Correctly render containers when a split container is focused

src/con.c

@@ -358,6 +358,18 @@ Con *con_inside_floating(Con *con) {
     return con_inside_floating(con->parent);
 }
 
+/*
+ * Checks if the given container is inside a focused container.
+ *
+ */
+Con *con_inside_focused(Con *con) {
+    if (con == focused)
+        return true;
+    if (!con->parent)
+        return false;
+    return con_inside_focused(con->parent);
+}
+
 /*
  * Returns the container with the given client window ID or NULL if no such
  * container exists.