--- a/dom/plugins/base/npapi.h
+++ b/dom/plugins/base/npapi.h
@@ -41,16 +41,17 @@
 #endif
 #endif
 
 #if defined(XP_UNIX)
 #include <stdio.h>
 #if defined(MOZ_X11)
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
+#include "X11UndefineNone.h"
 #endif
 #endif
 
 #if defined(XP_SYMBIAN)
 #include <QEvent>
 #include <QRegion>
 #endif
 

--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -2594,17 +2594,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
         // Get reference point relative to screen:
         LayoutDeviceIntPoint rootPoint(-1, -1);
         if (widget) {
           rootPoint = anEvent.mRefPoint + widget->WidgetToScreenOffset();
         }
 #ifdef MOZ_WIDGET_GTK
         Window root = GDK_ROOT_WINDOW();
 #else
-        Window root = None; // Could XQueryTree, but this is not important.
+        Window root = X11None; // Could XQueryTree, but this is not important.
 #endif
 
         switch (anEvent.mMessage) {
           case eMouseOver:
           case eMouseOut:
             {
               XCrossingEvent& event = pluginEvent.xcrossing;
               event.type = anEvent.mMessage == eMouseOver ?
@@ -2612,17 +2612,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
               event.root = root;
               event.time = anEvent.mTime;
               event.x = pluginPoint.x;
               event.y = pluginPoint.y;
               event.x_root = rootPoint.x;
               event.y_root = rootPoint.y;
               event.state = XInputEventState(mouseEvent);
               // information lost
-              event.subwindow = None;
+              event.subwindow = X11None;
               event.mode = -1;
               event.detail = NotifyDetailNone;
               event.same_screen = True;
               event.focus = mContentFocused;
             }
             break;
           case eMouseMove:
             {
@@ -2631,17 +2631,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
               event.root = root;
               event.time = anEvent.mTime;
               event.x = pluginPoint.x;
               event.y = pluginPoint.y;
               event.x_root = rootPoint.x;
               event.y_root = rootPoint.y;
               event.state = XInputEventState(mouseEvent);
               // information lost
-              event.subwindow = None;
+              event.subwindow = X11None;
               event.is_hint = NotifyNormal;
               event.same_screen = True;
             }
             break;
           case eMouseDown:
           case eMouseUp:
             {
               XButtonEvent& event = pluginEvent.xbutton;
@@ -2662,17 +2662,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
                 case WidgetMouseEvent::eRightButton:
                   event.button = 3;
                   break;
                 default: // WidgetMouseEvent::eLeftButton;
                   event.button = 1;
                   break;
                 }
               // information lost:
-              event.subwindow = None;
+              event.subwindow = X11None;
               event.same_screen = True;
             }
             break;
           default:
             break;
           }
       }
       break;
@@ -2706,17 +2706,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
               break;
             default:
               break;
             }
 #endif
 
           // Information that could be obtained from pluginEvent but we may not
           // want to promise to provide:
-          event.subwindow = None;
+          event.subwindow = X11None;
           event.x = 0;
           event.y = 0;
           event.x_root = -1;
           event.y_root = -1;
           event.same_screen = False;
         }
       else
         {
@@ -2748,17 +2748,17 @@ nsEventStatus nsPluginInstanceOwner::Pro
   if (!pluginEvent.type) {
     return rv;
   }
 
   // Fill in (useless) generic event information.
   XAnyEvent& event = pluginEvent.xany;
   event.display = widget ?
     static_cast<Display*>(widget->GetNativeData(NS_NATIVE_DISPLAY)) : nullptr;
-  event.window = None; // not a real window
+  event.window = X11None; // not a real window
   // information lost:
   event.serial = 0;
   event.send_event = False;
 
   int16_t response = kNPEventNotHandled;
   mInstance->HandleEvent(&pluginEvent, &response, NS_PLUGIN_CALL_SAFE_TO_REENTER_GECKO);
   if (response == kNPEventHandled)
     rv = nsEventStatus_eConsumeNoDefault;

