--- a/gfx/src/thebes/nsSystemFontsAndroid.cpp
+++ b/gfx/src/thebes/nsSystemFontsAndroid.cpp
@@ -60,17 +60,17 @@ nsresult
 nsSystemFontsAndroid::GetSystemFontInfo(const char *aClassName, nsString *aFontName,
                                         gfxFontStyle *aFontStyle) const
 {
     aFontStyle->style = FONT_STYLE_NORMAL;
     aFontStyle->systemFont = PR_TRUE;
     *aFontName = NS_LITERAL_STRING("Droid Sans");
     aFontStyle->weight = 400;
     aFontStyle->stretch = NS_FONT_STRETCH_NORMAL;
-    aFontStyle->size = 9.0 * float(gfxPlatform::GetDPI()) / 72.0f;
+    aFontStyle->size = 9.0 * 96.0f / 72.0f;
     return NS_OK;
 }
 
 
 nsresult
 nsSystemFontsAndroid::GetSystemFont(nsSystemFontID anID, nsString *aFontName,
                                     gfxFontStyle *aFontStyle) const
 {

--- a/gfx/src/thebes/nsSystemFontsGTK2.cpp
+++ b/gfx/src/thebes/nsSystemFontsGTK2.cpp
@@ -216,17 +216,17 @@ nsSystemFontsGTK2::GetSystemFontInfo(Gtk
     aFontStyle->stretch = NS_FONT_STRETCH_NORMAL;
 
     float size = float(pango_font_description_get_size(desc)) / PANGO_SCALE;
 
     // |size| is now either pixels or pango-points (not Mozilla-points!)
 
     if (!MOZ_pango_font_description_get_size_is_absolute(desc)) {
         // |size| is in pango-points, so convert to pixels.
-        size *= float(gfxPlatform::GetDPI()) / POINTS_PER_INCH_FLOAT;
+        size *= float(gfxPlatformGtk::GetDPI()) / POINTS_PER_INCH_FLOAT;
     }
 
     // |size| is now pixels
 
     aFontStyle->size = size;
   
     pango_font_description_free(desc);
 

--- a/gfx/src/thebes/nsSystemFontsQt.cpp
+++ b/gfx/src/thebes/nsSystemFontsQt.cpp
@@ -79,19 +79,17 @@ nsSystemFontsQt::GetSystemFontInfo(const
     *aFontName = quote + family + quote;
     aFontStyle->weight = qFont.weight();
     // FIXME: Set aFontStyle->stretch correctly!
     aFontStyle->stretch = NS_FONT_STRETCH_NORMAL;
     // use pixel size directly if it is set, otherwise compute from point size
     if (qFont.pixelSize() != -1) {
         aFontStyle->size = qFont.pixelSize();
     } else {
-        aFontStyle->size = qFont.pointSizeF()
-                           * float(gfxPlatform::GetDPI())
-                           / 72.0f;
+        aFontStyle->size = qFont.pointSizeF() * 96.0f / 72.0f;
     }
     return NS_OK;
 }
 
 
 nsresult
 nsSystemFontsQt::GetSystemFont(nsSystemFontID anID, nsString *aFontName,
                                  gfxFontStyle *aFontStyle) const

--- a/gfx/thebes/gfxOS2Platform.cpp
+++ b/gfx/thebes/gfxOS2Platform.cpp
@@ -216,27 +216,8 @@ gfxOS2Platform::FindFontForChar(PRUint32
             }
         }
     }
 
     // no match found, so add to the set of non-matching codepoints
     mCodepointsWithNoFonts.set(aCh);
     return nsnull;
 }
-
-void
-gfxOS2Platform::InitDisplayCaps()
-{
-    // create DC compatible with the screen
-    HDC dc = DevOpenDC((HAB)1, OD_MEMORY,"*",0L, NULL, NULLHANDLE);
-    if (dc > 0) {
-        // we do have a DC and we can query the DPI setting from it
-        LONG lDPI;
-        if (DevQueryCaps(dc, CAPS_VERTICAL_FONT_RES, 1, &lDPI))
-            gfxPlatform::sDPI = lDPI;
-        DevCloseDC(dc);
-    }
-
-    if (gfxPlatform::sDPI <= 0) {
-        // Fall back to something sane
-        gfxPlatform::sDPI = 96;
-    }
-}

