avm1: Implement Object.watch & Object.unwatch (#268)

core/src/avm1/color_transform_object.rs

@@ -229,6 +229,21 @@ impl<'gc> TObject<'gc> for ColorTransformObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base()
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base().remove_watcher(gc_context, name)
+    }
+
     fn has_property(
         &self,
         activation: &mut Activation<'_, 'gc>,

core/src/avm1/function.rs

@@ -624,6 +624,20 @@ impl<'gc> TObject<'gc> for FunctionObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base.set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base.remove_watcher(gc_context, name)
+    }
+
     fn has_property(
         &self,
         activation: &mut Activation<'_, 'gc>,

core/src/avm1/globals/object.rs

@@ -162,6 +162,55 @@ pub fn register_class<'gc>(
     Ok(Value::Undefined)
 }
 
+/// Implements `Object.prototype.watch`
+fn watch<'gc>(
+    activation: &mut Activation<'_, 'gc>,
+    context: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error<'gc>> {
+    let name = if let Some(name) = args.get(0) {
+        name.coerce_to_string(activation, context)?
+    } else {
+        return Ok(false.into());
+    };
+    let callback = if let Some(callback) = args.get(1) {
+        if let Some(callback) = callback
+            .coerce_to_object(activation, context)
+            .as_executable()
+        {
+            callback
+        } else {
+            return Ok(false.into());
+        }
+    } else {
+        return Ok(false.into());
+    };
+    let user_data = args.get(2).cloned().unwrap_or(Value::Undefined);
+
+    this.set_watcher(context.gc_context, name, callback, user_data);
+
+    Ok(true.into())
+}
+
+/// Implements `Object.prototype.unmwatch`
+fn unwatch<'gc>(
+    activation: &mut Activation<'_, 'gc>,
+    context: &mut UpdateContext<'_, 'gc, '_>,
+    this: Object<'gc>,
+    args: &[Value<'gc>],
+) -> Result<Value<'gc>, Error<'gc>> {
+    let name = if let Some(name) = args.get(0) {
+        name.coerce_to_string(activation, context)?
+    } else {
+        return Ok(false.into());
+    };
+
+    let result = this.remove_watcher(context.gc_context, name);
+
+    Ok(result.into())
+}
+
 /// Partially construct `Object.prototype`.
 ///
 /// `__proto__` and other cross-linked properties of this object will *not*
@@ -218,6 +267,20 @@ pub fn fill_proto<'gc>(
         DontDelete | DontEnum,
         Some(fn_proto),
     );
+    object_proto.as_script_object().unwrap().force_set_function(
+        "watch",
+        watch,
+        gc_context,
+        DontDelete | DontEnum,
+        Some(fn_proto),
+    );
+    object_proto.as_script_object().unwrap().force_set_function(
+        "unwatch",
+        unwatch,
+        gc_context,
+        DontDelete | DontEnum,
+        Some(fn_proto),
+    );
 }
 
 /// Implements `ASSetPropFlags`.

core/src/avm1/object.rs

@@ -259,6 +259,23 @@ pub trait TObject<'gc>: 'gc + Collect + Debug + Into<Object<'gc>> + Clone + Copy
         attributes: EnumSet<Attribute>,
     );
 
+    /// Set the 'watcher' of a given property.
+    ///
+    /// The property does not need to exist at the time of this being called.
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    );
+
+    /// Removed any assigned 'watcher' from the given property.
+    ///
+    /// The return value will indicate if there was a watcher present before this method was
+    /// called.
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool;
+
     /// Checks if the object has a given named property.
     fn has_property(
         &self,

core/src/avm1/script_object.rs

@@ -8,6 +8,7 @@ use core::fmt;
 use enumset::EnumSet;
 use gc_arena::{Collect, GcCell, MutationContext};
 use std::borrow::Cow;
+use std::collections::HashMap;
 
 pub const TYPE_OF_OBJECT: &str = "object";
 
@@ -18,6 +19,50 @@ pub enum ArrayStorage<'gc> {
     Properties { length: usize },
 }
 
