From fa2fdbe24ea1e69eed8010b38edca6106a703ef7 Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Thu, 19 Sep 2024 21:35:28 +0200
Subject: [PATCH] [Pale-Moon] Issue #1972 - Implement ghostbuster

---
 application/palemoon/app/profile/palemoon.js  |  3 ++
 .../palemoon/base/content/tabbrowser.xml      |  7 ++++
 .../palemoon/components/nsBrowserGlue.js      | 33 +++++++++++++++++++
 3 files changed, 43 insertions(+)

diff --git a/application/palemoon/app/profile/palemoon.js b/application/palemoon/app/profile/palemoon.js
index c2e1cd2cd5..0aba8f1074 100644
--- a/application/palemoon/app/profile/palemoon.js
+++ b/application/palemoon/app/profile/palemoon.js
@@ -501,6 +501,9 @@ pref("javascript.options.showInConsole",          true);
 pref("general.warnOnAboutConfig",                 false);
 #endif
 
+// Enable unlinking of ghost windows so they can be garbage collected.
+pref("browser.ghostbuster.enabled",               true);
+
 // This is the pref to control the location bar, change this to true to 
 // force this - this makes the origin of popup windows more obvious to avoid
 // spoofing. We would rather not do it by default because it affects UE for web
diff --git a/application/palemoon/base/content/tabbrowser.xml b/application/palemoon/base/content/tabbrowser.xml
index 52e39d898b..14cd720f64 100644
--- a/application/palemoon/base/content/tabbrowser.xml
+++ b/application/palemoon/base/content/tabbrowser.xml
@@ -2134,6 +2134,13 @@
             var browser = this.getBrowserForTab(aTab);
             this._outerWindowIDBrowserMap.delete(browser.outerWindowID);
 
+            if (Services.prefs.getBoolPref("browser.ghostbuster.enabled", true)) {
+              Cu.unlinkGhostWindows();
+#ifdef DEBUG
+              dump("Unlinking ghost windows has run on tab close.\n");
+#endif
+            }
+
             // Because of the way XBL works (fields just set JS
             // properties on the element) and the code we have in place
             // to preserve the JS objects for any elements that have
diff --git a/application/palemoon/components/nsBrowserGlue.js b/application/palemoon/components/nsBrowserGlue.js
index 958475a29e..b66881dbf6 100644
--- a/application/palemoon/components/nsBrowserGlue.js
+++ b/application/palemoon/components/nsBrowserGlue.js
@@ -62,6 +62,10 @@ const BOOKMARKS_BACKUP_INTERVAL = 86400 * 1000;
 // Maximum number of backups to create.  Old ones will be purged.
 const BOOKMARKS_BACKUP_MAX_BACKUPS = 10;
 
+// Use users' idle time to unlink ghost windows and clean up memory.
+// Trigger this by default every 5 minutes.
+const GHOSTBUSTER_INTERVAL = 5 * 60;
+
 // Factory object
 const BrowserGlueServiceFactory = {
   _instance: null,
@@ -82,6 +86,10 @@ function BrowserGlue() {
                                      "@mozilla.org/widget/idleservice;1",
                                      "nsIIdleService");
 
+  XPCOMUtils.defineLazyServiceGetter(this, "_ghostBusterService",
+                                     "@mozilla.org/widget/idleservice;1",
+                                     "nsIIdleService");
+
   XPCOMUtils.defineLazyGetter(this, "_distributionCustomizer", function() {
                                 Cu.import("resource:///modules/distribution.js");
                                 return new DistributionCustomizer();
@@ -109,6 +117,7 @@ BrowserGlue.prototype = {
   _isPlacesShutdownObserver: false,
   _isPlacesDatabaseLocked: false,
   _migrationImportsDefaultBookmarks: false,
+  _isGhostBusterObserver: false,
 
   _setPrefToSaveSession: function(aForce) {
     if (!this._saveSession && !aForce) {
@@ -241,6 +250,15 @@ BrowserGlue.prototype = {
         if (this._idleService.idleTime > BOOKMARKS_BACKUP_IDLE_TIME * 1000) {
           this._backupBookmarks();
         }
+        if (this._ghostBusterService.idleTime > GHOSTBUSTER_INTERVAL * 1000) {
+          if (Services.prefs.getBoolPref("browser.ghostbuster.enabled", true)) {
+            Cu.unlinkGhostWindows();
+            Cu.forceGC();
+#ifdef DEBUG
+            dump("Unlinking ghost windows + GC has run on idle.\n");
+#endif
+          }
+        }
         break;
       case "distribution-customization-complete":
         Services.obs.removeObserver(this, "distribution-customization-complete");
@@ -623,6 +641,13 @@ BrowserGlue.prototype = {
     DateTimePickerHelper.init();
 
     this._trackSlowStartup();
+
+    // Initialize ghost window idle observer.
+    if (!this._isGhostBusterObserver) {
+      this._ghostBusterService.addIdleObserver(this, GHOSTBUSTER_INTERVAL);
+      // Prevent re-entry.
+      this._isGhostBusterObserver = true;
+    }
   },
 
   /**
@@ -639,6 +664,14 @@ BrowserGlue.prototype = {
     FormValidationHandler.uninit();
     AutoCompletePopup.uninit();
     this._dispose();
+
+    // Shut down ghost window idle observer.
+    if (this._isGhostBusterObserver) {
+      this._ghostBusterService.removeIdleObserver(this, GHOSTBUSTER_INTERVAL);
+      this._isGhostBusterObserver = false;
+    }
+    // Do one final unlink to combat shutdown issues.
+    Cu.unlinkGhostWindows();
   },
 
   // All initial windows have opened.