PyQt - Toggle between two widgets withtout resizing qsplitter

I try to toggle a splitter container between two widgets keeping the actual size of the splitter. For this I use QSplitter.sizes() to read the actual size and QSplitter.setSizes() after I toggle my widgets.

The problem is that I have a QToolButton which I resize with setFixedSize() in a resizeEvent(), and because of this when I set the new size, it often doesn't work.

I write a little script to reproduce this : In the left part of the splitter, I have a button to toggle the right part of the splitter between two classes (which are QWidgets).

A little precision : I want to keep my QToolbutton in a 1:1 aspect ratio.

Here a demo : https://webmshare.com/play/5Bmvn

So here the script :

from PyQt4 import QtGui, QtCore

minSize = 50
maxSize = 350

class mainWindow(QtGui.QWidget):
    def __init__(self):
        super(mainWindow, self).__init__()

        self.layout = QtGui.QVBoxLayout(self)

        self.splitter = QtGui.QSplitter(QtCore.Qt.Horizontal, self)
        self.splitter.setHandleWidth(20)
        self.layout.addWidget(self.splitter)

        wgt_left = QtGui.QWidget()
        lyt_left = QtGui.QVBoxLayout(wgt_left)

        self.btn_toggleSplitter = QtGui.QPushButton('Toggle Button')
        self.btn_toggleSplitter.setSizePolicy(QtGui.QSizePolicy.Preferred, QtGui.QSizePolicy.Expanding)
        self.btn_toggleSplitter.setCheckable(True)
        lyt_left.addWidget(self.btn_toggleSplitter)

        self.splitter.addWidget(wgt_left)

        self.first = panel('1')
        self.second = panel('2')
        self.splitter.addWidget(self.first)

        self.width = self.first.size()


        self.btn_toggleSplitter.clicked.connect(self.ToggleParent)

    def ToggleParent(self):
        self.sizes = self.splitter.sizes()

        if self.btn_toggleSplitter.isChecked() == True:
            self.first.setParent(None)
            self.splitter.addWidget(self.second)

        else :
            self.second.setParent(None)
            self.splitter.addWidget(self.first)

        self.splitter.setSizes(self.sizes)


class panel(QtGui.QWidget):
    def __init__(self, text):
        super(panel, self).__init__()

        lyt_main = QtGui.QVBoxLayout(self)

        lyt_icon = QtGui.QHBoxLayout()

        self.tbtn_icon = QtGui.QToolButton()
        self.tbtn_icon.setText(text)

        self.tbtn_icon.setMinimumSize(QtCore.QSize(minSize,minSize))
        self.tbtn_icon.setMaximumSize(QtCore.QSize(maxSize,maxSize))
        lyt_icon.addWidget(self.tbtn_icon)

        lyt_horizontal = QtGui.QHBoxLayout()
        lyt_horizontal.addWidget(QtGui.QPushButton('3'))
        lyt_horizontal.addWidget(QtGui.QPushButton('4'))

        lyt_main.addWidget(QtGui.QLabel('Below me is the QToolButton'))
        lyt_main.addLayout(lyt_icon)
        lyt_main.addLayout(lyt_horizontal)
        lyt_main.addWidget(QtGui.QPlainTextEdit())


    def resizeEvent(self, event):
        w = panel.size(self).width()
        h = panel.size(self).height()
        size = min(h, w)-22
        if size >= maxSize:
            size = maxSize
        elif size <= minSize:
            size = minSize

        self.tbtn_icon.setFixedSize(size, size)


app = QtGui.QApplication([])
window = mainWindow()
window.resize(600,300)
window.show()
app.exec_()

Thanks

You are looking for QtGui.QStackedWidget. Adding the widgets to this on the right side of your splitter will change the code around self.first and self.second's construction to this:

    self.stack_right = QtGui.QStackedWidget()
    self.splitter.addWidget(self.stack_right)

    self.first = panel('1')
    self.second = panel('2')
    self.stack_right.addWidet(self.first)
    self.stack_right.addWidget(self.second)

Then your ToggleParent method:

def ToggleParent(self):
    if self.btn_toggleSplitter.isChecked() == True:
        self.stack_right.setCurrentWidget(self.second)
    else:
        self.stack_right.setCurrentWidget(self.first)

This will avoid the awkwardness of caching and manually resizing your widgets.

Addendum: The tool button scaling is really a separate question, but here's a tip:

Have a look at the heightForWidth layout setting for lyt_left. This will help you keep a 1:1 ratio for the QToolButton. You currently have a size policy of Preferred/Expanding, which doesn't make sense if you need a 1:1 aspect ratio. I highly recommend this over manually resizing the tool button while handling an event. Generally, calling setFixedSize more than once on a widget should be considered a last resort. Let the layouts do the work.

Addendum to addendum: doing a little poking (it's been awhile), you may need to inherit from QToolButton and reimplement the hasHeightForWidth() and heightForWidth() methods. There are a plethora of questions addressing the subject here. Just search for heightForWidth.