diff -up mozilla-release/widget/gtk/nsLookAndFeel.cpp.1144745-2 mozilla-release/widget/gtk/nsLookAndFeel.cpp

--- mozilla-release/widget/gtk/nsLookAndFeel.cpp.1144745-2	2015-05-13 10:30:08.204367309 +0200

+++ mozilla-release/widget/gtk/nsLookAndFeel.cpp	2015-05-13 10:30:08.208367321 +0200

@@ -18,6 +18,7 @@

 #include <fontconfig/fontconfig.h>

 #include "gfxPlatformGtk.h"

+#include "nsScreenGtk.h"

 #include "gtkdrawing.h"

 #include "nsStyleConsts.h"

@@ -742,12 +743,7 @@ GetSystemFontInfo(GtkWidget *aWidget,

     // Scale fonts up on HiDPI displays.

     // This would be done automatically with cairo, but we manually manage

     // the display scale for platform consistency.

-    static auto sGdkScreenGetMonitorScaleFactorPtr = (gint (*)(GdkScreen*,gint))

-        dlsym(RTLD_DEFAULT, "gdk_screen_get_monitor_scale_factor");

-    if (sGdkScreenGetMonitorScaleFactorPtr) {

-        GdkScreen *screen = gdk_screen_get_default();

-        size *= (*sGdkScreenGetMonitorScaleFactorPtr)(screen, 0);

-    }

+    size *= nsScreenGtk::GetGtkMonitorScaleFactor();

     // |size| is now pixels

diff -up mozilla-release/widget/gtk/nsNativeThemeGTK.cpp.1144745-2 mozilla-release/widget/gtk/nsNativeThemeGTK.cpp

--- mozilla-release/widget/gtk/nsNativeThemeGTK.cpp.1144745-2	2015-05-13 10:30:08.206367315 +0200

+++ mozilla-release/widget/gtk/nsNativeThemeGTK.cpp	2015-05-13 10:30:46.966488584 +0200

@@ -6,6 +6,7 @@

 #include "nsNativeThemeGTK.h"

 #include "nsThemeConstants.h"

 #include "gtkdrawing.h"

+#include "nsScreenGtk.h"

 #include "nsIObserverService.h"

 #include "nsIServiceManager.h"

@@ -89,23 +90,6 @@ nsNativeThemeGTK::RefreshWidgetWindow(ns

   vm->InvalidateAllViews();

 }

-gint

-nsNativeThemeGTK::GdkScaleFactor()

-{

-#if (MOZ_WIDGET_GTK >= 3)

-  // Since GDK 3.10

-  static auto sGdkScreenGetMonitorScaleFactorPtr = (gint (*)(GdkScreen*, gint))

-      dlsym(RTLD_DEFAULT, "gdk_screen_get_monitor_scale_factor");

-  if (sGdkScreenGetMonitorScaleFactorPtr) {

-      // FIXME: In the future, we'll want to fix this for GTK on Wayland which

-      // supports a variable scale factor per display.

-      GdkScreen *screen = gdk_screen_get_default();

-      return sGdkScreenGetMonitorScaleFactorPtr(screen, 0);

-  }

-#endif

-    return 1;

-}

-

 static bool IsFrameContentNodeInNamespace(nsIFrame *aFrame, uint32_t aNamespace)

 {

@@ -796,10 +780,11 @@ nsNativeThemeGTK::GetExtraSizeForWidget(

   default:

     return false;

   }

-  aExtra->top *= GdkScaleFactor();

-  aExtra->right *= GdkScaleFactor();

-  aExtra->bottom *= GdkScaleFactor();

-  aExtra->left *= GdkScaleFactor();

+  gint scale = nsScreenGtk::GetGtkMonitorScaleFactor();

+  aExtra->top *= scale;

+  aExtra->right *= scale;

+  aExtra->bottom *= scale;

+  aExtra->left *= scale;

   return true;

 }

@@ -827,7 +812,7 @@ nsNativeThemeGTK::DrawWidgetBackground(n

   gfxRect rect = presContext->AppUnitsToGfxUnits(aRect);

   gfxRect dirtyRect = presContext->AppUnitsToGfxUnits(aDirtyRect);

-  gint scaleFactor = GdkScaleFactor();

+  gint scaleFactor = nsScreenGtk::GetGtkMonitorScaleFactor();

   // Align to device pixels where sensible

   // to provide crisper and faster drawing.

