From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: David Sanders <dsanders11@ucsbalum.com>
Date: Wed, 8 Jan 2025 23:53:27 -0800
Subject: Revert "Code Health: Clean up stale MacWebContentsOcclusion"

Chrome has removed this WebContentsOcclusion feature flag upstream,
which is now causing our visibility tests to break. This patch
restores the legacy occlusion behavior to ensure the roll can continue
while we debug the issue.

This patch can be removed when the root cause because the visibility
specs failing on MacOS only is debugged and fixed. It should be removed
before Electron 35's stable date.

Refs: https://chromium-review.googlesource.com/c/chromium/src/+/6078344

This partially (leaves the removal of the feature flag) reverts
ef865130abd5539e7bce12308659b19980368f12.

diff --git a/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.h b/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.h
index 428902f90950b2e9434c8a624a313268ebb80cd4..afcc3bc481be6a16119f7e2af647276cb0dafa1e 100644
--- a/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.h
+++ b/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.h
@@ -12,6 +12,8 @@
 #import "content/app_shim_remote_cocoa/web_contents_view_cocoa.h"
 #include "content/common/web_contents_ns_view_bridge.mojom.h"
 
+extern CONTENT_EXPORT const base::FeatureParam<bool>
+    kEnhancedWindowOcclusionDetection;
 extern CONTENT_EXPORT const base::FeatureParam<bool>
     kDisplaySleepAndAppHideDetection;
 
diff --git a/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.mm b/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.mm
index 32523e6a6f800de3917d18825f94c66ef4ea4388..634d68b9a2840d7c9e7c3b5e23d8b1b8ac02456b 100644
--- a/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.mm
+++ b/content/app_shim_remote_cocoa/web_contents_occlusion_checker_mac.mm
@@ -19,6 +19,12 @@
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/common/content_client.h"
 
+using features::kMacWebContentsOcclusion;
+
+// Experiment features.
+const base::FeatureParam<bool> kEnhancedWindowOcclusionDetection{
+    &kMacWebContentsOcclusion, "EnhancedWindowOcclusionDetection", false};
+
 namespace {
 
 NSString* const kWindowDidChangePositionInWindowList =
@@ -127,7 +133,8 @@ - (void)dealloc {
 
 - (BOOL)isManualOcclusionDetectionEnabled {
   return [WebContentsOcclusionCheckerMac
-      manualOcclusionDetectionSupportedForCurrentMacOSVersion];
+             manualOcclusionDetectionSupportedForCurrentMacOSVersion] &&
+         kEnhancedWindowOcclusionDetection.Get();
 }
 
 // Alternative implementation of orderWindow:relativeTo:. Replaces
diff --git a/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm b/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm
index 2991489fae8a4eecad97b1ecb2271f096d9a9229..93b7aa620ad1da250ac06e3383ca689732de12cd 100644
--- a/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm
+++ b/content/app_shim_remote_cocoa/web_contents_view_cocoa.mm
@@ -29,6 +29,7 @@
 #include "ui/resources/grit/ui_resources.h"
 
 using content::DropData;
+using features::kMacWebContentsOcclusion;
 using remote_cocoa::mojom::DraggingInfo;
 using remote_cocoa::mojom::SelectionDirection;
 
@@ -126,12 +127,15 @@ @implementation WebContentsViewCocoa {
 
   gfx::Rect _windowControlsOverlayRect;
 
+  BOOL _inFullScreenTransition;
   BOOL _willSetWebContentsOccludedAfterDelay;
 }
 
 + (void)initialize {
-  // Create the WebContentsOcclusionCheckerMac shared instance.
-  [WebContentsOcclusionCheckerMac sharedInstance];
+  if (base::FeatureList::IsEnabled(kMacWebContentsOcclusion)) {
+    // Create the WebContentsOcclusionCheckerMac shared instance.
+    [WebContentsOcclusionCheckerMac sharedInstance];
+  }
 }
 
