avm2: Implement the programmatically-playing flag that governs `isPlaying` behavior.

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

@@ -278,7 +278,7 @@ pub fn is_playing<'gc>(
         .and_then(|o| o.as_display_object())
         .and_then(|dobj| dobj.as_movie_clip())
     {
-        return Ok(mc.playing().into());
+        return Ok((mc.programmatically_played() && mc.playing()).into());
     }
 
     Ok(Value::Undefined)
@@ -310,6 +310,7 @@ pub fn goto_and_play<'gc>(
         .and_then(|o| o.as_display_object())
         .and_then(|dobj| dobj.as_movie_clip())
     {
+        mc.set_programmatically_played(activation.context.gc_context);
         goto_frame(activation, mc, args, false)?;
     }
 
@@ -396,6 +397,7 @@ pub fn play<'gc>(
         .and_then(|o| o.as_display_object())
         .and_then(|dobj| dobj.as_movie_clip())
     {
+        mc.set_programmatically_played(activation.context.gc_context);
         mc.play(&mut activation.context);
     }
 

core/src/display_object/movie_clip.rs

@@ -588,6 +588,14 @@ impl<'gc> MovieClip<'gc> {
         self.0.read().playing()
     }
 
+    pub fn programmatically_played(self) -> bool {
+        self.0.read().programmatically_played()
+    }
+
+    pub fn set_programmatically_played(self, mc: MutationContext<'gc, '_>) {
+        self.0.write(mc).set_programmatically_played()
+    }
+
     pub fn next_frame(self, context: &mut UpdateContext<'_, 'gc, '_>) {
         if self.current_frame() < self.total_frames() {
             self.goto_frame(context, self.current_frame() + 1, true);
@@ -1877,6 +1885,14 @@ impl<'gc> MovieClipData<'gc> {
         }
     }
 
+    fn programmatically_played(&self) -> bool {
+        self.flags.contains(MovieClipFlags::ProgrammaticallyPlayed)
+    }
+
+    fn set_programmatically_played(&mut self) {
+        self.flags.insert(MovieClipFlags::ProgrammaticallyPlayed);
+    }
+
     fn first_child(&self) -> Option<DisplayObject<'gc>> {
         self.base.first_child()
     }
@@ -3100,6 +3116,12 @@ enum MovieClipFlags {
 
     /// Whether this `MovieClip` is playing or stopped.
     Playing,
+
+    /// Whether this `MovieClip` has been played as a result of an AS3 command.
+    ///
+    /// The AS3 `isPlaying` property is broken and yields false until you first
+    /// call `play` to unbreak it. This flag tracks that bug.
+    ProgrammaticallyPlayed,
 }
 
 /// Actions that are attached to a `MovieClip` event in

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

@@ -9,8 +9,6 @@ frame1
 [object FrameLabel],[object FrameLabel]
 //currentScene
 [object Scene]
-//enabled
-true
 //framesLoaded
 4
 //isPlaying
@@ -19,8 +17,7 @@ false
 [object Scene],[object Scene]
 //totalFrames
 4
-//trackAsMenu
-false
+undefined
 //Frame 2, Scene 1
 //currentFrame
 2
@@ -32,18 +29,14 @@ frame1
 [object FrameLabel],[object FrameLabel]
 //currentScene
 [object Scene]
-//enabled
-true
 //framesLoaded
 4
 //isPlaying
-false
+true
 //scenes
 [object Scene],[object Scene]
 //totalFrames
 4
-//trackAsMenu
-false
 //Frame 3, Scene 1
 //currentFrame
 3
@@ -55,18 +48,14 @@ frame3
 [object FrameLabel],[object FrameLabel]
 //currentScene
 [object Scene]
-//enabled
-true
 //framesLoaded
 4
 //isPlaying
-false
+true
 //scenes
 [object Scene],[object Scene]
 //totalFrames
 4
-//trackAsMenu
-false
 //Frame 1, Scene 2
 //currentFrame
 1
@@ -78,15 +67,13 @@ frame4
 [object FrameLabel]
 //currentScene
 [object Scene]
-//enabled
-true
 //framesLoaded
 4
 //isPlaying
-false
+true
 //scenes
 [object Scene],[object Scene]
 //totalFrames
 4
-//trackAsMenu
+//isPlaying
 false