# HG changeset patch
# Parent fd2da289a3c15b8c96c248df2710d879793f22c9
# User Wolfgang Rosenauer <wr@rosenauer.org>
Bug 526717 - remove non-working "Set as desktop background" from the UI for unsupported desktops

diff --git a/browser/base/content/nsContextMenu.js b/browser/base/content/nsContextMenu.js
--- a/browser/base/content/nsContextMenu.js
+++ b/browser/base/content/nsContextMenu.js
@@ -262,17 +262,17 @@ nsContextMenu.prototype = {
 
     // Set as Desktop background depends on whether an image was clicked on,
     // and only works if we have a shell service.
     var haveSetDesktopBackground = false;
 #ifdef HAVE_SHELL_SERVICE
     // Only enable Set as Desktop Background if we can get the shell service.
     var shell = getShellService();
     if (shell)
-      haveSetDesktopBackground = true;
+      haveSetDesktopBackground = shell.canSetDesktopBackground;
 #endif
     this.showItem("context-setDesktopBackground",
                   haveSetDesktopBackground && this.onLoadedImage);
 
     if (haveSetDesktopBackground && this.onLoadedImage) {
       document.getElementById("context-setDesktopBackground")
               .disabled = this.disableSetDesktopBackground();
     }
diff --git a/browser/components/shell/public/nsIShellService.idl b/browser/components/shell/public/nsIShellService.idl
--- a/browser/components/shell/public/nsIShellService.idl
+++ b/browser/components/shell/public/nsIShellService.idl
@@ -69,16 +69,25 @@ interface nsIShellService : nsISupports
   /** 
    * Used to determine whether or not to show a "Set Default Browser"
    * query dialog. This attribute is true if the application is starting
    * up and "browser.shell.checkDefaultBrowser" is true, otherwise it
    * is false.
    */
   attribute boolean shouldCheckDefaultBrowser;
 
+  /**
+   * Used to determine whether or not to offer "Set as desktop background"
+   * context menu item. Even if shell service is available it is not
+   * guaranteed that it is able to set the background for every desktop
+   * which is especially true for Linux with its many different desktop
+   * environments.
+   */
+  readonly attribute boolean canSetDesktopBackground;
+
   /** 
    * Flags for positioning/sizing of the Desktop Background image.
    */
   const long BACKGROUND_TILE      = 1;
   const long BACKGROUND_STRETCH   = 2;
   const long BACKGROUND_CENTER    = 3;
   const long BACKGROUND_FILL      = 4;
   const long BACKGROUND_FIT       = 5;
diff --git a/browser/components/shell/src/nsGNOMEShellService.cpp b/browser/components/shell/src/nsGNOMEShellService.cpp
--- a/browser/components/shell/src/nsGNOMEShellService.cpp
+++ b/browser/components/shell/src/nsGNOMEShellService.cpp
@@ -377,16 +377,31 @@ nsGNOMEShellService::SetShouldCheckDefau
     pserve->GetBranch("", getter_AddRefs(prefs));
 
   if (prefs)
     prefs->SetBoolPref(PREF_CHECKDEFAULTBROWSER, aShouldCheck);
 
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsGNOMEShellService::GetCanSetDesktopBackground(bool* aResult)
+{
+  // setting desktop background is currently only supported
+  // for Gnome or desktops using the same GSettings and GConf keys
+  const char* gnomeSession = getenv("GNOME_DESKTOP_SESSION_ID");
+  if (gnomeSession) {
+    *aResult = true;
+  } else {
+    *aResult = false;
+  }
+
+  return NS_OK;
+}
+
 static nsresult
 WriteImage(const nsCString& aPath, imgIContainer* aImage)
 {
 #ifndef MOZ_WIDGET_GTK2
   return NS_ERROR_NOT_AVAILABLE;
 #else
   nsCOMPtr<nsIImageToPixbuf> imgToPixbuf =
     do_GetService("@mozilla.org/widget/image-to-gdk-pixbuf;1");