mainwindow.ui Example File

<?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>MarkDown Editor</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QHBoxLayout" name="horizontalLayout">
    <item>
     <widget class="QSplitter" name="splitter">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>
      <widget class="QPlainTextEdit" name="editor"/>
      <widget class="QWebEngineView" name="preview" native="true"/>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>26</height>
    </rect>
   </property>
   <widget class="QMenu" name="menu_File">
    <property name="title">
     <string>&File</string>
    </property>
    <addaction name="actionNew"/>
    <addaction name="actionOpen"/>
    <addaction name="actionSave"/>
    <addaction name="actionSaveAs"/>
    <addaction name="separator"/>
    <addaction name="actionExit"/>
   </widget>
   <addaction name="menu_File"/>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
  <action name="actionOpen">
   <property name="text">
    <string>&Open...</string>
   </property>
   <property name="toolTip">
    <string>Open document</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+O</string>
   </property>
  </action>
  <action name="actionSave">
   <property name="text">
    <string>&Save</string>
   </property>
   <property name="toolTip">
    <string>Save current document</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+S</string>
   </property>
  </action>
  <action name="actionExit">
   <property name="text">
    <string>E&xit</string>
   </property>
   <property name="toolTip">
    <string>Exit editor</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+Q</string>
   </property>
  </action>
  <action name="actionSaveAs">
   <property name="text">
    <string>Save &As...</string>
   </property>
   <property name="toolTip">
    <string>Save document under different name</string>
   </property>
  </action>
  <action name="actionNew">
   <property name="text">
    <string>&New</string>
   </property>
   <property name="toolTip">
    <string>Create new document</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+N</string>
   </property>
  </action>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QWebEngineView</class>
   <extends>QWidget</extends>
   <header>qwebengineview.h</header>
   <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
</ui>