Keep track of multiple layout roots

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 90 matching lines @@
 // The maximum number of updateWidgets iterations that should be done before returning.
 static const unsigned maxUpdateWidgetsIterations = 2;
 static const double resourcePriorityUpdateDelayAfterScroll = 0.250;
 
 FrameView::FrameView(LocalFrame* frame)
     : m_frame(frame)
     , m_displayMode(WebDisplayModeBrowser)
     , m_canHaveScrollbars(true)
     , m_slowRepaintObjectCount(0)
     , m_hasPendingLayout(false)
-    , m_layoutSubtreeRoot(0)
     , m_inSynchronousPostLayout(false)
     , m_postLayoutTasksTimer(this, &FrameView::postLayoutTimerFired)
     , m_updateWidgetsTimer(this, &FrameView::updateWidgetsTimerFired)
     , m_isTransparent(false)
     , m_baseBackgroundColor(Color::white)
     , m_mediaType(MediaTypeNames::screen)
     , m_overflowStatusDirty(true)
     , m_viewportRenderer(0)
     , m_wasScrolledByUser(false)
     , m_inProgrammaticScroll(false)
@@ skipping 98 matching lines @@
     visitor->trace(m_horizontalScrollbar);
     visitor->trace(m_verticalScrollbar);
     visitor->trace(m_children);
 #endif
     Widget::trace(visitor);
 }
 
 void FrameView::reset()
 {
     m_hasPendingLayout = false;
-    m_layoutSubtreeRoot = nullptr;
     m_doFullPaintInvalidation = false;
     m_layoutSchedulingEnabled = true;
     m_inPerformLayout = false;
     m_inSynchronousPostLayout = false;
     m_layoutCount = 0;
     m_nestedLayoutCount = 0;
     m_postLayoutTasksTimer.stop();
     m_updateWidgetsTimer.stop();
     m_firstLayout = true;
     m_firstLayoutCallbackPending = false;
@@ skipping 509 matching lines @@
 
 bool FrameView::isEnclosedInCompositingLayer() const
 {
     // FIXME: It's a bug that compositing state isn't always up to date when this is called. crbug.com/366314
     DisableCompositingQueryAsserts disabler;
 
     LayoutObject* frameOwnerRenderer = m_frame->ownerRenderer();
     return frameOwnerRenderer && frameOwnerRenderer->enclosingLayer()->enclosingLayerForPaintInvalidationCrossingFrameBoundaries();
 }
 
-LayoutObject* FrameView::layoutRoot(bool onlyDuringLayout) const
+static inline void countObjectsNeedingLayoutInRoot(const LayoutObject* root, unsigned& needsLayoutObjects, unsigned& totalObjects)

[dsinclair, 2015/02/27 16:12:09]

Can the root be null? If not, can we make this LayoutObject&?

 {
-    return onlyDuringLayout && layoutPending() ? nullptr : m_layoutSubtreeRoot;
+    for (const LayoutObject* o = root; o; o = o->nextInPreOrder(root)) {
+        ++totalObjects;
+        if (o->needsLayout())
+            ++needsLayoutObjects;
+    }
+}
+
+void FrameView::countObjectsNeedingLayout(unsigned& needsLayoutObjects, unsigned& totalObjects, bool& isSubtree)
+{
+    needsLayoutObjects = 0;
+    totalObjects = 0;
+    if (isSubtreeLayout()) {
+        isSubtree = true;
+        for (auto& subtreeRoot : m_layoutSubtreeRoots)
+            countObjectsNeedingLayoutInRoot(subtreeRoot, needsLayoutObjects, totalObjects);
+    } else {
+        isSubtree = false;

[Julien - ping for review, 2015/02/27 16:38:09]

IMHO that would be more readable if it was outside the branch:

isSubtree = isSubtreeLayout();

+        countObjectsNeedingLayoutInRoot(layoutView(), needsLayoutObjects, totalObjects);
+    }
+}
+
+bool FrameView::isLayoutRoot(const LayoutObject& object) const
+{
+    return m_layoutSubtreeRoots.contains(const_cast<LayoutObject*>(&object));
 }
 
 inline void FrameView::forceLayoutParentViewIfNeeded()
 {
     LayoutPart* ownerRenderer = m_frame->ownerRenderer();
     if (!ownerRenderer || !ownerRenderer->frame())
         return;
 