@@ -1066,10 +1051,11 @@ nsNativeThemeGTK::GetWidgetPadding(nsDev

         aResult->left += horizontal_padding;

         aResult->right += horizontal_padding;

-        aResult->top *= GdkScaleFactor();

-        aResult->right *= GdkScaleFactor();

-        aResult->bottom *= GdkScaleFactor();

-        aResult->left *= GdkScaleFactor();

+        gint scale = nsScreenGtk::GetGtkMonitorScaleFactor();

+        aResult->top *= scale;

+        aResult->right *= scale;

+        aResult->bottom *= scale;

+        aResult->left *= scale;

         return true;

       }

@@ -1332,7 +1318,7 @@ nsNativeThemeGTK::GetMinimumWidgetSize(n

     break;

   }

-  *aResult = *aResult * GdkScaleFactor();

+  *aResult = *aResult * nsScreenGtk::GetGtkMonitorScaleFactor();

   return NS_OK;

 }

diff -up mozilla-release/widget/gtk/nsNativeThemeGTK.h.1144745-2 mozilla-release/widget/gtk/nsNativeThemeGTK.h

--- mozilla-release/widget/gtk/nsNativeThemeGTK.h.1144745-2	2015-05-13 10:30:08.206367315 +0200

+++ mozilla-release/widget/gtk/nsNativeThemeGTK.h	2015-05-13 10:30:08.209367325 +0200

@@ -81,7 +81,6 @@ private:

                                nsIntMargin* aExtra);

   void RefreshWidgetWindow(nsIFrame* aFrame);

-  gint GdkScaleFactor();

   uint8_t mDisabledWidgetTypes[32];

   uint8_t mSafeWidgetStates[1024];    // 256 widgets * 32 bits per widget

diff -up mozilla-release/widget/gtk/nsScreenGtk.cpp.1144745-2 mozilla-release/widget/gtk/nsScreenGtk.cpp

--- mozilla-release/widget/gtk/nsScreenGtk.cpp.1144745-2	2015-05-08 18:55:27.000000000 +0200

+++ mozilla-release/widget/gtk/nsScreenGtk.cpp	2015-05-13 10:30:08.209367325 +0200

@@ -63,6 +63,23 @@ nsScreenGtk :: GetAvailRect(int32_t *out

 } // GetAvailRect

+gint

+nsScreenGtk :: GetGtkMonitorScaleFactor()

+{

+#if (MOZ_WIDGET_GTK >= 3)

+  // Since GDK 3.10

+  static auto sGdkScreenGetMonitorScaleFactorPtr = (gint (*)(GdkScreen*, gint))

+      dlsym(RTLD_DEFAULT, "gdk_screen_get_monitor_scale_factor");

+  if (sGdkScreenGetMonitorScaleFactorPtr) {

+      // FIXME: In the future, we'll want to fix this for GTK on Wayland which

+      // supports a variable scale factor per display.

+      GdkScreen *screen = gdk_screen_get_default();

+      return sGdkScreenGetMonitorScaleFactorPtr(screen, 0);

+  }

+#endif

+    return 1;

+}

+

 double

 nsScreenGtk :: GetDPIScale()

 {

@@ -127,20 +144,9 @@ nsScreenGtk :: GetColorDepth(int32_t *aC

 void

 nsScreenGtk :: Init (GdkWindow *aRootWindow)

 {

-  gint width = gdk_screen_width();

-  gint height = gdk_screen_height();

-

-  // Since GDK 3.10

-  static auto sGdkScreenGetMonitorScaleFactorPtr = (gint (*)(GdkScreen*, gint))

-      dlsym(RTLD_DEFAULT, "gdk_screen_get_monitor_scale_factor");

-  if (sGdkScreenGetMonitorScaleFactorPtr) {

-      // FIXME: In the future, we'll want to fix this for GTK on Wayland which

-      // supports a variable scale factor per display.

-      GdkScreen *screen = gdk_window_get_screen(aRootWindow);

-      gint scale = sGdkScreenGetMonitorScaleFactorPtr(screen, 0);

-      width *= scale;

-      height *= scale;

-  }

+  gint scale = nsScreenGtk::GetGtkMonitorScaleFactor();

+  gint width = gdk_screen_width()*scale;

+  gint height = gdk_screen_height()*scale;

   // We listen for configure events on the root window to pick up

   // changes to this rect.  We could listen for "size_changed" signals

diff -up mozilla-release/widget/gtk/nsScreenGtk.h.1144745-2 mozilla-release/widget/gtk/nsScreenGtk.h

--- mozilla-release/widget/gtk/nsScreenGtk.h.1144745-2	2015-05-08 18:55:27.000000000 +0200

+++ mozilla-release/widget/gtk/nsScreenGtk.h	2015-05-13 10:30:08.209367325 +0200

@@ -43,7 +43,8 @@ public:

   void Init(XineramaScreenInfo *aScreenInfo);

 #endif /* MOZ_X11 */

-  static double GetDPIScale();

+  static gint    GetGtkMonitorScaleFactor();

+  static double  GetDPIScale();

 private:

   uint32_t mScreenNum;