diff -r 000000000000 -r 6474c204b198 widget/gtk/nsIdleServiceGTK.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/widget/gtk/nsIdleServiceGTK.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim:expandtab:shiftwidth=4:tabstop=4:
+ */
+/* 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/. */
+
+#include <gtk/gtk.h>
+
+#include "nsIdleServiceGTK.h"
+#include "nsIServiceManager.h"
+#include "nsDebug.h"
+#include "prlink.h"
+#include "prlog.h"
+
+#ifdef PR_LOGGING
+static PRLogModuleInfo* sIdleLog = nullptr;
+#endif
+
+typedef bool (*_XScreenSaverQueryExtension_fn)(Display* dpy, int* event_base,
+                                                 int* error_base);
+
+typedef XScreenSaverInfo* (*_XScreenSaverAllocInfo_fn)(void);
+
+typedef void (*_XScreenSaverQueryInfo_fn)(Display* dpy, Drawable drw,
+                                          XScreenSaverInfo *info);
+
+static bool sInitialized = false;
+static _XScreenSaverQueryExtension_fn _XSSQueryExtension = nullptr;
+static _XScreenSaverAllocInfo_fn _XSSAllocInfo = nullptr;
+static _XScreenSaverQueryInfo_fn _XSSQueryInfo = nullptr;
+
+NS_IMPL_ISUPPORTS_INHERITED0(nsIdleServiceGTK, nsIdleService)
+
+static void Initialize()
+{
+    // This will leak - See comments in ~nsIdleServiceGTK().
+    PRLibrary* xsslib = PR_LoadLibrary("libXss.so.1");
+    if (!xsslib) // ouch.
+    {
+#ifdef PR_LOGGING
+        PR_LOG(sIdleLog, PR_LOG_WARNING, ("Failed to find libXss.so!\n"));
+#endif
+        return;
+    }
+
+    _XSSQueryExtension = (_XScreenSaverQueryExtension_fn)
+        PR_FindFunctionSymbol(xsslib, "XScreenSaverQueryExtension");
+    _XSSAllocInfo = (_XScreenSaverAllocInfo_fn)
+        PR_FindFunctionSymbol(xsslib, "XScreenSaverAllocInfo");
+    _XSSQueryInfo = (_XScreenSaverQueryInfo_fn)
+        PR_FindFunctionSymbol(xsslib, "XScreenSaverQueryInfo");
+#ifdef PR_LOGGING
+    if (!_XSSQueryExtension)
+        PR_LOG(sIdleLog, PR_LOG_WARNING, ("Failed to get XSSQueryExtension!\n"));
+    if (!_XSSAllocInfo)
+        PR_LOG(sIdleLog, PR_LOG_WARNING, ("Failed to get XSSAllocInfo!\n"));
+    if (!_XSSQueryInfo)
+        PR_LOG(sIdleLog, PR_LOG_WARNING, ("Failed to get XSSQueryInfo!\n"));
+#endif
+
+    sInitialized = true;
+}
+
+nsIdleServiceGTK::nsIdleServiceGTK()
+    : mXssInfo(nullptr)
+{
+#ifdef PR_LOGGING
+    if (!sIdleLog)
+        sIdleLog = PR_NewLogModule("nsIIdleService");
+#endif
+
+    Initialize();
+}
+
+nsIdleServiceGTK::~nsIdleServiceGTK()
+{
+    if (mXssInfo)
+        XFree(mXssInfo);
+
+// It is not safe to unload libXScrnSaver until each display is closed because
+// the library registers callbacks through XESetCloseDisplay (Bug 397607).
+// (Also the library and its functions are scoped for the file not the object.)
+#if 0
+    if (xsslib) {
+        PR_UnloadLibrary(xsslib);
+        xsslib = nullptr;
+    }
+#endif
+}
+
+bool
+nsIdleServiceGTK::PollIdleTime(uint32_t *aIdleTime)
+{
+    if (!sInitialized) {
+        // For some reason, we could not find xscreensaver.
+        return false;
+    }
+
+    // Ask xscreensaver about idle time:
+    *aIdleTime = 0;
+
+    // We might not have a display (cf. in xpcshell)
+    Display *dplay = GDK_DISPLAY_XDISPLAY(gdk_display_get_default());
+    if (!dplay) {
+#ifdef PR_LOGGING
+        PR_LOG(sIdleLog, PR_LOG_WARNING, ("No display found!\n"));
+#endif
+        return false;
+    }
+
+    if (!_XSSQueryExtension || !_XSSAllocInfo || !_XSSQueryInfo) {
+        return false;
+    }
+
+    int event_base, error_base;
+    if (_XSSQueryExtension(dplay, &event_base, &error_base))
+    {
+        if (!mXssInfo)
+            mXssInfo = _XSSAllocInfo();
+        if (!mXssInfo)
+            return false;
+        _XSSQueryInfo(dplay, GDK_ROOT_WINDOW(), mXssInfo);
+        *aIdleTime = mXssInfo->idle;
+        return true;
+    }
+    // If we get here, we couldn't get to XScreenSaver:
+#ifdef PR_LOGGING
+    PR_LOG(sIdleLog, PR_LOG_WARNING, ("XSSQueryExtension returned false!\n"));
+#endif
+    return false;
+}
+
+bool
+nsIdleServiceGTK::UsePollMode()
+{
+    return sInitialized;
+}
+