--- a/dom/plugins/base/nsPluginNativeWindowGtk.cpp
+++ b/dom/plugins/base/nsPluginNativeWindowGtk.cpp
@@ -212,17 +212,17 @@ nsresult nsPluginNativeWindowGtk::Create
     return NS_ERROR_FAILURE;
 
   mWsInfo.display = GDK_WINDOW_XDISPLAY(gdkWindow);
 #if (MOZ_WIDGET_GTK == 2)
   mWsInfo.colormap = GDK_COLORMAP_XCOLORMAP(gdk_drawable_get_colormap(gdkWindow));
   GdkVisual* gdkVisual = gdk_drawable_get_visual(gdkWindow);
   mWsInfo.depth = gdkVisual->depth;
 #else
-  mWsInfo.colormap = None;
+  mWsInfo.colormap = X11None;
   GdkVisual* gdkVisual = gdk_window_get_visual(gdkWindow);
   mWsInfo.depth = gdk_visual_get_depth(gdkVisual);
 #endif
   mWsInfo.visual = GDK_VISUAL_XVISUAL(gdkVisual);
     
   return NS_OK;
 }
 

--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -1277,17 +1277,17 @@ PluginInstanceChild::AnswerNPP_SetWindow
                 // workaround https://bugzilla.gnome.org/show_bug.cgi?id=607061
                 // See wrap_gtk_plug_embedded in PluginModuleChild.cpp.
                 g_object_set_data(G_OBJECT(socket_window),
                                   "moz-existed-before-set-window",
                                   GUINT_TO_POINTER(1));
             }
         }
 
-        if (aWindow.visualID != None
+        if (aWindow.visualID != X11None
             && gtk_check_version(2, 12, 10) != nullptr) { // older
             // Workaround for a bug in Gtk+ (prior to 2.12.10) where deleting
             // a foreign GdkColormap will also free the XColormap.
             // http://git.gnome.org/browse/gtk+/log/gdk/x11/gdkcolor-x11.c?id=GTK_2_12_10
             GdkVisual *gdkvisual = gdkx_visual_get(aWindow.visualID);
             GdkColormap *gdkcolor =
                 gdk_x11_colormap_foreign_new(gdkvisual, aWindow.colormap);
 

--- a/dom/plugins/test/testplugin/nptest_gtk2.cpp
+++ b/dom/plugins/test/testplugin/nptest_gtk2.cpp
@@ -76,33 +76,33 @@ pluginInstanceInit(InstanceData* instanc
 #ifdef MOZ_X11
   instanceData->platformData = static_cast<PlatformData*>
     (NPN_MemAlloc(sizeof(PlatformData)));
   if (!instanceData->platformData)
     return NPERR_OUT_OF_MEMORY_ERROR;
 
   instanceData->platformData->display = nullptr;
   instanceData->platformData->visual = nullptr;
-  instanceData->platformData->colormap = None;  
+  instanceData->platformData->colormap = X11None;
   instanceData->platformData->plug = nullptr;
 
   return NPERR_NO_ERROR;
 #else
   // we only support X11 here, since thats what the plugin system uses
   return NPERR_INCOMPATIBLE_VERSION_ERROR;
 #endif
 }
 
 void
 pluginInstanceShutdown(InstanceData* instanceData)
 {
   if (instanceData->hasWidget) {
     Window window = reinterpret_cast<XID>(instanceData->window.window);
 
-    if (window != None) {
+    if (window != X11None) {
       // This window XID should still be valid.
       // See bug 429604 and bug 454756.
       XWindowAttributes attributes;
       if (!XGetWindowAttributes(instanceData->platformData->display, window,
                                 &attributes))
         g_error("XGetWindowAttributes failed at plugin instance shutdown");
     }
   }

--- a/gfx/2d/BorrowedContext.h
+++ b/gfx/2d/BorrowedContext.h
@@ -6,16 +6,17 @@
 #ifndef _MOZILLA_GFX_BORROWED_CONTEXT_H
 #define _MOZILLA_GFX_BORROWED_CONTEXT_H
 
