actually seperate act from render

main.ml

@@ -363,19 +363,20 @@ module Display = struct
   (* current window state to be passed to window renderer *)
   type state =
     { box: box2
-    ; (* This is cannonically box within which the next element should draw *)
-      time: float
-    ; events: Event.events
+          (* This is cannonically box within which the next element should draw *)
+    ; time: float
     ; wall: Wall.renderer }
 
   (* the box2 here is cannonically the place the returner drew
      (the Wall.image extents) *)
   type image = box2 * Wall.image
 
-  let empty : image = (Box2.empty, Image.empty)
+  let image_empty : image = (Box2.empty, Image.empty)
 
   type pane = state -> state * image
 
+  let pane_empty s = (s, image_empty)
+
   type frame =
     { sdl_win: Sdl.window
     ; gl: Sdl.gl_context
@@ -410,7 +411,7 @@ module Display = struct
       Ok {sdl_win; gl; wall; quit= false; fullscreen= false} )
       ~cleanup:(fun () -> Sdl.destroy_window sdl_win)
 
-  let display_frame frame render =
+  let get_events () =
     (* create and fill event list *)
     let ev = Sdl.Event.create () in
     let el = ref [`None] in
@@ -419,8 +420,13 @@ module Display = struct
       if e != `None then el := !el @ [e]
       (* HACK? *)
     done ;
-    (* Filter the events *)
-    el :=
+    !el
+
+  let last_pane = ref pane_empty
+
+  let display_frame frame actor =
+    let events =
+      (* Handle relevant events *)
       List.filter_map
         (function
           | `Quit ->
@@ -438,39 +444,32 @@ module Display = struct
                       else Sdl.Window.windowed )
                     : _ result ) ) ;
               None
-          | `Key_up a -> Some (`Key_up a)
-          | `Key_down a -> Some (`Key_down a)
-          | `Mouse a -> Some (`Mouse a)
           | a -> Some a (*| a -> Some a*) )
-        !el ;
-    if List.length !el > 0 then (
-      let width, height = Sdl.gl_get_drawable_size frame.sdl_win in
-      let _, (_, image) =
-        render
-          { box=
-              Box2.v (P2.v 0. 0.) (P2.v (float width) (float height))
-          ; time= ticks ()
-          ; events= !el
-          ; wall= frame.wall } in
-      Sdl.gl_make_current frame.sdl_win frame.gl
-      >>= fun () ->
-      let width, height = Sdl.gl_get_drawable_size frame.sdl_win in
-      Gl.viewport 0 0 width height ;
-      Gl.clear_color 0.0 0.0 0.0 1.0 ;
-      Gl.(
-        clear
-          ( color_buffer_bit lor depth_buffer_bit
-          lor stencil_buffer_bit )) ;
-      Gl.enable Gl.blend ;
-      Gl.blend_func_separate Gl.one Gl.src_alpha Gl.one
-        Gl.one_minus_src_alpha ;
-      Gl.enable Gl.cull_face_enum ;
-      Gl.disable Gl.depth_test ;
-      let width = float width and height = float height in
-      Wall.Renderer.render frame.wall ~width ~height image ;
-      Sdl.gl_swap_window frame.sdl_win ;
-      Ok () )
-    else Ok ()
+        (get_events ()) in
+    let width, height = Sdl.gl_get_drawable_size frame.sdl_win in
+    if List.length events > 0 then last_pane := actor events ;
+    let _, (_, image) =
+      !last_pane
+        { box= Box2.v (P2.v 0. 0.) (P2.v (float width) (float height))
+        ; time= ticks ()
+        ; wall= frame.wall } in
+    Sdl.gl_make_current frame.sdl_win frame.gl
+    >>= fun () ->
+    let width, height = Sdl.gl_get_drawable_size frame.sdl_win in
+    Gl.viewport 0 0 width height ;
+    Gl.clear_color 0.0 0.0 0.0 1.0 ;
+    Gl.(
+      clear
+        (color_buffer_bit lor depth_buffer_bit lor stencil_buffer_bit)) ;
+    Gl.enable Gl.blend ;
+    Gl.blend_func_separate Gl.one Gl.src_alpha Gl.one
+      Gl.one_minus_src_alpha ;
+    Gl.enable Gl.cull_face_enum ;
+    Gl.disable Gl.depth_test ;
+    let width = float width and height = float height in
+    Wall.Renderer.render frame.wall ~width ~height image ;
+    Sdl.gl_swap_window frame.sdl_win ;
+    Ok ()
 
   let run frame render () =
     let frame = get_result frame in
@@ -618,7 +617,9 @@ module Panel = struct
   type actor = Event.events -> Display.pane
 
   let blank =
-    { act= (fun panel _events -> (panel, fun s -> (s, Display.empty)))
+    { act=
+        (fun panel _events ->
+          (panel, fun s -> (s, Display.image_empty)) )
     ; subpanels= []
     ; tag= "blank pane" }
 
@@ -1109,10 +1110,7 @@ let () =
          [ Panel.draw (fun (s : Display.state) ->
                (s, Display.fill_box (Display.gray 0.125) s.box) )
          ; top_panel top_1 ] ) in
-  Display.(
-    run (make_frame ~title:"hi" ~w:1440 ~h:900 ()) (fun s ->
-        actor s.events s ))
-    ()
+  Display.(run (make_frame ~title:"hi" ~w:1440 ~h:900 ()) actor) ()
 
 (* Implement the "window management" as just toplevel defined functions that manipulate the window tree *)