scaffolding for concurrent ml

fcore/app-update.sml

@@ -0,0 +1,24 @@
+structure AppUpdate =
+struct
+  open AppType
+
+  open MailboxType
+  open DrawMsg
+  open InputMsg
+
+  fun resizeText (app: app_type, newWidth, newHeight) =
+    let
+      val {buffer, windowWidth, windowHeight} = app
+      val (textVec, newBuffer) =
+        TextBuilder.build (0, buffer, newWidth, newHeight)
+
+      val newApp =
+        {buffer = newBuffer, windowWidth = newWidth, windowHeight = newHeight}
+      val msg = REDRAW_TEXT textVec
+    in
+      (newApp, [DRAW msg])
+    end
+
+  fun update (app, msg) =
+    case msg of RESIZE_EVENT (width, height) => resizeText (app, width, height)
+end