what is the effect of leftLayout.addStretch(1) in this code example ? it seems that this program works the same even though leftLayout.addStretch(1) is commented .
from PyQt4 import QtCore, QtGui
class FindDialog(QtGui.QDialog):
def __init__(self, parent=None):
super(FindDialog, self).__init__(parent)
label = QtGui.QLabel("Find &what:")
lineEdit = QtGui.QLineEdit()
label.setBuddy(lineEdit)
caseCheckBox = QtGui.QCheckBox("Match &case")
fromStartCheckBox = QtGui.QCheckBox("Search from &start")
fromStartCheckBox.setChecked(True)
findButton = QtGui.QPushButton("&Find")
findButton.setDefault(True)
moreButton = QtGui.QPushButton("&More")
moreButton.setCheckable(True)
moreButton.setAutoDefault(False)
buttonBox = QtGui.QDialogButtonBox(QtCore.Qt.Vertical)
buttonBox.addButton(findButton, QtGui.QDialogButtonBox.ActionRole)
buttonBox.addButton(moreButton, QtGui.QDialogButtonBox.ActionRole)
extension = QtGui.QWidget()
wholeWordsCheckBox = QtGui.QCheckBox("&Whole words")
backwardCheckBox = QtGui.QCheckBox("Search &backward")
searchSelectionCheckBox = QtGui.QCheckBox("Search se&lection")
moreButton.toggled.connect(extension.setVisible)
extensionLayout = QtGui.QVBoxLayout()
extensionLayout.setMargin(0)
extensionLayout.addWidget(wholeWordsCheckBox)
extensionLayout.addWidget(backwardCheckBox)
extensionLayout.addWidget(searchSelectionCheckBox)
extension.setLayout(extensionLayout)
topLeftLayout = QtGui.QHBoxLayout()
topLeftLayout.addWidget(label)
topLeftLayout.addWidget(lineEdit)
leftLayout = QtGui.QVBoxLayout()
leftLayout.addLayout(topLeftLayout)
leftLayout.addWidget(caseCheckBox)
leftLayout.addWidget(fromStartCheckBox)
leftLayout.addStretch(1)###############################################
mainLayout = QtGui.QGridLayout()
mainLayout.setSizeConstraint(QtGui.QLayout.SetFixedSize)
mainLayout.addLayout(leftLayout, 0, 0)
mainLayout.addWidget(buttonBox, 0, 1)
mainLayout.addWidget(extension, 1, 0, 1, 2)
self.setLayout(mainLayout)
self.setWindowTitle("Extension")
extension.hide()
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
dialog = FindDialog()
sys.exit(dialog.exec_())
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