     LayoutBox* contentBox = embeddedContentBox();
     if (!contentBox)
@@ skipping 48 matching lines @@
 
     document->updateRenderTreeIfNeeded();
     lifecycle().advanceTo(DocumentLifecycle::StyleClean);
 }
 
 void FrameView::lineLayoutTime(double ms)
 {
     m_lineLayoutMs += ms;
 }
 
-void FrameView::performLayout(LayoutObject* rootForThisLayout, bool inSubtreeLayout)
+static void gatherDebugLayoutRects(LayoutObject& layoutRoot)
 {
+    bool isTracing;
+    TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("blink.debug.layout"), &isTracing);
+    if (!isTracing)
+        return;
+    if (!layoutRoot.enclosingLayer()->hasCompositedLayerMapping())
+        return;
+    // For access to compositedLayerMapping().
+    DisableCompositingQueryAsserts disabler;
+    GraphicsLayer* graphicsLayer = layoutRoot.enclosingLayer()->compositedLayerMapping()->mainGraphicsLayer();
+    if (!graphicsLayer)
+        return;
+
+    GraphicsLayerDebugInfo& debugInfo = graphicsLayer->debugInfo();
+
+    debugInfo.currentLayoutRects().clear();
+    for (LayoutObject* renderer = &layoutRoot; renderer; renderer = renderer->nextInPreOrder()) {
+        if (renderer->layoutDidGetCalledSinceLastFrame()) {
+            FloatQuad quad = renderer->localToAbsoluteQuad(FloatQuad(renderer->previousPaintInvalidationRect()));
+            LayoutRect rect = LayoutRect(quad.enclosingBoundingBox());
+            debugInfo.currentLayoutRects().append(rect);
+        }
+    }
+}
+
+static inline void layoutFromRootObject(LayoutObject& root)
+{
+    LayoutState layoutState(root);
+    root.layout();
+    gatherDebugLayoutRects(root);
+}
+
+void FrameView::performLayout(bool inSubtreeLayout)
+{
+    ASSERT(inSubtreeLayout || m_layoutSubtreeRoots.isEmpty());
+
     m_lineLayoutMs = 0;
     TRACE_EVENT0("blink,benchmark", "FrameView::performLayout");
     double start = WTF::currentTimeMS();
 
     ScriptForbiddenScope forbidScript;
 
     ASSERT(!isInPerformLayout());
     lifecycle().advanceTo(DocumentLifecycle::InPerformLayout);
 
     TemporaryChange<bool> changeInPerformLayout(m_inPerformLayout, true);
 
     // performLayout is the actual guts of layout().
     // FIXME: The 300 other lines in layout() probably belong in other helper functions
     // so that a single human could understand what layout() is actually doing.
 
-    LayoutState layoutState(*rootForThisLayout);
-
     forceLayoutParentViewIfNeeded();
 
-    rootForThisLayout->layout();
-    gatherDebugLayoutRects(rootForThisLayout);
+    if (inSubtreeLayout) {
+        while (m_layoutSubtreeRoots.size()) {
+            LayoutObject& root = *m_layoutSubtreeRoots.takeAny();
+            if (!root.needsLayout())
+                continue;
+            layoutFromRootObject(root);

[Julien - ping for review, 2015/02/27 16:38:09]

We could unify the 2 code paths by inserting the RenderView into the
m_layoutSubtreeRoots. This would require removing completely the concept of
subtree layout, which should be fine. This would reduce the complexity of layout
greatly but increase the layoutRoot insertion logic. It's better done in a
follow-up patch anyway.

[leviw_travelin_and_unemployed, 2015/02/27 20:09:28]

That's my ultimate goal :)

+
+            // We need to ensure that we mark up all renderers up to the LayoutView
+            // for paint invalidation. This simplifies our code as we just always
+            // do a full tree walk.
+            if (LayoutObject* container = root.container())
+                container->setMayNeedPaintInvalidation();
+        }
+    } else {
+        layoutFromRootObject(*layoutView());
+    }
 
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->updateAllImageResourcePriorities();
 
     lifecycle().advanceTo(DocumentLifecycle::AfterPerformLayout);
     int layoutMs = (WTF::currentTimeMS() - start);
     Platform::current()->histogramCustomCounts("Renderer.LayoutMs", layoutMs, 0, 1000 * 60, 50);
     // TODO(benjhayden): re-enable when safe
     // Platform::current()->histogramCustomCounts("Renderer.LineLayoutMs", m_lineLayoutMs, 0, 1000 * 60, 50);
 }
 
@@ skipping 55 matching lines @@
 
 #if !ENABLE(OILPAN)
     // If there is only one ref to this view left, then its going to be destroyed as soon as we exit,
     // so there's no point to continuing to layout
     if (protector->hasOneRef())
         return;
 #endif
 