 #include "2D.h"
 
 #ifdef MOZ_X11
 #include <X11/extensions/Xrender.h>
 #include <X11/Xlib.h>
+#include "X11UndefineNone.h"
 #endif
 
 struct _cairo;
 typedef struct _cairo cairo_t;
 
 namespace mozilla {
 
 namespace gfx {
@@ -82,26 +83,26 @@ private:
  * to see if it succeeded. The DrawTarget should not be used while
  * the drawable is borrowed. */
 class BorrowedXlibDrawable
 {
 public:
   BorrowedXlibDrawable()
     : mDT(nullptr),
       mDisplay(nullptr),
-      mDrawable(None),
+      mDrawable(X11None),
       mScreen(nullptr),
       mVisual(nullptr),
       mXRenderFormat(nullptr)
   {}
 
   explicit BorrowedXlibDrawable(DrawTarget *aDT)
     : mDT(nullptr),
       mDisplay(nullptr),
-      mDrawable(None),
+      mDrawable(X11None),
       mScreen(nullptr),
       mVisual(nullptr),
       mXRenderFormat(nullptr)
   {
     Init(aDT);
   }
 
   // We can optionally Init after construction in

--- a/gfx/2d/DrawTargetCairo.cpp
+++ b/gfx/2d/DrawTargetCairo.cpp
@@ -2109,17 +2109,17 @@ DrawTargetCairo::Draw3DTransformedSurfac
   XRenderSetPictureTransform(display, srcPict, (XTransform*)&xform);
 
   Picture dstPict = XRenderCreatePicture(display,
                                          cairo_xlib_surface_get_drawable(xformSurf),
                                          cairo_xlib_surface_get_xrender_format(xformSurf),
                                          0, nullptr);
 
   XRenderComposite(display, PictOpSrc,
-                   srcPict, None, dstPict,
+                   srcPict, X11None, dstPict,
                    0, 0, 0, 0, 0, 0,
                    xformBounds.width, xformBounds.height);
 
   XRenderFreePicture(display, srcPict);
   XRenderFreePicture(display, dstPict);
 
   cairo_device_release(device);
   cairo_surface_mark_dirty(xformSurf);
@@ -2259,17 +2259,17 @@ BorrowedCairoContext::ReturnCairoContext
 
 #ifdef MOZ_X11
 bool
 BorrowedXlibDrawable::Init(DrawTarget* aDT)
 {
   MOZ_ASSERT(aDT, "Caller should check for nullptr");
   MOZ_ASSERT(!mDT, "Can't initialize twice!");
   mDT = aDT;
-  mDrawable = None;
+  mDrawable = X11None;
 
 #ifdef CAIRO_HAS_XLIB_SURFACE
   if (aDT->GetBackendType() != BackendType::CAIRO ||
       aDT->IsDualDrawTarget() ||
       aDT->IsTiledDrawTarget()) {
     return false;
   }
 
@@ -2302,15 +2302,15 @@ BorrowedXlibDrawable::Init(DrawTarget* a
 
 void
 BorrowedXlibDrawable::Finish()
 {
   DrawTargetCairo* cairoDT = static_cast<DrawTargetCairo*>(mDT);
   cairo_surface_t* surf = cairo_get_group_target(cairoDT->mContext);
   cairo_surface_mark_dirty(surf);
   if (mDrawable) {
-    mDrawable = None;
+    mDrawable = X11None;
   }
 }
 #endif
 
 } // namespace gfx
 } // namespace mozilla

--- a/gfx/gl/GLContextProviderGLX.cpp
+++ b/gfx/gl/GLContextProviderGLX.cpp
@@ -6,16 +6,17 @@
 #ifdef MOZ_WIDGET_GTK
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
 #define GET_NATIVE_WINDOW(aWidget) GDK_WINDOW_XID((GdkWindow*) aWidget->GetNativeData(NS_NATIVE_WINDOW))
 #endif
 
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
+#include "X11UndefineNone.h"
 