+#[derive(Debug, Clone, Collect)]
+#[collect(no_drop)]
+pub struct Watcher<'gc> {
+    callback: Executable<'gc>,
+    user_data: Value<'gc>,
+}
+
+impl<'gc> Watcher<'gc> {
+    pub fn new(callback: Executable<'gc>, user_data: Value<'gc>) -> Self {
+        Self {
+            callback,
+            user_data,
+        }
+    }
+
+    #[allow(clippy::too_many_arguments)]
+    pub fn call(
+        &self,
+        activation: &mut Activation<'_, 'gc>,
+        context: &mut UpdateContext<'_, 'gc, '_>,
+        name: &str,
+        old_value: Value<'gc>,
+        new_value: Value<'gc>,
+        this: Object<'gc>,
+        base_proto: Option<Object<'gc>>,
+    ) -> Result<Value<'gc>, crate::avm1::error::Error<'gc>> {
+        let args = [
+            Value::String(name.to_string()),
+            old_value,
+            new_value,
+            self.user_data.clone(),
+        ];
+        self.callback.exec(
+            name,
+            activation,
+            context,
+            this,
+            base_proto,
+            &args,
+            ExecutionReason::Special,
+        )
+    }
+}
+
 #[derive(Debug, Copy, Clone, Collect)]
 #[collect(no_drop)]
 pub struct ScriptObject<'gc>(GcCell<'gc, ScriptObjectData<'gc>>);
@@ -28,6 +73,7 @@ pub struct ScriptObjectData<'gc> {
     interfaces: Vec<Object<'gc>>,
     type_of: &'static str,
     array: ArrayStorage<'gc>,
+    watchers: HashMap<String, Watcher<'gc>>,
 }
 
 unsafe impl<'gc> Collect for ScriptObjectData<'gc> {
@@ -36,6 +82,7 @@ unsafe impl<'gc> Collect for ScriptObjectData<'gc> {
         self.values.trace(cc);
         self.array.trace(cc);
         self.interfaces.trace(cc);
+        self.watchers.trace(cc);
     }
 }
 
@@ -45,6 +92,7 @@ impl fmt::Debug for ScriptObjectData<'_> {
             .field("prototype", &self.prototype)
             .field("values", &self.values)
             .field("array", &self.array)
+            .field("watchers", &self.watchers)
             .finish()
     }
 }
@@ -62,6 +110,7 @@ impl<'gc> ScriptObject<'gc> {
                 values: PropertyMap::new(),
                 array: ArrayStorage::Properties { length: 0 },
                 interfaces: vec![],
+                watchers: HashMap::new(),
             },
         ))
     }
@@ -78,6 +127,7 @@ impl<'gc> ScriptObject<'gc> {
                 values: PropertyMap::new(),
                 array: ArrayStorage::Vector(Vec::new()),
                 interfaces: vec![],
+                watchers: HashMap::new(),
             },
         ));
         object.sync_native_property("length", gc_context, Some(0.into()), false);
@@ -97,6 +147,7 @@ impl<'gc> ScriptObject<'gc> {
                 values: PropertyMap::new(),
                 array: ArrayStorage::Properties { length: 0 },
                 interfaces: vec![],
+                watchers: HashMap::new(),
             },
         ))
         .into()
@@ -116,6 +167,7 @@ impl<'gc> ScriptObject<'gc> {
                 values: PropertyMap::new(),
                 array: ArrayStorage::Properties { length: 0 },
                 interfaces: vec![],
+                watchers: HashMap::new(),
             },
         ))
     }
@@ -191,7 +243,7 @@ impl<'gc> ScriptObject<'gc> {
     pub(crate) fn internal_set(
         &self,
         name: &str,
-        value: Value<'gc>,
+        mut value: Value<'gc>,
         activation: &mut Activation<'_, 'gc>,
         context: &mut UpdateContext<'_, 'gc, '_>,
         this: Object<'gc>,
@@ -257,6 +309,28 @@ impl<'gc> ScriptObject<'gc> {
             //we'd resolve and return up there, but we have borrows that need
             //to end before we can do so.
             if !worked {
+                let watcher = self.0.read().watchers.get(name).cloned();
+                let mut return_value = Ok(());
+                if let Some(watcher) = watcher {
+                    let old_value = self.get(name, activation, context)?;
+                    value = match watcher.call(
+                        activation,
+                        context,
+                        name,
+                        old_value,
+                        value.clone(),
+                        this,
+                        base_proto,
+                    ) {
+                        Ok(value) => value,
+                        Err(Error::ThrownValue(error)) => {
+                            return_value = Err(Error::ThrownValue(error));
+                            Value::Undefined
+                        }
+                        Err(_) => Value::Undefined,
+                    };
+                }
+
                 let rval = match self
                     .0
                     .write(context.gc_context)
@@ -285,6 +359,8 @@ impl<'gc> ScriptObject<'gc> {
                         ExecutionReason::Special,
                     );
                 }
+
+                return return_value;
             }
         }
 
