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from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QGraphicsView
class customView(QGraphicsView):
"""
Defines custom QGraphicsView with zoom features, overriding wheel event
"""
def __init__(self, scene = None, parent=None):
if scene is not None: #overloaded constructor
super(customView, self).__init__(scene, parent)
else:
super(customView, self).__init__(parent)
self._zoom = 1
self.setDragMode(True)
def wheelEvent(self, QWheelEvent):
#overload wheelevent, to zoom if control is pressed, else scroll normally
if Qt.ControlModifier: #check if control is pressed
if QWheelEvent.source() == Qt.MouseEventNotSynthesized: #check if precision mouse(mac)
# angle delta is 1/8th of a degree per scroll unit
if self.zoom + QWheelEvent.angleDelta().y()/2880 > 0.1: # hit and trial value (2880)
self.zoom += QWheelEvent.angleDelta().y()/2880
else:
# precision delta is exactly equal to amount to scroll
if self.zoom + QWheelEvent.pixelDelta().y() > 0.1:
self.zoom += QWheelEvent.angleDelta().y()
QWheelEvent.accept() # accept event so that scrolling doesnt happen simultaneously
else:
return super().wheelEvent(self, QWheelEvent) # scroll if ctrl not pressed
@property
def zoom(self):
# property for zoom
return self._zoom
@zoom.setter
def zoom(self, value):
# set scale according to zoom value being set
temp = self.zoom
self._zoom = value
self.scale(self.zoom / temp, self.zoom / temp)
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