 #include "mozilla/MathAlgorithms.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/widget/CompositorWidget.h"
 
 #include "prenv.h"
 #include "GLContextProvider.h"
 #include "GLLibraryLoader.h"
@@ -302,36 +303,36 @@ GLXLibrary::SupportsVideoSync()
 
     return mHasVideoSync;
 }
 
 GLXPixmap
 GLXLibrary::CreatePixmap(gfxASurface* aSurface)
 {
     if (!SupportsTextureFromPixmap(aSurface)) {
-        return None;
+        return X11None;
     }
 
     gfxXlibSurface* xs = static_cast<gfxXlibSurface*>(aSurface);
     const XRenderPictFormat* format = xs->XRenderFormat();
     if (!format || format->type != PictTypeDirect) {
-        return None;
+        return X11None;
     }
     const XRenderDirectFormat& direct = format->direct;
     int alphaSize = FloorLog2(direct.alphaMask + 1);
     NS_ASSERTION((1 << alphaSize) - 1 == direct.alphaMask,
                  "Unexpected render format with non-adjacent alpha bits");
 
     int attribs[] = { LOCAL_GLX_DOUBLEBUFFER, False,
                       LOCAL_GLX_DRAWABLE_TYPE, LOCAL_GLX_PIXMAP_BIT,
                       LOCAL_GLX_ALPHA_SIZE, alphaSize,
                       (alphaSize ? LOCAL_GLX_BIND_TO_TEXTURE_RGBA_EXT
                        : LOCAL_GLX_BIND_TO_TEXTURE_RGB_EXT), True,
                       LOCAL_GLX_RENDER_TYPE, LOCAL_GLX_RGBA_BIT,
-                      None };
+                      X11None };
 
     int numConfigs = 0;
     Display* display = xs->XDisplay();
     int xscreen = DefaultScreen(display);
 
     ScopedXFree<GLXFBConfig> cfgs(xChooseFBConfig(display,
                                                   xscreen,
                                                   attribs,
@@ -345,17 +346,17 @@ GLXLibrary::CreatePixmap(gfxASurface* aS
         static_cast<unsigned long>(direct.greenMask) << direct.green;
     unsigned long blueMask =
         static_cast<unsigned long>(direct.blueMask) << direct.blue;
     // This is true if the Pixmap has bits for alpha or unused bits.
     bool haveNonColorBits =
         ~(redMask | greenMask | blueMask) != -1UL << format->depth;
 
     for (int i = 0; i < numConfigs; i++) {
-        int id = None;
+        int id = X11None;
         sGLXLibrary.xGetFBConfigAttrib(display, cfgs[i], LOCAL_GLX_VISUAL_ID, &id);
         Visual* visual;
         int depth;
         FindVisualAndDepth(display, id, &visual, &depth);
         if (!visual ||
             visual->c_class != TrueColor ||
             visual->red_mask != redMask ||
             visual->green_mask != greenMask ||
@@ -418,24 +419,24 @@ GLXLibrary::CreatePixmap(gfxASurface* aS
         matchIndex = i;
         break;
     }
     if (matchIndex == -1) {
         // GLX can't handle A8 surfaces, so this is not really unexpected. The
         // caller should deal with this situation.
         NS_WARN_IF_FALSE(format->depth == 8,
                          "[GLX] Couldn't find a FBConfig matching Pixmap format");
-        return None;
+        return X11None;
     }
 
     int pixmapAttribs[] = { LOCAL_GLX_TEXTURE_TARGET_EXT, LOCAL_GLX_TEXTURE_2D_EXT,
                             LOCAL_GLX_TEXTURE_FORMAT_EXT,
                             (alphaSize ? LOCAL_GLX_TEXTURE_FORMAT_RGBA_EXT
                              : LOCAL_GLX_TEXTURE_FORMAT_RGB_EXT),
-                            None};
+                            X11None};
 
