scaffolding in preparation for implementing undo

imperative-shell/input-callbacks.sml

@@ -8,10 +8,8 @@ struct
 
   fun mouseClickCallback mailbox (button, action) =
     if button = Input.LEFT_MOUSE_BUTTON () then
-      if action = Input.MOUSE_PRESSED () then
-        Mailbox.send (mailbox, MOUSE_LEFT_CLICK)
-      else
-        Mailbox.send (mailbox, MOUSE_LEFT_RELEASE)
+      if action = Input.PRESS () then Mailbox.send (mailbox, MOUSE_LEFT_CLICK)
+      else Mailbox.send (mailbox, MOUSE_LEFT_RELEASE)
     else
       ()
 
@@ -20,6 +18,13 @@ struct
     in Mailbox.send (mailbox, RESIZE_WINDOW {width = width, height = height})
     end
 
+  fun keyActionCallback mailbox (key, scancode, action, mods) =
+    if
+      key = Input.KEY_Z () andalso action <> Input.RELEASE ()
+      andalso mods = 0x0002
+    then Mailbox.send (mailbox, UNDO_ACTION)
+    else ()
+
   fun registerCallbacks (window, inputMailbox) =
     let
       val mouseMoveCallback = mouseMoveCallback inputMailbox
@@ -33,6 +38,10 @@ struct
       val resizeCallback = framebufferSizeCallback inputMailbox
       val _ = Input.exportFramebufferSizeCallback resizeCallback
       val _ = Input.setFramebufferSizeCallback window
+
+      val keyCallback = keyActionCallback inputMailbox
+      val _ = Input.exportKeyCallback keyCallback
+      val _ = Input.setKeyCallback window
     in
       ()
     end