fix: disable background throttling also in the viz::DisplayScheduler (#38924)

* fix: disable background throttling also in the `viz::DisplayScheduler`

`viz::DisplayScheduler` is responsible for drawing and swapping frames
in the `DisplayScheduler::DrawAndSwap` which is called from the
`DisplayScheduler::AttemptDrawAndSwap` if the `DisplayScheduler::ShouldDraw`
returns true. `ShouldDraw` depends on the `DisplayScheduler` visibility
and when it is not visible then it returns false.

In order to keep producing frames, disabling `backgroundThrottling`
should also prevent changing `DisplayScheduler` visibility to false.

`DisplayScheduler` lives in the `ui::Compositor` where every
`electron::NativewWindow` has its own `Compositor`. `electron::NativewWindow`
may be host of the multiple `electron::api::WebContents` instances which may
have different `WebPreferences` settings. Therefore if at least one
of the `WebContents` requires disabling throttling then all other `WebContents`
using the same window will have it disabled in the `ui::Compositor`.

BREAKING CHANGE:
`backgroundThrottling` set to false will disable frames throttling
in the `BrowserWindow` for all `WebContents` displayed by it.

Close: [#31016](https://github.com/electron/electron/issues/31016)

* fixup! fix: disable background throttling also in the `viz::DisplayScheduler`

* fixup! fix: disable background throttling also in the `viz::DisplayScheduler`

* fixup! fix: disable background throttling also in the `viz::DisplayScheduler`

---------

Co-authored-by: John Kleinschmidt <jkleinsc@electronjs.org>

shell/browser/api/electron_api_web_contents.cc

@@ -1029,6 +1029,9 @@ void WebContents::InitWithWebContents(
 }
 
 WebContents::~WebContents() {
+  if (owner_window_) {
+    owner_window_->RemoveBackgroundThrottlingSource(this);
+  }
   if (web_contents()) {
     content::RenderViewHost* host = web_contents()->GetRenderViewHost();
     if (host)
@@ -2226,10 +2229,15 @@ void WebContents::SetOwnerWindow(NativeWindow* owner_window) {
 
 void WebContents::SetOwnerWindow(content::WebContents* web_contents,
                                  NativeWindow* owner_window) {
+  if (owner_window_) {
+    owner_window_->RemoveBackgroundThrottlingSource(this);
+  }
+
   if (owner_window) {
     owner_window_ = owner_window->GetWeakPtr();
     NativeWindowRelay::CreateForWebContents(web_contents,
                                             owner_window->GetWeakPtr());
+    owner_window_->AddBackgroundThrottlingSource(this);
   } else {
     owner_window_ = nullptr;
     web_contents->RemoveUserData(NativeWindowRelay::UserDataKey());
@@ -2283,6 +2291,10 @@ bool WebContents::GetBackgroundThrottling() const {
 void WebContents::SetBackgroundThrottling(bool allowed) {
   background_throttling_ = allowed;
 
+  if (owner_window_) {
+    owner_window_->UpdateBackgroundThrottlingState();
+  }
+
   auto* rfh = web_contents()->GetPrimaryMainFrame();
   if (!rfh)
     return;

shell/browser/api/electron_api_web_contents.h

@@ -36,6 +36,7 @@
 #include "printing/buildflags/buildflags.h"
 #include "shell/browser/api/frame_subscriber.h"
 #include "shell/browser/api/save_page_handler.h"
+#include "shell/browser/background_throttling_source.h"
 #include "shell/browser/event_emitter_mixin.h"
 #include "shell/browser/extended_web_contents_observer.h"
 #include "shell/browser/ui/inspectable_web_contents.h"
@@ -107,7 +108,8 @@ class WebContents : public ExclusiveAccessContext,
                     public content::WebContentsDelegate,
                     public content::RenderWidgetHost::InputEventObserver,
                     public InspectableWebContentsDelegate,
-                    public InspectableWebContentsViewDelegate {
+                    public InspectableWebContentsViewDelegate,
+                    public BackgroundThrottlingSource {
  public:
   enum class Type {
     kBackgroundPage,  // An extension background page.
@@ -160,7 +162,7 @@ class WebContents : public ExclusiveAccessContext,
   void Close(absl::optional<gin_helper::Dictionary> options);
   base::WeakPtr<WebContents> GetWeakPtr() { return weak_factory_.GetWeakPtr(); }
 
