*** DO NOT LAND *** Attempt to understand Regions complexity

Source/core/dom/RenderTreeBuilder.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 15 matching lines @@
 #include "config.h"
 #include "core/dom/RenderTreeBuilder.h"
 
 #include "HTMLNames.h"
 #include "RuntimeEnabledFeatures.h"
 #include "SVGNames.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/FullscreenElementStack.h"
 #include "core/dom/Node.h"
 #include "core/dom/Text.h"
-#include "core/rendering/FlowThreadController.h"
 #include "core/rendering/RenderFullScreen.h"
-#include "core/rendering/RenderNamedFlowThread.h"
 #include "core/rendering/RenderObject.h"
 #include "core/rendering/RenderText.h"
 #include "core/rendering/RenderView.h"
 
 namespace WebCore {
 
 RenderObject* RenderTreeBuilder::nextRenderer() const
 {
     ASSERT(m_renderingParent);
 
     Element* element = m_node->isElementNode() ? toElement(m_node) : 0;
 
     if (element) {
         if (element->isInTopLayer())
             return NodeRenderingTraversal::nextInTopLayer(element);
         // FIXME: Reparented dialogs not in the top layer need to be in DOM tree order.
         // FIXME: The spec should not require magical behavior for <dialog>.
         if (element->hasTagName(HTMLNames::dialogTag) && m_style->position() == AbsolutePosition)
             return 0;
     }
 
-    if (m_parentFlowRenderer)
-        return m_parentFlowRenderer->nextRendererForNode(m_node);
-
     // Avoid an O(N^2) walk over the children when reattaching all children of a node.
     if (m_renderingParent->needsAttach())
         return 0;
 
     return NodeRenderingTraversal::nextSiblingRenderer(m_node);
 }
 
 RenderObject* RenderTreeBuilder::parentRenderer() const
 {
     ASSERT(m_renderingParent);
 
     Element* element = m_node->isElementNode() ? toElement(m_node) : 0;
 
     if (element && m_renderingParent->renderer()) {
         // FIXME: The spec should not require magical behavior for <dialog>. Note that the first
         // time we enter here the m_style might be null because of a call in shouldCreateRenderer()
         // which means we return the wrong wrong renderer for that check and then return a totally
         // different renderer (the RenderView) later when this method is called after setting m_style.
         if (element->hasTagName(HTMLNames::dialogTag) && m_style && m_style->position() == AbsolutePosition)
             return m_node->document().renderView();
 
         // FIXME: Guarding this by m_renderingParent->renderer() isn't quite right as the spec for
         // top layer only talks about display: none ancestors so putting a <dialog> inside an
         // <optgroup> seems like it should still work even though this check will prevent it.
         if (element->isInTopLayer())
             return m_node->document().renderView();
     }
 
-    // Even if the normal parent has no renderer we still can be flowed into a named flow.
-    // FIXME: This is bad, it breaks the assumption that if you have a renderer then
-    // NodeRenderingTraversal::parent(this) also has one which likely means lots of bugs
-    // with regions.
-    if (m_parentFlowRenderer)
-        return m_parentFlowRenderer;
-
     return m_renderingParent->renderer();
 }
 
 bool RenderTreeBuilder::shouldCreateRenderer() const
 {
     if (!m_renderingParent)
         return false;
     // SVG elements only render when inside <svg>, or if the element is an <svg> itself.
     if (m_node->isSVGElement() && !m_node->hasTagName(SVGNames::svgTag) && !m_renderingParent->isSVGElement())
         return false;
     RenderObject* parentRenderer = this->parentRenderer();
     if (!parentRenderer)
         return false;
     if (!parentRenderer->canHaveChildren())
         return false;
     if (!m_renderingParent->childShouldCreateRenderer(*m_node))
         return false;
     return true;
 }
 
