Qt调用示例的Python（PyQt5）版本

Question

标注示例

从QtCharts包：https://doc.qt.io/qt-5/qtcharts-callout-example.html

此（出色的）示例显示了如何在图表顶部绘制一个附加元素（标注）。

问题是是否可以在python中实现该示例？

Answer 1

我正在寻找移植到PyQt5（python）的示例，但未找到任何示例。因此，我自己写了这本书，并希望与您分享（以节省您的时间）。它是为Python 3.8编写的，但也应适用于较旧的版本，PyQt版本为5.14.1。

与原始的C ++实现只有一点区别。必须明确设置QGraphicsScene-在View构造函数类中，并且必须将每个新的Callout对象明确添加到场景中。坦白说，我不知道为什么，但我不在乎。与C ++中完全相同的Qt库版本不需要。

import sys
from typing import List

from PyQt5.QtChart import QChart, QLineSeries, QSplineSeries
from PyQt5.QtCore import QPointF, QRect, QRectF, QSizeF, Qt
from PyQt5.QtGui import QColor, QFont, QFontMetrics, QMouseEvent, QPainter, QPainterPath, QResizeEvent
from PyQt5.QtWidgets import QApplication, QGraphicsItem, QGraphicsScene, QGraphicsSceneMouseEvent, \
    QGraphicsSimpleTextItem, QGraphicsView, QStyleOptionGraphicsItem, QWidget


class Callout(QGraphicsItem):

    def __init__(self, parent: QChart):
        super().__init__()
        self.m_chart: QChart = parent
        self.m_text: str = ''
        self.m_anchor: QPointF = QPointF()
        self.m_font: QFont = QFont()
        self.m_textRect: QRectF = QRectF()
        self.m_rect: QRectF = QRectF()

    def setText(self, text: str):
        self.m_text = text
        metrics = QFontMetrics(self.m_font)
        self.m_textRect = QRectF(metrics.boundingRect(QRect(0, 0, 150, 150), Qt.AlignLeft, self.m_text))
        self.m_textRect.translate(5, 5)
        self.prepareGeometryChange()
        self.m_rect = QRectF(self.m_textRect.adjusted(-5, -5, 5, 5))
        self.updateGeometry()

    def updateGeometry(self):
        self.prepareGeometryChange()
        self.setPos(self.m_chart.mapToPosition(self.m_anchor) + QPointF(10, -50))

    def boundingRect(self) -> QRectF:
        from_parent = self.mapFromParent(self.m_chart.mapToPosition(self.m_anchor))
        anchor = QPointF(from_parent)
        rect = QRectF()
        rect.setLeft(min(self.m_rect.left(), anchor.x()))
        rect.setRight(max(self.m_rect.right(), anchor.x()))
        rect.setTop(min(self.m_rect.top(), anchor.y()))
        rect.setBottom(max(self.m_rect.bottom(), anchor.y()))
        return rect

    def paint(self, painter: QPainter, option: QStyleOptionGraphicsItem, widget: QWidget):
        path = QPainterPath()
        mr = self.m_rect
        path.addRoundedRect(mr, 5, 5)

        anchor = QPointF(self.mapFromParent(self.m_chart.mapToPosition(self.m_anchor)))
        if not mr.contains(anchor):
            point1 = QPointF()
            point2 = QPointF()

            # establish the position of the anchor point in relation to self.m_rect
            above = anchor.y() <= mr.top()
            above_center = mr.top() < anchor.y() <= mr.center().y()
            below_center = mr.center().y() < anchor.y() <= mr.bottom()
            below = anchor.y() > mr.bottom()

            on_left = anchor.x() <= mr.left()
            left_of_center = mr.left() < anchor.x() <= mr.center().x()
            right_of_center = mr.center().x() < anchor.x() <= mr.right()
            on_right = anchor.x() > mr.right()

            # get the nearest self.m_rect corner.
            x = (on_right + right_of_center) * mr.width()
            y = (below + below_center) * mr.height()
            corner_case = (above and on_left) or (above and on_right) or (below and on_left) or (below and on_right)
            vertical = abs(anchor.x() - x) > abs(anchor.y() - y)
            horizontal = bool(not vertical)

            x1 = x + left_of_center * 10 - right_of_center * 20 + corner_case * horizontal * (
                    on_left * 10 - on_right * 20)
            y1 = y + above_center * 10 - below_center * 20 + corner_case * vertical * (above * 10 - below * 20)
            point1.setX(x1)
            point1.setY(y1)