     GLXPixmap glxpixmap = xCreatePixmap(display,
                                         cfgs[matchIndex],
                                         xs->XDrawable(),
                                         pixmapAttribs);
 
     return glxpixmap;
 }
@@ -894,17 +895,17 @@ GLContextGLX::~GLContextGLX()
     if (!mOwnsContext) {
         return;
     }
 
     // see bug 659842 comment 76
 #ifdef DEBUG
     bool success =
 #endif
-    mGLX->xMakeCurrent(mDisplay, None, nullptr);
+    mGLX->xMakeCurrent(mDisplay, X11None, nullptr);
     MOZ_ASSERT(success,
                "glXMakeCurrent failed to release GL context before we call "
                "glXDestroyContext!");
 
     mGLX->xDestroyContext(mDisplay, mContext);
 
     if (mDeleteDrawable) {
         mGLX->xDestroyPixmap(mDisplay, mDrawable);
@@ -1231,17 +1232,17 @@ GLContextGLX::FindFBConfigForWindow(Disp
         return false;
     }
     const VisualID windowVisualID = XVisualIDFromVisual(windowAttrs.visual);
 #ifdef DEBUG
     printf("[GLX] window %lx has VisualID 0x%lx\n", window, windowVisualID);
 #endif
 
     for (int i = 0; i < numConfigs; i++) {
-        int visid = None;
+        int visid = X11None;
         sGLXLibrary.xGetFBConfigAttrib(display, cfgs[i], LOCAL_GLX_VISUAL_ID, &visid);
         if (!visid) {
             continue;
         }
         if (sGLXLibrary.IsATI()) {
             int depth;
             Visual* visual;
             FindVisualAndDepth(display, visid, &visual, &depth);

--- a/gfx/layers/ipc/ShadowLayerUtilsX11.cpp
+++ b/gfx/layers/ipc/ShadowLayerUtilsX11.cpp
@@ -6,16 +6,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "ShadowLayerUtilsX11.h"
 #include <X11/X.h>                      // for Drawable, XID
 #include <X11/Xlib.h>                   // for Display, Visual, etc
 #include <X11/extensions/Xrender.h>     // for XRenderPictFormat, etc
 #include <X11/extensions/render.h>      // for PictFormat
 #include "cairo-xlib.h"
+#include "X11UndefineNone.h"
 #include <stdint.h>                     // for uint32_t
 #include "GLDefs.h"                     // for GLenum
 #include "gfxPlatform.h"                // for gfxPlatform
 #include "gfxXlibSurface.h"             // for gfxXlibSurface
 #include "gfx2DGlue.h"                  // for Moz2D transistion helpers
 #include "mozilla/X11Util.h"            // for DefaultXDisplay, FinishX, etc
 #include "mozilla/gfx/Point.h"          // for IntSize
 #include "mozilla/layers/CompositableForwarder.h"
@@ -60,17 +61,17 @@ GetXRenderPictFormatFromId(Display* aDis
   tmplate.id = aFormatId;
   return XRenderFindFormat(aDisplay, PictFormatID, &tmplate, 0);
 }
 
 SurfaceDescriptorX11::SurfaceDescriptorX11(gfxXlibSurface* aSurf,
                                            bool aForwardGLX)
   : mId(aSurf->XDrawable())
   , mSize(aSurf->GetSize())
-  , mGLXPixmap(None)
+  , mGLXPixmap(X11None)
 {
   const XRenderPictFormat *pictFormat = aSurf->XRenderFormat();
   if (pictFormat) {
     mFormat = pictFormat->id;
   } else {
     mFormat = cairo_xlib_surface_get_visual(aSurf->CairoSurface())->visualid;
   }
 
