diff --git a/mozilla/gfx/src/os2/nsDeviceContextOS2.cpp b/mozilla/gfx/src/os2/nsDeviceContextOS2.cpp
index f0e58d06eea..9c38551fec1 100644
--- a/mozilla/gfx/src/os2/nsDeviceContextOS2.cpp
+++ b/mozilla/gfx/src/os2/nsDeviceContextOS2.cpp
@@ -35,6 +35,7 @@
 #include "nsHashTable.h" // For CreateFontAliasTable()
 
 #include "nsGfxDefs.h"
+#include "nsIPref.h"
 
 // Size of the color cube
 #define COLOR_CUBE_SIZE       216
@@ -43,6 +44,7 @@
 static PRBool gIsWarp4 = NOT_SETUP;
 
 PRUint32 nsDeviceContextOS2::sNumberOfScreens = 0;
+nscoord nsDeviceContextOS2::mDpi = 120;
 
 nsDeviceContextOS2 :: nsDeviceContextOS2()
   : DeviceContextImpl()
@@ -81,8 +83,14 @@ nsDeviceContextOS2::~nsDeviceContextOS2()
   {
     GFX (::GpiDestroyPS (mPrintPS), FALSE);
     ::DevCloseDC(mPrintDC);
+  } else {
+    nsresult rv;
+    nsCOMPtr<nsIPref> prefs = do_GetService(NS_PREF_CONTRACTID, &rv);
+    if (NS_SUCCEEDED(rv)) {
+      prefs->UnregisterCallback("browser.display.screen_resolution",
+                                prefChanged, (void *)this);
+    }
   }
-
   NS_IF_RELEASE(mSpec);
 }
 
@@ -92,6 +100,35 @@ nsresult nsDeviceContextOS2::Init( nsNativeWidget aWidget)
 
   CommonInit(::WinOpenWindowDC((HWND)aWidget));
 
+  static int initialized = 0;
+  PRInt32 prefVal = -1;
+  if (!initialized) {
+    initialized = 1;
+
+    // Set prefVal the value of the preference
+    // "browser.display.screen_resolution"
+    // or -1 if we can't get it.
+    // If it's negative, we pretend it's not set.
+    // If it's 0, it means force use of the operating system's logical
+    // resolution.
+    // If it's positive, we use it as the logical resolution
+    nsresult res;
+
+    nsCOMPtr<nsIPref> prefs(do_GetService(NS_PREF_CONTRACTID, &res));
+    if (NS_SUCCEEDED(res) && prefs) {
+      res = prefs->GetIntPref("browser.display.screen_resolution", &prefVal);
+      if (NS_FAILED(res)) {
+        prefVal = -1;
+      }
+      prefs->RegisterCallback("browser.display.screen_resolution", prefChanged,
+                              (void *)this);
+    }
+
+    SetDPI(prefVal);
+  } else {
+    SetDPI(mDpi); // to setup p2t and t2p
+  }
+
   return NS_OK;
 }
 
@@ -119,6 +156,8 @@ nsresult nsDeviceContextOS2::Init( nsNativeDeviceContext aContext,
 
   CommonInit( mPrintDC);
 
+  SetDPI(0);
+
   GetTwipsToDevUnits( newscale);
 
 // On OS/2, origscale can be different based on the video resolution.
@@ -158,10 +197,6 @@ void nsDeviceContextOS2 :: CommonInit(HDC aDC)
 
   GFX (::DevQueryCaps(aDC, CAPS_FAMILY, CAPS_DEVICE_POLYSET_POINTS, alArray), FALSE);
 
-  mTwipsToPixels = ((float)alArray [CAPS_VERTICAL_FONT_RES]) / (float)NSIntPointsToTwips(72);
-
-  mPixelsToTwips = 1.0f / mTwipsToPixels;
-
   mDepth = alArray[CAPS_COLOR_BITCOUNT];
 #ifdef COLOR_256
   mPaletteInfo.isPaletteDevice = !!(alArray[CAPS_ADDITIONAL_GRAPHICS] & CAPS_PALETTE_MANAGER);
@@ -565,6 +600,55 @@ NS_IMETHODIMP nsDeviceContextOS2::GetDepth(PRUint32& aDepth)
   return NS_OK;
 }
 