 - (instancetype)initWithViewsHostableView:(ui::ViewsHostableView*)v {
@@ -442,6 +446,7 @@ - (void)updateWebContentsVisibility:
     (remote_cocoa::mojom::Visibility)visibility {
   using remote_cocoa::mojom::Visibility;
 
+  DCHECK(base::FeatureList::IsEnabled(kMacWebContentsOcclusion));
   if (!_host)
     return;
 
@@ -487,6 +492,20 @@ - (void)updateWebContentsVisibility {
   [self updateWebContentsVisibility:visibility];
 }
 
+- (void)legacyUpdateWebContentsVisibility {
+  using remote_cocoa::mojom::Visibility;
+  if (!_host || _inFullScreenTransition)
+    return;
+  Visibility visibility = Visibility::kVisible;
+  if ([self isHiddenOrHasHiddenAncestor] || ![self window])
+    visibility = Visibility::kHidden;
+  else if ([[self window] occlusionState] & NSWindowOcclusionStateVisible)
+    visibility = Visibility::kVisible;
+  else
+    visibility = Visibility::kOccluded;
+  _host->OnWindowVisibilityChanged(visibility);
+}
+
 - (void)resizeSubviewsWithOldSize:(NSSize)oldBoundsSize {
   // Subviews do not participate in auto layout unless the the size this view
   // changes. This allows RenderWidgetHostViewMac::SetBounds(..) to select a
@@ -509,11 +528,39 @@ - (void)viewWillMoveToWindow:(NSWindow*)newWindow {
 
   NSWindow* oldWindow = [self window];
 
+  if (base::FeatureList::IsEnabled(kMacWebContentsOcclusion)) {
+    if (oldWindow) {
+      [notificationCenter
+          removeObserver:self
+                    name:NSWindowDidChangeOcclusionStateNotification
+                  object:oldWindow];
+    }
+
+    if (newWindow) {
+      [notificationCenter
+          addObserver:self
+             selector:@selector(windowChangedOcclusionState:)
+                 name:NSWindowDidChangeOcclusionStateNotification
+               object:newWindow];
+    }
+
+    return;
+  }
+
+  _inFullScreenTransition = NO;
   if (oldWindow) {
-    [notificationCenter
-        removeObserver:self
-                  name:NSWindowDidChangeOcclusionStateNotification
-                object:oldWindow];
+    NSArray* notificationsToRemove = @[
+      NSWindowDidChangeOcclusionStateNotification,
+      NSWindowWillEnterFullScreenNotification,
+      NSWindowDidEnterFullScreenNotification,
+      NSWindowWillExitFullScreenNotification,
+      NSWindowDidExitFullScreenNotification
+    ];
+    for (NSString* notificationName in notificationsToRemove) {
+      [notificationCenter removeObserver:self
+                                    name:notificationName
+                                  object:oldWindow];
+    }
   }
 
   if (newWindow) {
@@ -521,26 +568,66 @@ - (void)viewWillMoveToWindow:(NSWindow*)newWindow {
                            selector:@selector(windowChangedOcclusionState:)
                                name:NSWindowDidChangeOcclusionStateNotification
                              object:newWindow];
+    // The fullscreen transition causes spurious occlusion notifications.
+    // See https://crbug.com/1081229
+    [notificationCenter addObserver:self
+                           selector:@selector(fullscreenTransitionStarted:)
+                               name:NSWindowWillEnterFullScreenNotification
+                             object:newWindow];
+    [notificationCenter addObserver:self
+                           selector:@selector(fullscreenTransitionComplete:)
+                               name:NSWindowDidEnterFullScreenNotification
+                             object:newWindow];
+    [notificationCenter addObserver:self
+                           selector:@selector(fullscreenTransitionStarted:)
+                               name:NSWindowWillExitFullScreenNotification
+                             object:newWindow];
+    [notificationCenter addObserver:self
+                           selector:@selector(fullscreenTransitionComplete:)
+                               name:NSWindowDidExitFullScreenNotification
+                             object:newWindow];
   }
 }
 