@@ -81,17 +82,17 @@ SurfaceDescriptorX11::SurfaceDescriptorX
 #endif
 }
 
 SurfaceDescriptorX11::SurfaceDescriptorX11(Drawable aDrawable, XID aFormatID,
                                            const gfx::IntSize& aSize)
   : mId(aDrawable)
   , mFormat(aFormatID)
   , mSize(aSize)
-  , mGLXPixmap(None)
+  , mGLXPixmap(X11None)
 { }
 
 already_AddRefed<gfxXlibSurface>
 SurfaceDescriptorX11::OpenForeign() const
 {
   Display* display = DefaultXDisplay();
   Screen* screen = DefaultScreenOfDisplay(display);
 

new file mode 100644
--- /dev/null
+++ b/gfx/src/X11UndefineNone.h
@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_GFX_X11UNDEFINENONE_H_
+#define MOZILLA_GFX_X11UNDEFINENONE_H_
+
+// The header <X11/X.h> defines "None" as a macro that expands to "0L".
+// This is terrible because many enumerations have an enumerator named "None".
+// To work around this, we undefine the macro "None", and define a replacement
+// macro named "X11None".
+// Include this header after including X11 headers, where necessary.
+#ifdef None
+#  undef None
+#  define X11None 0L
+// <X11/X.h> also defines "RevertToNone" as a macro that expands to "(int)None".
+// Since we are undefining "None", that stops working. To keep it working,
+// we undefine "RevertToNone" and redefine it in terms of "X11None".
+#  ifdef RevertToNone
+#    undef RevertToNone
+#    define RevertToNone (int)X11None
+#  endif
+#endif
+
+#endif /* MOZILLA_GFX_X11UNDEFINENONE_H_ */

--- a/gfx/src/X11Util.cpp
+++ b/gfx/src/X11Util.cpp
@@ -24,17 +24,17 @@ FindVisualAndDepth(Display* aDisplay, Vi
             if (visual->visualid == aVisualID) {
                 *aVisual = visual;
                 *aDepth = d_info->depth;
                 return;
             }
         }
     }
 
-    NS_ASSERTION(aVisualID == None, "VisualID not on Screen.");
+    NS_ASSERTION(aVisualID == X11None, "VisualID not on Screen.");
     *aVisual = nullptr;
     *aDepth = 0;
     return;
 }
 
 void
 FinishX(Display* aDisplay)
 {

--- a/gfx/src/X11Util.h
+++ b/gfx/src/X11Util.h
@@ -8,16 +8,17 @@
 #ifndef mozilla_X11Util_h
 #define mozilla_X11Util_h
 
 // Utilities common to all X clients, regardless of UI toolkit.
 
 #if defined(MOZ_WIDGET_GTK)
 #  include <gdk/gdk.h>
 #  include <gdk/gdkx.h>
+#  include "X11UndefineNone.h"
 #else
 #  error Unknown toolkit
 #endif
 
 #include <string.h>                     // for memset
 #include "mozilla/Scoped.h"             // for SCOPED_TEMPLATE
 
 namespace mozilla {

--- a/gfx/src/moz.build
+++ b/gfx/src/moz.build
@@ -34,16 +34,17 @@ EXPORTS += [
     'nsRegion.h',
     'nsRegionFwd.h',
     'nsRenderingContext.h',
     'nsSize.h',
     'nsThemeConstants.h',
     'nsTransform2D.h',
     'PingPongRegion.h',
     'RegionBuilder.h',
+    'X11UndefineNone.h'
 ]
 
 EXPORTS.mozilla += [
     'AppUnits.h',
     'ArrayView.h',
 ]
 
 EXPORTS.mozilla.gfx += [

--- a/gfx/thebes/gfxXlibSurface.cpp
+++ b/gfx/thebes/gfxXlibSurface.cpp
@@ -20,59 +20,59 @@
 #include "mozilla/CheckedInt.h"
 
 using namespace mozilla;
 using namespace mozilla::gfx;
 
 gfxXlibSurface::gfxXlibSurface(Display *dpy, Drawable drawable, Visual *visual)
     : mPixmapTaken(false), mDisplay(dpy), mDrawable(drawable)
 #if defined(GL_PROVIDER_GLX)
-    , mGLXPixmap(None)
+    , mGLXPixmap(X11None)
 #endif
 {
     const gfx::IntSize size = DoSizeQuery();
     cairo_surface_t *surf = cairo_xlib_surface_create(dpy, drawable, visual, size.width, size.height);
     Init(surf);
 }
 
