QSS未应用于QVBoxLayout (复合小部件)中的第一个QSS

Question

如下图所示，小部件TestWidget包含一个QFrame和一个CSS样式的QSizeGrip。几个TestWidget实例放置在一个QVBoxLayout中

from PySide import QtGui, QtCore
import sys

class TestWidget(QtGui.QWidget):
    def __init__(self , parent=None):
        super(TestWidget , self).__init__(parent)

        layout = QtGui.QVBoxLayout()
        layout.setContentsMargins( 0 , 0 , 0 , 0 )

        frame = QtGui.QFrame()
        frame.setFrameShape(QtGui.QFrame.StyledPanel)
        frame.setMinimumHeight( 100 )

        grip = QtGui.QSizeGrip(self)
        grip.setStyleSheet( "QSizeGrip { image: url(dots.png); }")
        grip.setCursor(QtCore.Qt.SplitVCursor)

        layout.addWidget(frame)
        layout.addWidget( grip , 0 , QtCore.Qt.AlignBottom | QtCore.Qt.AlignRight )

        self.setLayout(layout)

class TestApp(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(TestApp, self).__init__(parent)

        track1 = TestWidget()
        track2 = TestWidget()
        track3 = TestWidget()

        centralWidget = QtGui.QWidget()
        layout = QtGui.QVBoxLayout(centralWidget)

        layout.addWidget(track1)
        layout.addWidget(track2)
        layout.addWidget(track3)

        self.setCentralWidget(centralWidget)
        self.show() 

if __name__=="__main__":
    app=QtGui.QApplication(sys.argv)
    myapp = TestApp();
    sys.exit(app.exec_())   

如下所示，只有当TestWidget是布局中的唯一元素时，QVBoxLayout中第一个TestWidget的大小抓地力才会出现。

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Qt版本4.8.7

PySide版本1.2.2

程序的PySide2版本(下面)也有相同的问题

from PySide2 import QtCore
from PySide2.QtWidgets import QApplication, QWidget , QMainWindow , QGraphicsView , QVBoxLayout , QFrame , QSizeGrip , QWidget

import sys

class TestWidget(QWidget):
    def __init__(self , parent=None):
        super(TestWidget , self).__init__(parent)

        layout = QVBoxLayout()
        layout.setContentsMargins( 0 , 0 , 0 , 0 )

        frame = QFrame()
        frame.setFrameShape(QFrame.StyledPanel)
        frame.setMinimumHeight( 100 )

        grip = QSizeGrip(self)
        grip.setStyleSheet( "QSizeGrip { image: url(dots.png); }")
        grip.setCursor(QtCore.Qt.SplitVCursor)

        layout.addWidget(frame)
        layout.addWidget( grip , 0 , QtCore.Qt.AlignBottom | QtCore.Qt.AlignRight )

        self.setLayout(layout)

class TestApp(QMainWindow):
    def __init__(self, parent=None):
        super(TestApp, self).__init__(parent)

        track1 = TestWidget()
        track2 = TestWidget()
        track3 = TestWidget()

        centralWidget = QWidget()
        layout = QVBoxLayout(centralWidget)

        layout.addWidget(track1)
        layout.addWidget(track2)
        layout.addWidget(track3)

        self.setCentralWidget(centralWidget)
        self.show() 

if __name__=="__main__":
    app = QApplication(sys.argv)
    myapp = TestApp();
    sys.exit(app.exec_())   

PySide2版本5.12.1

Answer 1

所观察到的是预先确定的行为，但没有记录在案，如果修改了源代码，就会观察到：

Qt::Corner QSizeGripPrivate::corner() const
{
    Q_Q(const QSizeGrip);
    QWidget *tlw = qt_sizegrip_topLevelWidget(const_cast<QSizeGrip *>(q));
    const QPoint sizeGripPos = q->mapTo(tlw, QPoint(0, 0));
    bool isAtBottom = sizeGripPos.y() >= tlw->height() / 2;
    bool isAtLeft = sizeGripPos.x() <= tlw->width() / 2;
    if (isAtLeft)
        return isAtBottom ? Qt::BottomLeftCorner : Qt::TopLeftCorner;
    else
        return isAtBottom ? Qt::BottomRightCorner : Qt::TopRightCorner;
}

如果sizeGrip位于窗口的上部，就会被观察到，这就是它所观察到的行为的原因。

解决方法是覆盖QSizeGrip的QSizeGrip方法：

PySide2:

import sys
from PySide2 import QtCore, QtGui, QtWidgets

class SizeGrip(QtWidgets.QSizeGrip):
    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        opt = QtWidgets.QStyleOptionSizeGrip()
        opt.initFrom(self)
        opt.corner = QtCore.Qt.BottomRightCorner
        self.style().drawControl(QtWidgets.QStyle.CE_SizeGrip, opt, painter, self)

class TestWidget(QtWidgets.QWidget):
    def __init__(self , parent=None):
        super(TestWidget , self).__init__(parent)
        layout = QtWidgets.QVBoxLayout(self)
        layout.setContentsMargins( 0 , 0 , 0 , 0 )
        frame = QtWidgets.QFrame()
        frame.setFrameShape(QtWidgets.QFrame.StyledPanel)
        frame.setMinimumHeight( 100 )
        grip = SizeGrip(self)
        grip.setStyleSheet('''QSizeGrip { 
            image: url(dots.png);
        }''')
        layout.addWidget(frame)
        layout.addWidget(grip , 0 , QtCore.Qt.AlignBottom | QtCore.Qt.AlignRight )

class TestApp(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(TestApp, self).__init__(parent)
        centralWidget = QtWidgets.QWidget()
        layout = QtWidgets.QVBoxLayout(centralWidget)
        for _ in range(3):
            layout.addWidget(TestWidget())
        self.setCentralWidget(centralWidget)
        self.show()

if __name__=="__main__":
    app = QtWidgets.QApplication(sys.argv)
    myapp = TestApp();
    sys.exit(app.exec_())   

PySide:

import sys
from PySide import QtCore, QtGui

class SizeGrip(QtGui.QSizeGrip):
    def paintEvent(self, event):
        painter = QtGui.QPainter(self)
        opt = QtGui.QStyleOptionSizeGrip()
        opt.initFrom(self)
        opt.corner = QtCore.Qt.BottomRightCorner
        self.style().drawControl(QtGui.QStyle.CE_SizeGrip, opt, painter, self)

class TestWidget(QtGui.QWidget):
    def __init__(self , parent=None):
        super(TestWidget , self).__init__(parent)
        layout = QtGui.QVBoxLayout(self)
        layout.setContentsMargins( 0 , 0 , 0 , 0 )
        frame = QtGui.QFrame()
        frame.setFrameShape(QtGui.QFrame.StyledPanel)
        frame.setMinimumHeight( 100 )
        grip = SizeGrip(self)
        grip.setStyleSheet('''QSizeGrip { 
            image: url(dots.png);
        }''')
        grip.setCursor(QtCore.Qt.SplitVCursor)
        layout.addWidget(frame)
        layout.addWidget(grip , 0 , QtCore.Qt.AlignBottom | QtCore.Qt.AlignRight )

class TestApp(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(TestApp, self).__init__(parent)
        centralWidget = QtGui.QWidget()
        layout = QtGui.QVBoxLayout(centralWidget)
        for _ in range(3):
            layout.addWidget(TestWidget())
        self.setCentralWidget(centralWidget)
        self.show()

if __name__=="__main__":
    app = QtGui.QApplication(sys.argv)
    myapp = TestApp();
    sys.exit(app.exec_())   

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