diff --git a/toonz/sources/toonzqt/imageutils.cpp b/toonz/sources/toonzqt/imageutils.cpp
index 66f49a0..a42c11f 100644
--- a/toonz/sources/toonzqt/imageutils.cpp
+++ b/toonz/sources/toonzqt/imageutils.cpp
@@ -7,6 +7,10 @@
 #include "toonzqt/dvdialog.h"
 #include "toonzqt/gutil.h"
 
+// Qt Includes:
+#include <QScreen>
+#include <QWindow>
+
 // TnzLib includes
 #include "toonz/preferences.h"
 #include "toonz/namebuilder.h"
@@ -900,29 +904,165 @@ void FullScreenWidget::setWidget(QWidget *widget) {
   if ((m_widget = widget)) layout->addWidget(m_widget);
 }
 
-//---------------------------------------------------------------------------------
-
-bool FullScreenWidget::toggleFullScreen(bool quit) {
-  if (windowState() & Qt::WindowFullScreen) {
-    hide();
-    setWindowFlags(windowFlags() & ~(Qt::Window | Qt::WindowStaysOnTopHint));
-    showNormal();
-    m_widget->setFocus();
 
-    return true;
-  } else if (!quit) {
-    setWindowFlags(windowFlags() | Qt::Window | Qt::WindowStaysOnTopHint);
-#ifdef _WIN32
-    // http://doc.qt.io/qt-5/windows-issues.html#fullscreen-opengl-based-windows
-    winId();
-    QWindowsWindowFunctions::setHasBorderInFullScreen(windowHandle(), true);
-#endif
-    showFullScreen();
+//=============================================================
+	bool							FullScreenWidget::toggleFullScreen(
+//=============================================================
 
-    return true;
-  }
+		const bool					kfApplicationQuitInProgress )		// Indicates whether the application is quiting.
 
-  return false;
+/*
+ *	DESCRIPTION:
+ *
+ *		Sets the size and location of the widget to either full
+ *		screen or normal.
+ *		
+ *		Entering full screen has to be done manually in order to
+ *		avoid having the window placed on the wrong monitor on
+ *		systems running X11 with multiple monitors.
+ */
+{
+	// Initialize the return value.
+	bool			fFullScreenStateToggled = false;
+	
+	
+	// Define some constants for setting and clearing window flags.
+	const Qt::WindowFlags		kwfFullScreenWidgetFlags =
+											Qt::Window                |	// <-- Make the widget become a window.
+											Qt::WindowStaysOnTopHint  |	// <-- Ensure the window stays on top.
+											Qt::FramelessWindowHint;		// <-- Full screen windows have no border.
+	
+	const Qt::WindowFlags		kwfFullScreenWidgetExcludedFlagsMask =
+											(Qt::WindowFlags)~Qt::WindowTitleHint;	// <-- Full screen windows have no titlebar.
+	
+	
+	// Determine whether to enter or leave full screen mode
+	if (this->windowState() & Qt::WindowFullScreen)
+	{
+		this->hide();
+		
+		this->setWindowFlags( this->windowFlags() & ~kwfFullScreenWidgetFlags );
+		
+		this->showNormal();
+		
+		this->m_widget->setFocus();
+		
+		
+		// Set the return value to indicate that the full screen mode has been changed.
+		fFullScreenStateToggled = true;
+	}
+	else
+	{
+		// There's no point to switching into full screen if the
+		// application is in the process of quiting.
+		if (!kfApplicationQuitInProgress)
+		{
+#if	!defined( _WIN32 )
+			//==============================================================
+			//
+			//	NOTE:
+			//	
+			//		This new way of going into full screen mode does
+			//		things manually in order to bypass Qt's incorrect
+			//		policy of always relocating a widget to desktop
+			//		coordinates (0,0) when the widget becomes a window
+			//		via setting the Qt::Window flag.
+			//		
+			//		This makes full screen mode work MUCH better on X11
+			//		systems with multiple displays.
+			//
+			//==============================================================
+			//	
+			//	STRATEGY:
+			//
+			//		1.		Obtain the rectangle of the screen that the widgets host window is on.
+			//				This has to be done first, otherwise the CORRECT screen info can
+			//				potentially become unavailable in the following steps.
+			//
+			//		2.		Manually set all the necessary flags for the full screen window
+			//				attributes and state. Qt WILL hide the widget/window when this is done.
+			//		
+			//		3.		Set the window geometry/rect to be the same as the screen from Step 1.
+			//		
+			//		4.		Make the window visible again.
+			//
+			//
+			
+			
+			//---------------------------------------------------
+			// STEP 1:
+			
+			// Get the window widget that contains this widget.
+			QWidget *			ptrWindowWidget = this->window();
+			if (ptrWindowWidget)
+			{
+				// Get the access to the QWindow object of the containing window.
+				QWindow *		ptrContainingQWindow = ptrWindowWidget->windowHandle();
+				if (ptrContainingQWindow)
+				{
+					// Get access to the screen the window is on.
+					QScreen *		ptrScreenThisWindowIsOn = ptrContainingQWindow->screen();
+					if (ptrScreenThisWindowIsOn)
+					{
+						// Get the geometry rect for the correct screen.
+						QRect				qrcScreen = ptrScreenThisWindowIsOn->geometry();
+						
+						
+						//---------------------------------------------------
+						// STEP 2:
+						
+						// Set the window flags to be frameless and with no titlebar.
+						// 
+						// This call will turn the widget into a "window", and HIDE it. This
+						// is because Qt always hides a widget when it transforms a widget
+						//	into a window, or turns a window into a widget.
+						//
+						this->setWindowFlags(
+							(this->windowFlags() & kwfFullScreenWidgetExcludedFlagsMask)  |
+							kwfFullScreenWidgetFlags
+						);
+						
+						// Set the window state flag to indicate that it's now in fullscreen mode.
+						//
+						// If this state flag isn't set, the test for whether to enter or leave
+						//	full screen mode won't work correctly.
+						this->setWindowState( Qt::WindowFullScreen );
+						
+						
+						//---------------------------------------------------
+						// STEP 3:
+						
+						// Set the window to the geometry rect of the correct screen.
+						this->setGeometry( qrcScreen );
+						
+						
+						//---------------------------------------------------
+						// STEP 4:
+						
+						// Make the window visible. This also causes all the changes to the widget's
+						//	flags, state and geometry that was just set to take effect.
+						this->show();
+					}
+				}
+			}
+#else
+			this->setWindowFlags( this->windowFlags() | Qt::Window | Qt::WindowStaysOnTopHint );
+
+			// http://doc.qt.io/qt-5/windows-issues.html#fullscreen-opengl-based-windows
+			this->winId();
+			QWindowsWindowFunctions::setHasBorderInFullScreen( this->windowHandle(), true );
+
+			this->showFullScreen();
+#endif
+			
+			
+			// Set the return value to indicate that the full screen mode has been changed.
+			fFullScreenStateToggled = true;
+		}
+	}
+	
+	
+	return( fFullScreenStateToggled );
 }
 
 }  // namespace ImageUtils