avm2: Impl `TextField.multiline`

core/src/avm2/globals/flash/text/textfield.rs

@@ -373,6 +373,42 @@ pub fn length<'gc>(
     Ok(Value::Undefined)
 }
 
+pub fn multiline<'gc>(
+    _activation: &mut Activation<'_, 'gc, '_>,
+    this: Option<Object<'gc>>,
+    _args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error> {
+    if let Some(this) = this
+        .and_then(|this| this.as_display_object())
+        .and_then(|this| this.as_edit_text())
+    {
+        return Ok(this.is_multiline().into());
+    }
+
+    Ok(Value::Undefined)
+}
+
+pub fn set_multiline<'gc>(
+    activation: &mut Activation<'_, 'gc, '_>,
+    this: Option<Object<'gc>>,
+    args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error> {
+    if let Some(this) = this
+        .and_then(|this| this.as_display_object())
+        .and_then(|this| this.as_edit_text())
+    {
+        let is_multiline = args
+            .get(0)
+            .cloned()
+            .unwrap_or(Value::Undefined)
+            .coerce_to_boolean();
+
+        this.set_multiline(is_multiline, &mut activation.context);
+    }
+
+    Ok(Value::Undefined)
+}
+
 /// Construct `TextField`'s class.
 pub fn create_class<'gc>(mc: MutationContext<'gc, '_>) -> GcCell<'gc, Class<'gc>> {
     let class = Class::new(
@@ -453,6 +489,14 @@ pub fn create_class<'gc>(mc: MutationContext<'gc, '_>) -> GcCell<'gc, Class<'gc>
         QName::new(Namespace::public(), "length"),
         Method::from_builtin(length),
     ));
+    write.define_instance_trait(Trait::from_getter(
+        QName::new(Namespace::public(), "multiline"),
+        Method::from_builtin(multiline),
+    ));
+    write.define_instance_trait(Trait::from_setter(
+        QName::new(Namespace::public(), "multiline"),
+        Method::from_builtin(set_multiline),
+    ));
 
     class
 }