     Document* document = m_frame->document();
     bool inSubtreeLayout = isSubtreeLayout();
-    LayoutObject* rootForThisLayout = inSubtreeLayout ? m_layoutSubtreeRoot : document->layoutView();
+
+    // FIXME: The notion of a single root for layout is no longer applicable. Remove or update this code. crbug.com/460596
+    LayoutObject* rootForThisLayout = inSubtreeLayout ? *(m_layoutSubtreeRoots.begin()) : layoutView();
     if (!rootForThisLayout) {
         // FIXME: Do we need to set m_size here?
         ASSERT_NOT_REACHED();
         return;
     }
 
     FontCachePurgePreventer fontCachePurgePreventer;
-    Layer* layer;
     {
         TemporaryChange<bool> changeSchedulingEnabled(m_layoutSchedulingEnabled, false);
 
         m_nestedLayoutCount++;
         if (!inSubtreeLayout) {
-            Document* document = m_frame->document();
+            clearLayoutSubtreeRootsAndMarkContainingBlocks();
             Node* body = document->body();
             if (body && body->renderer()) {
                 if (isHTMLFrameSetElement(*body)) {
                     body->renderer()->setChildNeedsLayout();
                 } else if (isHTMLBodyElement(*body)) {
                     if (!m_firstLayout && m_size.height() != layoutSize().height() && body->renderer()->enclosingBox()->stretchesToViewport())
                         body->renderer()->setChildNeedsLayout();
                 }
             }
         }
         updateCounters();
 
         ScrollbarMode hMode;
         ScrollbarMode vMode;
         calculateScrollbarModesForLayoutAndSetViewportRenderer(hMode, vMode);
 
         if (!inSubtreeLayout) {
             // Now set our scrollbar state for the layout.
             ScrollbarMode currentHMode = horizontalScrollbarMode();
             ScrollbarMode currentVMode = verticalScrollbarMode();
 
             if (m_firstLayout) {
                 setScrollbarsSuppressed(true);
 
                 m_doFullPaintInvalidation = true;
                 m_firstLayout = false;
                 m_firstLayoutCallbackPending = true;
                 m_lastViewportSize = layoutSize(IncludeScrollbars);
-                m_lastZoomFactor = rootForThisLayout->style()->zoom();
+                m_lastZoomFactor = layoutView()->style()->zoom();
 
                 // Set the initial vMode to AlwaysOn if we're auto.
                 if (vMode == ScrollbarAuto)
                     setVerticalScrollbarMode(ScrollbarAlwaysOn); // This causes a vertical scrollbar to appear.
                 // Set the initial hMode to AlwaysOff if we're auto.
                 if (hMode == ScrollbarAuto)
                     setHorizontalScrollbarMode(ScrollbarAlwaysOff); // This causes a horizontal scrollbar to disappear.
 
                 setScrollbarModes(hMode, vMode);
                 setScrollbarsSuppressed(false, true);
@@ skipping 15 matching lines @@
                     bodyRenderer->setChildNeedsLayout();
                 else if (rootRenderer && rootRenderer->stretchesToViewport())
                     rootRenderer->setChildNeedsLayout();
             }
 
             // We need to set m_doFullPaintInvalidation before triggering layout as LayoutObject::checkForPaintInvalidation
             // checks the boolean to disable local paint invalidations.
             m_doFullPaintInvalidation |= layoutView()->shouldDoFullPaintInvalidationForNextLayout();
         }
 
-        layer = rootForThisLayout->enclosingLayer();
+        performLayout(inSubtreeLayout);
 
-        performLayout(rootForThisLayout, inSubtreeLayout);
-
-        m_layoutSubtreeRoot = nullptr;
-        // We need to ensure that we mark up all renderers up to the LayoutView
-        // for paint invalidation. This simplifies our code as we just always
-        // do a full tree walk.
-        if (LayoutObject* container = rootForThisLayout->container())
-            container->setMayNeedPaintInvalidation();
+        ASSERT(m_layoutSubtreeRoots.isEmpty());
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
-    if (!inSubtreeLayout && !toLayoutView(rootForThisLayout)->document().printing())
+    if (!inSubtreeLayout && !document->printing())
         adjustViewSize();
 
-    layer->updateLayerPositionsAfterLayout();
+    // FIXME: Could find the common ancestor layer of all dirty subtrees and mark from there.

[dsinclair, 2015/02/27 16:12:09]

crbug link?

