Added scroll()

kiln-core/src/action.rs

@@ -29,6 +29,19 @@ use rhai::{Dynamic, ImmutableString, Module};
 /// How long a move occupies an object before it can act again, in seconds.
 pub(crate) const MOVE_COST: f64 = 0.25;
 
+/// One line of content in a [`Action::Scroll`] overlay.
+///
+/// Each element of the array passed to the `scroll()` Rhai function becomes a
+/// `ScrollLine`: a plain string becomes [`Text`](ScrollLine::Text); a two-element
+/// array `[choice, display]` becomes a [`Choice`](ScrollLine::Choice).
+pub enum ScrollLine {
+    /// Plain text, word-wrapped to the scroll window width.
+    Text(String),
+    /// A selectable option: `choice` is the event name sent back to the source
+    /// object via `send`, and `display` is the label shown to the player.
+    Choice { choice: String, display: String },
+}
+
 /// One deferred mutation emitted by a script, applied by [`crate::game::GameState`]
 /// after it is promoted onto the board queue.
 ///
@@ -52,6 +65,9 @@ pub(crate) enum Action {
     SetColor { fg: Option<Rgba8>, bg: Option<Rgba8> },
     /// Call `fn_name` on `target` object, optionally passing `arg`.
     Send { target: ObjectId, fn_name: String, arg: Option<ScriptArg> },
+    /// Open a scrollable text overlay. Pauses game ticks while shown; a choice
+    /// selection dispatches [`Send`](Action::Send) to the source object.
+    Scroll(Vec<ScrollLine>),
 }
 
 // ── Direction helpers ─────────────────────────────────────────────────────────
@@ -128,6 +144,10 @@ pub(crate) fn action_to_map(action: &Action) -> rhai::Map {
                 m.insert("arg".into(), dyn_arg);
             }
         }
+        // Scroll lines are not round-trippable via the queue map API; emit type only.
+        Action::Scroll(_) => {
+            ins_str(&mut m, "type", "Scroll");
+        }
     }
     m
 }
@@ -202,6 +222,7 @@ impl TryFrom<rhai::Map> for Action {
                 };
                 Ok(Action::Send { target: target as ObjectId, fn_name, arg })
             }
+            "Scroll" => Err("Scroll actions cannot be constructed from maps".to_string()),
             other => Err(format!("unknown action type: '{other}'")),
         }
     }