelsAndFunctions = [
                ("edit properties", lambda: SecondaryTempoChangeMenu(self.scene().parentView.mainWindow, staticExportTempoItem = self.staticExportItem)),
                ]
            if not self.staticExportItem["positionInBlock"] == 0:
                listOfLabelsAndFunctions.append(("delete", lambda: api.removeTempoItem(self.staticExportItem["id"])))
            callContextMenu(listOfLabelsAndFunctions)
        else:
            event.accept()

class TimeLine(QtWidgets.QGraphicsItem):
    """Displays the real time."""

    class TimePoint(QtWidgets.QGraphicsSimpleTextItem):

        instances = []

        def __init__(self, parent, positionInSeconds):
            self.__class__.instances.append(self)
            m, s = divmod(positionInSeconds, 60)
            text = "{}:{} min".format(str(int(m)).zfill(2), str(int(s)).zfill(2))
            super().__init__(text)

            marker = QtWidgets.QGraphicsLineItem(0, 0, 0, -10) #vertical marker to connect to the conductor line
            marker.setParentItem(self)


    def __init__(self, parent):
        super().__init__()
        self.setFlag(QtWidgets.QGraphicsItem.ItemHasNoContents, True) #only child items. Without this we get notImplementedError: QGraphicsItem.paint() is abstract and must be overridden
        self.parent = parent #
        self.gridInSeconds = 10
        api.callbacks.updateTempoTrackBlocks.append(self.redraw)
        #no redraw on init. self.parent.staticPoints is not set yet.

    def boundingRect(self):
        return self.parent.boundingRect()

    def redraw(self, staticRepresentationList):
        if not self.parent.staticPoints:
            return None
        removeInstancesFromScene(self.TimePoint)
        sliceStartInSeconds = 0 #counted, not calculated
        gridCounter = 0 # int("how often was a gridMarker generated")
        result = []
        for nowPoint, nextPoint in pairwise(self.parent.staticPoints):
            """Values we can't calculate:
                sliceEndInTicks / ticksPerSecond . sliceEndInTicks is an absolute position.
                    but ticksPerSecond changes with every slice. Therefore you would discard all
                    ticksPerSecond value except the last and calculate a wrong value.
                    Instead we need to calculate the seconds always in the slice and then count
                    the overall length.
            """

            tempoForThisSlice = abs(nowPoint["value"])

            sliceDurationInTicks = nextPoint["position"] - nowPoint["position"]
            ticksPerSecondForThisSlice = tempoForThisSlice * api.D4 / 60  # ["value"] is normalized beatsPerMinute(!) for quarter notes. calculated from "units" and "referenceTicks"
            sliceDurationInSeconds = sliceDurationInTicks / ticksPerSecondForThisSlice
            sliceEndInSeconds = sliceStartInSeconds + sliceDurationInSeconds

            while sliceStartInSeconds < (gridCounter+1) * self.gridInSeconds <= sliceEndInSeconds: #is the next grid marker(+1) in the current slice?
                gridCounter += 1
                secondsSinceLastTempoChange = gridCounter * self.gridInSeconds - sliceStartInSeconds

                posInTicks = nowPoint["position"] + secondsSinceLastTempoChange * ticksPerSecondForThisSlice
                assert nowPoint["position"] <= posInTicks <= nextPoint["position"], (nowPoint["position"], posInTicks, nextPoint["position"])
                result.append((posInTicks, gridCounter * self.gridInSeconds))

            sliceStartInSeconds = sliceEndInSeconds

        #After the loop both sliceStartInSeconds and sliceEndInSeconds are equal to the overall length of the track in seconds
        #Add an end marker to the results and create the qGraphicItems to display the time markers.
        if nextPoint["position"] > 0:
            result.append((nextPoint["position"], sliceEndInSeconds))

        for tickPos, secPos in result:
            timePoint = self.TimePoint(self, secPos)
            timePoint.setParentItem(self)
            timePoint.setPos(tickPos / constantsAndConfigs.ticksToPixelRatio, 10)


    def stretchXCoordinates(self, factor):
        """Does NOT just reposition the existing items but displays a different
        time grid"""
        for timePoint in self.TimePoint.instances:
            timePoint.setX(timePoint.pos().x() * factor)