+nsresult
+nsDeviceContextOS2::SetDPI(PRInt32 aPrefDPI)
+{
+  // Set OSVal to what the operating system thinks the logical resolution is.
+  long OSVal;
+  HPS ps = ::WinGetScreenPS(HWND_DESKTOP);
+  HDC hdc = GFX (::GpiQueryDevice (ps), HDC_ERROR);
+  GFX (::DevQueryCaps(hdc, CAPS_HORIZONTAL_FONT_RES, 1, &OSVal), FALSE);
+  ::WinReleasePS(ps);
+
+  if ((aPrefDPI == 0) || (mPrintDC)) {
+    // If the pref is 0 or we are printing force use of OS value
+    mDpi = OSVal;
+  } else if (aPrefDPI > 0) {
+    // If there's a valid pref value for the logical resolution,
+    // use it.
+    mDpi = aPrefDPI;
+  } else {
+    // if we couldn't get the pref or it's negative then use 120
+    mDpi = 120;
+  }
+
+  int pt2t = 72;
+
+  // make p2t a nice round number - this prevents rounding problems
+  mPixelsToTwips = float(NSToIntRound(float(NSIntPointsToTwips(pt2t)) / float(mDpi)));
+  mTwipsToPixels = 1.0f / mPixelsToTwips;
+
+  // XXX need to reflow all documents
+  return NS_OK;
+}
+
+int prefChanged(const char *aPref, void *aClosure)
+{
+  nsDeviceContextOS2 *context = (nsDeviceContextOS2*)aClosure;
+  nsresult rv;
+  
+  if (nsCRT::strcmp(aPref, "browser.display.screen_resolution")==0) {
+    PRInt32 dpi;
+    nsCOMPtr<nsIPref> prefs(do_GetService(NS_PREF_CONTRACTID, &rv));
+    rv = prefs->GetIntPref(aPref, &dpi);
+    if (NS_SUCCEEDED(rv))
+      context->SetDPI(dpi);
+
+  }
+  
+  return 0;
+}
+
 #ifdef COLOR_256
 NS_IMETHODIMP nsDeviceContextOS2::GetILColorSpace(IL_ColorSpace*& aColorSpace)
 {
diff --git a/mozilla/gfx/src/os2/nsDeviceContextOS2.h b/mozilla/gfx/src/os2/nsDeviceContextOS2.h
index ba06bb9473e..b1e0245c10a 100644
--- a/mozilla/gfx/src/os2/nsDeviceContextOS2.h
+++ b/mozilla/gfx/src/os2/nsDeviceContextOS2.h
@@ -71,6 +71,7 @@ public:
 
   NS_IMETHOD  GetDepth(PRUint32& aDepth);
 
+
 #ifdef COLOR_256
   NS_IMETHOD  GetILColorSpace(IL_ColorSpace*& aColorSpace);
 
@@ -97,6 +98,7 @@ public:
 
   // Static Helper Methods
   static char* GetACPString(const nsString& aStr);
+  nsresult   SetDPI(PRInt32 aPrefDPI);
 
 protected:
   virtual ~nsDeviceContextOS2();
@@ -123,6 +125,7 @@ protected:
 
   nsCOMPtr<nsIScreenManager> mScreenManager;
   static PRUint32 sNumberOfScreens;
+  static nscoord mDpi;
 
 public:
   HDC                   mPrintDC;
@@ -141,4 +144,6 @@ public:
   nsresult nsDeviceContextOS2::CreateFontAliasTable();
 };
 
