"Look At Me" for Doodad Scripts

* New script API method: Self.CameraFollowMe() to draw camera focus toward
  your doodad (it sets the Canvas.FollowActor target.)
* The camera will go back to following the player on any action inputs
  (arrow keys, jump, use, etc.); if the player is constantly on the move
  the camera stays on him even if another actor is trying to take the focus.
* The first few ticks of Play Mode the player character is always followed,
  to allow for Anvils to settle into place without taking the focus.
* Canvas FollowActor: if the actor is 4 times the max scroll speed away,
  allow scrolling in greater leaps of 4 times the max scroll speed.

New and Changed Doodads

* Anvils will take the camera focus while they are falling.
* New doodad: "Look At Me" - a 'camera region' technical doodad. Link it to
  any power source such as a Button - when this doodad receives power it will
  take the camera focus for a few frames. Use it to highlight a door that
  opened far off screen by linking the Button to both an Electric Door and
  a "Look At Me" near the door.

pkg/balance/numbers.go

@@ -46,6 +46,11 @@ var (
 	SwimJumpCooldown    uint64  = 24 // number of frames of cooldown between swim-jumps
 	SlopeMaxHeight              = 8  // max pixel height for player to walk up a slope
 
+	// Number of game ticks to insist the canvas follows the player at the start
+	// of a level - to overcome Anvils settling into their starting positions so
+	// they don't steal the camera focus straight away.
+	FollowPlayerFirstTicks uint64 = 60
+
 	// Default chunk size for canvases.
 	ChunkSize = 128
 

pkg/play_scene.go

@@ -68,16 +68,17 @@ type PlayScene struct {
 	debLoadUnload *string
 
 	// Player character
-	Player              *uix.Actor
-	playerPhysics       *physics.Mover
-	lastCheckpoint      render.Point
-	playerLastDirection float64   // player's heading last tick
-	antigravity         bool      // Cheat: disable player gravity
-	noclip              bool      // Cheat: disable player clipping
-	godMode             bool      // Cheat: player can't die
-	godModeUntil        time.Time // Invulnerability timer at respawn.
-	playerJumpCounter   int       // limit jump length
-	jumpCooldownUntil   uint64    // future game tick for jump cooldown (swimming esp.)
+	Player                *uix.Actor
+	playerPhysics         *physics.Mover
+	lastCheckpoint        render.Point
+	playerLastDirection   float64   // player's heading last tick
+	antigravity           bool      // Cheat: disable player gravity
+	noclip                bool      // Cheat: disable player clipping
+	godMode               bool      // Cheat: player can't die
+	godModeUntil          time.Time // Invulnerability timer at respawn.
+	playerJumpCounter     int       // limit jump length
+	jumpCooldownUntil     uint64    // future game tick for jump cooldown (swimming esp.)
+	mustFollowPlayerUntil uint64    // first frames where anvils don't take focus from player
 
 	// Inventory HUD. Impl. in play_inventory.go
 	invenFrame   *ui.Frame

pkg/player_physics.go

@@ -115,5 +115,18 @@ func (s *PlayScene) movePlayer(ev *event.State) {
 	// If the "Use" key is pressed, set an actor flag on the player.
 	s.Player.SetUsing(keybind.Use(ev))
 
+	// Camera behaviors: Anvils can take the camera's focus while they're falling
+	// but player inputs will take control back to the player. Most anvils will fall
+	// a couple pixels upon level load - prevent them taking the camera's focus for
+	// the first few frames of gameplay.
+	if s.mustFollowPlayerUntil == 0 {
+		s.mustFollowPlayerUntil = shmem.Tick + balance.FollowPlayerFirstTicks
+	}
+
+	// If we insist that the canvas follow the player doodad.
+	if shmem.Tick < s.mustFollowPlayerUntil || keybind.Up(ev) || keybind.Left(ev) || keybind.Right(ev) || keybind.Use(ev) {
+		s.drawing.FollowActor = s.Player.ID()
+	}
+
 	s.scripting.To(s.Player.ID()).Events.RunKeypress(keybind.FromEvent(ev))
 }

pkg/uix/actor.go

@@ -413,7 +413,9 @@ func (a *Actor) ShowLayerNamed(name string) error {
 		a.Actor.Filename,
 		name,
 	)
-	return fmt.Errorf("the layer named %s was not found", name)
+
+	// XX: returning an error raises a JavaScript exception in doodads. :/ Warning log is enough.
+	return nil
 }
 
 // Destroy deletes the actor from the running level.

pkg/uix/canvas_scrolling.go

@@ -246,6 +246,18 @@ func (w *Canvas) loopFollowActor(ev *event.State) error {
 			scrollBy.Y = delta
 		}
 
+		// If we are VERY FAR away, allow greater leaps.
+		if scrollBy.X > balance.FollowActorMaxScrollSpeed*4 {
+			scrollBy.X = balance.FollowActorMaxScrollSpeed * 4
+		} else if scrollBy.X < -balance.FollowActorMaxScrollSpeed*4 {
+			scrollBy.X = -balance.FollowActorMaxScrollSpeed * 4
+		}
+		if scrollBy.Y > balance.FollowActorMaxScrollSpeed*4 {
+			scrollBy.Y = balance.FollowActorMaxScrollSpeed * 4
+		} else if scrollBy.Y < -balance.FollowActorMaxScrollSpeed*4 {
+			scrollBy.Y = -balance.FollowActorMaxScrollSpeed * 4
+		}
+
 		// Constrain the maximum scroll speed.
 		if scrollBy.X > balance.FollowActorMaxScrollSpeed {
 			scrollBy.X = balance.FollowActorMaxScrollSpeed

pkg/uix/scripting.go

@@ -132,5 +132,11 @@ func (w *Canvas) MakeSelfAPI(actor *Actor) map[string]interface{} {
 			}
 			return result
 		},
+
+		// Attract the camera's attention.
+		"CameraFollowMe": func() {
+			// Update the doodad that the camera should focus on.
+			w.FollowActor = actor.ID()
+		},
 	}
 }