我如何应用 BlurEffect(QtWidgets.QGraphicsBlurEffect) 两次？

Question

I have this code

import sys                                                         # +++
from PyQt5.QtCore import Qt, QUrl
from PyQt5.QtWidgets import QApplication, QWidget, QMainWindow, QVBoxLayout, QLabel
from PyQt5.QtQml import QQmlApplicationEngine
from PyQt5.QtCore import (QCoreApplication, QMetaObject, QObject, QPoint,
    QRect, QSize, QUrl, Qt)
from PyQt5 import QtCore, QtGui, QtWidgets


'''
from PySide2.QtCore import Qt, QUrl
from PySide2.QtWidgets import QApplication, QWidget, QMainWindow, QVBoxLayout, QLabel
from PySide2.QtQml import QQmlApplicationEngine
from PySide2.QtCore import (QCoreApplication, QMetaObject, QObject, QPoint,
    QRect, QSize, QUrl, Qt)
from PySide2 import QtCore, QtGui, QtWidgets
'''



class BlurEffect(QtWidgets.QGraphicsBlurEffect):
    effectRect = None

    def setEffectRect(self, rect):
        self.effectRect = rect
        self.update()

    def draw(self, qp):
        if self.effectRect is None or self.effectRect.isNull():
            # no valid effect rect to be used, use the default implementation
            super().draw(qp)
            print('bao')
        else:
            qp.save()
            # clip the drawing so that it's restricted to the effectRect
            qp.setClipRect(self.effectRect)
            # call the default implementation, which will draw the effect
            super().draw(qp)
            # get the full region that should be painted
            fullRegion = QtGui.QRegion(qp.viewport())
            # and subtract the effect rectangle
            fullRegion -= QtGui.QRegion(self.effectRect)
            qp.setClipRegion(fullRegion)
            # draw the *source*, which has no effect applied
            self.drawSource(qp)
            qp.restore()


class Window(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        background = QtGui.QPixmap('background.png')

        # apply a background to this widget, note that this only serves for the
        # graphics effect to know what's outside the boundaries
        p = self.palette()
        p.setBrush(p.Window, QtGui.QBrush(background))
        self.setPalette(p)

        self.resize(background.size())

        # this layout is only for the child "sub" widget
        mainLayout = QtWidgets.QVBoxLayout(self)
        mainLayout.setContentsMargins(0, 0, 0, 0)

        # the "sub" widget, that contains the main interface
        self.subWidget = QtWidgets.QWidget()
        mainLayout.addWidget(self.subWidget)
        # set the background for the subwidget; note that we can't use setPalette()
        # because palette and fonts are inherited by children; using ".QWidget"
        # we ensure that the background is only applied to the subwidget
        self.subWidget.setStyleSheet('''
            .QWidget {
                background-image: url(background.png);
            }
        ''')

        # some random widgets
        subLayout = QtWidgets.QGridLayout(self.subWidget)
        for row in range(3):
            for col in range(3):
                btn = QtWidgets.QPushButton()
                subLayout.addWidget(btn, row, col)

        btn.setText('Open menu')
        btn.setFocus()
        btn.clicked.connect(self.openMenu)

        # create an instance of our effect subclass, and apply it to the subwidget
        self.effect = BlurEffect()
        self.subWidget.setGraphicsEffect(self.effect)
        self.effect.setEnabled(False)
        self.effect.setBlurRadius(10)









        # create the menu container, that *HAS* to have this main widget as parent
        self.topMenu = QtWidgets.QWidget(self)
        self.topMenu.setVisible(False)
        self.topMenu.setFixedWidth(200)
        # move the menu outside the window left margin
        self.topMenu.move(-self.topMenu.width(), 0)

        menuLayout = QtWidgets.QVBoxLayout(self.topMenu)
        menuLayout.addSpacing(20)
        for b in range(4):
            btn = QtWidgets.QPushButton('Button {}'.format(b + 1))
            menuLayout.addWidget(btn)

        menuLayout.addSpacing(10)

        closeButton = QtWidgets.QPushButton('Close menu')
        menuLayout.addWidget(closeButton)
        closeButton.clicked.connect(self.closeMenu)
        # a stretch to ensure that the items are always aligned on top
        menuLayout.addStretch(1)

