Index: ps/trunk/source/gui/CGUI.h
===================================================================
--- ps/trunk/source/gui/CGUI.h
+++ ps/trunk/source/gui/CGUI.h
@@ -29,6 +29,7 @@
 #include "gui/SGUIStyle.h"
 #include "lib/input.h"
 #include "maths/Rect.h"
+#include "maths/Size2D.h"
 #include "maths/Vector2D.h"
 #include "ps/XML/Xeromyces.h"
 #include "scriptinterface/ScriptForward.h"
@@ -177,16 +178,21 @@
 	/**
 	 * Returns the current screen coordinates of the cursor.
 	 */
-	const CVector2D& GetMousePos() const { return m_MousePos; };
+	const CVector2D& GetMousePos() const { return m_MousePos; }
 
 	/**
 	 * Returns the currently pressed mouse buttons.
 	 */
-	const unsigned int& GetMouseButtons() { return m_MouseButtons; };
+	const unsigned int& GetMouseButtons() { return m_MouseButtons; }
 
 	const SGUIScrollBarStyle* GetScrollBarStyle(const CStr& style) const;
 
 	/**
+	 * Returns the current GUI window size.
+	 */
+	CSize2D GetWindowSize() const;
+
+	/**
 	 * The GUI needs to have all object types inputted and
 	 * their constructors. Also it needs to associate a type
 	 * by a string name of the type.
Index: ps/trunk/source/gui/CGUI.cpp
===================================================================
--- ps/trunk/source/gui/CGUI.cpp
+++ ps/trunk/source/gui/CGUI.cpp
@@ -419,6 +419,11 @@
 	return pNearest;
 }
 
+CSize2D CGUI::GetWindowSize() const
+{
+	return CSize2D{static_cast<float>(g_xres) / g_GuiScale, static_cast<float>(g_yres) / g_GuiScale};
+}
+
 void CGUI::SetFocusedObject(IGUIObject* pObject)
 {
 	if (pObject == m_FocusedObject)
Index: ps/trunk/source/gui/ObjectBases/IGUIObject.cpp
===================================================================
--- ps/trunk/source/gui/ObjectBases/IGUIObject.cpp
+++ ps/trunk/source/gui/ObjectBases/IGUIObject.cpp
@@ -25,7 +25,6 @@
 #include "gui/Scripting/JSInterface_GUIProxy.h"
 #include "js/Conversions.h"
 #include "ps/CLogger.h"
-#include "ps/GameSetup/Config.h"
 #include "ps/Profile.h"
 #include "scriptinterface/Object.h"
 #include "scriptinterface/ScriptContext.h"
@@ -208,7 +207,7 @@
 	if (!m_Absolute && m_pParent && !IsRootObject())
 		m_CachedActualSize = m_Size->GetSize(m_pParent->m_CachedActualSize);
 	else
-		m_CachedActualSize = m_Size->GetSize(CRect(0.f, 0.f, g_xres / g_GuiScale, g_yres / g_GuiScale));
+		m_CachedActualSize = m_Size->GetSize(CRect(m_pGUI.GetWindowSize()));
 
 	// In a few cases, GUI objects have to resize to fill the screen
 	// but maintain a constant aspect ratio.
Index: ps/trunk/source/gui/ObjectTypes/CDropDown.cpp
===================================================================
--- ps/trunk/source/gui/ObjectTypes/CDropDown.cpp
+++ ps/trunk/source/gui/ObjectTypes/CDropDown.cpp
@@ -348,9 +348,7 @@
 
 void CDropDown::SetupListRect()
 {
-	extern int g_yres;
-	extern float g_GuiScale;
-	const float yres = g_yres / g_GuiScale;
+	const CSize2D windowSize = m_pGUI.GetWindowSize();
 
