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_partialLayout(PartialLayoutState())
 {
     init();
 
     // FIXME: Can m_frame ever be null here?
     if (!m_frame)
         return;
 
     Page* page = m_frame->page();
     if (!page)
         return;
@@ skipping 80 matching lines @@
     m_trackedRepaintRects.clear();
     m_lastPaintTime = 0;
     m_paintBehavior = PaintBehaviorNormal;
     m_isPainting = false;
     m_visuallyNonEmptyCharacterCount = 0;
     m_visuallyNonEmptyPixelCount = 0;
     m_isVisuallyNonEmpty = false;
     m_firstVisuallyNonEmptyLayoutCallbackPending = true;
     m_maintainScrollPositionAnchor = 0;
     m_disableRepaints = 0;
+    m_partialLayout.reset();
 }
 
 void FrameView::removeFromAXObjectCache()
 {
     if (AXObjectCache* cache = axObjectCache())
         cache->remove(this);
 }
 
 void FrameView::clearFrame()
 {
@@ skipping 577 matching lines @@
     // the layout beats any sort of style recalc update that needs to occur.
     TemporaryChange<bool> changeDoingPreLayoutStyleUpdate(m_doingPreLayoutStyleUpdate, true);
     document->updateStyleIfNeeded();
 }
 
 void FrameView::performLayout(RenderObject* rootForThisLayout, bool inSubtreeLayout)
 {
     // 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.
+    {
+        bool disableLayoutState = false;
+        if (inSubtreeLayout) {
+            RenderView* view = rootForThisLayout->view();
+            disableLayoutState = view->shouldDisableLayoutStateForSubtree(rootForThisLayout);
+            view->pushLayoutState(rootForThisLayout);
+        }
+        LayoutStateDisabler layoutStateDisabler(disableLayoutState ? rootForThisLayout->view() : 0);
 
-    bool disableLayoutState = false;
-    if (inSubtreeLayout) {
-        RenderView* view = rootForThisLayout->view();
-        disableLayoutState = view->shouldDisableLayoutStateForSubtree(rootForThisLayout);
-        view->pushLayoutState(rootForThisLayout);
+        m_inLayout = true;
+        beginDeferredRepaints();
+        forceLayoutParentViewIfNeeded();
+
+        // Text Autosizing requires two-pass layout which is incompatible with partial layout. If
+        // enabled, only do partial layout for the second layout.
+        // FIXME (crbug.com/256657): Do not do two layouts for text autosizing.
+        PartialLayoutDisabler partialLayoutDisabler(partialLayout(), m_frame->settings() && m_frame->settings()->textAutosizingEnabled());
+        rootForThisLayout->layout(); // THIS IS WHERE LAYOUT ACTUALLY HAPPENS.
     }
-    LayoutStateDisabler layoutStateDisabler(disableLayoutState ? rootForThisLayout->view() : 0);
-
-    m_inLayout = true;
-    beginDeferredRepaints();
-    forceLayoutParentViewIfNeeded();
-
-    rootForThisLayout->layout(); // THIS IS WHERE LAYOUT ACTUALLY HAPPENS.
 
     bool autosized = frame()->document()->textAutosizer()->processSubtree(rootForThisLayout);
     if (autosized && rootForThisLayout->needsLayout()) {
         TRACE_EVENT0("webkit", "2nd layout due to Text Autosizing");
         rootForThisLayout->layout();
     }
 
     endDeferredRepaints();
     m_inLayout = false;
 
@@ skipping 36 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;
 
+    ASSERT(!m_partialLayout.shouldStop());
+
     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 83 matching lines @@
                         bodyRenderer->setChildNeedsLayout();
                     else if (rootRenderer && rootRenderer->stretchesToViewport())
                         rootRenderer->setChildNeedsLayout();
                 }
             }
         }
 
         layer = rootForThisLayout->enclosingLayer();
 
         m_actionScheduler->pause();
+        // Non-overlay scrollbars can cause a second layout; disable partial layout for the first of these layouts.
+        PartialLayoutDisabler partialLayoutDisabler(partialLayout(), m_frame->settings() && !m_frame->settings()->usesOverlayScrollbars());
         performLayout(rootForThisLayout, inSubtreeLayout);
         m_layoutRoot = 0;
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
+    if (partialLayout().shouldStop())
+        return;
+
     bool neededFullRepaint = m_doFullRepaint;
 
     if (!inSubtreeLayout && !toRenderView(rootForThisLayout)->printing())
         adjustViewSize();
 
+    // adjustViewSize() can cause a layout due to scrollbars so a second shouldStop() check is required.
+    if (partialLayout().shouldStop())
+        return;
+
     m_doFullRepaint = neededFullRepaint;
 
     // Now update the positions of all layers.
     beginDeferredRepaints();
     if (m_doFullRepaint) {
         // 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.
         rootForThisLayout->view()->repaint();
     }
@@ skipping 2289 matching lines @@
 }
 
 AXObjectCache* FrameView::axObjectCache() const
 {
     if (frame() && frame()->document())
         return frame()->document()->existingAXObjectCache();
     return 0;
 }
 
 } // namespace WebCore