Add initial prototype.

3-mid/opengl/source/platform/egl/opengl-screen.ads

@@ -0,0 +1,24 @@
+package openGL.Screen
+--
+--  Models an openGL screen.
+--
+is
+
+   type Item is tagged limited private;
+
+
+--     function  Thin    (Self : in     Item)     return xcb.xcb_screen_t.Pointer;
+--     procedure Thin_is (Self : in out Item;   Now : in xcb.xcb_screen_t.Pointer);
+
+
+
+private
+
+   type Item is tagged limited
+      record
+         null; -- Thin : xcb.xcb_screen_t.Pointer;
+      end record;
+
+   procedure dummy;
+
+end openGL.Screen;