+    layoutView()->enclosingLayer()->updateLayerPositionsAfterLayout();
 
     layoutView()->compositor()->didLayout();
 
     m_layoutCount++;
 
-    if (AXObjectCache* cache = rootForThisLayout->document().axObjectCache()) {
-        const KURL& url = rootForThisLayout->document().url();
+    if (AXObjectCache* cache = document->axObjectCache()) {
+        const KURL& url = document->url();
         if (url.isValid() && !url.isAboutBlankURL())
-            cache->handleLayoutComplete(rootForThisLayout);
+            cache->handleLayoutComplete(document);
     }
     updateAnnotatedRegions();
 
-    ASSERT(!rootForThisLayout->needsLayout());
-
     if (document->hasListenerType(Document::OVERFLOWCHANGED_LISTENER))
         updateOverflowStatus(layoutSize().width() < contentsWidth(), layoutSize().height() < contentsHeight());
 
     scheduleOrPerformPostLayoutTasks();
 
+    // FIXME: The notion of a single root for layout is no longer applicable. Remove or update this code. crbug.com/460596
     TRACE_EVENT_END1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "Layout", "endData", InspectorLayoutEvent::endData(rootForThisLayout));
-    InspectorInstrumentation::didLayout(m_frame.get(), rootForThisLayout);
+    InspectorInstrumentation::didLayout(m_frame.get());
 
     m_nestedLayoutCount--;
     if (m_nestedLayoutCount)
         return;
 
 #if ENABLE(ASSERT)
     // Post-layout assert that nobody was re-marked as needing layout during layout.
-    document->layoutView()->assertSubtreeIsLaidOut();
+    layoutView()->assertSubtreeIsLaidOut();
 #endif
 
     // FIXME: It should be not possible to remove the FrameView from the frame/page during layout
     // however m_inPerformLayout is not set for most of this function, so none of our RELEASE_ASSERTS
     // in LocalFrame/Page will fire. One of the post-layout tasks is disconnecting the LocalFrame from
     // the page in fast/frames/crash-remove-iframe-during-object-beforeload-2.html
     // necessitating this check here.
     // ASSERT(frame()->page());
     if (frame().page())
         frame().page()->chrome().client().layoutUpdated(m_frame.get());
@@ skipping 33 matching lines @@
 
     if (m_frame->selection().isCaretBoundsDirty())
         m_frame->selection().invalidateCaretRect();
 }
 
 DocumentLifecycle& FrameView::lifecycle() const
 {
     return m_frame->document()->lifecycle();
 }
 
-void FrameView::gatherDebugLayoutRects(LayoutObject* layoutRoot)
-{
-    bool isTracing;
-    TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("blink.debug.layout"), &isTracing);
-    if (!isTracing)
-        return;
-    if (!layoutRoot->enclosingLayer()->hasCompositedLayerMapping())
-        return;
-    // For access to compositedLayerMapping().
-    DisableCompositingQueryAsserts disabler;
-    GraphicsLayer* graphicsLayer = layoutRoot->enclosingLayer()->compositedLayerMapping()->mainGraphicsLayer();
-    if (!graphicsLayer)
-        return;
-
-    GraphicsLayerDebugInfo& debugInfo = graphicsLayer->debugInfo();
-
-    debugInfo.currentLayoutRects().clear();
-    for (LayoutObject* renderer = layoutRoot; renderer; renderer = renderer->nextInPreOrder()) {
-        if (renderer->layoutDidGetCalledSinceLastFrame()) {
-            FloatQuad quad = renderer->localToAbsoluteQuad(FloatQuad(renderer->previousPaintInvalidationRect()));
-            LayoutRect rect = LayoutRect(quad.enclosingBoundingBox());
-            debugInfo.currentLayoutRects().append(rect);
-        }
-    }
-}
-
 LayoutBox* FrameView::embeddedContentBox() const
 {
     LayoutView* layoutView = this->layoutView();
     if (!layoutView)
         return nullptr;
 
     LayoutObject* firstChild = layoutView->firstChild();
     if (!firstChild || !firstChild->isBox())
         return nullptr;
 
@@ skipping 654 matching lines @@
 
 void FrameView::handleLoadCompleted()
 {
     // Once loading has completed, allow autoSize one last opportunity to
     // reduce the size of the frame.
     if (m_autoSizeInfo)
         m_autoSizeInfo->autoSizeIfNeeded();
     maintainScrollPositionAtAnchor(0);
 }
 
+void FrameView::clearLayoutSubtreeRoot(const LayoutObject* root)

[dsinclair, 2015/02/27 16:12:09]

Can this be a reference?

