GTK: Set WMCLASS in a way docks notice while still solving display issues on XFCE.

chrome/browser/ui/gtk/browser_window_gtk.cc

Index: chrome/browser/ui/gtk/browser_window_gtk.cc
diff --git a/chrome/browser/ui/gtk/browser_window_gtk.cc b/chrome/browser/ui/gtk/browser_window_gtk.cc
index ac24d2c07b125a66db2e854086743b46a78b0a32..afa5015eaa1a4afae14962138de0e3012a10bfdf 100644
--- a/chrome/browser/ui/gtk/browser_window_gtk.cc
+++ b/chrome/browser/ui/gtk/browser_window_gtk.cc
@@ -11,11 +11,13 @@
 
 #include "base/base_paths.h"
 #include "base/command_line.h"
+#include "base/environment.h"
 #include "base/i18n/file_util_icu.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
+#include "base/nix/xdg_util.h"
 #include "base/path_service.h"
 #include "base/string_util.h"
 #include "base/time.h"
@@ -325,9 +327,26 @@ void BrowserWindowGtk::Init() {
     std::string app_name = browser_->app_name();
     if (app_name != DevToolsWindow::kDevToolsApp) {
       std::string wmclassname = web_app::GetWMClassFromAppName(app_name);
-      gtk_window_set_wmclass(window_,
-                             wmclassname.c_str(),
-                             gdk_get_program_class());
+
+      scoped_ptr<base::Environment> env(base::Environment::Create());
+      if (base::nix::GetDesktopEnvironment(env.get()) ==
+          base::nix::DESKTOP_ENVIRONMENT_XFCE) {

[Marco Trevisan (Treviño), 2011/04/21 21:02:29]

If you prefer you can also mix these two cases into the single (as it was at the
beginninng):

gtk_window_set_wmclass(window_, wmclassname.c_str(), wmclassname.c_str());

[Elliot Glaysher, 2011/04/21 21:25:17]

I don't think that helps. The whole point is that wmclassname should never be
presented to the user. XFCE takes wmclass_class and displays it to the user so I
don't want to change the program name there.

+        // Workaround for XFCE. XFCE seems to treat the class as a user
+        // displayed title, which our app name certainly isn't. They don't have
+        // a dock or application based behaviour so do what looks good.

[Evan Martin, 2011/04/21 20:54:34]

Relevant docs:
http://developer.gimp.org/api/2.0/gtk/GtkWindow.html#gtk-window-set-wmclass says
"class" and "name" hints.

In the GTK source, these make their way into:

  GdkWindowAttr attributes;
  ...
  attributes.wmclass_name = window->wmclass_name;
  attributes.wmclass_class = window->wmclass_class;

Plumbs through to X,
          class_hint = XAllocClassHint ();
          class_hint->res_name = attributes->wmclass_name;
          class_hint->res_class = attributes->wmclass_class;
          XSetClassHint (xdisplay, xid, class_hint);

Which uses this structure
http://tronche.com/gui/x/xlib/ICC/client-to-window-manager/wm-class.html#XCla...

Which says that it's setting WM_CLASS, not WM_NAME.  Perhaps we need to set
WM_NAME explicitly so XFCE doesn't get confused?

[Daniel Erat, 2011/04/21 21:10:28]

(Sorry if I'm stating stuff that you guys already know.)

WM_NAME is the original ICCCM property containing the title that the window
manager should display for a window: http://tronche.com/gui/x/icccm/sec-4.html. 
It is stupid (doesn't specify encoding).

_NET_WM_NAME is the UTF-8 replacement from EWMH:
http://standards.freedesktop.org/wm-spec/wm-spec-latest.html#id2551374

We should (and do, as far as I can see) set both properties.  The "name" hint
referred to in the GTK docs is one half of the WM_CLASS property, not WM_NAME --
see XSetClassHint(3).

I have no idea why a WM would display WM_CLASS as a window's title if
_NET_WM_NAME or WM_NAME is supplied, though.  That sounds wrong.

[Elliot Glaysher, 2011/04/21 21:23:31]

It's not setting the window title; xfce's alt-tab switcher displays wm_class /
icon / wm_name as you alt-tab through them. WM_NAME is being set correctly and
is being displayed.

+        gtk_window_set_wmclass(window_,
+                               wmclassname.c_str(),
+                               gdk_get_program_class());
+      } else {
+        // Most everything else uses the wmclass_class to group windows
+        // together (docks, per application stuff, etc). Hopefully they won't
+        // display wmclassname to the user.
+        gtk_window_set_wmclass(window_,
+                               window_->wmclass_name,
+                               wmclassname.c_str());
+      }
+
+      gtk_window_set_role(window_, wmclassname.c_str());
     }
   }