+static int PR_CALLBACK prefChanged(const char *aPref, void *aClosure);
+
 #endif /* nsDeviceContextOS2_h___ */
diff --git a/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp b/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp
index c349e3098b7..811175f833b 100644
--- a/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp
+++ b/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp
@@ -68,7 +68,6 @@ static NS_DEFINE_CID(kLocaleServiceCID, NS_LOCALESERVICE_CID);
 nsVoidArray  *nsFontMetricsOS2::gGlobalFonts = nsnull;
 PRBool        nsFontMetricsOS2::gSubstituteVectorFonts = PR_TRUE;
 PLHashTable  *nsFontMetricsOS2::gFamilyNames = nsnull;
-nscoord       nsFontMetricsOS2::gDPI = 0;
 long          nsFontMetricsOS2::gSystemRes = 0;
 int           nsFontMetricsOS2::gCachedIndex = 0;
 nsICollation *nsFontMetricsOS2::gCollation = nsnull;
@@ -249,31 +248,12 @@ nsFontOS2::DrawString( HPS aPS, nsDrawingSurfaceOS2* aSurface,
 /**********************************************************
     nsFontMetricsOS2
  **********************************************************/    
-int PR_CALLBACK
-prefChanged(const char *aPref, void *aClosure)
-{
-  nsresult rv;
-
-  if( PL_strcmp(aPref, "browser.display.screen_resolution") == 0 )
-  {
-    PRInt32 dpi;
-    rv = gPref->GetIntPref( aPref, &dpi );
-    if( NS_SUCCEEDED(rv) && dpi != 0)
-      nsFontMetricsOS2::gDPI = dpi;
-    else
-      nsFontMetricsOS2::gDPI = nsFontMetricsOS2::gSystemRes;
-  }
-
-  return 0;
-}
 
 static void
 FreeGlobals(void)
 {
   gInitialized = 0;
 
-  gPref->UnregisterCallback( "browser.display.screen_resolution", prefChanged, NULL );
-
 #ifdef WINCODE
   NS_IF_RELEASE(gCharsetManager);
 #endif
@@ -423,25 +403,6 @@ InitGlobals(void)
     }
   }
 
-  // Set prefVal the value of the pref "browser.display.screen_resolution"
-  // When a new profile is created, the pref is set to 0.  This tells the code
-  // to default to font resolution of the screen (96 or 120)
-  nsresult res;
-  PRInt32 prefVal = -1;
-
-  res = gPref->GetIntPref( "browser.display.screen_resolution", &prefVal );
-  if (NS_FAILED(res))
-    prefVal = 0;
-
-  gPref->RegisterCallback( "browser.display.screen_resolution", prefChanged, NULL );
-
-  if (prefVal == 0)
-  {
-    prefVal = nsFontMetricsOS2::gSystemRes;
-  }
-
-  nsFontMetricsOS2::gDPI = prefVal;
-
   //register an observer to take care of cleanup
   gFontCleanupObserver = new nsFontCleanupObserver();
   NS_ASSERTION(gFontCleanupObserver, "failed to create observer");
@@ -568,7 +529,7 @@ nsFontMetricsOS2::SetFontHandle( HPS aPS, nsFontOS2* aFont )
      // points size is less than the minimum or more than the maximum point
      // size available for Tms Rmn and Helv.
     if( gSubstituteVectorFonts &&
-        (points > 18 || points < 8 || (gDPI != 96 && gDPI != 120)) &&
+        (points > 18 || points < 8) &&
         GetVectorSubstitute( aPS, fattrs->szFacename, alias ))
     {
       PL_strcpy( fattrs->szFacename, alias );
@@ -650,11 +611,9 @@ nsFontMetricsOS2::SetFontHandle( HPS aPS, nsFontOS2* aFont )
   float app2dev, fHeight;
   mDeviceContext->GetAppUnitsToDevUnits( app2dev );
 
-  if( !mDeviceContext->mPrintDC ) /* if not printing */
-    if( fattrs->fsFontUse == 0 )    /* if image font */
-      fHeight = points * gDPI / 72;
-    else
-      fHeight = mFont.size * app2dev * gDPI / nsFontMetricsOS2::gSystemRes;
+  /* if image font and not printing */
+  if ((fattrs->fsFontUse == 0) && (!mDeviceContext->mPrintDC))
+    fHeight = NSIntPointsToTwips(points) * app2dev;
   else
     fHeight = mFont.size * app2dev;
 
diff --git a/mozilla/gfx/src/os2/nsFontMetricsOS2.h b/mozilla/gfx/src/os2/nsFontMetricsOS2.h
index 49b827e68b1..c44c7c827b7 100644
--- a/mozilla/gfx/src/os2/nsFontMetricsOS2.h
+++ b/mozilla/gfx/src/os2/nsFontMetricsOS2.h
@@ -198,7 +198,6 @@ class nsFontMetricsOS2 : public nsIFontMetrics
 
   static nsVoidArray*  gGlobalFonts;
   static PLHashTable*  gFamilyNames;
-  static nscoord       gDPI;
   static long          gSystemRes;
   static nsICollation* gCollation;