deleteselectioncommand.cpp

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    // typing style at the start of the selection, nor is there a reason to 
    // compute the style at the start of the selection after deletion (see the 
    // early return in calculateTypingStyleAfterDelete).
    if (m_upstreamStart.node() == m_downstreamEnd.node() && m_upstreamStart.node()->isTextNode())
        return;
        
    // Figure out the typing style in effect before the delete is done.
    RefPtr<CSSComputedStyleDeclaration> computedStyle = positionBeforeTabSpan(m_selectionToDelete.start()).computedStyle();
    m_typingStyle = computedStyle->copyInheritableProperties();
    
    removeEnclosingAnchorStyle(m_typingStyle.get(), m_selectionToDelete.start());
    
    // If we're deleting into a Mail blockquote, save the style at end() instead of start()
    // We'll use this later in computeTypingStyleAfterDelete if we end up outside of a Mail blockquote
    if (nearestMailBlockquote(m_selectionToDelete.start().node())) {
        computedStyle = m_selectionToDelete.end().computedStyle();
        m_deleteIntoBlockquoteStyle = computedStyle->copyInheritableProperties();
    } else
        m_deleteIntoBlockquoteStyle = 0;
}

bool DeleteSelectionCommand::handleSpecialCaseBRDelete()
{
    // Check for special-case where the selection contains only a BR on a line by itself after another BR.
    bool upstreamStartIsBR = m_upstreamStart.node()->hasTagName(brTag);
    bool downstreamStartIsBR = m_downstreamStart.node()->hasTagName(brTag);
    bool isBROnLineByItself = upstreamStartIsBR && downstreamStartIsBR && m_downstreamStart.node() == m_upstreamEnd.node();
    if (isBROnLineByItself) {
        removeNode(m_downstreamStart.node());
        return true;
    }

    // Not a special-case delete per se, but we can detect that the merging of content between blocks
    // should not be done.
    if (upstreamStartIsBR && downstreamStartIsBR) {
        m_mergeBlocksAfterDelete = false;
        m_endingPosition = m_downstreamEnd;
    }
    
    return false;
}

static void updatePositionForNodeRemoval(Node* node, Position& position)
{
    if (position.isNull())
        return;
    if (node->parent() == position.node() && node->nodeIndex() < (unsigned)position.offset())
        position = Position(position.node(), position.offset() - 1);
    if (position.node() == node || position.node()->isDescendantOf(node))
        position = positionBeforeNode(node);
}

void DeleteSelectionCommand::removeNode(PassRefPtr<Node> node)
{
    if (!node)
        return;
        
    if (m_startRoot != m_endRoot && !(node->isDescendantOf(m_startRoot.get()) && node->isDescendantOf(m_endRoot.get()))) {
        // If a node is not in both the start and end editable roots, remove it only if its inside an editable region.
        if (!node->parentNode()->isContentEditable()) {
            // Don't remove non-editable atomic nodes.
            if (!node->firstChild())
                return;
            // Search this non-editable region for editable regions to empty.
            RefPtr<Node> child = node->firstChild();
            while (child) {
                RefPtr<Node> nextChild = child->nextSibling();
                removeNode(child.get());
                // Bail if nextChild is no longer node's child.
                if (nextChild && nextChild->parentNode() != node)
                    return;
                child = nextChild;
            }
            
            // Don't remove editable regions that are inside non-editable ones, just clear them.
            return;
        }
    }
    
    if (isTableStructureNode(node.get()) || node == node->rootEditableElement()) {
        // Do not remove an element of table structure; remove its contents.
        // Likewise for the root editable element.
        Node* child = node->firstChild();
        while (child) {
            Node* remove = child;
            child = child->nextSibling();
            removeNode(remove);
        }
        
        // make sure empty cell has some height
        updateLayout();
        RenderObject *r = node->renderer();
        if (r && r->isTableCell() && static_cast<RenderTableCell*>(r)->contentHeight() <= 0)
            insertBlockPlaceholder(Position(node,0));
        return;
    }
    
    if (node == m_startBlock && !isEndOfBlock(VisiblePosition(m_startBlock.get(), 0, DOWNSTREAM).previous()))
        m_needPlaceholder = true;
    else if (node == m_endBlock && !isStartOfBlock(VisiblePosition(m_endBlock.get(), maxDeepOffset(m_endBlock.get()), DOWNSTREAM).next()))
        m_needPlaceholder = true;
    
