From 21c408e0d5fe4c24ff2b396f251697d7569d4332 Mon Sep 17 00:00:00 2001
From: Paul Rouget <me@paulrouget.com>
Date: Fri, 6 Mar 2020 06:20:11 +0100
Subject: [PATCH] Stop embedder calls and fake rAF when window not visible

---
 components/compositing/compositor.rs | 4 +---
 components/script/dom/document.rs    | 5 ++---
 components/script/dom/window.rs      | 8 ++++++++
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/components/compositing/compositor.rs b/components/compositing/compositor.rs
index aa58e10b05f..6d5ae4918c3 100644
--- a/components/compositing/compositor.rs
+++ b/components/compositing/compositor.rs
@@ -483,9 +483,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                 ShutdownState::NotShuttingDown,
             ) => {
                 self.pipeline_details(pipeline_id).visible = visible;
-                if visible {
-                    self.process_animations();
-                }
+                self.process_animations();
             },
 
             (Msg::PipelineExited(pipeline_id, sender), _) => {
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 1253202ed8b..303c51660f0 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -1636,11 +1636,10 @@ impl Document {
             .borrow_mut()
             .push((ident, Some(callback)));
 
-        // TODO: Should tick animation only when document is visible
-
         // If we are running 'fake' animation frames, we unconditionally
         // set up a one-shot timer for script to execute the rAF callbacks.
-        if self.is_faking_animation_frames() {
+        if self.is_faking_animation_frames() && self.window().visible() {
+            warn!("Scheduling fake animation frame. Animation frames tick too fast.");
             let callback = FakeRequestAnimationFrameCallback {
                 document: Trusted::new(self),
             };
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index e06eb243856..6b3b51f9a79 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -332,6 +332,8 @@ pub struct Window {
     /// A mechanism to force the compositor to process events.
     #[ignore_malloc_size_of = "traits are cumbersome"]
     event_loop_waker: Option<Box<dyn EventLoopWaker>>,
+
+    visible: Cell<bool>,
 }
 
 impl Window {
@@ -2185,6 +2187,7 @@ impl Window {
 
     /// Slow down/speed up timers based on visibility.
     pub fn alter_resource_utilization(&self, visible: bool) {
+        self.visible.set(visible);
         if visible {
             self.upcast::<GlobalScope>().speed_up_timers();
         } else {
@@ -2192,6 +2195,10 @@ impl Window {
         }
     }
 
+    pub fn visible(&self) -> bool {
+        self.visible.get()
+    }
+
     pub fn unminified_js_dir(&self) -> Option<String> {
         self.unminified_js_dir.borrow().clone()
     }
@@ -2339,6 +2346,7 @@ impl Window {
             replace_surrogates,
             player_context,
             event_loop_waker,
+            visible: Cell::new(true),
         });
 
         unsafe { WindowBinding::Wrap(JSContext::from_ptr(runtime.cx()), win) }