@@ -479,6 +555,24 @@ impl<'gc> TObject<'gc> for ScriptObject<'gc> {
         );
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.0
+            .write(gc_context)
+            .watchers
+            .insert(name.to_string(), Watcher::new(callback, user_data));
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        let old = self.0.write(gc_context).watchers.remove(name.as_ref());
+        old.is_some()
+    }
+
     fn define_value(
         &self,
         gc_context: MutationContext<'gc, '_>,

core/src/avm1/shared_object.rs

@@ -191,6 +191,21 @@ impl<'gc> TObject<'gc> for SharedObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base()
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base().remove_watcher(gc_context, name)
+    }
+
     fn has_property(
         &self,
         activation: &mut Activation<'_, 'gc>,

core/src/avm1/sound_object.rs

@@ -251,6 +251,21 @@ impl<'gc> TObject<'gc> for SoundObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base()
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base().remove_watcher(gc_context, name)
+    }
+
     fn has_property(
         &self,
         activation: &mut Activation<'_, 'gc>,

core/src/avm1/stage_object.rs

@@ -332,6 +332,23 @@ impl<'gc> TObject<'gc> for StageObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.0
+            .read()
+            .base
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.0.read().base.remove_watcher(gc_context, name)
+    }
+
     fn has_property(
         &self,
         activation: &mut Activation<'_, 'gc>,

core/src/avm1/super_object.rs

@@ -237,6 +237,21 @@ impl<'gc> TObject<'gc> for SuperObject<'gc> {
         //`super` cannot have properties defined on it
     }
 
+    fn set_watcher(
+        &self,
+        _gc_context: MutationContext<'gc, '_>,
+        _name: Cow<str>,
+        _callback: Executable<'gc>,
+        _user_data: Value<'gc>,
+    ) {
+        //`super` cannot have properties defined on it
+    }
+
+    fn remove_watcher(&self, _gc_context: MutationContext<'gc, '_>, _name: Cow<str>) -> bool {
+        //`super` cannot have properties defined on it
+        false
+    }
+
     fn has_property(
         &self,
         activation: &mut Activation<'_, 'gc>,

core/src/avm1/value_object.rs

@@ -231,6 +231,26 @@ impl<'gc> TObject<'gc> for ValueObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.0
+            .read()
+            .base
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.0
+            .write(gc_context)
+            .base
+            .remove_watcher(gc_context, name)
+    }
+
     fn define_value(
         &self,
         gc_context: MutationContext<'gc, '_>,

core/src/avm1/xml_attributes_object.rs

@@ -157,6 +157,21 @@ impl<'gc> TObject<'gc> for XMLAttributesObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base()
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base().remove_watcher(gc_context, name)
+    }
+
     fn define_value(
         &self,
         gc_context: MutationContext<'gc, '_>,

core/src/avm1/xml_idmap_object.rs

@@ -155,6 +155,21 @@ impl<'gc> TObject<'gc> for XMLIDMapObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base()
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base().remove_watcher(gc_context, name)
+    }
+
     fn define_value(
         &self,
         gc_context: MutationContext<'gc, '_>,

core/src/avm1/xml_object.rs

@@ -145,6 +145,21 @@ impl<'gc> TObject<'gc> for XMLObject<'gc> {
             .add_property_with_case(activation, gc_context, name, get, set, attributes)
     }
 
+    fn set_watcher(
+        &self,
+        gc_context: MutationContext<'gc, '_>,
+        name: Cow<str>,
+        callback: Executable<'gc>,
+        user_data: Value<'gc>,
+    ) {
+        self.base()
+            .set_watcher(gc_context, name, callback, user_data);
+    }
+
+    fn remove_watcher(&self, gc_context: MutationContext<'gc, '_>, name: Cow<str>) -> bool {
+        self.base().remove_watcher(gc_context, name)
+    }
+
     fn define_value(
         &self,
         gc_context: MutationContext<'gc, '_>,

core/tests/regression_tests.rs

@@ -193,6 +193,8 @@ swf_tests! {
     (loadvariables_method, "avm1/loadvariables_method", 3),
     (xml_load, "avm1/xml_load", 1),
     (with_return, "avm1/with_return", 1),
+    (watch, "avm1/watch", 1),
+    #[ignore] (watch_virtual_property, "avm1/watch_virtual_property", 1),
     (cross_movie_root, "avm1/cross_movie_root", 5),
     (roots_and_levels, "avm1/roots_and_levels", 1),
     (swf6_case_insensitive, "avm1/swf6_case_insensitive", 1),

core/tests/swfs/avm1/watch/LoggingWatcher.as

@@ -0,0 +1,25 @@
+class LoggingWatcher {
+    var count = 0;
+    var value = true;
+
+    function LoggingWatcher() {
+        trace("// this.watch(\"value\", this.log)");
+        this.watch("value", this.log);
+    }
+
+    function log(property, oldValue, newValue, bounds) {
+        var userdata;
+        if (typeof bounds === "object") {
+            userdata = "{ ";
+            for (var key in bounds) {
+                userdata += key + "=" + bounds[key] + " ";
+            }
+            userdata += "}";
+        } else {
+            userdata = bounds;
+        }
+        this.count++;
+        trace("LoggingWatcher count " + this.count + ": " + property + " changed from " + oldValue + " to " + newValue + " with userdata " + userdata);
+        return newValue;
+    }
+}

