Add infrastructure for partial layouts

Source/core/page/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 161 matching lines @@
     , m_isTrackingRepaints(false)
     , m_shouldUpdateWhileOffscreen(true)
     , m_deferSetNeedsLayouts(0)
     , m_setNeedsLayoutWasDeferred(false)
     , m_scrollCorner(0)
     , m_shouldAutoSize(false)
     , m_inAutoSize(false)
     , m_didRunAutosize(false)
     , m_hasSoftwareFilters(false)
     , m_visibleContentScaleFactor(1)
+    , m_canStopPartialLayout(false)
+    , m_stopLayoutAtRenderer(0)
 {
     init();
 
     // FIXME: Can m_frame ever be null here?
     if (!m_frame)
         return;
 
     Page* page = m_frame->page();
     if (!page)
         return;
@@ skipping 645 matching lines @@
 void FrameView::layout(bool allowSubtree)
 {
     // We should never layout a Document which is not in a Frame.
     ASSERT(m_frame);
     ASSERT(m_frame->view() == this);
     ASSERT(m_frame->page());
 
     if (m_inLayout)
         return;
 
+    if (m_canStopPartialLayout) {
+        resetPartialLayoutState();
+        return;
+    }
+    //ASSERT(!m_canStopPartialLayout);
+
     TRACE_EVENT0("webkit", "FrameView::layout");
     TRACE_EVENT_SCOPED_SAMPLING_STATE("Blink", "Layout");
 
     // Protect the view from being deleted during layout (in recalcStyle)
     RefPtr<FrameView> protector(this);
 
     // Every scroll that happens during layout is programmatic.
     TemporaryChange<bool> changeInProgrammaticScroll(m_inProgrammaticScroll, true);
 
     m_layoutTimer.stop();
@@ skipping 146 matching lines @@
 
             endDeferredRepaints();
             m_inLayout = false;
 
             if (inSubtreeLayout)
                 rootForThisLayout->view()->popLayoutState(rootForThisLayout);
         }
         m_layoutRoot = 0;
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
+    if (m_canStopPartialLayout) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
     bool neededFullRepaint = m_doFullRepaint;
 
     if (!inSubtreeLayout && !toRenderView(rootForThisLayout)->printing())
         adjustViewSize();
 
     m_doFullRepaint = neededFullRepaint;
 
     // Now update the positions of all layers.
     beginDeferredRepaints();
     if (m_doFullRepaint)
         rootForThisLayout->view()->repaint(); // FIXME: This isn't really right, since the RenderView doesn't fully encompass the visibleContentRect(). It just happens
                                  // to work out most of the time, since first layouts and printing don't have you scrolled anywhere.
 
     layer->updateLayerPositionsAfterLayout(renderView()->layer(), updateLayerPositionFlags(layer, inSubtreeLayout, m_doFullRepaint));
 
     endDeferredRepaints();
 
     updateCompositingLayersAfterLayout();
 
     m_layoutCount++;
 
     if (AXObjectCache* cache = rootForThisLayout->document()->existingAXObjectCache())
         cache->postNotification(rootForThisLayout, AXObjectCache::AXLayoutComplete, true);
     updateAnnotatedRegions();
 
+    if (m_canStopPartialLayout) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
     layoutLazyBlocks();
 
-    ASSERT(!rootForThisLayout->needsLayout());
+    if (m_canStopPartialLayout) {
+        // Reset partial layout state post-layout.
+        resetPartialLayoutState();
+        return;
+    }
+
+    if (!m_canStopPartialLayout)
+        ASSERT(!rootForThisLayout->needsLayout());
 
     updateCanBlitOnScrollRecursively();
 
     if (document->hasListenerType(Document::OVERFLOWCHANGED_LISTENER))
         updateOverflowStatus(layoutWidth() < contentsWidth(), layoutHeight() < contentsHeight());
 
     if (!m_postLayoutTasksTimer.isActive()) {
         if (!m_inSynchronousPostLayout) {
             if (frame()->document()->shouldDisplaySeamlesslyWithParent()) {
                 if (RenderView* renderView = this->renderView())
                     renderView->updateWidgetPositions();
             } else {
                 m_inSynchronousPostLayout = true;
                 // Calls resumeScheduledEvents()
                 performPostLayoutTasks();

[achicu, 2013/08/15 13:48:21]

I think that the biggest performance improvement comes from not running
updateCompositingLayersAfterLayout() and performPostLayoutTasks().