--- a/gfx/thebes/gfxOS2Platform.h
+++ b/gfx/thebes/gfxOS2Platform.h
@@ -82,18 +82,16 @@ public:
     already_AddRefed<gfxOS2Font> FindFontForChar(PRUint32 aCh, gfxOS2Font *aFont);
 
     // return true if it's already known that we don't have a font for this char
     PRBool noFontWithChar(PRUint32 aCh) {
         return mCodepointsWithNoFonts.test(aCh);
     }
 
 protected:
-    void InitDisplayCaps();
-
     static gfxFontconfigUtils *sFontconfigUtils;
 
 private:
     // when font lookup fails for a character, cache it to skip future searches
     gfxSparseBitSet mCodepointsWithNoFonts;
 };
 
 #endif /* GFX_OS2_PLATFORM_H */

--- a/gfx/thebes/gfxPangoFonts.cpp
+++ b/gfx/thebes/gfxPangoFonts.cpp
@@ -707,28 +707,40 @@ gfx_pango_fc_font_get_coverage(PangoFont
             self->mCoverage =
                 pango_coverage_ref(downloadedFontEntry->GetPangoCoverage());
         }
     }
 
     return pango_coverage_ref(self->mCoverage);
 }
 
+static PRInt32
+GetDPI()
+{
+#if defined(MOZ_WIDGET_GTK2)
+    return gfxPlatformGtk::GetDPI();
+#elif defined(MOZ_WIDGET_QT)
+    return gfxQtPlatform::GetDPI();
+#else
+    return 96;
+#endif
+}
+
 static PangoFontDescription *
 gfx_pango_fc_font_describe(PangoFont *font)
 {
     gfxPangoFcFont *self = GFX_PANGO_FC_FONT(font);
     PangoFcFont *fcFont = &self->parent_instance;
     PangoFontDescription *result =
         pango_font_description_copy(fcFont->description);
 
     gfxFcFont *gfxFont = gfxPangoFcFont::GfxFont(self);
     if (gfxFont) {
         double pixelsize = gfxFont->GetStyle()->size;
-        double dpi = gfxPlatform::GetDPI();
+        double dpi = GetDPI();
         gint size = moz_pango_units_from_double(pixelsize * dpi / 72.0);
         pango_font_description_set_size(result, size);
     }
     return result;
 }
 
 static PangoFontDescription *
 gfx_pango_fc_font_describe_absolute(PangoFont *font)
@@ -1715,18 +1727,17 @@ gfx_pango_font_map_load_fontset(PangoFon
     return gfxPangoFontset::NewFontset(fontGroup, language);
 }
 
 static double
 gfx_pango_font_map_get_resolution(PangoFcFontMap *fcfontmap,
                                   PangoContext *context)
 {
     // This merely enables the FC_SIZE field of the pattern to be accurate.
-    // We use gfxPlatform::GetDPI() much of the time...
-    return gfxPlatform::GetDPI();
+    return GetDPI();
 }
 
 #ifdef MOZ_WIDGET_GTK2
 static void ApplyGdkScreenFontOptions(FcPattern *aPattern);
 #endif
 
 // Apply user settings and defaults to pattern in preparation for matching.
 static void

--- a/gfx/thebes/gfxPlatform.cpp
+++ b/gfx/thebes/gfxPlatform.cpp
@@ -81,18 +81,16 @@
 #include "nsCRT.h"
 #include "GLContext.h"
 #include "GLContextProvider.h"
 
