鼠标悬停在PySide QGraphicsPathItem上

Question

当我尝试在QGraphicsPathItem上注册鼠标悬停事件时，我遇到了奇怪的行为。

在示例代码中（我从qt5弹性节点示例中入侵）我绘制了一条简单的曲线。将鼠标悬停在曲线上会改变曲线的颜色，但悬停事件不会记录在曲线的右下半部分。此外，只有曲线的左上半部分实际上会改变颜色。

我添加了一个QPainterPathStroker，认为悬停事件将在此区域内注册，但事实并非如此。

我的目标是将鼠标移动到QPainterPathStroker区域中，作为QGraphicsPathItem上的悬停事件。

任何帮助表示赞赏。谢谢

from PySide import QtCore, QtGui

class Edge(QtGui.QGraphicsPathItem):

    def __init__(self):
        QtGui.QGraphicsPathItem.__init__(self)
        self.setAcceptsHoverEvents(True)
        path = QtGui.QPainterPath()
        x1 = -100
        x2 = 120
        y1 = -100
        y2 = 120
        dx = abs(x1-x2)/2
        dy = abs(y1-y2)/2
        a = QtCore.QPointF(x1, y1)
        b = QtCore.QPointF(x1+dx, y1)
        c = QtCore.QPointF(x2-dy, y2)
        d = QtCore.QPointF(x2, y2)
        path.moveTo(a)
        path.cubicTo(b,c,d)
        self.setPath(path)

        self.hover = False

    def hoverEnterEvent(self, event):

        self.hover = True
        QtGui.QGraphicsPathItem.hoverEnterEvent(self, event)

    def hoverMoveEvent(self, event):

        QtGui.QGraphicsPathItem.hoverMoveEvent(self, event)

    def hoverLeaveEvent(self, event):

        self.hover = False
        QtGui.QGraphicsPathItem.hoverLeaveEvent(self, event)        

    def boundingRect(self):
        return QtCore.QRectF(-100,-100,120,120)

    def paint(self, painter, option, widget):

        if self.hover:
            c = QtCore.Qt.red
        else:
            c = QtCore.Qt.black
        painter.setPen(QtGui.QPen(c, 10, QtCore.Qt.SolidLine, QtCore.Qt.RoundCap, QtCore.Qt.RoundJoin))
        painter.drawPath(self.path())

        painter.setPen(QtGui.QPen(QtCore.Qt.blue, 1, QtCore.Qt.SolidLine, QtCore.Qt.RoundCap, QtCore.Qt.RoundJoin))
        painter.drawPath(self.shape())

    def shape(self):
        s = QtGui.QPainterPathStroker()    
        s.setWidth(30)
        s.setCapStyle(QtCore.Qt.RoundCap)
        path = s.createStroke(self.path())
        return path


class GraphWidget(QtGui.QGraphicsView):
    def __init__(self):
        QtGui.QGraphicsView.__init__(self)

        scene = QtGui.QGraphicsScene(self)
        scene.setItemIndexMethod(QtGui.QGraphicsScene.NoIndex)
        scene.setSceneRect(-200, -200, 400, 400)
        self.setScene(scene)
        self.setRenderHint(QtGui.QPainter.Antialiasing)
        self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QtGui.QGraphicsView.AnchorViewCenter)

        self.edge = Edge()
        scene.addItem(self.edge)

        self.scale(0.8, 0.8)
        self.setMinimumSize(400, 400)
        self.setWindowTitle(self.tr("Elastic Nodes"))

    def wheelEvent(self, event):
        self.scaleView(math.pow(2.0, -event.delta() / 240.0))

