Python PyQt/PySide QMdiArea subwindows scroll not working in TabbedView

Question

I have setup simple example using PyQt designer.See below. I have mdiarea in in which i am adding a form as subwindow. I made form a bit lengthier than mainwindow to see if scroll-bar appears for child sub-window.

PROBLEM: If i set mdiarea to setViewMode(QtGui.QMdiArea.TabbedView) scrollbars stop working and disappear. Howeevr If i dont use TabbedView, scrollbars work fine. Can anyone tell me whats wrong ? I need TabbedView of mdiarea with working scrollbars.

I am using Python 2.7,PyQT 4.8.4/PySide 1.2.1 on win7.

Python Sample Code: Comment the line self.mdiArea.setViewMode to see example working.

import sys
from PyQt4 import QtCore, QtGui

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName( "MainWindow" )
        MainWindow.resize(500, 400)
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName( "centralwidget" )
        self.verticalLayout = QtGui.QVBoxLayout(self.centralwidget)
        self.verticalLayout.setObjectName( "verticalLayout" )
        self.mdiArea = QtGui.QMdiArea(self.centralwidget)
        self.mdiArea.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAsNeeded)
        self.mdiArea.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAsNeeded)
        self.mdiArea.setActivationOrder(QtGui.QMdiArea.CreationOrder)
        self.mdiArea.setViewMode(QtGui.QMdiArea.TabbedView)
        self.mdiArea.setTabsClosable(True)
        self.mdiArea.setTabsMovable(True)
        self.mdiArea.setObjectName( "mdiArea" )
        self.verticalLayout.addWidget(self.mdiArea)
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 508, 21))
        self.menubar.setObjectName( "menubar" )
        self.menuAdd = QtGui.QMenu(self.menubar)
        self.menuAdd.setObjectName( "menuAdd" )
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName( "statusbar" )
        MainWindow.setStatusBar(self.statusbar)
        self.menubar.addAction(self.menuAdd.menuAction())

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(   "MainWindow" )
        self.menuAdd.setTitle( "&Add Form" )

class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName( ("Form"))
        Form.resize(400, 800)
        self.gridLayout = QtGui.QGridLayout(Form)
        self.gridLayout.setObjectName( ("gridLayout"))
        self.plainTextEdit = QtGui.QPlainTextEdit(Form)
        self.plainTextEdit.setMinimumSize(QtCore.QSize(0, 731))
        self.plainTextEdit.setObjectName( ("plainTextEdit"))
        self.gridLayout.addWidget(self.plainTextEdit, 0, 0, 1, 1)
        self.buttonBox = QtGui.QDialogButtonBox(Form)
        self.buttonBox.setStandardButtons(QtGui.QDialogButtonBox.Cancel|QtGui.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName( ("buttonBox"))
        self.gridLayout.addWidget(self.buttonBox, 1, 0, 1, 1)

        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        Form.setWindowTitle( "Lengthy subwindow" )
        self.plainTextEdit.setPlainText( "Lengthy Form" ) 


class MyApp(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MyApp, self).__init__(parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

    def Add_Subwindow(self):
        widget = QtGui.QWidget()
        self.subwin_abq = Ui_Form()
        self.subwin_abq.setupUi(widget)
        self.subwindow = QtGui.QMdiSubWindow(self.ui.mdiArea) 
        widget.setParent(self.subwindow)
        self.subwindow.setWidget(widget)  
        self.subwindow.setWindowTitle("testing")
        self.ui.mdiArea.addSubWindow(self.subwindow)
        widget.show()
        self.subwindow.show()
        self.subwindow.widget().show()

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    window = MyApp()
    window.show()
    window.Add_Subwindow()
    sys.exit(app.exec_())

Answer 1

Just wanted to say thanks for the code in OP - was looking for a simple MDI example in PyQT, and yours helped I lot! I don't exactly have an answer, but this is what I can note so far: I have Python 2.7,PyQT 4.8.3, and just with commenting the setTabsClosable and setTabsMovable line, I could get your example to show like this:

I downloaded designer-qt4 and looked there about QMdiArea, there seems to be nothing called TabbedView. So I found this:

QtWidgets 5.0: QMdiArea Class | Documentation | Qt Project

enum ViewMode { SubWindowView, TabbedView }
This enum describes the view mode of the area; i.e. how sub-windows will be displayed.
SubWindowView 0 Display sub-windows with window frames (default).
TabbedView 1 Display sub-windows with tabs in a tab bar.
documentMode: This property holds whether the tab bar is set to document mode in tabbed view mode.

The way I read this: either you get to display subwindows in MDI fashion (so they can be larger than the window, with scrollbars) or the subwindows become tabs in tabbed view - and there the size of the subwindow doesn't matter anymore, so it expands to take up the available tabbed area. Also, in your code, self.ui.mdiArea.documentMode() returns False in both cases.

I also added this snippet at end of your MyApp.Add_Subwindow():

    sp = self.subwindow.sizePolicy()
    print sp.__dict__
    #print dir(sp)
    for attr in dir(sp):
      try:
        print "obj.%s = %s" % (attr, getattr(sp, attr))
      except: pass

This dumps some interesting data (I'm not sure if those are object properties, though):

obj.ButtonBox = 2
obj.CheckBox = 4
obj.ComboBox = 8
obj.ControlType = <class 'PyQt4.QtGui.ControlType'>
obj.ControlTypes = <class 'PyQt4.QtGui.ControlTypes'>
obj.DefaultType = 1
obj.ExpandFlag = 2
obj.Expanding = 7
obj.Fixed = 0
obj.Frame = 16
...

... but also these don't change in running tabbed vs. MDI mode.

So, maybe this is the intended behavior? If that is so, that would mean you'd have to find something like a "lone" tab display widget; add programmatically several QMdiAreas; hide all of them but the default one at start; and then bind a click on respective tabs to show "their" QMdiArea and hide the others (but needless to say, I haven't tested it).