avm2: Implement `removeChildren`.

This also changes the underlying `DisplayObjectContainer` method to accept any type of range. Turns out enum trait objects aren't actually trait objects and don't need to worry about object safety!

core/src/avm2/globals/flash/display/displayobjectcontainer.rs

@@ -11,6 +11,7 @@ use crate::avm2::Error;
 use crate::context::UpdateContext;
 use crate::display_object::{DisplayObject, TDisplayObject, TDisplayObjectContainer};
 use gc_arena::{GcCell, MutationContext};
+use std::cmp::min;
 
 /// Implements `flash.display.DisplayObjectContainer`'s instance constructor.
 pub fn instance_init<'gc>(
@@ -370,6 +371,57 @@ pub fn remove_child_at<'gc>(
     Ok(Value::Undefined)
 }
 
+/// Implements `DisplayObjectContainer.removeChildren`
+pub fn remove_children<'gc>(
+    activation: &mut Activation<'_, 'gc, '_>,
+    this: Option<Object<'gc>>,
+    args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error> {
+    if let Some(parent) = this.and_then(|this| this.as_display_object()) {
+        if let Some(mut ctr) = parent.as_container() {
+            let from = args
+                .get(0)
+                .cloned()
+                .unwrap_or_else(|| 0.into())
+                .coerce_to_i32(activation)?;
+            let to = args
+                .get(1)
+                .cloned()
+                .unwrap_or_else(|| i32::MAX.into())
+                .coerce_to_i32(activation)?;
+
+            if from >= ctr.num_children() as i32 || from < 0 {
+                return Err(format!(
+                    "RangeError: Starting position {} does not exist in the child list (valid range is 0 to {})",
+                    from,
+                    ctr.num_children()
+                )
+                .into());
+            }
+
+            if (to >= ctr.num_children() as i32 || to < 0) && to != i32::MAX {
+                return Err(format!(
+                    "RangeError: Ending position {} does not exist in the child list (valid range is 0 to {})",
+                    to,
+                    ctr.num_children()
+                )
+                .into());
+            }
+
+            if from > to {
+                return Err(format!("RangeError: Range {} to {} is invalid", from, to).into());
+            }
+
+            ctr.remove_range_of_ids(
+                &mut activation.context,
+                from as usize..min(ctr.num_children(), to as usize + 1),
+            );
+        }
+    }
+
+    Ok(Value::Undefined)
+}
+
 /// Construct `DisplayObjectContainer`'s class.
 pub fn create_class<'gc>(mc: MutationContext<'gc, '_>) -> GcCell<'gc, Class<'gc>> {
     let class = Class::new(
@@ -421,6 +473,10 @@ pub fn create_class<'gc>(mc: MutationContext<'gc, '_>) -> GcCell<'gc, Class<'gc>
         QName::new(Namespace::public_namespace(), "removeChildAt"),
         Method::from_builtin(remove_child_at),
     ));
+    write.define_instance_trait(Trait::from_method(
+        QName::new(Namespace::public_namespace(), "removeChildren"),
+        Method::from_builtin(remove_children),
+    ));
 
     class
 }

core/src/display_object/container.rs

@@ -10,7 +10,7 @@ use ruffle_macros::enum_trait_object;
 use std::cmp::Ordering;
 use std::collections::BTreeMap;
 use std::fmt::Debug;
-use std::ops::Range;
+use std::ops::RangeBounds;
 
 #[enum_trait_object(
     #[derive(Clone, Collect, Debug, Copy)]
@@ -113,11 +113,9 @@ pub trait TDisplayObjectContainer<'gc>:
 
     /// Remove a set of children identified by their render list IDs from this
     /// container's render, depth, and execution lists.
-    fn remove_range_of_ids(
+    fn remove_range_of_ids<R>(&mut self, context: &mut UpdateContext<'_, 'gc, '_>, range: R)
-        &mut self,
+    where
-        context: &mut UpdateContext<'_, 'gc, '_>,
+        R: RangeBounds<usize>;
-        range: Range<usize>,
-    );
 
     /// Clear all three lists in the container.
     fn clear(&mut self, context: MutationContext<'gc, '_>);
@@ -238,11 +236,10 @@ macro_rules! impl_display_object_container {
                 .remove_child(context, child)
         }
 
-        fn remove_range_of_ids(
+        fn remove_range_of_ids<R>(&mut self, context: &mut UpdateContext<'_, 'gc, '_>, range: R)
-            &mut self,
+        where
-            context: &mut UpdateContext<'_, 'gc, '_>,
+            R: RangeBounds<usize>,
-            range: Range<usize>,
+        {
-        ) {
             self.0
                 .write(context.gc_context)
                 .$field
@@ -625,11 +622,10 @@ impl<'gc> ChildContainer<'gc> {
 
     /// Remove a set of children identified by their render list IDs from this
     /// container's render, depth, and execution lists.
-    pub fn remove_range_of_ids(
+    pub fn remove_range_of_ids<R>(&mut self, context: &mut UpdateContext<'_, 'gc, '_>, range: R)
-        &mut self,
+    where
-        context: &mut UpdateContext<'_, 'gc, '_>,
+        R: RangeBounds<usize>,
-        range: Range<usize>,
+    {
-    ) {
         let removed_list: Vec<DisplayObject<'gc>> = self.render_list.drain(range).collect();
 
         for removed in removed_list {

core/src/prelude.rs

@@ -7,7 +7,7 @@ pub use crate::{
     impl_display_object, impl_display_object_container, impl_display_object_sansbounds,
 };
 pub use log::{error, info, trace, warn};
-pub use std::ops::Range;
+pub use std::ops::RangeBounds;
 pub use swf::Matrix;
 pub use swf::{CharacterId, Color, Twips};
 

core/tests/regression_tests.rs

@@ -426,6 +426,7 @@ swf_tests! {
     (as3_displayobjectcontainer_contains, "avm2/displayobjectcontainer_contains", 5),
     (as3_displayobjectcontainer_getchildindex, "avm2/displayobjectcontainer_getchildindex", 5),
     (as3_displayobjectcontainer_removechildat, "avm2/displayobjectcontainer_removechildat", 1),
+    (as3_displayobjectcontainer_removechildren, "avm2/displayobjectcontainer_removechildren", 5),
 }
 
 // TODO: These tests have some inaccuracies currently, so we use approx_eq to test that numeric values are close enough.

core/tests/swfs/avm2/displayobjectcontainer_removechildren/output.txt

@@ -0,0 +1,40 @@
+//var chx = this.getChildAt(0)
+//var chy = this.getChildAt(1)
+//var chz = this.getChildAt(2)
+//this.removeChildren(0, 1)
+//this.getChildAt(0) === chz
+true
+//this.numChildren
+1
+//this.removeChildren(0,0x7fffffff)
+//this.numChildren
+0
+//var chx = this.getChildAt(0)
+//var chy = this.getChildAt(1)
+//var chz = this.getChildAt(2)
+//this.removeChildren(1)
+//this.getChildAt(0) === chx
+true
+//this.numChildren
+1
+//this.removeChildren()
+//this.numChildren
+0
+//var chx = this.getChildAt(0)
+//var chy = this.getChildAt(1)
+//var chz = this.getChildAt(2)
+//this.removeChildren(0, 0)
+//this.getChildAt(0) === chy
+true
+//this.getChildAt(1) === chz
+true
+//this.numChildren
+2
+//this.removeChildren(0, 0)
+//this.getChildAt(0) === chz
+true
+//this.numChildren
+1
+//this.removeChildren(0, 0)
+//this.numChildren
+0