Merge lp:~teemperor/pantheon-greeter/fix-first-wallpaper-fails-to-show into lp:~elementary-pantheon/pantheon-greeter/trunk

[Raphael Isemann]

Correctly ignore Exceptions due to cancelled loading. This prevents multiple load-calls that close behind each other from aborting each other, thus causing the default wallpaper to load.

There is a race-condition in the loading-code. When the same background is loaded twice in a short period, the second loading-attempt cancels the first. This causes the the first-loading attempt to reach the catch-block and will start to load the backup-wallpaper. The attempt to load the backup-wallpaper will then cancel the second attempt and we only see the default-wallpaper.

The reason for the catch-block was that we use the fallback in case we can't load the actual wallpaper. However, cancelling a operation also causes a exception and the current code assumes that there was an actual error with the wallpaper, but instead he should just stop loading.

This patch will catch the CANCELLED-Errors and will not start to load the default-wallpaper in this case (which is the correct behaviour and prevents the race-condition).

[Raphael Isemann (teemperor)]

Important: The switchboard-plug-pantheon is a bit broken and is not informing accountsservices about your wallpaper. So you have to use the set-wallpaper-contract of files to set your background before testing this!.

[Gero.Bare (gero-bare)]

Yeah, that worked!.

To activate that service use dconf-editor
go to: org > gnome> settings-daemon > plugins> background
there check Active.

Worked in Freya.

I was trying to make a patch for switchboar-plug-pantheon-shell to solve that problem.

=== modified file 'src/Wallpaper.vala'
--- src/Wallpaper.vala	2014-03-13 17:16:53 +0000
+++ src/Wallpaper.vala	2014-10-21 20:31:40 +0000
@@ -25,11 +25,11 @@
  */
 public class Wallpaper : Clutter.Group {
     /**
-     * 
+     *
      */
     List<GtkClutter.Texture> wallpapers = new List<GtkClutter.Texture> ();
     List<Cancellable> loading_wallpapers = new List<Cancellable> ();
-    
+
     /**
      * Contains old Textures that were used for wallpapers. They are recycled
      * in the @make_texture method.
@@ -118,6 +118,9 @@
             }
             wallpapers.append (new_wallpaper);
 
+        } catch (IOError.CANCELLED e) {
+            message (@"Cancelled to load '$path'");
+            // do nothing, we cancelled on purpose
         } catch (Error e) {
             if (get_default() != path) {
                 set_wallpaper (get_default ());