 	if (m_ItemsYPositions.empty())
 	{
@@ -362,13 +360,13 @@
 	else if (m_ItemsYPositions.back() > m_DropDownSize)
 	{
 		// Place items below if at least some items can be placed below
-		if (m_CachedActualSize.bottom + m_DropDownBuffer + m_DropDownSize <= yres)
+		if (m_CachedActualSize.bottom + m_DropDownBuffer + m_DropDownSize <= windowSize.Height)
 			m_CachedListRect = CRect(m_CachedActualSize.left, m_CachedActualSize.bottom + m_DropDownBuffer,
 			                         m_CachedActualSize.right, m_CachedActualSize.bottom + m_DropDownBuffer + m_DropDownSize);
-		else if ((m_ItemsYPositions.size() > m_MinimumVisibleItems && yres - m_CachedActualSize.bottom - m_DropDownBuffer >= m_ItemsYPositions[m_MinimumVisibleItems]) ||
-		         m_CachedActualSize.top < yres - m_CachedActualSize.bottom)
+		else if ((m_ItemsYPositions.size() > m_MinimumVisibleItems && windowSize.Height - m_CachedActualSize.bottom - m_DropDownBuffer >= m_ItemsYPositions[m_MinimumVisibleItems]) ||
+		         m_CachedActualSize.top < windowSize.Height - m_CachedActualSize.bottom)
 			m_CachedListRect = CRect(m_CachedActualSize.left, m_CachedActualSize.bottom + m_DropDownBuffer,
-			                         m_CachedActualSize.right, yres);
+			                         m_CachedActualSize.right, windowSize.Height);
 		// Not enough space below, thus place items above
 		else
 			m_CachedListRect = CRect(m_CachedActualSize.left, std::max(0.f, m_CachedActualSize.top - m_DropDownBuffer - m_DropDownSize),
@@ -379,18 +377,18 @@
 	else
 	{
 		// Enough space below, no scrollbar needed
-		if (m_CachedActualSize.bottom + m_DropDownBuffer + m_ItemsYPositions.back() <= yres)
+		if (m_CachedActualSize.bottom + m_DropDownBuffer + m_ItemsYPositions.back() <= windowSize.Height)
 		{
 			m_CachedListRect = CRect(m_CachedActualSize.left, m_CachedActualSize.bottom + m_DropDownBuffer,
 			                         m_CachedActualSize.right, m_CachedActualSize.bottom + m_DropDownBuffer + m_ItemsYPositions.back());
 			m_HideScrollBar = true;
 		}
 		// Enough space below for some items, but not all, so place items below and use a scrollbar
-		else if ((m_ItemsYPositions.size() > m_MinimumVisibleItems && yres - m_CachedActualSize.bottom - m_DropDownBuffer >= m_ItemsYPositions[m_MinimumVisibleItems]) ||
-		         m_CachedActualSize.top < yres - m_CachedActualSize.bottom)
+		else if ((m_ItemsYPositions.size() > m_MinimumVisibleItems && windowSize.Height - m_CachedActualSize.bottom - m_DropDownBuffer >= m_ItemsYPositions[m_MinimumVisibleItems]) ||
+		         m_CachedActualSize.top < windowSize.Height - m_CachedActualSize.bottom)
 		{
 			m_CachedListRect = CRect(m_CachedActualSize.left, m_CachedActualSize.bottom + m_DropDownBuffer,
-			                         m_CachedActualSize.right, yres);
+			                         m_CachedActualSize.right, windowSize.Height);
 			m_HideScrollBar = false;
 		}
 		// Not enough space below, thus place items above. Hide the scrollbar accordingly
Index: ps/trunk/source/gui/ObjectTypes/CTooltip.cpp
===================================================================
--- ps/trunk/source/gui/ObjectTypes/CTooltip.cpp
+++ ps/trunk/source/gui/ObjectTypes/CTooltip.cpp
@@ -91,22 +91,30 @@
 	}
 
 
-	// Reposition the tooltip if it's falling off the screen:
-
-	extern int g_xres, g_yres;
-	extern float g_GuiScale;
-	float screenw = g_xres / g_GuiScale;
-	float screenh = g_yres / g_GuiScale;
+	// Reposition the tooltip if it's falling off in the GUI window.
+	const CSize2D windowSize = m_pGUI.GetWindowSize();
 
 	if (size.pixel.top < 0.f)
-		size.pixel.bottom -= size.pixel.top, size.pixel.top = 0.f;
-	else if (size.pixel.bottom > screenh)
-		size.pixel.top -= (size.pixel.bottom-screenh), size.pixel.bottom = screenh;
+	{
+		size.pixel.bottom -= size.pixel.top;
+		size.pixel.top = 0.f;
+	}
+	else if (size.pixel.bottom > windowSize.Height)
+	{
+		size.pixel.top -= size.pixel.bottom - windowSize.Height;
+		size.pixel.bottom = windowSize.Height;
+	}
 
 	if (size.pixel.left < 0.f)
-		size.pixel.right -= size.pixel.left, size.pixel.left = 0.f;
-	else if (size.pixel.right > screenw)
-		size.pixel.left -= (size.pixel.right-screenw), size.pixel.right = screenw;
+	{
+		size.pixel.right -= size.pixel.left;
+		size.pixel.left = 0.f;
+	}
+	else if (size.pixel.right > windowSize.Width)
+	{
+		size.pixel.left -= size.pixel.right - windowSize.Width;
+		size.pixel.right = windowSize.Width;
+	}
 
 	m_Size.Set(size, true);
 }