Improve desktop environment detection

Add code that works for Wayland, and any DE

interface/wx/apptrait.h

@@ -79,11 +79,9 @@ class wxAppTraits
     virtual wxRendererNative* CreateRenderer() = 0;
 
     /**
-        This method returns the name of the desktop environment currently
-        running in a Unix desktop. Currently only "KDE" or "GNOME" are
-        supported and the code uses the X11 session protocol vendor name
-        to figure out, which desktop environment is running. The method
-        returns an empty string otherwise and on all other platforms.
+        Returns the name of the desktop environment currently running on a Unix
+        desktop. It returns an empty string for platforms other than wxGTK, or
+        if the desktop environment could not be determined.
     */
     virtual wxString GetDesktopEnvironment() const = 0;
 

src/gtk/utilsgtk.cpp

@@ -386,18 +386,33 @@ bool wxGUIAppTraits::ShowAssertDialog(const wxString& msg)
 wxString wxGUIAppTraits::GetDesktopEnvironment() const
 {
     wxString de = wxSystemOptions::GetOption(wxT("gtk.desktop"));
+    if (!de.empty())
+        return de;
+
+    de = wxGetenv(wxS("XDG_CURRENT_DESKTOP"));
+    if (!de.empty())
+    {
+        // Can be a colon separated list according to
+        // https://wiki.archlinux.org/title/Environment_variables#Examples
+        de = de.BeforeFirst(':');
+    }
 #if wxUSE_DETECT_SM
     if ( de.empty() )
     {
-        static const wxString s_SM = GetSM().Upper();
-
-        if (s_SM.Contains(wxT("GNOME")))
-            de = wxT("GNOME");
-        else if (s_SM.Contains(wxT("KDE")))
-            de = wxT("KDE");
+        static const wxString s_SM(GetSM());
+        de = s_SM;
+        de.Replace(wxS("-session"), wxString());
     }
 #endif // wxUSE_DETECT_SM
 
+    de.MakeUpper();
+    if (de.Contains(wxS("GNOME")))
+        de = wxS("GNOME");
+    else if (de.Contains(wxS("KDE")))
+        de = wxS("KDE");
+    else if (de.Contains(wxS("XFCE")))
+        de = wxS("XFCE");
+
     return de;
 }