python - sceneRect().translated(x,y) 无法与缩放正常工作

Question

一个月前，我问，如何翻译场景，我得到了很大的帮助，并理解了它如何工作，在使用它/添加人员一个月后，我注意到当你放大到非常接近几何体或某处时否则，翻译就会变得越来越有值(value)。

您必须放大到非常接近几何体才能看到问题。这是一些代码:

from PyQt5.QtGui import QColor, QPolygonF, QPen, QBrush
from PyQt5.QtCore import Qt, QPointF, QPoint, pyqtSignal
from PyQt5.QtWidgets import QDialog, QVBoxLayout, QGraphicsView, QGraphicsScene, QGraphicsPolygonItem, QApplication, \
    QFrame, QSizePolicy
points_list = [[60.1, 19.6, 0.0], [60.1, 6.5, 0.0], [60.1, -6.5, 0.0], [60.1, -19.6, 0.0], [60.1, -19.6, 0.0],
               [20.0, -19.6, 0.0], [-20, -19.6, 0.0], [-60.1, -19.6, 0.0], [-60.1, -19.6, 0.0], [-60.1, -6.5, 0.0],
               [-60.1, 6.5, 0.0], [-60.1, 19.6, 0.0], [-60.1, 19.6, 0.0], [-20.0, 19.6, 0.0], [20.0, 19.6, 0.0],
               [60.1, 19.6, 0.0]]


class MainWindow(QDialog):
    def __init__(self, parent=None):
        QDialog.__init__(self, parent=parent)
        self.create()

    def create(self, **kwargs):
        main_layout = QVBoxLayout()
        graphics = MainGraphicsWidget()
        main_layout.addWidget(graphics)
        self.setLayout(main_layout)

class MainGraphicsWidget(QGraphicsView):
    zoom_signal = pyqtSignal(bool)

    def __init__(self, parent=None):
        super(MainGraphicsWidget, self).__init__(parent)
        self._scene = QGraphicsScene(backgroundBrush=Qt.gray)
        self.__zoom = 0
        self.setScene(self._scene)
        self.setTransformationAnchor(QGraphicsView.NoAnchor)
        #self.setTransformationAnchor(QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QGraphicsView.AnchorUnderMouse)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setBackgroundBrush(QBrush(QColor(30, 30, 30)))
        self.setFrameShape(QFrame.NoFrame)
        self.setSizePolicy(QSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding))
        # self.sceneRect = self._scene.sceneRect()
        self.testButton = GraphicsButton()
        self._scene.addItem(self.testButton)
        self.startPos = None


    def mousePressEvent(self, event):
        if event.modifiers() & Qt.AltModifier and event.button() == Qt.LeftButton:
            self.startPos = event.pos()
        else:
            super(MainGraphicsWidget, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        modifierPressed = QApplication.keyboardModifiers()
        if self.startPos is not None:
            delta = self.startPos - event.pos()
            transform = self.transform()
            deltaX = delta.x() / transform.m11()
            deltaY = delta.y() / transform.m22() 
            self.setSceneRect(self.sceneRect().translated(deltaX, deltaY))
            self.startPos = event.pos()
        else:
            super(MainGraphicsWidget, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        self.startPos = None
        super(MainGraphicsWidget, self).mouseReleaseEvent(event)


    def wheelEvent(self, event):
        if event.angleDelta().y() > 0:
            factor = 1.25
            self.__zoom += 1
        else:
            factor = 0.8
            self.__zoom -= 1
        self.scale(factor, factor)
        self.zoom_signal.emit(self.__zoom < 10)


class GraphicsButton(QGraphicsPolygonItem):
    def __init__(self, parent=None):
        super(GraphicsButton, self).__init__(parent)
        self.myPolygon = QPolygonF([QPointF(v1, v2) for v1, v2, v3 in points_list])
        self.setPen(QPen(QColor(0, 0, 0), 0, Qt.SolidLine, Qt.FlatCap, Qt.MiterJoin))
        self.setPolygon(self.myPolygon)
        self.setBrush(QColor(220, 40, 30))


if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = MainWindow()
    window.setGeometry(500, 100, 500, 900)
    window.show()
    sys.exit(app.exec_())

(翻译开始使用Alt + 左键单击)

我猜问题是，当你放大得太近时，你的光标仍然沿着相同的坐标移动(它们不会变小)并且它开始翻译得更慢，我在代码中没有考虑这一点。但为什么有时我的 sceneRect().translated() 根本停止移动呢？我是否放大到至少不与光标交叉的点(1x，1y)？

所以我的问题是，如果我的理论正确，有人可以建议我如何计算delta、放大和缩小吗？谢谢你，抱歉我的英语不好

编辑:这是您需要放大多少才能看到问题的屏幕截图。

Answer 1

sceneRect位于场景的坐标中，而不是 View 的坐标中，因此为了进行计算，您必须使用 mapToScene 方法将鼠标点转换为场景的坐标。此修改还应该应用于投影在场景中的视口(viewport)矩形，因为它不等于 sceneRect

class MainGraphicsWidget(QGraphicsView):
    zoom_signal = pyqtSignal(bool)

    def __init__(self, parent=None):
        # ...
        self.startPos = QPointF()

    def mousePressEvent(self, event):
        if event.modifiers() & Qt.AltModifier and event.button() == Qt.LeftButton:
            self.startPos = self.mapToScene(event.pos())
        else:
            super(MainGraphicsWidget, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        if not self.startPos.isNull():
            delta = self.startPos - self.mapToScene(event.pos())
            r = self.mapToScene(self.viewport().rect()).boundingRect()
            self.setSceneRect(r.translated(delta))
        else:
            super(MainGraphicsWidget, self).mouseMoveEvent(event)

    def mouseReleaseEvent(self, event):
        self.startPos = QPointF()
        super(MainGraphicsWidget, self).mouseReleaseEvent(event)

    def wheelEvent(self, event):
        # ...