 #include "mozilla/FunctionTimer.h"
 
 gfxPlatform *gPlatform = nsnull;
 
-PRInt32 gfxPlatform::sDPI = -1;
-
 // These two may point to the same profile
 static qcms_profile *gCMSOutputProfile = nsnull;
 static qcms_profile *gCMSsRGBProfile = nsnull;
 
 static qcms_transform *gCMSRGBTransform = nsnull;
 static qcms_transform *gCMSInverseRGBTransform = nsnull;
 static qcms_transform *gCMSRGBATransform = nsnull;
 
@@ -1058,23 +1056,16 @@ static void MigratePrefs()
         rv = prefs->GetBoolPref(CMPrefNameOld, &CMWasEnabled);
         if (NS_SUCCEEDED(rv) && (CMWasEnabled == PR_TRUE))
             prefs->SetIntPref(CMPrefName, eCMSMode_All);
         prefs->ClearUserPref(CMPrefNameOld);
     }
 
 }
 
-void
-gfxPlatform::InitDisplayCaps()
-{
-    // Fall back to something sane
-    gfxPlatform::sDPI = 96;
-}
-
 // default SetupClusterBoundaries, based on Unicode properties;
 // platform subclasses may override if they wish
 static nsIUGenCategory* gGenCategory = nsnull;
 
 static nsIUGenCategory*
 GetGenCategory()
 {
     if (!gGenCategory) {

--- a/gfx/thebes/gfxPlatform.h
+++ b/gfx/thebes/gfxPlatform.h
@@ -332,44 +332,27 @@ public:
      */
     static qcms_transform* GetCMSInverseRGBTransform();
 
     /**
      * Return sRGBA -> output device transform.
      */
     static qcms_transform* GetCMSRGBATransform();
 
-    /**
-     * Return display DPI
-     */
-    static PRInt32 GetDPI() {
-        if (sDPI < 0) {
-            gfxPlatform::GetPlatform()->InitDisplayCaps();
-        }
-        NS_ASSERTION(sDPI > 0, "Something is wrong");
-        return sDPI;
-    }
-
     virtual void FontsPrefsChanged(nsIPrefBranch *aPrefBranch, const char *aPref);
 
 protected:
     gfxPlatform();
     virtual ~gfxPlatform();
 
     static PRBool GetBoolPref(const char *aPref, PRBool aDefault);
 
     void AppendCJKPrefLangs(eFontPrefLang aPrefLangs[], PRUint32 &aLen, 
                             eFontPrefLang aCharLang, eFontPrefLang aPageLang);
                                                
-    /**
-     * Initialize any needed display metrics (such as DPI)
-     */
-    virtual void InitDisplayCaps();
-    static PRInt32 sDPI;
-
     PRBool  mAllowDownloadableFonts;
 
     // whether to use the HarfBuzz layout engine
     PRInt8  mUseHarfBuzzLevel;
 
 private:
     virtual qcms_profile* GetPlatformCMSOutputProfile();
 

--- a/gfx/thebes/gfxPlatformGtk.cpp
+++ b/gfx/thebes/gfxPlatformGtk.cpp
@@ -470,27 +470,32 @@ gfxPlatformGtk::CreateFontGroup(const ns
                                const gfxFontStyle *aStyle,
                                 gfxUserFontSet * /*aUserFontSet*/)
 {
     return new gfxFT2FontGroup(aFamilies, aStyle);
 }
 