core/tests/swfs/avm1/watch/output.txt

@@ -0,0 +1,118 @@
+// watch()
+false
+
+// watch("variable")
+false
+
+// watch("variable", true)
+false
+
+// watch("variable", clamper, {min: 5, max: 10})
+true
+
+// variable = 5
+Clamper: variable changed from undefined to 5 with userdata { min=5 max=10 }
+// variable
+5
+
+// variable = 10
+Clamper: variable changed from 5 to 10 with userdata { min=5 max=10 }
+// variable
+10
+
+// variable = 4
+Clamper: variable changed from 10 to 4 with userdata { min=5 max=10 }
+// variable
+5
+
+// variable = 11
+Clamper: variable changed from 5 to 11 with userdata { min=5 max=10 }
+// variable
+10
+
+// variable = 6
+Clamper: variable changed from 10 to 6 with userdata { min=5 max=10 }
+// variable
+6
+
+// delete(variable)
+
+// variable = 3
+Clamper: variable changed from undefined to 3 with userdata { min=5 max=10 }
+// variable
+5
+
+// watch("variable", clamper, {min: 15, max: 20})
+true
+
+// variable = 14
+Clamper: variable changed from 5 to 14 with userdata { min=15 max=20 }
+// variable
+15
+
+// variable = 21
+Clamper: variable changed from 15 to 21 with userdata { min=15 max=20 }
+// variable
+20
+
+// variable = 18
+Clamper: variable changed from 20 to 18 with userdata { min=15 max=20 }
+// variable
+18
+
+// watch("variable", exceptionalClamper, {min: 15, max: 20})
+true
+
+// variable = 14
+exceptionalClamper: variable changed from 18 to 14 with userdata { min=15 max=20 }
+ERROR: too low!
+// variable
+undefined
+
+// variable = 21
+exceptionalClamper: variable changed from undefined to 21 with userdata { min=15 max=20 }
+ERROR: too high!
+// variable
+undefined
+
+// variable = 18
+exceptionalClamper: variable changed from undefined to 18 with userdata { min=15 max=20 }
+// variable
+18
+
+// unwatch("variable")
+true
+
+// variable = 4
+// variable
+4
+
+// variable = 11
+// variable
+11
+
+// unwatch("variable")
+false
+
+// unwatch()
+false
+
+// variable = 6
+// variable
+6
+
+// delete(variable)
+
+
+// var loggingWatcher = new LoggingWatcher()
+// this.watch("value", this.log)
+
+// loggingWatcher.value = true
+LoggingWatcher count 1: value changed from true to true with userdata undefined
+
+// loggingWatcher.value = false
+LoggingWatcher count 2: value changed from true to false with userdata undefined
+
+// loggingWatcher.count
+2
+

core/tests/swfs/avm1/watch_virtual_property/output.txt

@@ -0,0 +1,61 @@
+// watch("variable", plusOne)
+true
+
+// addProperty("variable", getter, setter)
+plusOne: variable changed from undefined to undefined with userdata undefined
+true
+
+// variable = 10
+plusOne: variable changed from NaN to 10 with userdata undefined
+setter: ignoring new value of 11
+// variable
+getter: returning 5
+5
+
+// variable = 4
+plusOne: variable changed from 11 to 4 with userdata undefined
+setter: ignoring new value of 5
+// variable
+getter: returning 5
+5
+
+// unwatch("variable")
+false
+
+// variable = 10
+plusOne: variable changed from 5 to 10 with userdata undefined
+setter: ignoring new value of 11
+// variable
+getter: returning 5
+5
+
+// variable = 4
+plusOne: variable changed from 11 to 4 with userdata undefined
+setter: ignoring new value of 5
+// variable
+getter: returning 5
+5
+
+// watch("variable", plusOne)
+true
+
+// variable = 10
+plusOne: variable changed from 5 to 10 with userdata undefined
+setter: ignoring new value of 11
+// variable
+getter: returning 5
+5
+
+// variable = 4
+plusOne: variable changed from 11 to 4 with userdata undefined
+setter: ignoring new value of 5
+// variable
+getter: returning 5
+5
+
+// delete(variable)
+
+// addProperty("variable", getter, null)
+plusOne: variable changed from undefined to undefined with userdata undefined
+true
+