-  bool GetBackgroundThrottling() const;
+  bool GetBackgroundThrottling() const override;
   void SetBackgroundThrottling(bool allowed);
   int GetProcessID() const;
   base::ProcessId GetOSProcessID() const;

shell/browser/background_throttling_source.h

@@ -0,0 +1,18 @@
+// Copyright 2023 OpenFin. All rights reserved.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ELECTRON_SHELL_BROWSER_BACKGROUND_THROTTLING_SOURCE
+#define ELECTRON_SHELL_BROWSER_BACKGROUND_THROTTLING_SOURCE
+
+namespace electron {
+
+class BackgroundThrottlingSource {
+ public:
+  virtual ~BackgroundThrottlingSource() = default;
+  virtual bool GetBackgroundThrottling() const = 0;
+};
+
+}  // namespace electron
+
+#endif  // ELECTRON_SHELL_BROWSER_BACKGROUND_THROTTLING_SOURCE

shell/browser/native_window.cc

@@ -14,6 +14,7 @@
 #include "base/values.h"
 #include "content/public/browser/web_contents_user_data.h"
 #include "include/core/SkColor.h"
+#include "shell/browser/background_throttling_source.h"
 #include "shell/browser/browser.h"
 #include "shell/browser/native_window_features.h"
 #include "shell/browser/ui/drag_util.h"
@@ -24,6 +25,7 @@
 #include "shell/common/options_switches.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/base/hit_test.h"
+#include "ui/compositor/compositor.h"
 #include "ui/views/widget/widget.h"
 
 #if !BUILDFLAG(IS_MAC)
@@ -767,6 +769,37 @@ void NativeWindow::RemoveDraggableRegionProvider(
       [&provider](DraggableRegionProvider* p) { return p == provider; });
 }
 
+void NativeWindow::AddBackgroundThrottlingSource(
+    BackgroundThrottlingSource* source) {
+  auto result = background_throttling_sources_.insert(source);
+  DCHECK(result.second) << "Added already stored BackgroundThrottlingSource.";
+  UpdateBackgroundThrottlingState();
+}
+
+void NativeWindow::RemoveBackgroundThrottlingSource(
+    BackgroundThrottlingSource* source) {
+  auto result = background_throttling_sources_.erase(source);
+  DCHECK(result == 1)
+      << "Tried to remove non existing BackgroundThrottlingSource.";
+  UpdateBackgroundThrottlingState();
+}
+
+void NativeWindow::UpdateBackgroundThrottlingState() {
+  if (!GetWidget() || !GetWidget()->GetCompositor()) {
+    return;
+  }
+  bool enable_background_throttling = true;
+  for (const auto* background_throttling_source :
+       background_throttling_sources_) {
+    if (!background_throttling_source->GetBackgroundThrottling()) {
+      enable_background_throttling = false;
+      break;
+    }
+  }
+  GetWidget()->GetCompositor()->SetBackgroundThrottling(
+      enable_background_throttling);
+}
+
 views::Widget* NativeWindow::GetWidget() {
   return widget();
 }

shell/browser/native_window.h

@@ -47,6 +47,7 @@ class PersistentDictionary;
 namespace electron {
 
 class ElectronMenuModel;
+class BackgroundThrottlingSource;
 class NativeBrowserView;
 
 namespace api {
@@ -401,6 +402,17 @@ class NativeWindow : public base::SupportsUserData,
 
   bool IsTranslucent() const;
 
+  // Adds |source| to |background_throttling_sources_|, triggers update of
+  // background throttling state.
+  void AddBackgroundThrottlingSource(BackgroundThrottlingSource* source);
+  // Removes |source| to |background_throttling_sources_|, triggers update of
+  // background throttling state.
+  void RemoveBackgroundThrottlingSource(BackgroundThrottlingSource* source);
+  // Updates `ui::Compositor` background throttling state based on
+  // |background_throttling_sources_|. If at least one of the sources disables
+  // throttling, then throttling in the `ui::Compositor` will be disabled.
+  void UpdateBackgroundThrottlingState();
+
  protected:
   friend class api::BrowserView;
 
@@ -495,6 +507,8 @@ class NativeWindow : public base::SupportsUserData,
   // Observers of this window.
   base::ObserverList<NativeWindowObserver> observers_;
 
+  std::set<BackgroundThrottlingSource*> background_throttling_sources_;
+
   // Accessible title.
   std::u16string accessible_title_;