    // FIXME: Update the endpoints of the range being deleted.
    updatePositionForNodeRemoval(node.get(), m_endingPosition);
    updatePositionForNodeRemoval(node.get(), m_leadingWhitespace);
    updatePositionForNodeRemoval(node.get(), m_trailingWhitespace);
    
    CompositeEditCommand::removeNode(node);
}

static void updatePositionForTextRemoval(Node* node, int offset, int count, Position& position)
{
    if (position.node() == node) {
        if (position.offset() > offset + count)
            position = Position(position.node(), position.offset() - count);
        else if (position.offset() > offset)
            position = Position(position.node(), offset);
    }
}

void DeleteSelectionCommand::deleteTextFromNode(PassRefPtr<Text> node, unsigned offset, unsigned count)
{
    // FIXME: Update the endpoints of the range being deleted.
    updatePositionForTextRemoval(node.get(), offset, count, m_endingPosition);
    updatePositionForTextRemoval(node.get(), offset, count, m_leadingWhitespace);
    updatePositionForTextRemoval(node.get(), offset, count, m_trailingWhitespace);
    
    CompositeEditCommand::deleteTextFromNode(node, offset, count);
}

void DeleteSelectionCommand::handleGeneralDelete()
{
    int startOffset = m_upstreamStart.offset();
    Node* startNode = m_upstreamStart.node();
    
    // Never remove the start block unless it's a table, in which case we won't merge content in.
    if (startNode == m_startBlock && startOffset == 0 && canHaveChildrenForEditing(startNode) && !startNode->hasTagName(tableTag)) {
        startOffset = 0;
        startNode = startNode->traverseNextNode();
    }

    if (startOffset >= caretMaxOffset(startNode) && startNode->isTextNode()) {
        Text *text = static_cast<Text *>(startNode);
        if (text->length() > (unsigned)caretMaxOffset(startNode))
            deleteTextFromNode(text, caretMaxOffset(startNode), text->length() - caretMaxOffset(startNode));
    }

    if (startOffset >= maxDeepOffset(startNode)) {
        startNode = startNode->traverseNextSibling();
        startOffset = 0;
    }

    // Done adjusting the start.  See if we're all done.
    if (!startNode)
        return;

    if (startNode == m_downstreamEnd.node()) {
        // The selection to delete is all in one node.
        if (!startNode->renderer() || 
            (startOffset == 0 && m_downstreamEnd.offset() >= maxDeepOffset(startNode))) {
            // just delete
            removeNode(startNode);
        } else if (m_downstreamEnd.offset() - startOffset > 0) {
            if (startNode->isTextNode()) {
                // in a text node that needs to be trimmed
                Text *text = static_cast<Text *>(startNode);
                deleteTextFromNode(text, startOffset, m_downstreamEnd.offset() - startOffset);
            } else {
                removeChildrenInRange(startNode, startOffset, m_downstreamEnd.offset());
                m_endingPosition = m_upstreamStart;
            }
        }
    }
    else {
        bool startNodeWasDescendantOfEndNode = m_upstreamStart.node()->isDescendantOf(m_downstreamEnd.node());
        // The selection to delete spans more than one node.
        RefPtr<Node> node(startNode);
        
        if (startOffset > 0) {
            if (startNode->isTextNode()) {
                // in a text node that needs to be trimmed
                Text *text = static_cast<Text *>(node.get());
                deleteTextFromNode(text, startOffset, text->length() - startOffset);
                node = node->traverseNextNode();
            } else {
                node = startNode->childNode(startOffset);
            }
        }
        
