Add infrastructure for partial layouts

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 133 matching lines @@
 #include "core/page/MouseEventWithHitTestResults.h"
 #include "core/page/Page.h"
 #include "core/page/PageConsole.h"
 #include "core/page/PointerLockController.h"
 #include "core/page/Settings.h"
 #include "core/page/animation/AnimationController.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "core/platform/DateComponents.h"
 #include "core/platform/HistogramSupport.h"
 #include "core/platform/Language.h"
+#include "core/platform/ScrollbarTheme.h"
 #include "core/platform/Timer.h"
 #include "core/platform/chromium/TraceEvent.h"
 #include "core/platform/network/HTTPParsers.h"
 #include "core/platform/text/PlatformLocale.h"
 #include "core/platform/text/SegmentedString.h"
 #include "core/rendering/HitTestRequest.h"
 #include "core/rendering/HitTestResult.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/RenderWidget.h"
 #include "core/rendering/TextAutosizer.h"
@@ skipping 1577 matching lines @@
         oe->document()->updateLayout();
 
     updateStyleIfNeeded();
 
     StackStats::LayoutCheckPoint layoutCheckPoint;
 
     // Only do a layout if changes have occurred that make it necessary.
     if (frameView && renderer() && (frameView->layoutPending() || renderer()->needsLayout()))
         frameView->layout();
 
+    if (frameView)
+        frameView->resetPartialLayoutState();
+
     setNeedsFocusedElementCheck();
 }
 
 void Document::setNeedsFocusedElementCheck()
 {
     // FIXME: Using a Task doesn't look a good idea.
     if (!m_focusedElement || m_didPostCheckFocusedElementTask)
         return;
     postTask(CheckFocusedElementTask::create());
     m_didPostCheckFocusedElementTask = true;
@@ skipping 26 matching lines @@
             // may not have had their real style calculated yet. Normally this gets cleaned when style sheets arrive
             // but here we need up-to-date style immediately.
             recalcStyle(Force);
     }
 
     updateLayout();
 
     m_ignorePendingStylesheets = oldIgnore;
 }
 
+void Document::tryPartialUpdateLayoutIgnorePendingStylesheets(RenderObject* stopLayoutAtRenderer)

[esprehn, 2013/08/18 03:43:15]

This should take a Node, not a renderer. You need to do a style recalc just like
in updateLayoutIgnorePendingStylesheet (you probably want to refactor that
method) to make sure the renderer for Node is correct, then you can set it as
the stop renderer.

[pdr., 2013/08/20 06:19:10]

Great catch!

I refactored the common style recalc as
"recalcStyleForLayoutIgnoringPendingStylesheets()".

+{
+    if (stopLayoutAtRenderer) {
+        // Non-overlay scrollbars can cause layout during layout.
+        // FIXME: Temporarily ignore non-overlay scrollbars for test coverage.
+        if (true || ScrollbarTheme::theme()->usesOverlayScrollbars()) {

[esprehn, 2013/08/18 03:43:15]

true? You should probably delete this.

[pdr., 2013/08/20 06:19:10]

I'd like to leave this in for a bit longer since it makes performance testing
possible on Linux. Android and OSX have overlay scrollbars which don't take up
space (or CSS causes them to always take up space). Linux unfortunately has
scrollbars that appear if there's enough content which will force a second
layout, which breaks partial layout. I've updated the comment to be explicit
about why I've left it in, and I'll remove this before landing. The layouttests
will keep me honest here ;)

+            // FIXME: Text autosizing will not work with partial layout.
+            bool canPartialLayout = true;
+            RenderObject* renderer = stopLayoutAtRenderer;
+            do {
+                if (!renderer->supportsPartialLayout()) {
+                    canPartialLayout = false;
+                    break;
+                }
+            } while ((renderer = renderer->parent()));

[esprehn, 2013/08/18 03:43:15]

This is wrong, the style recalc inside updateLayoutIgnorePendingStylesheet can
change all these renderers and then your check here is not correct.

[pdr., 2013/08/20 06:19:10]

Done.

+            if (canPartialLayout)
+                view()->setStopLayoutAtRenderer(stopLayoutAtRenderer);

[esprehn, 2013/08/18 03:43:15]

You don't call any methods on it, but storing a renderer before a recalc style
is a use after free.

[pdr., 2013/08/20 06:19:10]

No use so... just "after free"? :)

Fixed.

+        }
+    }
+
+    updateLayoutIgnorePendingStylesheets();
+}
+
 PassRefPtr<RenderStyle> Document::styleForElementIgnoringPendingStylesheets(Element* element)
 {
     ASSERT_ARG(element, element->document() == this);
     TemporaryChange<bool> ignoreStyleSheets(m_ignorePendingStylesheets, true);
     return styleResolver()->styleForElement(element, element->parentNode() ? element->parentNode()->computedStyle() : 0);
 }
 
 PassRefPtr<RenderStyle> Document::styleForPage(int pageIndex)
 {
     return styleResolver()->styleForPage(pageIndex);
@@ skipping 3386 matching lines @@
 {
     return DocumentLifecycleNotifier::create(this);
 }
 
 DocumentLifecycleNotifier* Document::lifecycleNotifier()
 {
     return static_cast<DocumentLifecycleNotifier*>(ScriptExecutionContext::lifecycleNotifier());
 }
 
 } // namespace WebCore