[gnome-shell] ShellWindowTracker: complete WM_CLASS fix

[Giovanni Campagna <gcampagna src gnome org>]

commit 2a95273b7920939760dedadccbb7e1ce88d5f394
Author: Giovanni Campagna <gcampagn redhat com>
Date:   Thu Aug 8 10:40:01 2013 +0200

    ShellWindowTracker: complete WM_CLASS fix
    
    Chromium (but not google-chrome) has a StartupWMClass in the desktop
    file, so we must match the instance part first to have chrome
    web apps working.
    Also, we must take care of apps without a wm_class or instance at
    all.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=673657

 src/shell-app-system.c     |    7 +++++--
 src/shell-window-tracker.c |   27 ++++++++++++++++-----------
 2 files changed, 21 insertions(+), 13 deletions(-)
---
diff --git a/src/shell-app-system.c b/src/shell-app-system.c
index a6587be..7f43bd4 100644
--- a/src/shell-app-system.c
+++ b/src/shell-app-system.c
@@ -541,7 +541,7 @@ shell_app_system_lookup_heuristic_basename (ShellAppSystem *system,
 /**
  * shell_app_system_lookup_desktop_wmclass:
  * @system: a #ShellAppSystem
- * @wmclass: A WM_CLASS value
+ * @wmclass: (allow-none): A WM_CLASS value
  *
  * Find a valid application whose .desktop file, without the extension
  * and properly canonicalized, matches @wmclass.
@@ -578,7 +578,7 @@ shell_app_system_lookup_desktop_wmclass (ShellAppSystem *system,
 /**
  * shell_app_system_lookup_startup_wmclass:
  * @system: a #ShellAppSystem
- * @wmclass: A WM_CLASS value
+ * @wmclass: (allow-none): A WM_CLASS value
  *
  * Find a valid application whose .desktop file contains a
  * StartupWMClass entry matching @wmclass.
@@ -589,6 +589,9 @@ ShellApp *
 shell_app_system_lookup_startup_wmclass (ShellAppSystem *system,
                                          const char     *wmclass)
 {
+  if (wmclass == NULL)
+    return NULL;
+
   return g_hash_table_lookup (system->priv->startup_wm_class_to_app, wmclass);
 }
 
diff --git a/src/shell-window-tracker.c b/src/shell-window-tracker.c
index 09653e4..e922cdd 100644
--- a/src/shell-window-tracker.c
+++ b/src/shell-window-tracker.c
@@ -225,31 +225,36 @@ get_app_from_window_wmclass (MetaWindow  *window)
      with
 
      StartupWMClass=crx_blpcfgokakmgnkcojhhkbfbldkacnbeo
-  */
 
-  /* first try a match from WM_CLASS to StartupWMClass */
-  wm_class = meta_window_get_wm_class (window);
-  app = shell_app_system_lookup_startup_wmclass (appsys, wm_class);
-  if (app != NULL)
-    return g_object_ref (app);
+     Note that chromium (but not google-chrome!) includes a StartupWMClass=chromium
+     in their .desktop file, so we must match the instance first.
+
+     Also note that in the good case (regular gtk+ app without hacks), instance and
+     class are the same except for case and there is no StartupWMClass at all.
+  */
 
-  /* then try a match from WM_CLASS (instance part) to StartupWMClass */
+  /* first try a match from WM_CLASS (instance part) to StartupWMClass */
   wm_instance = meta_window_get_wm_class_instance (window);
   app = shell_app_system_lookup_startup_wmclass (appsys, wm_instance);
   if (app != NULL)
     return g_object_ref (app);
 
-  /* then try a match from WM_CLASS to .desktop */
-  app = shell_app_system_lookup_desktop_wmclass (appsys, wm_class);
+  /* then try a match from WM_CLASS to StartupWMClass */
+  wm_class = meta_window_get_wm_class (window);
+  app = shell_app_system_lookup_startup_wmclass (appsys, wm_class);
   if (app != NULL)
     return g_object_ref (app);
 
-  /* finally, try a match from WM_CLASS (instance part) to .desktop
-     (unlikely to find anything at this point, but still worth a try) */
+  /* then try a match from WM_CLASS (instance part) to .desktop */
   app = shell_app_system_lookup_desktop_wmclass (appsys, wm_instance);
   if (app != NULL)
     return g_object_ref (app);
 
+  /* finally, try a match from WM_CLASS to .desktop */
+  app = shell_app_system_lookup_desktop_wmclass (appsys, wm_class);
+  if (app != NULL)
+    return g_object_ref (app);
+
   return NULL;
 }