dt_gui_get_session_type: New routine, returns the session kind at runtime.

Either Wayland, X11 or Quartz.

Author: TurboGit

src/gui/gtk.c

@@ -975,6 +975,25 @@ static gboolean _osx_openfile_callback(GtkosxApplication *OSXapp,
 }
 #endif
 
+dt_gui_session_type_t dt_gui_get_session_type(void)
+{
+#ifdef GDK_WINDOWING_QUARTZ
+  return DT_GUI_SESSION_QUARTZ;
+#elif defined(GDK_WINDOWING_WAYLAND)
+  GdkDisplay* disp = gdk_display_get_default();
+  return G_TYPE_CHECK_INSTANCE_TYPE(disp, GDK_TYPE_WAYLAND_DISPLAY)
+    ? DT_GUI_SESSION_WAYLAND
+    : DT_GUI_SESSION_X11;
+#elif defined(GDK_WINDOWING_X11)
+  GdkDisplay* disp = gdk_display_get_default();
+  retun G_TYPE_CHECK_INSTANCE_TYPE(disp, GDK_TYPE_X11_DISPLAY)
+    ? DT_GUI_SESSION_X11
+    : DT_GUI_SESSION_WAYLAND;
+#else
+  return DT_GUI_SESSION_UNKNOWN;
+#endif
+}
+
 static gboolean _configure(GtkWidget *da,
                            GdkEventConfigure *event,
                            const gpointer user_data)

src/gui/gtk.h

@@ -100,6 +100,14 @@ typedef enum dt_gui_color_t
   DT_GUI_COLOR_LAST
 } dt_gui_color_t;
 
+typedef enum dt_gui_session_type_t
+{
+  DT_GUI_SESSION_UNKNOWN,
+  DT_GUI_SESSION_X11,
+  DT_GUI_SESSION_QUARTZ,
+  DT_GUI_SESSION_WAYLAND,
+} dt_gui_session_type_t;
+
 typedef struct dt_gui_gtk_t
 {
   struct dt_ui_t *ui;
@@ -627,6 +635,9 @@ void dt_gui_commit_on_focus_loss(GtkCellRenderer *renderer, GtkCellEditable **ac
 // restore dialog size from config file
 void dt_gui_dialog_restore_size(GtkDialog *dialog, const char *conf);
 
+// returns the session type at runtime
+dt_gui_session_type_t dt_gui_get_session_type(void);
+
 G_END_DECLS
 
 // clang-format off