core: Handle the case where frame rate is set to 0 or NaN

Author: Toad06

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

@@ -218,7 +218,12 @@ pub fn get_frame_rate<'gc>(
     _this: Object<'gc>,
     _args: &[Value<'gc>],
 ) -> Result<Value<'gc>, Error<'gc>> {
-    Ok((*activation.context.frame_rate).into())
+    let mut frame_rate = *activation.context.frame_rate;
+    if frame_rate < 0.0 {
+        // Uncommon frame rate from the SWF header.
+        frame_rate = frame_rate.rem_euclid(256.0);
+    }
+    Ok(frame_rate.into())
 }
 
 /// Implement `frameRate`'s setter
@@ -228,7 +233,7 @@ pub fn set_frame_rate<'gc>(
     args: &[Value<'gc>],
 ) -> Result<Value<'gc>, Error<'gc>> {
     if !activation.context.forced_frame_rate {
-        let new_frame_rate = args.get_f64(activation, 0)?;
+        let new_frame_rate = args.get_f64(activation, 0)?.clamp(0.01, 1000.0);
         *activation.context.frame_rate = new_frame_rate;
     }
 

core/src/player.rs

@@ -475,7 +475,7 @@ impl Player {
         if self.recent_run_frame_timings.is_empty() {
             5
         } else {
-            let frame_time = 1000.0 / self.frame_rate;
+            let frame_time = self.frame_time(1000.0);
             let average_run_frame_time = self.recent_run_frame_timings.iter().sum::<f64>()
                 / self.recent_run_frame_timings.len() as f64;
             ((frame_time / average_run_frame_time) as u32).clamp(1, MAX_FRAMES_PER_TICK)
@@ -489,11 +489,19 @@ impl Player {
         }
     }
 
+    fn frame_time(&self, time_unit: f64) -> f64 {
+        let frame_rate = self.frame_rate;
+        if frame_rate == 0.0 || frame_rate.is_nan() {
+            0.0
+        } else {
+            time_unit / frame_rate
+        }
+    }
+
     pub fn tick(&mut self, dt: f64) {
         if self.is_playing() {
             self.frame_accumulator += dt;
-            let frame_rate = self.frame_rate;
-            let frame_time = 1000.0 / frame_rate;
+            let frame_time = self.frame_time(1000.0);
 
             let max_frames_per_tick = self.max_frames_per_tick();
             let mut frame = 0;
@@ -556,7 +564,7 @@ impl Player {
     /// Returns the approximate duration of time until the next frame is due to run.
     /// This is only an approximation to be used for sleep durations.
     pub fn time_til_next_frame(&self) -> std::time::Duration {
-        let frame_time = 1000.0 / self.frame_rate;
+        let frame_time = self.frame_time(1000.0);
         let mut dt = if self.frame_accumulator <= 0.0 {
             frame_time
         } else if self.frame_accumulator >= frame_time {
@@ -1874,7 +1882,8 @@ impl Player {
 
     #[instrument(level = "debug", skip_all)]
     pub fn run_frame(&mut self) {
-        let frame_time = Duration::from_nanos((750_000_000.0 / self.frame_rate) as u64);
+        let frame_time = self.frame_time(750_000_000.0);
+        let frame_time = Duration::from_nanos(frame_time as u64);
         let (mut execution_limit, may_execute_while_streaming) = match self.load_behavior {
             LoadBehavior::Streaming => (
                 ExecutionLimit::with_max_ops_and_time(10000, frame_time),

tests/tests/swfs/avm2/stage_framerate_nan/output.txt

@@ -0,0 +1,7 @@
+// stage.frameRate (SWF header = 30)
+30
+// stage.frameRate = NaN;
+NaN
+// Event.ENTER_FRAME
+// Event.ENTER_FRAME
+// Event.ENTER_FRAME

tests/tests/swfs/avm2/stage_framerate_nan/source.as

@@ -0,0 +1,31 @@
+// Test made using JPEXS Free Flash Decompiler.
+// The frame rate in the SWF header is set to 30.
+
+package
+{
+   import flash.display.Sprite;
+   import flash.events.Event;
+   
+   public class Test extends Sprite
+   {
+      public function Test()
+      {
+         super();
+         this.init();
+      }
+      
+      private function init() : void
+      {
+         var enterFrame = function()
+         {
+            trace("// Event.ENTER_FRAME");
+         };
+         addEventListener(Event.ENTER_FRAME, enterFrame);
+         trace("// stage.frameRate (SWF header = 30)");
+         trace(stage.frameRate);
+         trace("// stage.frameRate = NaN;");
+         stage.frameRate = NaN;
+         trace(stage.frameRate);
+      }
+   }
+}

tests/tests/swfs/avm2/stage_framerate_nan/test.swf

@@ -0,0 +1 @@
+num_frames = 4

tests/tests/swfs/avm2/stage_framerate_nan/test.toml

@@ -0,0 +1,6 @@
+// stage.frameRate (SWF header = -43.75)
+212.25
+// stage.frameRate = -43.75;
+0.01
+// stage.frameRate = 212.25;
+212.25

tests/tests/swfs/avm2/stage_framerate_negative/output.txt

@@ -0,0 +1,28 @@
+// Test made using JPEXS Free Flash Decompiler.
+// The frame rate in the SWF header is set to -43.75.
+
+package
+{
+   import flash.display.Sprite;
+   
+   public class Test extends Sprite
+   {
+      public function Test()
+      {
+         super();
+         this.init();
+      }
+      
+      private function init() : void
+      {
+         trace("// stage.frameRate (SWF header = -43.75)");
+         trace(stage.frameRate);
+         trace("// stage.frameRate = -43.75;");
+         stage.frameRate = -43.75;
+         trace(stage.frameRate);
+         trace("// stage.frameRate = 212.25;");
+         stage.frameRate = 212.25;
+         trace(stage.frameRate);
+      }
+   }
+}

tests/tests/swfs/avm2/stage_framerate_negative/source.as

@@ -0,0 +1 @@
+num_frames = 1