Throttle rendering pipeline for invisible frames

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1513 matching lines @@
         return false;
     return true;
 }
 
 void Document::scheduleLayoutTreeUpdate()
 {
     ASSERT(!hasPendingStyleRecalc());
     ASSERT(shouldScheduleLayoutTreeUpdate());
     ASSERT(needsLayoutTreeUpdate());
 
-    page()->animator().scheduleVisualUpdate();
+    if (!view() || !view()->shouldThrottleRendering())

[esprehn, 2015/10/14 22:09:46]

we shouldn't be able to get here without a view(), it would hit one of the
asserts above because the document wouldn't be isActive(). no need to null check
view()

[Sami, 2015/10/16 16:48:08]

Thanks, I didn't realize isActive() implies view().

+        page()->animator().scheduleVisualUpdate();
     m_lifecycle.ensureStateAtMost(DocumentLifecycle::VisualUpdatePending);
 
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "ScheduleStyleRecalculation", TRACE_EVENT_SCOPE_THREAD, "data", InspectorRecalculateStylesEvent::data(frame()));
     InspectorInstrumentation::didScheduleStyleRecalculation(this);
 
     ++m_styleVersion;
 }
 
 bool Document::hasPendingForcedStyleRecalc() const
 {
@@ skipping 169 matching lines @@
 
 void Document::updateLayoutTree(StyleRecalcChange change)
 {
     ASSERT(isMainThread());
 
     ScriptForbiddenScope forbidScript;
 
     if (!view() || !isActive())
         return;
 
+    if (view()->shouldThrottleRenderingIfAllowed())
+        return;
+
     if (change != Force && !needsLayoutTreeUpdate()) {
         ASSERT(lifecycle().state() != DocumentLifecycle::VisualUpdatePending);
         return;
     }
 
     if (inStyleRecalc())
         return;
 
     // Entering here from inside layout or paint would be catastrophic since recalcStyle can
     // tear down the layout tree or (unfortunately) run script. Kill the whole layoutObject if
@@ skipping 47 matching lines @@
     TRACE_EVENT_END1("blink,devtools.timeline", "UpdateLayoutTree", "elementCount", m_styleRecalcElementCounter);
     InspectorInstrumentation::didRecalculateStyle(cookie, m_styleRecalcElementCounter);
 
 #if ENABLE(ASSERT)
     assertLayoutTreeUpdated(*this);
 #endif
 }
 
 void Document::updateStyle(StyleRecalcChange change)
 {
+    if (view() && view()->shouldThrottleRenderingIfAllowed())

[esprehn, 2015/10/14 22:09:46]

you must have a view here, no need to null check, you can add an
ASSERT(isActive()) if you want

[Sami, 2015/10/16 16:48:08]

Done.

+        return;
+
     TRACE_EVENT_BEGIN0("blink,blink_style", "Document::updateStyle");
     unsigned initialResolverAccessCount = styleEngine().resolverAccessCount();
 
     HTMLFrameOwnerElement::UpdateSuspendScope suspendWidgetHierarchyUpdates;
     m_lifecycle.advanceTo(DocumentLifecycle::InStyleRecalc);
 
     NthIndexCache nthIndexCache(*this);
 
     if (styleChangeType() >= SubtreeStyleChange)
         change = Force;
@@ skipping 97 matching lines @@
     RefPtrWillBeRawPtr<FrameView> frameView = view();
     if (frameView && frameView->isInPerformLayout()) {
         // View layout should not be re-entrant.
         ASSERT_NOT_REACHED();
         return;
     }
 
     if (HTMLFrameOwnerElement* owner = ownerElement())
         owner->document().updateLayout();
 
+    lifecycle().setThrottlingMode(DocumentLifecycle::ThrottlingMode::Disallow);

[esprehn, 2015/10/14 22:09:45]

Lets add a scope object for this instead of manual setting/unsetting.

DocumentLifecycle::ThrottleScope

[Sami, 2015/10/16 16:48:08]

Much cleaner, done. In case it isn't obvious, I made the scope signify that
throttling is *not* allowed because that is generally what call sites want to do
(e.g., doing a synchronous style recalc inside a context that otherwise allows
throttling).

     updateLayoutTreeIfNeeded();
 
-    if (!isActive())
-        return;
+    if (isActive()) {
+        if (frameView->needsLayout())
+            frameView->layout();
 
-    if (frameView->needsLayout())
-        frameView->layout();
+        if (lifecycle().state() < DocumentLifecycle::LayoutClean)
+            lifecycle().advanceTo(DocumentLifecycle::LayoutClean);
+    }
 
-    if (lifecycle().state() < DocumentLifecycle::LayoutClean)
-        lifecycle().advanceTo(DocumentLifecycle::LayoutClean);
+    lifecycle().setThrottlingMode(DocumentLifecycle::ThrottlingMode::Allow);
 }
 
 void Document::layoutUpdated()
 {
     markers().updateRenderedRectsForMarkers();
 
     // The layout system may perform layouts with pending stylesheets. When
     // recording first layout time, we ignore these layouts, since painting is
     // suppressed for them. We're interested in tracking the time of the
     // first real or 'paintable' layout.
@@ skipping 3840 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     Document::WeakDocumentSet& set = Document::liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif