x11: ensure WM class is not null even if display is initialized early

With gtkmm, when using `Application()`, the display is initialized
before we know the application name and therefore, the program class
associated to the display is NULL.

Instead of providing a default value, we set it equal to program name
when NULL. Moreover, we give up on capitalizing the class name to keep
the code super simple. Also, not using a capitalized name is
consistent with `gdk_x11_display_open()`. If someone has a good reason
to use a capitalized name, here is how to do it.

```c
  class_hint = XAllocClassHint ();
  class_hint->res_name = (char *) g_get_prgname ();
  if (display_x11->program_class)
    {
      class_hint->res_class = (char *) g_strdup (display_x11->program_class);
    }
  else if (class_hint->res_name && class_hint->res_name[0])
    {
      class_hint->res_class = (char *) g_strdup (class_hint->res_name);
      class_hint->res_class[0] = g_ascii_toupper (class_hint->res_class[0]);
    }
  XSetClassHint (xdisplay, impl->xid, class_hint);
  g_free (class_hint->res_class);
  XFree (class_hint);
```

Fix eff53c023a26 ("x11: set a default value for program_class")

2 files changed, 4 insertions, 4 deletions

diff --git a/gdk/x11/gdkdisplay-x11.c b/gdk/x11/gdkdisplay-x11.c
index 30d040a132..33a3648f4e 100644
--- a/gdk/x11/gdkdisplay-x11.c
+++ b/gdk/x11/gdkdisplay-x11.c
@@ -204,9 +204,6 @@ static void
 gdk_x11_display_init (GdkX11Display *self)
 {
   self->monitors = g_list_store_new (GDK_TYPE_MONITOR);
-  self->program_class = g_strdup (g_get_prgname ());
-  if (self->program_class && self->program_class[0])
-    self->program_class[0] = g_ascii_toupper (self->program_class[0]);
 }
 
 static void
diff --git a/gdk/x11/gdksurface-x11.c b/gdk/x11/gdksurface-x11.c
index 505fbd2b9a..dd1d0d3bd2 100644
--- a/gdk/x11/gdksurface-x11.c
+++ b/gdk/x11/gdksurface-x11.c
@@ -1282,7 +1282,10 @@ _gdk_x11_display_create_surface (GdkDisplay     *display,
 
   class_hint = XAllocClassHint ();
   class_hint->res_name = (char *) g_get_prgname ();
-  class_hint->res_class = (char *) display_x11->program_class;
+  if (display_x11->program_class)
+    class_hint->res_class = (char *) display_x11->program_class;
+  else
+    class_hint->res_class = class_hint->res_name;
   XSetClassHint (xdisplay, impl->xid, class_hint);
   XFree (class_hint);