Optimize QQuickTextEdit for larger documents.

The rationale is to not end up re-processing the whole document on each update
Since we know where the editing takes place, we can break down the text edit's
contents in several text nodes and only re-create the affected text nodes upon
editing.

This requires ripping out the SelectionEngine helper class from QQuickTextNode
so that QQuickTextEdit can tap into its functionality directly.

A positive side-effect of this exercise is that it should be much harder to
to come across GlyphNodes packing more than 16300 glyphs or so.

Task-number: QTBUG-29596
Change-Id: Id29b0709baa43f5b29c44ab02398ba996be3e28a
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

1 files changed, 35 insertions, 1094 deletions

diff --git a/src/quick/items/qquicktextnode.cpp b/src/quick/items/qquicktextnode.cpp
index 5e1b20c032..d46959464a 100644
--- a/src/quick/items/qquicktextnode.cpp
+++ b/src/quick/items/qquicktextnode.cpp
@@ -41,6 +41,8 @@
 
 #include "qquicktextnode_p.h"
 
+#include "qquicktextnodeengine_p.h"
+
 #include <QtQuick/qsgsimplerectnode.h>
 #include <private/qsgadaptationlayer_p.h>
 #include <private/qsgdistancefieldglyphnode_p.h>
@@ -53,20 +55,28 @@
 #include <qtextlayout.h>
 #include <qabstracttextdocumentlayout.h>
 #include <qxmlstream.h>
-#include <qrawfont.h>
-#include <qtexttable.h>
-#include <qtextlist.h>
 #include <private/qquickstyledtext_p.h>
-#include <private/qquicktext_p_p.h>
 #include <private/qfont_p.h>
 #include <private/qfontengine_p.h>
-#include <private/qrawfont_p.h>
-#include <private/qtextimagehandler_p.h>
+
 #include <private/qtextdocumentlayout_p.h>
 #include <qhash.h>
 
 QT_BEGIN_NAMESPACE
 
+namespace {
+
+    class ProtectedLayoutAccessor: public QAbstractTextDocumentLayout
+    {
+    public:
+        inline QTextCharFormat formatAccessor(int pos)
+        {
+            return format(pos);
+        }
+    };
+
+}
+
 /*!
   Creates an empty QQuickTextNode
 */
@@ -166,937 +176,14 @@ void QQuickTextNode::setCursor(const QRectF &rect, const QColor &color)
     appendChildNode(m_cursorNode);
 }
 