For updateCompositingLayersAfterLayout there's already a bug in WebKit:
https://bugs.webkit.org/show_bug.cgi?id=84393 . As per their comments it might
be dangerous to not call this function.

I have a local patch where I renamed all the ::layout() functions to
::internalLayout() and made the RenderObject::layout() a non-virtual method that
does a TRACE_EVENT and then calls internalLayout. It seems like even on
complicated pages the incremental layout is amazingly fast compared to the
amount of time spent in FrameView::layout.

                 m_inSynchronousPostLayout = false;
             }
         }
 
         if (!m_postLayoutTasksTimer.isActive() && (needsLayout() || m_inSynchronousPostLayout || frame()->document()->shouldDisplaySeamlesslyWithParent())) {
             // If we need layout or are already in a synchronous call to postLayoutTasks(),
             // defer widget updates and event dispatch until after we return. postLayoutTasks()
             // can make us need to update again, and we can get stuck in a nasty cycle unless
             // we call it through the timer here.
             m_postLayoutTasksTimer.startOneShot(0);
             if (needsLayout()) {
                 m_actionScheduler->pause();
                 layout();
             }
         }
     } else {
         m_actionScheduler->resume();
     }
 
     InspectorInstrumentation::didLayout(cookie, rootForThisLayout);
 
     m_nestedLayoutCount--;
     if (m_nestedLayoutCount)
         return;
 
 #ifndef NDEBUG
-    // Post-layout assert that nobody was re-marked as needing layout during layout.
-    for (RenderObject* renderer = document->renderer(); renderer; renderer = renderer->nextInPreOrder())
-        ASSERT(!renderer->needsLayout());
+    if (!m_canStopPartialLayout) {
+        // Post-layout assert that nobody was re-marked as needing layout during layout.
+        for (RenderObject* renderer = document->renderer(); renderer; renderer = renderer->nextInPreOrder())
+            ASSERT(!renderer->needsLayout());
+    }
 #endif
 
+    // Reset partial layout state post-layout.
+    resetPartialLayoutState();
+
     // FIXME: It should be not possible to remove the FrameView from the frame/page during layout
     // however m_inLayout is not set for most of this function, so none of our RELEASE_ASSERTS
     // in Frame/Page will fire. One of the post-layout tasks is disconnecting the Frame from
     // the page in fast/frames/crash-remove-iframe-during-object-beforeload-2.html
     // necessitating this check here.
     ASSERT(frame());
     // ASSERT(frame()->page());
     if (frame() && frame()->page())
         frame()->page()->chrome().client()->layoutUpdated(frame());
 }
@@ skipping 20 matching lines @@
     // Next walk all lazy blocks and find nested ones, these need another layout
     // since the first one would not have placed them correctly inside the viewport.
     for (RenderLazyBlock* block = renderView()->firstLazyBlock(); block; block = block->next()) {
         if (!block->isNested())
             continue;
         block->setNeedsLayout();
         layout();
     }
 }
 
+void FrameView::checkPartialLayoutComplete(RenderObject* renderer)
+{
+    if (renderer == m_stopLayoutAtRenderer) {
+        //fprintf(stderr, "stopping partial layout!\n");
+        //BACKTRACE();
+        m_canStopPartialLayout = true;
+    }
+}
+
 RenderBox* FrameView::embeddedContentBox() const
 {
     RenderView* renderView = this->renderView();
     if (!renderView)
         return 0;
 
     RenderObject* firstChild = renderView->firstChild();
     if (!firstChild || !firstChild->isBox())
         return 0;
 
@@ skipping 2219 matching lines @@
 }
 
 AXObjectCache* FrameView::axObjectCache() const
 {
     if (frame() && frame()->document())
         return frame()->document()->existingAXObjectCache();
     return 0;
 }
 
 } // namespace WebCore