Create GUI from .ui files. Events do not propagate correctly.

event_trace

PySide.QtCore.QEvent.Type.ChildAdded <PySide.QtGui.QFrame object at 0x17787a0>
PySide.QtCore.QEvent.Type.ChildAdded <PySide.QtGui.QFrame object at 0x17787e8>
PySide.QtCore.QEvent.Type.ParentChange <PySide.QtGui.QFrame object at 0x17787a0>
PySide.QtCore.QEvent.Type.Polish <PySide.QtGui.QFrame object at 0x17787a0>
PySide.QtCore.QEvent.Type(70) <PySide.QtGui.QFrame object at 0x17787a0>
PySide.QtCore.QEvent.Type.ParentChange <PySide.QtGui.QFrame object at 0x17787e8>
PySide.QtCore.QEvent.Type.Polish <PySide.QtGui.QFrame object at 0x17787e8>
PySide.QtCore.QEvent.Type(70) <PySide.QtGui.QFrame object at 0x17787e8>

main_window.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QHBoxLayout" name="horizontalLayout_2">
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
      <item>
       <widget class="QMdiArea" name="mdiArea"/>
      </item>
     </layout>
    </item>
   </layout>
  </widget>
 </widget>
 <resources>
  <include location="../resources.qrc"/>
 </resources>
 <connections/>
</ui>

MainWindow.py

from PySide.QtCore import *
from PySide.QtGui import *

from ui.uiloader import UiLoader

class CloseEventFilter(QObject):
    def eventFilter(self, target, event):
        print event.type(), target
        return False

class MainWindow(QMainWindow):
    def __init__(self, parent=None, wflags=Qt.WindowFlags()):
        super(MainWindow, self).__init__(parent, wflags)

        UiLoader.loadUi(self, ':/UI/ui/main_window.ui')

        mdi_area = self.findChild(QMdiArea, 'mdiArea')

        ev_filter = CloseEventFilter()

        qframe1 = QFrame(self)
        qframe2 = QFrame(self)

        qframe1.installEventFilter(ev_filter)
        qframe2.installEventFilter(ev_filter)

        qhbox1 = QHBoxLayout(qframe1)
        qhbox2 = QHBoxLayout(qframe2)

        qframe1.setLayout(qhbox1)
        sw1 = mdi_area.addSubWindow(qframe1, Qt.WA_DeleteOnClose)

        qframe2.setLayout(qhbox2)
        sw2 = mdi_area.addSubWindow(qframe2, Qt.WA_DeleteOnClose)

        QtGui.qApp.lastWindowClosed.connect(lambda: mdi_area.closeAllSubWindows())

resources.qrc

<RCC>
  <qresource prefix="UI">
    <file>ui/main_window.ui</file>
  </qresource>
</RCC>

subwindow-ui.py

import sys
import os

from PySide.QtCore import *
from PySide.QtGui import *
from PySide.QtXml import *
from PySide.QtUiTools import *

from ui.MainWindow import MainWindow

if __name__ == '__main__':

    app = QApplication(sys.argv)

    resource_abs_file = os.path.join(
        os.path.realpath(
            os.path.dirname(sys.argv[0]
            )
        ), 'resources/resources.rcc')

    if not QResource.registerResource(resource_abs_file):
        raise IOError('Enable to load resource file: ', resource_abs_file)

    main_window = MainWindow()
    main_window.show()

    sys.exit(app.exec_())