            x2 = x + left_of_center * 20 - right_of_center * 10 + corner_case * horizontal * (
                    on_left * 20 - on_right * 10)
            y2 = y + above_center * 20 - below_center * 10 + corner_case * vertical * (above * 20 - below * 10)
            point2.setX(x2)
            point2.setY(y2)

            path.moveTo(point1)
            path.lineTo(anchor)
            path.lineTo(point2)
            path = path.simplified()

        painter.setPen(QColor(30, 30, 30))
        painter.setBrush(QColor(255, 255, 255))
        painter.drawPath(path)
        painter.drawText(self.m_textRect, self.m_text)

    def mousePressEvent(self, event: QGraphicsSceneMouseEvent):
        event.setAccepted(True)

    def mouseMoveEvent(self, event: QGraphicsSceneMouseEvent):
        if event.buttons() & Qt.LeftButton:
            self.setPos(self.mapToParent(event.pos() - event.buttonDownPos(Qt.LeftButton)))
            event.setAccepted(True)
        else:
            event.setAccepted(False)


class View(QGraphicsView):

    def __init__(self, parent=None):
        super().__init__(parent)
        self.m_callouts: List[Callout] = []
        self.setDragMode(QGraphicsView.NoDrag)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)

        # chart
        self.m_chart = QChart(parent)
        self.m_chart.setMinimumSize(640, 480)
        self.m_chart.setTitle("Hover the line to show callout. Click the line to make it stay")
        self.m_chart.legend().hide()
        series = QLineSeries()
        series.append(1, 3)
        series.append(4, 5)
        series.append(5, 4.5)
        series.append(7, 1)
        series.append(11, 2)
        self.m_chart.addSeries(series)

        series2 = QSplineSeries()
        series2.append(1.6, 1.4)
        series2.append(2.4, 3.5)
        series2.append(3.7, 2.5)
        series2.append(7, 4)
        series2.append(10, 2)
        self.m_chart.addSeries(series2)

        self.m_chart.createDefaultAxes()
        self.m_chart.setAcceptHoverEvents(True)

        self.setRenderHint(QPainter.Antialiasing)

        self.setScene(QGraphicsScene())
        self.scene().addItem(self.m_chart)

        self.m_coordX = QGraphicsSimpleTextItem(self.m_chart)
        self.m_coordX.setPos(self.m_chart.size().width() / 2 - 50, self.m_chart.size().height() - 20)
        self.m_coordX.setText("X: ")
        self.m_coordY = QGraphicsSimpleTextItem(self.m_chart)
        self.m_coordY.setPos(self.m_chart.size().width() / 2 + 50, self.m_chart.size().height() - 20)
        self.m_coordY.setText("Y: ")

        self.m_tooltip = Callout(self.m_chart)
        self.scene().addItem(self.m_tooltip)

        series.clicked.connect(self.keep_callout)
        series.hovered.connect(self.tooltip)
        series2.clicked.connect(self.keep_callout)
        series2.hovered.connect(self.tooltip)

        self.setMouseTracking(True)

    def resizeEvent(self, event: QResizeEvent):
        if scene := self.scene():
            scene.setSceneRect(QRectF(QPointF(0, 0), QSizeF(event.size())))
            self.m_chart.resize(QSizeF(event.size()))
            self.m_coordX.setPos(self.m_chart.size().width() / 2 - 50, self.m_chart.size().height() - 20)
            self.m_coordY.setPos(self.m_chart.size().width() / 2 + 50, self.m_chart.size().height() - 20)

            for callout in self.m_callouts:
                callout.updateGeometry()

        super().resizeEvent(event)

    def mouseMoveEvent(self, event: QMouseEvent):
        from_chart = self.m_chart.mapToValue(event.pos())
        self.m_coordX.setText(f"X: {from_chart.x()}")
        self.m_coordX.setText(f"Y: {from_chart.y()}")
        super().mouseMoveEvent(event)

    def keep_callout(self):
        self.m_callouts.append(self.m_tooltip)
        self.m_tooltip = Callout(self.m_chart)
        self.scene().addItem(self.m_tooltip)

    def tooltip(self, point: QPointF, state: bool):
        if not self.m_tooltip:
            self.m_tooltip = Callout(self.m_chart)

        if state:
            self.m_tooltip.setText(f"X: {point.x()} \nY: {point.x()} ")
            self.m_tooltip.m_anchor = point
            self.m_tooltip.setZValue(11)
            self.m_tooltip.updateGeometry()
            self.m_tooltip.show()
        else:
            self.m_tooltip.hide()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = View()
    window.resize(640, 480)
    window.show()
    sys.exit(app.exec_())