 gfxXlibSurface::gfxXlibSurface(Display *dpy, Drawable drawable, Visual *visual, const gfx::IntSize& size)
     : mPixmapTaken(false), mDisplay(dpy), mDrawable(drawable)
 #if defined(GL_PROVIDER_GLX)
-    , mGLXPixmap(None)
+    , mGLXPixmap(X11None)
 #endif
 {
     NS_ASSERTION(Factory::CheckSurfaceSize(size, XLIB_IMAGE_SIDE_SIZE_LIMIT),
                  "Bad size");
 
     cairo_surface_t *surf = cairo_xlib_surface_create(dpy, drawable, visual, size.width, size.height);
     Init(surf);
 }
 
 gfxXlibSurface::gfxXlibSurface(Screen *screen, Drawable drawable, XRenderPictFormat *format,
                                const gfx::IntSize& size)
     : mPixmapTaken(false), mDisplay(DisplayOfScreen(screen)),
       mDrawable(drawable)
 #if defined(GL_PROVIDER_GLX)
-      , mGLXPixmap(None)
+      , mGLXPixmap(X11None)
 #endif
 {
     NS_ASSERTION(Factory::CheckSurfaceSize(size, XLIB_IMAGE_SIDE_SIZE_LIMIT),
                  "Bad Size");
 
     cairo_surface_t *surf =
         cairo_xlib_surface_create_with_xrender_format(mDisplay, drawable,
                                                       screen, format,
                                                       size.width, size.height);
     Init(surf);
 }
 
 gfxXlibSurface::gfxXlibSurface(cairo_surface_t *csurf)
     : mPixmapTaken(false)
 #if defined(GL_PROVIDER_GLX)
-      , mGLXPixmap(None)
+      , mGLXPixmap(X11None)
 #endif
 {
     NS_PRECONDITION(cairo_surface_status(csurf) == 0,
                     "Not expecting an error surface");
 
     mDrawable = cairo_xlib_surface_get_drawable(csurf);
     mDisplay = cairo_xlib_surface_get_display(csurf);
 
@@ -92,19 +92,19 @@ gfxXlibSurface::~gfxXlibSurface()
     }
 }
 
 static Drawable
 CreatePixmap(Screen *screen, const gfx::IntSize& size, unsigned int depth,
              Drawable relatedDrawable)
 {
     if (!Factory::CheckSurfaceSize(size, XLIB_IMAGE_SIDE_SIZE_LIMIT))
-        return None;
+        return X11None;
 
-    if (relatedDrawable == None) {
+    if (relatedDrawable == X11None) {
         relatedDrawable = RootWindowOfScreen(screen);
     }
     Display *dpy = DisplayOfScreen(screen);
     // X gives us a fatal error if we try to create a pixmap of width
     // or height 0
     return XCreatePixmap(dpy, relatedDrawable,
                          std::max(1, size.width), std::max(1, size.height),
                          depth);
@@ -269,17 +269,17 @@ gfxXlibSurface::CreateSimilarSurface(gfx
 }
 
 void
 gfxXlibSurface::Finish()
 {
 #if defined(GL_PROVIDER_GLX)
     if (mPixmapTaken && mGLXPixmap) {
         gl::sGLXLibrary.DestroyPixmap(mDisplay, mGLXPixmap);
-        mGLXPixmap = None;
+        mGLXPixmap = X11None;
     }
 #endif
     gfxASurface::Finish();
 }
 
 const gfx::IntSize
 gfxXlibSurface::GetSize() const
 {

--- a/gfx/thebes/gfxXlibSurface.h
+++ b/gfx/thebes/gfxXlibSurface.h
@@ -5,16 +5,17 @@
 
 #ifndef GFX_XLIBSURFACE_H
 #define GFX_XLIBSURFACE_H
 
 #include "gfxASurface.h"
 
 #include <X11/extensions/Xrender.h>
 #include <X11/Xlib.h>
+#include "X11UndefineNone.h"
 