-// Check the specific case of elements that are children of regions but are flowed into a flow thread themselves.
-bool RenderTreeBuilder::elementInsideRegionNeedsRenderer()
-{
-    if (!RuntimeEnabledFeatures::cssRegionsEnabled())
-        return false;
-    Element& element = toElement(*m_node);
-    RenderObject* parentRenderer = this->parentRenderer();
-    if ((parentRenderer && !parentRenderer->canHaveChildren() && parentRenderer->isRenderNamedFlowFragmentContainer())
-        || (!parentRenderer && element.parentElement() && element.parentElement()->isInsideRegion())) {
-
-        // Children of this element will only be allowed to be flowed into other flow-threads if display is NOT none.
-        if (element.rendererIsNeeded(style()))
-            element.setIsInsideRegion(true);
-
-        return shouldMoveToFlowThread();
-    }
-
-    return false;
-}
-
-bool RenderTreeBuilder::shouldMoveToFlowThread() const
-{
-    Element& element = toElement(*m_node);
-    RenderStyle& style = this->style();
-
-    if (style.flowThread().isEmpty())
-        return false;
-
-    if (FullscreenElementStack::isActiveFullScreenElement(&element))
-        return false;
-
-    if (element.isInShadowTree())
-        return false;
-
-    // As per http://dev.w3.org/csswg/css3-regions/#flow-into, pseudo-elements such as
-    // ::first-line, ::first-letter, ::before or ::after cannot be directly collected
-    // into a named flow.
-    if (element.isPseudoElement())
-        return false;
-
-    // Allow only svg root elements to be directly collected by a render flow thread.
-    if (element.isSVGElement()) {
-        if (!element.hasTagName(SVGNames::svgTag))
-            return false;
-        if (!element.parentNode())
-            return false;
-        if (element.parentNode()->isSVGElement())
-            return false;
-    }
-
-    return !element.isRegisteredWithNamedFlow();
-}
-
-void RenderTreeBuilder::moveToFlowThreadIfNeeded()
-{
-    if (!RuntimeEnabledFeatures::cssRegionsEnabled())
-        return;
-
-    if (!shouldMoveToFlowThread())
-        return;
-
-    FlowThreadController* flowThreadController = m_node->document().renderView()->flowThreadController();
-    m_parentFlowRenderer = flowThreadController->ensureRenderFlowThreadWithName(style().flowThread());
-    flowThreadController->registerNamedFlowContentNode(m_node, m_parentFlowRenderer);
-}
-
 RenderStyle& RenderTreeBuilder::style() const
 {
     if (!m_style)
         m_style = toElement(m_node)->styleForRenderer();
     return *m_style;
 }
 
 void RenderTreeBuilder::createRendererForElementIfNeeded()
 {
     ASSERT(!m_node->renderer());
 
     // If we're out of composition then we can't render since there's no parent to inherit from.
     if (!m_renderingParent)
         return;
 
     Element* element = toElement(m_node);
 
-    if (!shouldCreateRenderer() && !elementInsideRegionNeedsRenderer())
+    if (!shouldCreateRenderer())
         return;
 
-    moveToFlowThreadIfNeeded();
-
     RenderStyle& style = this->style();
 
     if (!element->rendererIsNeeded(style))
         return;
 
     RenderObject* newRenderer = element->createRenderer(&style);
     if (!newRenderer)
         return;
 
     RenderObject* parentRenderer = this->parentRenderer();
 
     if (!parentRenderer->isChildAllowed(newRenderer, &style)) {
         newRenderer->destroy();
         return;
     }
 
-    // Make sure the RenderObject already knows it is going to be added to a RenderFlowThread before we set the style
-    // for the first time. Otherwise code using inRenderFlowThread() in the styleWillChange and styleDidChange will fail.
-    newRenderer->setFlowThreadState(parentRenderer->flowThreadState());
-
     RenderObject* nextRenderer = this->nextRenderer();
     element->setRenderer(newRenderer);
     newRenderer->setAnimatableStyle(&style); // setAnimatableStyle() can depend on renderer() already being set.
 
     if (FullscreenElementStack::isActiveFullScreenElement(element)) {
         newRenderer = RenderFullScreen::wrapRenderer(newRenderer, parentRenderer, &element->document());
         if (!newRenderer)
             return;
     }
 
@@ skipping 22 matching lines @@
 
     if (!textNode->textRendererIsNeeded(*m_style, *parentRenderer))
         return;
 
     RenderText* newRenderer = textNode->createTextRenderer(m_style.get());
     if (!parentRenderer->isChildAllowed(newRenderer, m_style.get())) {
         newRenderer->destroy();
         return;
     }
 
-    // Make sure the RenderObject already knows it is going to be added to a RenderFlowThread before we set the style
-    // for the first time. Otherwise code using inRenderFlowThread() in the styleWillChange and styleDidChange will fail.
-    newRenderer->setFlowThreadState(parentRenderer->flowThreadState());
-
     RenderObject* nextRenderer = this->nextRenderer();
     textNode->setRenderer(newRenderer);
     // Parent takes care of the animations, no need to call setAnimatableStyle.
     newRenderer->setStyle(m_style.release());
     parentRenderer->addChild(newRenderer, nextRenderer);
 }
 
 }