posix-session: check for Wayland display envars

Also check for the WAYLAND_DISPLAY environment variable when determining
if a graphical session/display exists for POSIX systems.

Author: mjcheetham

src/shared/Core/CommandContext.cs

@@ -134,7 +134,6 @@ public CommandContext()
             else if (PlatformUtils.IsLinux())
             {
                 FileSystem        = new LinuxFileSystem();
-                // TODO: support more than just 'Posix' or X11
                 SessionManager    = new PosixSessionManager();
                 Environment       = new PosixEnvironment(FileSystem);
                 ProcessManager    = new ProcessManager(Trace2);

src/shared/Core/Interop/Posix/PosixSessionManager.cs

@@ -9,7 +9,9 @@ public PosixSessionManager()
             PlatformUtils.EnsurePosix();
         }
 
-        // Check if we have an X11 environment available
-        public virtual bool IsDesktopSession => !string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("DISPLAY"));
+        // Check if we have an X11 or Wayland display environment available
+        public virtual bool IsDesktopSession =>
+            !string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("DISPLAY")) ||
+            !string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("WAYLAND_DISPLAY"));
     }
 }