 #if defined(GL_PROVIDER_GLX)
 #include "GLXLibrary.h"
 #endif
 
 #include "nsSize.h"
 
 // Although the dimension parameters in the xCreatePixmapReq wire protocol are
@@ -41,23 +42,23 @@ public:
     explicit gfxXlibSurface(cairo_surface_t *csurf);
 
     // create a new Pixmap and wrapper surface.
     // |relatedDrawable| provides a hint to the server for determining whether
     // the pixmap should be in video or system memory.  It must be on
     // |screen| (if specified).
     static already_AddRefed<gfxXlibSurface>
     Create(Screen *screen, Visual *visual, const mozilla::gfx::IntSize& size,
-           Drawable relatedDrawable = None);
+           Drawable relatedDrawable = X11None);
     static cairo_surface_t *
     CreateCairoSurface(Screen *screen, Visual *visual, const mozilla::gfx::IntSize& size,
-                       Drawable relatedDrawable = None);
+                       Drawable relatedDrawable = X11None);
     static already_AddRefed<gfxXlibSurface>
     Create(Screen* screen, XRenderPictFormat *format, const mozilla::gfx::IntSize& size,
-           Drawable relatedDrawable = None);
+           Drawable relatedDrawable = X11None);
 
     virtual ~gfxXlibSurface();
 
     virtual already_AddRefed<gfxASurface>
     CreateSimilarSurface(gfxContentType aType,
                          const mozilla::gfx::IntSize& aSize) override;
     virtual void Finish() override;
 

--- a/widget/gtk/nsClipboard.cpp
+++ b/widget/gtk/nsClipboard.cpp
@@ -1025,17 +1025,17 @@ wait_for_text(GtkClipboard *clipboard)
     return static_cast<gchar*>(context->Wait());
 }
 
 static GdkFilterReturn
 selection_request_filter(GdkXEvent *gdk_xevent, GdkEvent *event, gpointer data)
 {
     XEvent *xevent = static_cast<XEvent*>(gdk_xevent);
     if (xevent->xany.type == SelectionRequest) {
-        if (xevent->xselectionrequest.requestor == None)
+        if (xevent->xselectionrequest.requestor == X11None)
             return GDK_FILTER_REMOVE;
 
         GdkDisplay *display = gdk_x11_lookup_xdisplay(
                 xevent->xselectionrequest.display);
         if (!display)
             return GDK_FILTER_REMOVE;
 
         GdkWindow *window = gdk_x11_window_foreign_new_for_display(display,

--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -447,17 +447,17 @@ nsWindow::nsWindow()
     mSizeState           = nsSizeMode_Normal;
     mLastSizeMode        = nsSizeMode_Normal;
     mSizeConstraints.mMaxSize = GetSafeWindowSize(mSizeConstraints.mMaxSize);
 
 #ifdef MOZ_X11
     mOldFocusWindow      = 0;
 
     mXDisplay = nullptr;
-    mXWindow  = None;
+    mXWindow  = X11None;
     mXVisual  = nullptr;
     mXDepth   = 0;
 #endif /* MOZ_X11 */
     mPluginType          = PluginType_NONE;
 
     if (!gGlobalsInitialized) {
         gGlobalsInitialized = true;
 
@@ -4609,17 +4609,17 @@ nsWindow::ClearTransparencyBitmap()
 
 #ifdef MOZ_X11
     if (!mGdkWindow)
         return;
 
     Display* xDisplay = GDK_WINDOW_XDISPLAY(mGdkWindow);
     Window xWindow = gdk_x11_window_get_xid(mGdkWindow);
 
-    XShapeCombineMask(xDisplay, xWindow, ShapeBounding, 0, 0, None, ShapeSet);
+    XShapeCombineMask(xDisplay, xWindow, ShapeBounding, 0, 0, X11None, ShapeSet);
 #endif
 }
 
 nsresult
 nsWindow::UpdateTranslucentWindowAlphaInternal(const nsIntRect& aRect,
                                                uint8_t* aAlphas, int32_t aStride)
 {
     if (!mShell) {