Source/core/editing/SimplifyMarkupCommand.cpp

/*
 * Copyright (C) 2012 Apple Computer, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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#include "config.h"
#include "core/editing/SimplifyMarkupCommand.h"

#include "core/dom/NodeRenderStyle.h"
#include "core/dom/NodeTraversal.h"
#include "core/rendering/RenderInline.h"
#include "core/rendering/RenderObject.h"
#include "core/rendering/style/RenderStyle.h"

namespace WebCore {

SimplifyMarkupCommand::SimplifyMarkupCommand(Document* document, Node* firstNode, Node* nodeAfterLast) 
    : CompositeEditCommand(document), m_firstNode(firstNode), m_nodeAfterLast(nodeAfterLast)
{
}
    
void SimplifyMarkupCommand::doApply()
{
    Node* rootNode = m_firstNode->parentNode();
    Vector<RefPtr<Node> > nodesToRemove;
    
    // Walk through the inserted nodes, to see if there are elements that could be removed
    // without affecting the style. The goal is to produce leaner markup even when starting
    // from a verbose fragment.
    // We look at inline elements as well as non top level divs that don't have attributes. 
    for (Node* node = m_firstNode.get(); node && node != m_nodeAfterLast; node = NodeTraversal::next(node)) {
        if (node->firstChild() || (node->isTextNode() && node->nextSibling()))
            continue;
        
        Node* startingNode = node->parentNode();
        if (!startingNode)
            continue;
        RenderStyle* startingStyle = startingNode->renderStyle();
        if (!startingStyle)
            continue;
        Node* currentNode = startingNode;
        Node* topNodeWithStartingStyle = 0;
        while (currentNode != rootNode) {
            if (currentNode->parentNode() != rootNode && isRemovableBlock(currentNode))
                nodesToRemove.append(currentNode);
            
            currentNode = currentNode->parentNode();
            if (!currentNode)
                break;

            if (!currentNode->renderer() || !currentNode->renderer()->isRenderInline() || toRenderInline(currentNode->renderer())->alwaysCreateLineBoxes())
                continue;
            
            if (currentNode->firstChild() != currentNode->lastChild()) {
                topNodeWithStartingStyle = 0;
                break;
            }
            
            unsigned context;
            if (currentNode->renderStyle()->diff(startingStyle, context) == StyleDifferenceEqual)
                topNodeWithStartingStyle = currentNode;
            
        }
        if (topNodeWithStartingStyle) {
            for (Node* node = startingNode; node != topNodeWithStartingStyle; node = node->parentNode())
                nodesToRemove.append(node);
        }
    }

    // we perform all the DOM mutations at once.
    for (size_t i = 0; i < nodesToRemove.size(); ++i) {
        // FIXME: We can do better by directly moving children from nodesToRemove[i].
        int numPrunedAncestors = pruneSubsequentAncestorsToRemove(nodesToRemove, i);
        if (numPrunedAncestors < 0)
            continue;
        removeNodePreservingChildren(nodesToRemove[i], AssumeContentIsAlwaysEditable);
        i += numPrunedAncestors;
    }
}

int SimplifyMarkupCommand::pruneSubsequentAncestorsToRemove(Vector<RefPtr<Node> >& nodesToRemove, size_t startNodeIndex)
{
    size_t pastLastNodeToRemove = startNodeIndex + 1;
    for (; pastLastNodeToRemove < nodesToRemove.size(); ++pastLastNodeToRemove) {
        if (nodesToRemove[pastLastNodeToRemove - 1]->parentNode() != nodesToRemove[pastLastNodeToRemove])
            break;
        ASSERT(nodesToRemove[pastLastNodeToRemove]->firstChild() == nodesToRemove[pastLastNodeToRemove]->lastChild());
    }

    Node* highestAncestorToRemove = nodesToRemove[pastLastNodeToRemove - 1].get();
    RefPtr<ContainerNode> parent = highestAncestorToRemove->parentNode();
    if (!parent) // Parent has already been removed.
        return -1;
    
    if (pastLastNodeToRemove == startNodeIndex + 1)
        return 0;

    removeNode(nodesToRemove[startNodeIndex], AssumeContentIsAlwaysEditable);
    insertNodeBefore(nodesToRemove[startNodeIndex], highestAncestorToRemove, AssumeContentIsAlwaysEditable);
    removeNode(highestAncestorToRemove, AssumeContentIsAlwaysEditable);

    return pastLastNodeToRemove - startNodeIndex - 1;
}

} // namespace WebCore