 #endif
 
-void
-gfxPlatformGtk::InitDisplayCaps()
+static PRInt32 sDPI = 0;
+
+PRInt32
+gfxPlatformGtk::GetDPI()
 {
-    // Make sure init is run so we have a resolution
-    GdkScreen *screen = gdk_screen_get_default();
-    gtk_settings_get_for_screen(screen);
-    gfxPlatform::sDPI = PRInt32(round(gdk_screen_get_resolution(screen)));
-    if (gfxPlatform::sDPI <= 0) {
-        // Fall back to something sane
-        gfxPlatform::sDPI = 96;
+    if (!sDPI) {
+        // Make sure init is run so we have a resolution
+        GdkScreen *screen = gdk_screen_get_default();
+        gtk_settings_get_for_screen(screen);
+        sDPI = PRInt32(round(gdk_screen_get_resolution(screen)));
+        if (sDPI <= 0) {
+            // Fall back to something sane
+            sDPI = 96;
+        }
     }
+    return sDPI;
 }
 
 qcms_profile *
 gfxPlatformGtk::GetPlatformCMSOutputProfile()
 {
 #ifdef MOZ_X11
     const char EDID1_ATOM_NAME[] = "XFree86_DDC_EDID1_RAWDATA";
     const char ICC_PROFILE_ATOM_NAME[] = "_ICC_PROFILE";

--- a/gfx/thebes/gfxPlatformGtk.h
+++ b/gfx/thebes/gfxPlatformGtk.h
@@ -117,18 +117,18 @@ public:
 #ifndef MOZ_PANGO
     FT_Library GetFTLibrary();
 #endif
 
     static void SetGdkDrawable(gfxASurface *target,
                                GdkDrawable *drawable);
     static GdkDrawable *GetGdkDrawable(gfxASurface *target);
 
+    static PRInt32 GetDPI();
+
 protected:
-    void InitDisplayCaps();
-
     static gfxFontconfigUtils *sFontconfigUtils;
 
 private:
     virtual qcms_profile *GetPlatformCMSOutputProfile();
 };
 
 #endif /* GFX_PLATFORM_GTK_H */

--- a/gfx/thebes/gfxQtPlatform.cpp
+++ b/gfx/thebes/gfxQtPlatform.cpp
@@ -565,19 +565,18 @@ gfxQtPlatform::GetPrefFontEntries(const 
     return mPrefFonts.Get(aKey, array);
 }
 
 void
 gfxQtPlatform::SetPrefFontEntries(const nsCString& aKey, nsTArray<nsRefPtr<gfxFontEntry> >& array)
 {
     mPrefFonts.Put(aKey, array);
 }
+
 #endif
 
-void
-gfxQtPlatform::InitDisplayCaps()
+PRInt32
+gfxQtPlatform::GetDPI()
 {
     QDesktopWidget* rootWindow = qApp->desktop();
-    sDPI = rootWindow->logicalDpiY(); // y-axis DPI for fonts
-    if (sDPI <= 0)
-        sDPI = 96; // something more sensible
+    PRInt32 dpi = rootWindow->logicalDpiY(); // y-axis DPI for fonts
+    return dpi <= 0 ? 96 : dpi;
 }
-

--- a/gfx/thebes/gfxQtPlatform.h
+++ b/gfx/thebes/gfxQtPlatform.h
@@ -126,19 +126,20 @@ public:
 
 #ifndef MOZ_PANGO
     FT_Library GetFTLibrary();
 #endif
 
     RenderMode GetRenderMode() { return mRenderMode; }
     void SetRenderMode(RenderMode rmode) { mRenderMode = rmode; }
 
+    static PRInt32 GetDPI();
+
 protected:
     static gfxFontconfigUtils *sFontconfigUtils;
-    void InitDisplayCaps();
 
 private:
     virtual qcms_profile *GetPlatformCMSOutputProfile();
 
     // TODO: unify this with mPrefFonts (NB: holds families, not fonts) in gfxPlatformFontList
     nsDataHashtable<nsCStringHashKey, nsTArray<nsRefPtr<gfxFontEntry> > > mPrefFonts;
 
     RenderMode mRenderMode;

