core: PlaceObjectAction::Replace swaps out graphic handles

A `PlaceObjectAction::Replace` signals that a shape should
be swapped with a different shape. Previously we instantiated a
completely new `Graphic`, but this is incorrect; instead the
underlying shape handle should be swapped out, but the outer object
remains. This is visible in AVM2 where you can access `Shape` as
a normal display object.

core/src/display_object.rs

@@ -1114,23 +1114,10 @@ pub trait TDisplayObject<'gc>:
         }
     }
 
-    fn copy_display_properties_from(
-        &self,
-        gc_context: MutationContext<'gc, '_>,
-        other: DisplayObject<'gc>,
-    ) {
-        self.set_matrix(gc_context, &*other.matrix());
-        self.set_color_transform(gc_context, &*other.color_transform());
-        self.set_clip_depth(gc_context, other.clip_depth());
-        self.set_name(gc_context, &*other.name());
-        if let (Some(mut me), Some(other)) = (self.as_morph_shape(), other.as_morph_shape()) {
-            me.set_ratio(gc_context, other.ratio());
-        }
-        // onEnterFrame actions only apply to movie clips.
-        if let (Some(me), Some(other)) = (self.as_movie_clip(), other.as_movie_clip()) {
-            me.set_clip_actions(gc_context, other.clip_actions().iter().cloned().collect());
-        }
-        // TODO: More in here eventually.
+    /// Called when this object should be replaced by a PlaceObject tag.
+    #[allow(unused_variables)]
+    fn replace_with(&self, context: &mut UpdateContext<'_, 'gc, '_>, id: CharacterId) {
+        // Noop for most symbols; only shapes can replace their innards with another graphic.
     }
 
     fn object(&self) -> Avm1Value<'gc> {

core/src/display_object/graphic.rs

@@ -146,6 +146,21 @@ impl<'gc> TDisplayObject<'gc> for Graphic<'gc> {
         }
     }
 
+    fn replace_with(&self, context: &mut UpdateContext<'_, 'gc, '_>, id: CharacterId) {
+        // Only a graphic can replace themselves with another graphic via a Replace PlaceObject tag.
+        // This does not create a new graphic instance, but instead swaps out the underlying handle to point to
+        // the new art.
+        if let Some(new_graphic) = context
+            .library
+            .library_for_movie_mut(self.movie().unwrap())
+            .get_graphic(id)
+        {
+            self.0.write(context.gc_context).static_data = new_graphic.0.read().static_data;
+        } else {
+            log::warn!("PlaceObject: expected graphic at character ID {}", id);
+        }
+    }
+
     fn run_frame(&self, _context: &mut UpdateContext) {
         // Noop
     }

core/src/display_object/movie_clip.rs

@@ -1092,14 +1092,12 @@ impl<'gc> MovieClip<'gc> {
     }
 
     /// Instantiate a given child object on the timeline at a given depth.
-    #[allow(clippy::too_many_arguments)]
     fn instantiate_child(
         self,
         context: &mut UpdateContext<'_, 'gc, '_>,
         id: CharacterId,
         depth: Depth,
         place_object: &swf::PlaceObject,
-        copy_previous_properties: bool,
     ) -> Option<DisplayObject<'gc>> {
         match context
             .library
@@ -1122,11 +1120,7 @@ impl<'gc> MovieClip<'gc> {
                     } else {
                         child.set_place_frame(context.gc_context, self.current_frame());
                     }
-                    if copy_previous_properties {
-                        if let Some(prev_child) = prev_child {
-                            child.copy_display_properties_from(context.gc_context, prev_child);
-                        }
-                    }
+
                     // Run first frame.
                     child.apply_place_object(context, self.movie(), place_object);
                     child.construct_frame(context);
@@ -1317,7 +1311,6 @@ impl<'gc> MovieClip<'gc> {
                         params.id(),
                         params.depth(),
                         &params.place_object,
-                        params.modifies_original_item(),
                     ) {
                         // Set the place frame to the frame where the object *would* have been placed.
                         child.set_place_frame(context.gc_context, params.frame);
@@ -3114,28 +3107,28 @@ impl<'gc, 'a> MovieClip<'gc> {
         }?;
         use swf::PlaceObjectAction;
         match place_object.action {
-            PlaceObjectAction::Place(id) | PlaceObjectAction::Replace(id) => {
-                if let Some(child) = self.instantiate_child(
-                    context,
-                    id,
-                    place_object.depth.into(),
-                    &place_object,
-                    matches!(place_object.action, PlaceObjectAction::Replace(_)),
-                ) {
-                    child
+            PlaceObjectAction::Place(id) => {
+                self.instantiate_child(context, id, place_object.depth.into(), &place_object);
+            }
+            PlaceObjectAction::Replace(id) => {
+                if let Some(child) = self.child_by_depth(place_object.depth.into()) {
+                    child.replace_with(context, id);
+                    child.apply_place_object(context, self.movie(), &place_object);
+                    if child.avm_type() == AvmType::Avm2 {
+                        // In AVM2 instantiation happens before frame advance so we
+                        // have to special-case that
+                        child.set_place_frame(context.gc_context, self.current_frame() + 1);
                     } else {
-                    return Ok(());
+                        child.set_place_frame(context.gc_context, self.current_frame());
+                    }
                 }
             }
             PlaceObjectAction::Modify => {
                 if let Some(child) = self.child_by_depth(place_object.depth.into()) {
                     child.apply_place_object(context, self.movie(), &place_object);
-                    child
-                } else {
-                    return Ok(());
                 }
             }
-        };
+        }
 
         Ok(())
     }
@@ -3373,14 +3366,6 @@ impl<'a> GotoPlaceObject<'a> {
         }
     }
 
-    #[inline]
-    fn modifies_original_item(&self) -> bool {
-        matches!(
-            &self.place_object.action,
-            swf::PlaceObjectAction::Replace(_)
-        )
-    }
-
     #[inline]
     fn depth(&self) -> Depth {
         self.place_object.depth.into()

core/src/library.rs

@@ -3,7 +3,7 @@ use crate::avm1::property_map::PropertyMap as Avm1PropertyMap;
 use crate::avm2::{Domain as Avm2Domain, Object as Avm2Object};
 use crate::backend::audio::SoundHandle;
 use crate::character::Character;
-use crate::display_object::{Bitmap, TDisplayObject};
+use crate::display_object::{Bitmap, Graphic, TDisplayObject};
 use crate::font::{Font, FontDescriptor};
 use crate::prelude::*;
 use crate::tag_utils::SwfMovie;
@@ -287,6 +287,16 @@ impl<'gc> MovieLibrary<'gc> {
         self.fonts.get(&descriptor).copied()
     }
 
+    /// Returns the graphic with the given character ID.
+    /// Returns `None` if the ID does not exist or is not a `Graphic`.
+    pub fn get_graphic(&self, id: CharacterId) -> Option<Graphic<'gc>> {
+        if let Some(&Character::Graphic(graphic)) = self.characters.get(&id) {
+            Some(graphic)
+        } else {
+            None
+        }
+    }
+
     pub fn get_sound(&self, id: CharacterId) -> Option<SoundHandle> {
         if let Some(Character::Sound(sound)) = self.characters.get(&id) {
             Some(*sound)