-namespace {
-
-    struct BinaryTreeNode {
-        enum SelectionState {
-            Unselected,
-            Selected
-        };
-
-        BinaryTreeNode()
-            : selectionState(Unselected)
-            , clipNode(0)
-            , decorations(QQuickTextNode::NoDecoration)
-            , ascent(0.0)
-            , leftChildIndex(-1)
-            , rightChildIndex(-1)
-        {
-
-        }
-
-        BinaryTreeNode(const QRectF &brect, const QImage &i, SelectionState selState, qreal a)
-            : boundingRect(brect)
-            , selectionState(selState)
-            , clipNode(0)
-            , decorations(QQuickTextNode::NoDecoration)
-            , image(i)
-            , ascent(a)
-            , leftChildIndex(-1)
-            , rightChildIndex(-1)
-        {
-        }
-
-        BinaryTreeNode(const QGlyphRun &g, SelectionState selState, const QRectF &brect,
-                       const QQuickTextNode::Decorations &decs, const QColor &c, const QColor &bc,
-                       const QPointF &pos, qreal a)
-            : glyphRun(g)
-            , boundingRect(brect)
-            , selectionState(selState)
-            , clipNode(0)
-            , decorations(decs)
-            , color(c)
-            , backgroundColor(bc)
-            , position(pos)
-            , ascent(a)
-            , leftChildIndex(-1)
-            , rightChildIndex(-1)
-        {
-        }
-
-        QGlyphRun glyphRun;
-        QRectF boundingRect;
-        SelectionState selectionState;
-        QQuickDefaultClipNode *clipNode;
-        QQuickTextNode::Decorations decorations;
-        QColor color;
-        QColor backgroundColor;
-        QPointF position;
-        QImage image;
-        qreal ascent;
-
-        int leftChildIndex;
-        int rightChildIndex;
-
-        static void insert(QVarLengthArray<BinaryTreeNode> *binaryTree,
-                           const QRectF &rect,
-                           const QImage &image,
-                           qreal ascent,
-                           SelectionState selectionState)
-        {
-            insert(binaryTree, BinaryTreeNode(rect, image, selectionState, ascent));
-        }
-
-        static void insert(QVarLengthArray<BinaryTreeNode> *binaryTree,
-                           const QGlyphRun &glyphRun,
-                           SelectionState selectionState,
-                           QQuickTextNode::Decorations decorations,
-                           const QColor &textColor,
-                           const QColor &backgroundColor,
-                           const QPointF &position)
-        {
-            QRectF searchRect = glyphRun.boundingRect();
-            searchRect.translate(position);
-
-            if (qFuzzyIsNull(searchRect.width()) || qFuzzyIsNull(searchRect.height()))
-                return;
-
-            decorations |= (glyphRun.underline() ? QQuickTextNode::Underline : QQuickTextNode::NoDecoration);
-            decorations |= (glyphRun.overline()  ? QQuickTextNode::Overline  : QQuickTextNode::NoDecoration);
-            decorations |= (glyphRun.strikeOut() ? QQuickTextNode::StrikeOut : QQuickTextNode::NoDecoration);
-            decorations |= (backgroundColor.isValid() ? QQuickTextNode::Background : QQuickTextNode::NoDecoration);
-
-            qreal ascent = glyphRun.rawFont().ascent();
-            insert(binaryTree, BinaryTreeNode(glyphRun, selectionState, searchRect, decorations,
-                                              textColor, backgroundColor, position, ascent));
-        }
-
-        static void insert(QVarLengthArray<BinaryTreeNode> *binaryTree,
-                           const BinaryTreeNode &binaryTreeNode)
-        {
-            int newIndex = binaryTree->size();
-            binaryTree->append(binaryTreeNode);
-            if (newIndex == 0)
-                return;
-
-            int searchIndex = 0;
-            forever {
-                BinaryTreeNode *node = binaryTree->data() + searchIndex;
-                if (binaryTreeNode.boundingRect.left() < node->boundingRect.left()) {
-                    if (node->leftChildIndex < 0) {
-                        node->leftChildIndex = newIndex;
-                        break;
-                    } else {
-                        searchIndex = node->leftChildIndex;
-                    }
-                } else {
-                    if (node->rightChildIndex < 0) {
-                        node->rightChildIndex = newIndex;
-                        break;
-                    } else {
-                        searchIndex = node->rightChildIndex;
-                    }
-                }
-            }
-        }
-
-        static void inOrder(const QVarLengthArray<BinaryTreeNode> &binaryTree,
-                            QVarLengthArray<int> *sortedIndexes,
-                            int currentIndex = 0)
-        {
-            Q_ASSERT(currentIndex < binaryTree.size());
-
-            const BinaryTreeNode *node = binaryTree.data() + currentIndex;
-            if (node->leftChildIndex >= 0)
-                inOrder(binaryTree, sortedIndexes, node->leftChildIndex);
-
-            sortedIndexes->append(currentIndex);
-
-            if (node->rightChildIndex >= 0)
-                inOrder(binaryTree, sortedIndexes, node->rightChildIndex);
-        }
-    };
-
-    // Engine that takes glyph runs as input, and produces a set of glyph nodes, clip nodes,
-    // and rectangle nodes to represent the text, decorations and selection. Will try to minimize
-    // number of nodes, and join decorations in neighbouring items
-    class SelectionEngine
-    {
-    public:
-        SelectionEngine() : m_hasSelection(false) {}
-
-        QTextLine currentLine() const { return m_currentLine; }
-
-        void setCurrentLine(const QTextLine &currentLine)
-        {
-            if (m_currentLine.isValid())
-                processCurrentLine();
-
-            m_currentLine = currentLine;
-        }
-
-        void addBorder(const QRectF &rect, qreal border, QTextFrameFormat::BorderStyle borderStyle,