    def drawBackground(self, painter, rect):
        sceneRect = self.sceneRect()
        rightShadow = QtCore.QRectF(sceneRect.right(), sceneRect.top() + 5, 5, sceneRect.height())
        bottomShadow = QtCore.QRectF(sceneRect.left() + 5, sceneRect.bottom(), sceneRect.width(), 5)
        if rightShadow.intersects(rect) or rightShadow.contains(rect):
            painter.fillRect(rightShadow, QtCore.Qt.darkGray)
        if bottomShadow.intersects(rect) or bottomShadow.contains(rect):
            painter.fillRect(bottomShadow, QtCore.Qt.darkGray)

        gradient = QtGui.QLinearGradient(sceneRect.topLeft(), sceneRect.bottomRight())
        gradient.setColorAt(0, QtCore.Qt.white)
        gradient.setColorAt(1, QtCore.Qt.lightGray)
        painter.fillRect(rect.intersect(sceneRect), QtGui.QBrush(gradient))
        painter.setBrush(QtCore.Qt.NoBrush)
        painter.drawRect(sceneRect)

    def scaleView(self, scaleFactor):
        factor = self.matrix().scale(scaleFactor, scaleFactor).mapRect(QtCore.QRectF(0, 0, 1, 1)).width()

        if factor < 0.07 or factor > 100:
            return

        self.scale(scaleFactor, scaleFactor)

    def mouseMoveEvent(self, event):

        self.edge.update()
        QtGui.QGraphicsView.mouseMoveEvent(self, event)


widget = GraphWidget()
widget.show()

Answer 1

在这种情况下的问题是boundingRect()没有涵盖完整的path()，这是由paint()方法使用，解决方案是返回self.shape().boundingRect()：

class Edge(QtGui.QGraphicsPathItem):
    def __init__(self):
        QtGui.QGraphicsPathItem.__init__(self)
        self.setAcceptsHoverEvents(True)
        path = QtGui.QPainterPath()
        x1 = -100
        x2 = 120
        y1 = -100
        y2 = 120
        dx = abs(x1-x2)/2
        dy = abs(y1-y2)/2
        a = QtCore.QPointF(x1, y1)
        b = a + QtCore.QPointF(dx, 0)
        d = QtCore.QPointF(x2, y2)
        c = d - QtCore.QPointF(dy, 0)
        path.moveTo(a)
        path.cubicTo(b,c,d)
        self.setPath(path)

        self.hover = False

    def hoverEnterEvent(self, event):
        QtGui.QGraphicsPathItem.hoverEnterEvent(self, event)
        self.hover = True
        self.update()

    def hoverMoveEvent(self, event):
        # print(event)
        QtGui.QGraphicsPathItem.hoverMoveEvent(self, event)

    def hoverLeaveEvent(self, event):
        QtGui.QGraphicsPathItem.hoverLeaveEvent(self, event)
        self.hover = False
        self.update()        

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

    def paint(self, painter, option, widget):
        c = QtCore.Qt.red if self.hover else QtCore.Qt.black
        painter.setPen(QtGui.QPen(c, 10, QtCore.Qt.SolidLine, QtCore.Qt.RoundCap, QtCore.Qt.RoundJoin))
        painter.drawPath(self.path())

        painter.setPen(QtGui.QPen(QtCore.Qt.blue, 1, QtCore.Qt.SolidLine, QtCore.Qt.RoundCap, QtCore.Qt.RoundJoin))
        painter.drawPath(self.shape())

    def shape(self):
        s = QtGui.QPainterPathStroker()    
        s.setWidth(30)
        s.setCapStyle(QtCore.Qt.RoundCap)
        path = s.createStroke(self.path())
        return path

Answer 2

使用PySide2，上面的代码有两个问题：

在Edge.__init__而不是

self.setAcceptsHoverEvents(True)

使用：

self.setAcceptHoverEvents(True)

（方法名称中没有's'）。

在GraphWidget.drawBackground，而不是

painter.fillRect(rect.intersects(sceneRect), QBrush(gradient))

使用其中一个

painter.fillRect(rect.intersected(sceneRect), QBrush(gradient))

（'ed'而不是方法名称中的's'）或

painter.fillRect(rect & sceneRect, QBrush(gradient))