仓库地址 https://gitlab.com/pavel.krupala/pyqt-node-editor-tutorials.git

image.png

效果图

image.png

代码

增加 拖拽画布 和 滚轮缩放效果

• node_graphics_view.py

from PyQt5.QtWidgets import QGraphicsView
from PyQt5.QtCore import *
from PyQt5.QtGui import *


class QDMGraphicsView(QGraphicsView):
    def __init__(self, grScene, parent=None):
        super().__init__(parent)
        self.grScene = grScene

        self.initUI()

        self.setScene(self.grScene)

        self.zoomInFactor = 1.25
        self.zoomClamp = False
        self.zoom = 10
        self.zoomStep = 1
        self.zoomRange = [0, 10]


    def initUI(self):
        # 图像品质
        self.setRenderHints(QPainter.Antialiasing | QPainter.HighQualityAntialiasing | QPainter.TextAntialiasing | QPainter.SmoothPixmapTransform)
        # 全部刷新
        self.setViewportUpdateMode(QGraphicsView.FullViewportUpdate)
        # 关闭滚动条
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)

        self.setTransformationAnchor(QGraphicsView.AnchorUnderMouse)

    # 判断鼠标按下的类型
    def mousePressEvent(self, event):
        if event.button() == Qt.MiddleButton:
            self.middleMouseButtonPress(event)
        elif event.button() == Qt.LeftButton:
            self.rightMouseButtonPress(event)
        elif event.button() == Qt.RightButton:
            self.rightMouseButtonPress(event)
        else:
            super().mousePressEvent(event)
    # 判断鼠标松开的类型
    def mouseReleaseEvent(self, event):
        if event.button() == Qt.MiddleButton:
            self.middleMouseButtonRelease(event)
        elif event.button() == Qt.LeftButton:
            self.leftMouseButtonRelease(event)
        elif event.button() == Qt.RightButton:
            self.rightMouseButtonRelease(event)
        else:
            super().mouseReleaseEvent(event)

    # 拖拽功能 - 按下 的实现 
    def middleMouseButtonPress(self, event):
        # 这几句没看懂 , 有懂的朋友解释一下
        releaseEvent = QMouseEvent(QEvent.MouseButtonRelease, 
                            event.localPos(), event.screenPos(),
                             Qt.LeftButton, Qt.NoButton, event.modifiers())
        super().mouseReleaseEvent(releaseEvent)
        # 设置画布拖拽
        self.setDragMode(QGraphicsView.ScrollHandDrag)
        fakeEvent = QMouseEvent(event.type(), event.localPos(), 
                            event.screenPos(),
                            Qt.LeftButton, event.buttons() | Qt.LeftButton, 
                            event.modifiers())
        super().mousePressEvent(fakeEvent)


    # 拖拽功能 - 松开 的实现 
    def middleMouseButtonRelease(self, event):
        fakeEvent = QMouseEvent(event.type(), event.localPos(), 
                              event.screenPos(),
                              Qt.LeftButton, event.buttons() & ~Qt.LeftButton, 
                              event.modifiers())
        super().mouseReleaseEvent(fakeEvent)
        # 取消拖拽
        self.setDragMode(QGraphicsView.NoDrag)


    def leftMouseButtonPress(self, event):
        return super().mousePressEvent(event)

    def leftMouseButtonRelease(self, event):
        return super().mouseReleaseEvent(event)

    def rightMouseButtonPress(self, event):
        return super().mousePressEvent(event)

    def rightMouseButtonRelease(self, event):
        return super().mouseReleaseEvent(event)


    # 滚轮缩放的实现
    def wheelEvent(self, event):
        # calculate our zoom Factor
      
        zoomOutFactor = 1 / self.zoomInFactor

        # calculate zoom
        # 放大触发
        if event.angleDelta().y() > 0:
            #放大比例 1.25
            zoomFactor = self.zoomInFactor
            self.zoom += self.zoomStep
        # 缩小触发
        else:
            # 缩小的比例 0.8
            zoomFactor = zoomOutFactor
            self.zoom -= self.zoomStep
        # self.zoomRange[0] = 0 , self.zoomRange[1] =10
        # 限制缩放的极致 , 缩小到self.zoom = -1 或者放大到self.zoom=11 时,
        # 取消 缩放 , 
        clamped = False
        if self.zoom < self.zoomRange[0]: 
                  self.zoom, clamped = self.zoomRange[0], True
        if self.zoom > self.zoomRange[1]: 
                  self.zoom, clamped = self.zoomRange[1], True

        # set scene scale
        if not clamped or self.zoomClamp is False:
            # 缩放实现的函数
            self.scale(zoomFactor, zoomFactor)