Add initial prototype.

4-high/gel/source/platform/sdl/gel-window-sdl.ads

@@ -0,0 +1,57 @@
+private
+with
+     sdl.Video.Windows,
+     sdl.Video.GL;
+
+package gel.Window.sdl
+--
+-- Provides an SDL implementation of a window.
+--
+is
+   type Item is new gel.Window.item with private;
+   type View is access all Item'Class;
+
+
+   ---------
+   --- Forge
+   --
+
+   procedure define  (Self : in     View;   Title  : in String;
+                                            Width  : in Natural;
+                                            Height : in Natural);
+   overriding
+   procedure destroy (Self : in out Item);
+
+
+   package Forge
+   is
+      function new_Window (Title  : in String;
+                           Width  : in Natural;
+                           Height : in Natural) return Window.sdl.view;
+   end Forge;
+
+
+   --------------
+   --- Operations
+   --
+
+   overriding
+   procedure emit_Events (Self : in out Item);
+   overriding
+   procedure enable_GL   (Self : in     Item);
+   overriding
+   procedure disable_GL  (Self : in     Item);
+   overriding
+   procedure swap_GL     (Self : in out Item);
+
+
+
+private
+
+   type Item is new gel.Window.item with
+      record
+         window_Handle : standard.sdl.Video.Windows.Window;
+         GL_Context    : standard.sdl.Video.GL.Contexts;
+      end record;
+
+end gel.Window.sdl;