        // handle deleting all nodes that are completely selected
        while (node && node != m_downstreamEnd.node()) {
            if (Range::compareBoundaryPoints(Position(node.get(), 0), m_downstreamEnd) >= 0) {
                // traverseNextSibling just blew past the end position, so stop deleting
                node = 0;
            } else if (!m_downstreamEnd.node()->isDescendantOf(node.get())) {
                RefPtr<Node> nextNode = node->traverseNextSibling();
                // if we just removed a node from the end container, update end position so the
                // check above will work
                if (node->parentNode() == m_downstreamEnd.node()) {
                    ASSERT(node->nodeIndex() < (unsigned)m_downstreamEnd.offset());
                    m_downstreamEnd = Position(m_downstreamEnd.node(), m_downstreamEnd.offset() - 1);
                }
                removeNode(node.get());
                node = nextNode.get();
            } else {
                Node* n = node->lastDescendant();
                if (m_downstreamEnd.node() == n && m_downstreamEnd.offset() >= caretMaxOffset(n)) {
                    removeNode(node.get());
                    node = 0;
                } else
                    node = node->traverseNextNode();
            }
        }
        
        if (m_downstreamEnd.node() != startNode && !m_upstreamStart.node()->isDescendantOf(m_downstreamEnd.node()) && m_downstreamEnd.node()->inDocument() && m_downstreamEnd.offset() >= caretMinOffset(m_downstreamEnd.node())) {
            if (m_downstreamEnd.offset() >= maxDeepOffset(m_downstreamEnd.node()) && !canHaveChildrenForEditing(m_downstreamEnd.node())) {
                // The node itself is fully selected, not just its contents.  Delete it.
                removeNode(m_downstreamEnd.node());
            } else {
                if (m_downstreamEnd.node()->isTextNode()) {
                    // in a text node that needs to be trimmed
                    Text *text = static_cast<Text *>(m_downstreamEnd.node());
                    if (m_downstreamEnd.offset() > 0) {
                        deleteTextFromNode(text, 0, m_downstreamEnd.offset());
                        m_downstreamEnd = Position(text, 0);
                    }
                // Remove children of m_downstreamEnd.node() that come after m_upstreamStart.
                // Don't try to remove children if m_upstreamStart was inside m_downstreamEnd.node()
                // and m_upstreamStart has been removed from the document, because then we don't 
                // know how many children to remove.
                // FIXME: Make m_upstreamStart a position we update as we remove content, then we can
                // always know which children to remove.
                } else if (!(startNodeWasDescendantOfEndNode && !m_upstreamStart.node()->inDocument())) {
                    int offset = 0;
                    if (m_upstreamStart.node()->isDescendantOf(m_downstreamEnd.node())) {
                        Node *n = m_upstreamStart.node();
                        while (n && n->parentNode() != m_downstreamEnd.node())
                            n = n->parentNode();
                        if (n)
                            offset = n->nodeIndex() + 1;
                    }
                    removeChildrenInRange(m_downstreamEnd.node(), offset, m_downstreamEnd.offset());
                    m_downstreamEnd = Position(m_downstreamEnd.node(), offset);
                }
            }
        }
    }
}

void DeleteSelectionCommand::fixupWhitespace()
{
    updateLayout();
    // FIXME: isRenderedCharacter should be removed, and we should use VisiblePosition::characterAfter and VisiblePosition::characterBefore
    if (m_leadingWhitespace.isNotNull() && !m_leadingWhitespace.isRenderedCharacter()) {
        Text* textNode = static_cast<Text*>(m_leadingWhitespace.node());
        ASSERT(!textNode->renderer() || textNode->renderer()->style()->collapseWhiteSpace());
        replaceTextInNode(textNode, m_leadingWhitespace.offset(), 1, nonBreakingSpaceString());
    }
    if (m_trailingWhitespace.isNotNull() && !m_trailingWhitespace.isRenderedCharacter()) {
        Text* textNode = static_cast<Text*>(m_trailingWhitespace.node());
        ASSERT(!textNode->renderer() ||textNode->renderer()->style()->collapseWhiteSpace());
        replaceTextInNode(textNode, m_trailingWhitespace.offset(), 1, nonBreakingSpaceString());
    }
}

// If a selection starts in one block and ends in another, we have to merge to bring content before the
// start together with content after the end.
void DeleteSelectionCommand::mergeParagraphs()