        # an animation that will move the menu laterally
        self.menuAnimation = QtCore.QVariantAnimation()
        self.menuAnimation.setDuration(500)
        self.menuAnimation.setEasingCurve(QtCore.QEasingCurve.OutQuart)
        self.menuAnimation.setStartValue(-self.topMenu.width())
        self.menuAnimation.setEndValue(0)
        self.menuAnimation.valueChanged.connect(self.resizeMenu)
        self.menuAnimation.finished.connect(self.animationFinished)

        # a simple transparent widget that is used to hide the menu when
        # clicking outside it; the event filter is to capture click events
        # it may receive
        self.clickGrabber = QtWidgets.QWidget(self)
        self.clickGrabber.installEventFilter(self)
        self.clickGrabber.setVisible(False)

    def resizeMenu(self, value):
        # move the menu and set its geometry to the effect
        self.topMenu.move(value, 0)
        self.effect.setEffectRect(self.topMenu.geometry())

    def openMenu(self):
        if self.topMenu.x() >= 0:
            # the menu is already visible
            return
        # ensure that the menu starts hidden (that is, with its right border
        # aligned to the left of the main widget)
        self.topMenu.move(-self.topMenu.width(), 0)
        self.topMenu.setVisible(True)
        self.topMenu.setFocus()

        # enable the effect, set the forward direction for the animation, and
        # start it; it's important to set the effect rectangle here too, otherwise
        # some flickering might show at the beginning
        self.effect.setEffectRect(self.topMenu.geometry())
        self.effect.setEnabled(True)
        self.menuAnimation.setDirection(QtCore.QVariantAnimation.Forward)
        self.menuAnimation.start()

        # "show" the grabber (it's invisible, but it's there) and resize it
        # to cover the whole window area
        self.clickGrabber.setGeometry(self.rect())
        self.clickGrabber.setVisible(True)
        # ensure that it is stacked under the menu and above everything else
        self.clickGrabber.stackUnder(self.topMenu)

    def closeMenu(self):
        # in case that the menu has changed its size, set again the "start" value
        # to its negative width, then set the animation direction to backwards
        # and start it
        self.menuAnimation.setStartValue(-self.topMenu.width())
        self.menuAnimation.setDirection(QtCore.QVariantAnimation.Backward)
        self.menuAnimation.start()
        # hide the click grabber
        self.clickGrabber.setVisible(False)

    def animationFinished(self):
        # if the animation has ended and the direction was backwards it means that
        # the menu has been closed, hide it and disable the effect
        if self.menuAnimation.direction() == QtCore.QVariantAnimation.Backward:
            self.topMenu.hide()
            self.effect.setEnabled(False)

    def focusNextPrevChild(self, next):
        if self.topMenu.isVisible():
            # a small hack to prevent tab giving focus to widgets when the
            # menu is visible
            return False
        return super().focusNextPrevChild(next)

    def eventFilter(self, source, event):
        if source == self.clickGrabber and event.type() == QtCore.QEvent.MouseButtonPress:
            # the grabber has been clicked, close the menu
            self.closeMenu()
        return super().eventFilter(source, event)

    def resizeEvent(self, event):
        super().resizeEvent(event)
        # always set the menu height to that of the window
        self.topMenu.setFixedHeight(self.height())
        # resize the grabber to the window rectangle, even if it's invisible
        self.clickGrabber.setGeometry(self.rect())
        if self.topMenu.isVisible():
            # resize the effect rectangle
            self.effect.setEffectRect(self.topMenu.geometry())



if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)

    w = Window()
    w.resize(640, 570)  
    w.show()
    sys.exit(app.exec_())

I need to be able to apply blur effect to multiple widget at one time

And the problem is when I add

    self.effect2 = BlurEffect()
    self.subWidget.setGraphicsEffect(self.effect2)
    self.effect2.setEnabled(False)
    self.effect2.setBlurRadius(10)

after

    self.effect = BlurEffect()
    self.subWidget.setGraphicsEffect(self.effect)
    self.effect.setEnabled(False)
    self.effect.setBlurRadius(10)

I get this error

Traceback (most recent call last): File "C:\\Users\\user\\Desktop\\test\\widgets\\menu.py", line 157, in openMenu self.effect.setEffectRect(self.topMenu.geometry()) File "C:\\Users\\user\\Desktop\\test\\widgets\\menu.py", line 15, in setEffectRect self.update() RuntimeError: wrapped C/C++ object of type BlurEffect has been deleted

Does anyone know how to fix this?

photoshop

Answer 1

You can't. Only one effect can be applied at once on a widget (and after that, no effect can be applied on any of its children or parents), at least for QWidgets.