--- a/gfx/thebes/gfxWindowsPlatform.cpp
+++ b/gfx/thebes/gfxWindowsPlatform.cpp
@@ -623,26 +623,16 @@ gfxWindowsPlatform::WindowsOSVersion()
         } else {
             winVersion = PRInt32(vinfo.dwMajorVersion << 16) + vinfo.dwMinorVersion;
         }
     }
     return winVersion;
 }
 
 void
-gfxWindowsPlatform::InitDisplayCaps()
-{
-    HDC dc = GetDC((HWND)nsnull);
-
-    gfxPlatform::sDPI = GetDeviceCaps(dc, LOGPIXELSY);
-
-    ReleaseDC((HWND)nsnull, dc);
-}
-
-void
 gfxWindowsPlatform::FontsPrefsChanged(nsIPrefBranch *aPrefBranch, const char *aPref)
 {
     PRBool clearTextFontCaches = PR_TRUE;
 
     gfxPlatform::FontsPrefsChanged(aPrefBranch, aPref);
 
     if (!aPref) {
         mUseClearTypeForDownloadableFonts = UNINITIALIZED_VALUE;

--- a/gfx/thebes/gfxWindowsPlatform.h
+++ b/gfx/thebes/gfxWindowsPlatform.h
@@ -221,18 +221,16 @@ public:
     cairo_device_t *GetD2DDevice() { return mD2DDevice; }
 #endif
 
 #ifdef MOZ_FT2_FONTS
     FT_Library GetFTLibrary();
 #endif
 
 protected:
-    void InitDisplayCaps();
-
     RenderMode mRenderMode;
 
     PRBool mUseClearTypeForDownloadableFonts;
     PRBool mUseClearTypeAlways;
 
 private:
     void Init();
 

--- a/widget/src/os2/nsWindow.cpp
+++ b/widget/src/os2/nsWindow.cpp
@@ -563,16 +563,38 @@ nsIWidget* nsWindow::GetParent()
   if (mFrame || mIsDestroying || mOnDestroyCalled ||
       !mParent || mParent->mIsDestroying) {
     return 0;
   }
 
   return mParent;
 }
 
+static PRInt32 sDPI = 0;
+
+float nsWindow::GetDPI()
+{
+    if (!sDPI) {
+        // create DC compatible with the screen
+        HDC dc = DevOpenDC((HAB)1, OD_MEMORY,"*",0L, NULL, NULLHANDLE);
+        if (dc > 0) {
+            // we do have a DC and we can query the DPI setting from it
+            LONG lDPI;
+            if (DevQueryCaps(dc, CAPS_VERTICAL_FONT_RES, 1, &lDPI))
+                sDPI = lDPI;
+            DevCloseDC(dc);
+        }
+        if (sDPI <= 0) {
+            // Fall back to something sane
+            sDPI = 96;
+        }
+    }
+    return sDPI;  
+}
+
 //-----------------------------------------------------------------------------
 
 NS_METHOD nsWindow::Enable(PRBool aState)
 {
   HWND hMain = GetMainWindow();
   if (hMain) {
     WinEnableWindow(hMain, aState);
   }

--- a/widget/src/os2/nsWindow.h
+++ b/widget/src/os2/nsWindow.h
@@ -166,16 +166,17 @@ public:
                                const nsIntRect& aRect,
                                EVENT_CALLBACK aHandleEventFunction,
                                nsIDeviceContext* aContext,
                                nsIAppShell* aAppShell = nsnull,
                                nsIToolkit* aToolkit = nsnull,
                                nsWidgetInitData* aInitData = nsnull);
   NS_IMETHOD            Destroy();
   virtual nsIWidget*    GetParent();
+  virtual float         GetDPI();
   NS_IMETHOD            Enable(PRBool aState);
   NS_IMETHOD            IsEnabled(PRBool* aState);
   NS_IMETHOD            Show(PRBool aState);
   NS_IMETHOD            IsVisible(PRBool& aState);
   NS_IMETHOD            SetFocus(PRBool aRaise);
   NS_IMETHOD            Invalidate(const nsIntRect& aRect,
                                    PRBool aIsSynchronous);
   NS_IMETHOD            Update();