+{
+    m_layoutSubtreeRoots.remove(const_cast<LayoutObject*>(root));
+}
+
+void FrameView::clearLayoutSubtreeRootsAndMarkContainingBlocks()
+{
+    for (auto& iter : m_layoutSubtreeRoots)
+        iter->markContainingBlocksForLayout(false);
+    m_layoutSubtreeRoots.clear();
+}
+
 void FrameView::scheduleRelayout()
 {
     ASSERT(m_frame->view() == this);
 
-    if (isSubtreeLayout()) {
-        m_layoutSubtreeRoot->markContainingBlocksForLayout(false);
-        m_layoutSubtreeRoot = nullptr;
-    }
     if (!m_layoutSchedulingEnabled)
         return;
     if (!needsLayout())
         return;
     if (!m_frame->document()->shouldScheduleLayout())
         return;
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "InvalidateLayout", "data", InspectorInvalidateLayoutEvent::data(m_frame.get()));
 
+    clearLayoutSubtreeRootsAndMarkContainingBlocks();
+
     if (m_hasPendingLayout)
         return;
     m_hasPendingLayout = true;
 
     page()->animator().scheduleVisualUpdate(m_frame.get());
     lifecycle().ensureStateAtMost(DocumentLifecycle::StyleClean);
 }
 
-static bool isObjectAncestorContainerOf(LayoutObject* ancestor, LayoutObject* descendant)
-{
-    for (LayoutObject* r = descendant; r; r = r->container()) {
-        if (r == ancestor)
-            return true;
-    }
-    return false;
-}
-
 void FrameView::scheduleRelayoutOfSubtree(LayoutObject* relayoutRoot)
 {
     ASSERT(m_frame->view() == this);
 
     // FIXME: Should this call shouldScheduleLayout instead?
     if (!m_frame->document()->isActive())
         return;
 
     LayoutView* layoutView = this->layoutView();
     if (layoutView && layoutView->needsLayout()) {
         if (relayoutRoot)
             relayoutRoot->markContainingBlocksForLayout(false);
         return;
     }
 
-    if (layoutPending() || !m_layoutSchedulingEnabled) {
-        if (m_layoutSubtreeRoot != relayoutRoot) {
-            if (isObjectAncestorContainerOf(m_layoutSubtreeRoot, relayoutRoot)) {
-                // Keep the current root
-                relayoutRoot->markContainingBlocksForLayout(false, m_layoutSubtreeRoot);
-                ASSERT(!m_layoutSubtreeRoot->container() || !m_layoutSubtreeRoot->container()->needsLayout());
-            } else if (isSubtreeLayout() && isObjectAncestorContainerOf(relayoutRoot, m_layoutSubtreeRoot)) {
-                // Re-root at relayoutRoot
-                m_layoutSubtreeRoot->markContainingBlocksForLayout(false, relayoutRoot);
-                m_layoutSubtreeRoot = relayoutRoot;
-                ASSERT(!m_layoutSubtreeRoot->container() || !m_layoutSubtreeRoot->container()->needsLayout());
-            } else {
-                // Just do a full relayout
-                if (isSubtreeLayout())
-                    m_layoutSubtreeRoot->markContainingBlocksForLayout(false);
-                m_layoutSubtreeRoot = nullptr;
-                relayoutRoot->markContainingBlocksForLayout(false);
-            }
-        }
-    } else if (m_layoutSchedulingEnabled) {
-        m_layoutSubtreeRoot = relayoutRoot;
-        ASSERT(!m_layoutSubtreeRoot->container() || !m_layoutSubtreeRoot->container()->needsLayout());
+    if (relayoutRoot == layoutView)
+        clearLayoutSubtreeRootsAndMarkContainingBlocks();
+    else
+        m_layoutSubtreeRoots.add(relayoutRoot);
+    if (m_layoutSchedulingEnabled) {
         m_hasPendingLayout = true;
 
         page()->animator().scheduleVisualUpdate(m_frame.get());
         lifecycle().ensureStateAtMost(DocumentLifecycle::StyleClean);
     }
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "InvalidateLayout", "data", InspectorInvalidateLayoutEvent::data(m_frame.get()));
 }
 
 bool FrameView::layoutPending() const
 {
@@ skipping 2194 matching lines @@
 {
     Settings* settings = frame().settings();
     if (!settings || !settings->rootLayerScrolls())
         return this;
 
     LayoutView* layoutView = this->layoutView();
     return layoutView ? layoutView->scrollableArea() : nullptr;
 }
 
 } // namespace blink