-                       const QBrush &borderBrush);
-        void addFrameDecorations(QTextDocument *document, QTextFrame *frame);
-        void addImage(const QRectF &rect, const QImage &image, qreal ascent,
-                      BinaryTreeNode::SelectionState selectionState,
-                      QTextFrameFormat::Position layoutPosition);
-        int addText(const QTextBlock &block,
-                    const QTextCharFormat &charFormat,
-                    const QColor &textColor,
-                    const QVarLengthArray<QTextLayout::FormatRange> &colorChanges,
-                    int textPos, int fragmentEnd,
-                    int selectionStart, int selectionEnd);
-        void addTextObject(const QPointF &position, const QTextCharFormat &format,
-                           BinaryTreeNode::SelectionState selectionState,
-                           QTextDocument *textDocument, int pos,
-                           QTextFrameFormat::Position layoutPosition = QTextFrameFormat::InFlow);
-        void addSelectedGlyphs(const QGlyphRun &glyphRun);
-        void addUnselectedGlyphs(const QGlyphRun &glyphRun);
-        void addGlyphsInRange(int rangeStart, int rangeEnd,
-                              const QColor &color, const QColor &backgroundColor,
-                              int selectionStart, int selectionEnd);
-        void addGlyphsForRanges(const QVarLengthArray<QTextLayout::FormatRange> &ranges,
-                                int start, int end,
-                                int selectionStart, int selectionEnd);
-
-        void addToSceneGraph(QQuickTextNode *parent,
-                             QQuickText::TextStyle style = QQuickText::Normal,
-                             const QColor &styleColor = QColor());
-
-        void setSelectionColor(const QColor &selectionColor)
-        {
-            m_selectionColor = selectionColor;
-        }
-
-        void setSelectedTextColor(const QColor &selectedTextColor)
-        {
-            m_selectedTextColor = selectedTextColor;
-        }
-
-        void setTextColor(const QColor &textColor)
-        {
-            m_textColor = textColor;
-        }
-
-        void setAnchorColor(const QColor &anchorColor)
-        {
-            m_anchorColor = anchorColor;
-        }
-
-        void setPosition(const QPointF &position)
-        {
-            m_position = position;
-        }
-
-    private:
-        struct TextDecoration
-        {
-            TextDecoration() : selectionState(BinaryTreeNode::Unselected) {}
-            TextDecoration(const BinaryTreeNode::SelectionState &s,
-                           const QRectF &r,
-                           const QColor &c)
-                : selectionState(s)
-                , rect(r)
-                , color(c)
-            {
-            }
-
-            BinaryTreeNode::SelectionState selectionState;
-            QRectF rect;
-            QColor color;
-        };
-
-        void processCurrentLine();
-        void addTextDecorations(const QVarLengthArray<TextDecoration> &textDecorations,
-                                qreal offset, qreal thickness);
-
-        QColor m_selectionColor;
-        QColor m_textColor;
-        QColor m_backgroundColor;
-        QColor m_selectedTextColor;
-        QColor m_anchorColor;
-        QPointF m_position;
-
-        QTextLine m_currentLine;
-        bool m_hasSelection;
-
-        QList<QPair<QRectF, QColor> > m_backgrounds;
-        QList<QRectF> m_selectionRects;
-        QVarLengthArray<BinaryTreeNode> m_currentLineTree;
-
-        QList<TextDecoration> m_lines;
-        QVector<BinaryTreeNode> m_processedNodes;
-
-        QList<QPair<QRectF, QImage> > m_images;
-    };
-
-    int SelectionEngine::addText(const QTextBlock &block,
-                                 const QTextCharFormat &charFormat,
-                                 const QColor &textColor,
-                                 const QVarLengthArray<QTextLayout::FormatRange> &colorChanges,
-                                 int textPos, int fragmentEnd,
-                                 int selectionStart, int selectionEnd)
-    {
-        if (charFormat.foreground().style() != Qt::NoBrush)
-            setTextColor(charFormat.foreground().color());
-        else
-            setTextColor(textColor);
-
-        while (textPos < fragmentEnd) {
-            int blockRelativePosition = textPos - block.position();
-            QTextLine line = block.layout()->lineForTextPosition(blockRelativePosition);
-            if (!currentLine().isValid()
-                || line.lineNumber() != currentLine().lineNumber()) {
-                setCurrentLine(line);
-            }
-
-            Q_ASSERT(line.textLength() > 0);
-            int lineEnd = line.textStart() + block.position() + line.textLength();
-
-            int len = qMin(lineEnd - textPos, fragmentEnd - textPos);
-            Q_ASSERT(len > 0);
-
-            int currentStepEnd = textPos + len;
-
-            addGlyphsForRanges(colorChanges,
-                               textPos - block.position(),
-                               currentStepEnd - block.position(),
-                               selectionStart - block.position(),
-                               selectionEnd - block.position());
-
-            textPos = currentStepEnd;
-        }
-        return textPos;
-    }
-
-    void SelectionEngine::addTextDecorations(const QVarLengthArray<TextDecoration> &textDecorations,
-                                             qreal offset, qreal thickness)
-    {
-        for (int i=0; i<textDecorations.size(); ++i) {
-            TextDecoration textDecoration = textDecorations.at(i);
-
-            {
-                QRectF &rect = textDecoration.rect;
-                rect.setY(qRound(rect.y() + m_currentLine.ascent() + offset));
-                rect.setHeight(thickness);
-            }
-
-            m_lines.append(textDecoration);
-        }
-    }
-
-    void SelectionEngine::processCurrentLine()