 - (void)windowChangedOcclusionState:(NSNotification*)aNotification {
-  // Only respond to occlusion notifications sent by the occlusion checker.
-  NSDictionary* userInfo = [aNotification userInfo];
-  NSString* occlusionCheckerKey = [WebContentsOcclusionCheckerMac className];
-  if (userInfo[occlusionCheckerKey] != nil)
-    [self updateWebContentsVisibility];
+  if (!base::FeatureList::IsEnabled(kMacWebContentsOcclusion)) {
+    [self legacyUpdateWebContentsVisibility];
+    return;
+  }
+}
+
+- (void)fullscreenTransitionStarted:(NSNotification*)notification {
+  _inFullScreenTransition = YES;
+}
+
+- (void)fullscreenTransitionComplete:(NSNotification*)notification {
+  _inFullScreenTransition = NO;
 }
 
 - (void)viewDidMoveToWindow {
+  if (!base::FeatureList::IsEnabled(kMacWebContentsOcclusion)) {
+    [self legacyUpdateWebContentsVisibility];
+    return;
+  }
+
   [self updateWebContentsVisibility];
 }
 
 - (void)viewDidHide {
+  if (!base::FeatureList::IsEnabled(kMacWebContentsOcclusion)) {
+    [self legacyUpdateWebContentsVisibility];
+    return;
+  }
+
   [self updateWebContentsVisibility];
 }
 
 - (void)viewDidUnhide {
+  if (!base::FeatureList::IsEnabled(kMacWebContentsOcclusion)) {
+    [self legacyUpdateWebContentsVisibility];
+    return;
+  }
+
   [self updateWebContentsVisibility];
 }
 
diff --git a/content/common/features.cc b/content/common/features.cc
index 2f413423e29bfab95c2527f6a25cbd69da6911c1..2d144b8b81b5bcf6a01be4afed76489498063f34 100644
--- a/content/common/features.cc
+++ b/content/common/features.cc
@@ -256,6 +256,14 @@ BASE_FEATURE(kIOSurfaceCapturer,
              base::FEATURE_ENABLED_BY_DEFAULT);
 #endif
 
+// Feature that controls whether WebContentsOcclusionChecker should handle
+// occlusion notifications.
+#if BUILDFLAG(IS_MAC)
+BASE_FEATURE(kMacWebContentsOcclusion,
+             "MacWebContentsOcclusion",
+             base::FEATURE_ENABLED_BY_DEFAULT);
+#endif
+
 // If this feature is enabled, media-device enumerations use a cache that is
 // invalidated upon notifications sent by base::SystemMonitor. If disabled, the
 // cache is considered invalid on every enumeration request.
diff --git a/content/common/features.h b/content/common/features.h
index 9e2bcef76f5698c1908a0b8173b4d71c6b821bad..38e7bd60ff0fc87540ef22d29f33e8d607966100 100644
--- a/content/common/features.h
+++ b/content/common/features.h
@@ -67,6 +67,9 @@ CONTENT_EXPORT BASE_DECLARE_FEATURE(kInterestGroupUpdateIfOlderThan);
 #if BUILDFLAG(IS_MAC)
 CONTENT_EXPORT BASE_DECLARE_FEATURE(kIOSurfaceCapturer);
 #endif
+#if BUILDFLAG(IS_MAC)
+CONTENT_EXPORT BASE_DECLARE_FEATURE(kMacWebContentsOcclusion);
+#endif
 CONTENT_EXPORT BASE_DECLARE_FEATURE(kMediaDevicesSystemMonitorCache);
 CONTENT_EXPORT BASE_DECLARE_FEATURE(kMediaStreamTrackTransfer);
 CONTENT_EXPORT BASE_DECLARE_FEATURE(kMojoDedicatedThread);
