SCENERTISTER（）。转换后的（x，y）无法与缩放一起正常工作

Question

一个月前，我在问，如何翻译场景，我得到了很大的帮助，了解了如何使其工作，在与它合作/添加工作人员一个月后，我注意到，当你放大到非常接近几何体或其他地方时，翻译变得越来越有价值

必须放大非常接近几何体的区域才能看到问题。下面是一些代码：

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）

我想问题是当你们放大太近的时候，你们的光标仍然沿着相同的坐标移动（它们并没有变小），它开始变慢，我的代码中并没有考虑这一点。但是为什么有时候我的sceneRect().translated()会停止移动呢？我是否放大到了一个点，而我的光标（1x，1y）至少没有交叉

所以我的问题是，如果我的理论正确，有人能建议我如何计算delta，放大和缩小吗？谢谢你，对不起我的英语

编辑：这是一个屏幕截图，显示您需要放大多少才能看到问题

Answer 1

以上答案部分正确。在我看来，您的方法是尝试通过分解视口比例来转换场景。“m11和m22”。但是，放大时，视口比例将小于1。 translate函数不接受低于1的值。尝试打印出DeltaX放大时，您将看到只有在DeltaX>；1.

您可以采取的两种方法是：

A）当增量轴'大于0时，手动将其四舍五入到1.1左右，即大于1

transform = self.transform()
deltaX = delta.x() / transform.m11()
deltaY = delta.y() / transform.m22()
            
if 1 > deltaX > 0.1:
   deltaX = 1.1
            
if 1 > deltaY > 0.1:
   deltaY = 1.1

B）像上面提到的eyllanesc一样，将视口投影到场景中，这样所做的任何转换都将在相对于视口空间的场景空间中进行。此外，为了使缩放定位保持一致，还可以在缩放场景时将鼠标位置转换为场景空间。最后，eyllanesc添加了一行冗余的代码，可以正确地进行翻译。按下鼠标按钮时，无需重置鼠标的原点位置

因此，你可以得到这样的结果

def __init__(self, parent):
    super(GraphicsThingy, self).__init__(parent)

    self.setTransformationAnchor(QGraphicsView.NoAnchor)
    self.setResizeAnchor(QGraphicsView.NoAnchor)

    self.installEventFilter(self)

    self.mousePos = None

def wheelEvent(self, event):

    if event.modifiers() & Qt.ControlModifier:
        scaleDelta = event.angleDelta().y() / 35
        factor = pow(self.zoomMultiplier, scaleDelta)

        originalPos = self.mapToScene(event.pos())

        self.scale(factor, factor)
        newPos = self.mapToScene(event.pos())

        deltaPos = newPos - originalPos
        self.translate(deltaPos.x(), deltaPos.y())

    event.accept()

def mousePressEvent(self, event):

    if event.button() == Qt.MiddleButton:
        self.mousePos = self.mapToScene(event.pos())

    event.accept()

def mouseMoveEvent(self, event):

    if self.movePos is not None:
        delta = self.mousePos - self.mapFromScene(event.pos())
        # Keeps scrolling speed consistent with zoom. Max(v,1) Ensures that the scale value will not multiply the scrolling speed. 
        delta.setX(delta.x() / max(self.transform().m11(),1))
        delta.setY(delta.y() / max(self.transform().m22(),1))

        # Change scene scene rect position based on delta
        rect = self.mapToScene(self.viewport().rect()).boundingRect()
        self.setSceneRect(rect.translated(delta))
        
        self.update()

    event.accept()

def mouseReleaseEvent(self, event):

    self.mousePos = None

Answer 2

^{}位于场景的坐标中，而不是视图的坐标中，因此在进行计算时，必须使用mapToScene方法将鼠标点转换为场景的坐标。此修改还应应用于场景中投影的视口矩形，因为该矩形不等于场景

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):
        # ...