[FEATURE][composer] Full screen mode for composer

This change adds a full screen mode for the composer. Full screen
mode can be enabled via a shortcut key (F11) or via a menu action.

src/app/composer/qgscomposer.cpp

@@ -342,6 +342,7 @@ QgsComposer::QgsComposer( QgisApp *qgis, const QString& title )
   mToolbarMenu = new QMenu( tr( "&Toolbars" ), this );
   mToolbarMenu->setObjectName( "mToolbarMenu" );
   viewMenu->addSeparator();
+  viewMenu->addAction( mActionToggleFullScreen );
   viewMenu->addMenu( mPanelMenu );
   viewMenu->addMenu( mToolbarMenu );
   // toolBar already exists, add other widgets as they are created
@@ -1233,6 +1234,18 @@ void QgsComposer::on_mActionAtlasSettings_triggered()
   mAtlasDock->raise();
 }
 
+void QgsComposer::on_mActionToggleFullScreen_triggered()
+{
+  if ( mActionToggleFullScreen->isChecked() )
+  {
+    showFullScreen();
+  }
+  else
+  {
+    showNormal();
+  }
+}
+
 void QgsComposer::disablePreviewMode()
 {
   if ( !mView )

src/app/composer/qgscomposer.h

@@ -359,6 +359,9 @@ class QgsComposer: public QMainWindow, private Ui::QgsComposerBase
     //! Atlas settings
     void on_mActionAtlasSettings_triggered();
 
+    //! Toggle full screen mode
+    void on_mActionToggleFullScreen_triggered();
+
     //! Save window state
     void saveWindowState();
 

src/ui/qgscomposerbase.ui

@@ -1023,6 +1023,20 @@
     <string>Ctrl+Shift+B</string>
    </property>
   </action>
+  <action name="mActionToggleFullScreen">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="text">
+    <string>Toggle Full Scr&amp;een</string>
+   </property>
+   <property name="toolTip">
+    <string>Toggle full screen mode</string>
+   </property>
+   <property name="shortcut">
+    <string>F11</string>
+   </property>
+  </action>
  </widget>
  <resources>
   <include location="../../python/plugins/fTools/resources.qrc"/>