From QWidget.setGraphicsEffect() :

If there already is an effect installed on this widget, QWidget before installing the new effect.

What happens is that as soon as you apply self.effect2 on subWidget, self.effect is removed from it and actually deleted. In PyQt terms, it means that the python object still exists, but not its C++ counterpart.

UPDATE

It seems that you still don't understand how a QGraphicsEffect works. The effect is NOT applied on the widgets you see with the blurred background. It is applied on the underlying widget ( subWidget , in this case), and only on the rectangle(s) specified using the geometries of the widgets. You could even set the effectRect to any rect you want, even without any other widgets other than subWidget .

If you need to apply the effect to more than one rectangle, then you should use setClipRegion and use a composite QRegion with it.
Assuming you will always use QWidgets as a reference for the effect, and that the effect will always be applied to a widget that occupies the whole area of the window, you can use a "watch list" of widgets that need to be tracked, and update the effect whenever their geometry change.

class BlurEffect(QtWidgets.QGraphicsBlurEffect):
    shouldEnable = True
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.watched = []

    def watchWidget(self, widget):
        widget.installEventFilter(self)
        self.watched.append(widget)

    def unwatchWidget(self, widget):
        if widget in self.watched:
            self.watched.remove(widget)
            self.update()

    def setEnabled(self, enabled):
        # in case you want to manually disable the effect, keep track of
        # the selected behavior
        self.shouldEnable = enabled
        super().setEnabled(enabled)

    def draw(self, qp):
        rects = []
        for widget in self.watched:
            if widget.isVisible():
                rect = widget.rect()
                if rect.isNull():
                    continue
                # map the widget geometry to the window
                rect.translate(
                    widget.mapTo(widget.window(), QtCore.QPoint()))
                rects.append(rect)
            if not self.isEnabled() and self.shouldEnable:
                super().setEnabled(True)
        if not rects:
            # no valid rect to be used, disable the effect if we should
            if not self.shouldEnable:
                super().setEnabled(False)
            # otherwise, keep drawing the source with the effect applied
            # to the whole area of the widget
            else:
                self.drawSource(qp)
        else:
            qp.save()
            # create a region that includes all rects
            rectRegion = QtGui.QRegion()
            for rect in rects:
               rectRegion |= QtGui.QRegion(rect) 
            # clip the effect painting to the region
            qp.setClipRegion(rectRegion)
            # call the default implementation, which will draw the effect
            super().draw(qp)
            # get the full region that should be painted
            fullRegion = QtGui.QRegion(qp.viewport())
            # and subtract the effect rectangle used before
            fullRegion -= rectRegion
            qp.setClipRegion(fullRegion)
            # draw the *source*, which has no effect applied
            self.drawSource(qp)
            qp.restore()

    def eventFilter(self, source, event):
        # update the effect whenever a widget changes its geometry or
        # becomes visible
        if event.type() in (QtCore.QEvent.Resize, QtCore.QEvent.Move, 
            QtCore.QEvent.Show) and source.isVisible():
                super().setEnabled(True)
                self.update()
        # if a widget is going to be deleted, remove it from the list
        # of watched list; this is **VERY** important
        elif event.type() == QtCore.QEvent.DeferredDelete:
            self.unwatchWidget(source)
        return super().eventFilter(source, event)

Important notes:

• you have to use watchWidget for any widget for which you want to see the effect, including the topMenu; again, this doesn't mean that the effect is applied to those widget, but that their geometry is used for that;
• obviously, there's no setEffectRect anymore;
• with this implementation the effect disables itself automatically if all the watched widgets are hidden or their geometry is null, which means that you don't need to call self.effect.setEnabled() anymore;
• even in this case (no watched widgets visible), you can still enable the effect to the whole area by explicitly calling setEnabled(True);

Finally, I strongly suggest you to carefully study this code (and the previous) and the documentation about both QGraphicsEffect and QPainter (including the clipping section and all the related pages), and create some simple tests and examples by yourself to better understand how they work, before attempting to do what you're trying to achieve.