[EZGL][Warnings] Removed Use of Deprecated Enum

The G_APPLICATION_FLAGS_NONE enum was deprecated in recent versions of
GLib and was replaced by G_APPLICATION_DEFAULT_FLAGS; however, the
replacement enum was not introduced until GLib 2.74. Added code that
will select which enum to use depending on the GLib version to keep EZGL
backwards compatible.

Author: AlexandreSinger

libs/EXTERNAL/libezgl/src/application.cpp

@@ -18,6 +18,16 @@
 
 #include "ezgl/application.hpp"
 
+// GLib deprecated G_APPLICATION_FLAGS_NONE and replaced it with G_APPLICATION_DEFAULT_FLAGS,
+// however, this enum was not introduced until GLib 2.74. These lines of code allow EZGL
+// to be backwards compatible with older versions of GLib, while not using the deprecated
+// enum.
+#if GLIB_CHECK_VERSION(2, 74, 0)
+static constexpr GApplicationFlags EZGL_APPLICATION_DEFAULT_FLAGS = G_APPLICATION_DEFAULT_FLAGS;
+#else
+static constexpr GApplicationFlags EZGL_APPLICATION_DEFAULT_FLAGS = G_APPLICATION_FLAGS_NONE;
+#endif
+
 namespace ezgl {
 
 // A flag to disable event loop (default is false)
@@ -86,7 +96,7 @@ application::application(application::settings s)
     , m_window_id(s.window_identifier)
     , m_canvas_id(s.canvas_identifier)
     , m_application_id(s.application_identifier)
-    , m_application(gtk_application_new(s.application_identifier.c_str(), G_APPLICATION_FLAGS_NONE))
+    , m_application(gtk_application_new(s.application_identifier.c_str(), EZGL_APPLICATION_DEFAULT_FLAGS))
     , m_builder(gtk_builder_new())
     , m_register_callbacks(s.setup_callbacks)
 {
@@ -205,7 +215,7 @@ int application::run(setup_callback_fn initial_setup_user_callback,
     g_object_unref(m_builder);
 
     // Reconstruct the GTK application
-    m_application = (gtk_application_new(m_application_id.c_str(), G_APPLICATION_FLAGS_NONE));
+    m_application = (gtk_application_new(m_application_id.c_str(), EZGL_APPLICATION_DEFAULT_FLAGS));
     m_builder = (gtk_builder_new());
     g_signal_connect(m_application, "startup", G_CALLBACK(startup), this);
     g_signal_connect(m_application, "activate", G_CALLBACK(activate), this);
@@ -478,4 +488,4 @@ void set_disable_event_loop(bool new_setting)
 {
   disable_event_loop = new_setting;
 }
-}
+}