-    {
-        // No glyphs, do nothing
-        if (m_currentLineTree.isEmpty())
-            return;
-
-        // 1. Go through current line and get correct decoration position for each node based on
-        // neighbouring decorations. Add decoration to global list
-        // 2. Create clip nodes for all selected text. Try to merge as many as possible within
-        // the line.
-        // 3. Add QRects to a list of selection rects.
-        // 4. Add all nodes to a global processed list
-        QVarLengthArray<int> sortedIndexes; // Indexes in tree sorted by x position
-        BinaryTreeNode::inOrder(m_currentLineTree, &sortedIndexes);
-
-        Q_ASSERT(sortedIndexes.size() == m_currentLineTree.size());
-
-        BinaryTreeNode::SelectionState currentSelectionState = BinaryTreeNode::Unselected;
-        QRectF currentRect;
-
-        QQuickTextNode::Decorations currentDecorations = QQuickTextNode::NoDecoration;
-        qreal underlineOffset = 0.0;
-        qreal underlineThickness = 0.0;
-
-        qreal overlineOffset = 0.0;
-        qreal overlineThickness = 0.0;
-
-        qreal strikeOutOffset = 0.0;
-        qreal strikeOutThickness = 0.0;
-
-        QRectF decorationRect = currentRect;
-
-        QColor lastColor;
-        QColor lastBackgroundColor;
-
-        QVarLengthArray<TextDecoration> pendingUnderlines;
-        QVarLengthArray<TextDecoration> pendingOverlines;
-        QVarLengthArray<TextDecoration> pendingStrikeOuts;
-        if (!sortedIndexes.isEmpty()) {
-            QQuickDefaultClipNode *currentClipNode = m_hasSelection ? new QQuickDefaultClipNode(QRectF()) : 0;
-            bool currentClipNodeUsed = false;
-            for (int i=0; i<=sortedIndexes.size(); ++i) {
-                BinaryTreeNode *node = 0;
-                if (i < sortedIndexes.size()) {
-                    int sortedIndex = sortedIndexes.at(i);
-                    Q_ASSERT(sortedIndex < m_currentLineTree.size());
-
-                    node = m_currentLineTree.data() + sortedIndex;
-                }
-
-                if (i == 0)
-                    currentSelectionState = node->selectionState;
-
-                // Update decorations
-                if (currentDecorations != QQuickTextNode::NoDecoration) {
-                    decorationRect.setY(m_position.y() + m_currentLine.y());
-                    decorationRect.setHeight(m_currentLine.height());
-
-                    if (node != 0)
-                        decorationRect.setRight(node->boundingRect.left());
-
-                    TextDecoration textDecoration(currentSelectionState, decorationRect, lastColor);
-                    if (currentDecorations & QQuickTextNode::Underline)
-                        pendingUnderlines.append(textDecoration);
-
-                    if (currentDecorations & QQuickTextNode::Overline)
-                        pendingOverlines.append(textDecoration);
-
-                    if (currentDecorations & QQuickTextNode::StrikeOut)
-                        pendingStrikeOuts.append(textDecoration);
-
-                    if (currentDecorations & QQuickTextNode::Background)
-                        m_backgrounds.append(qMakePair(decorationRect, lastBackgroundColor));
-                }
-
-                // If we've reached an unselected node from a selected node, we add the
-                // selection rect to the graph, and we add decoration every time the
-                // selection state changes, because that means the text color changes
-                if (node == 0 || node->selectionState != currentSelectionState) {
-                    if (node != 0)
-                        currentRect.setRight(node->boundingRect.left());
-                    currentRect.setY(m_position.y() + m_currentLine.y());
-                    currentRect.setHeight(m_currentLine.height());
-
-                    // Draw selection all the way up to the left edge of the unselected item
-                    if (currentSelectionState == BinaryTreeNode::Selected)
-                        m_selectionRects.append(currentRect);
-
-                    if (currentClipNode != 0) {
-                        if (!currentClipNodeUsed) {
-                            delete currentClipNode;
-                        } else {
-                            currentClipNode->setIsRectangular(true);
-                            currentClipNode->setRect(currentRect);
-                            currentClipNode->update();
-                        }
-                    }
-
-                    if (node != 0 && m_hasSelection)
-                        currentClipNode = new QQuickDefaultClipNode(QRectF());
-                    else
-                        currentClipNode = 0;
-                    currentClipNodeUsed = false;
-
-                    if (node != 0) {
-                        currentSelectionState = node->selectionState;
-                        currentRect = node->boundingRect;
-
-                        // Make sure currentRect is valid, otherwise the unite won't work
-                        if (currentRect.isNull())
-                            currentRect.setSize(QSizeF(1, 1));
-                    }
-                } else {
-                    if (currentRect.isNull())
-                        currentRect = node->boundingRect;
-                    else
-                        currentRect = currentRect.united(node->boundingRect);
-                }
-
-                if (node != 0) {
-                    node->clipNode = currentClipNode;
-                    currentClipNodeUsed = true;
-
-                    decorationRect = node->boundingRect;
-
-                    // If previous item(s) had underline and current does not, then we add the
-                    // pending lines to the lists and likewise for overlines and strikeouts
-                    if (!pendingUnderlines.isEmpty()
-                      && !(node->decorations & QQuickTextNode::Underline)) {
-                        addTextDecorations(pendingUnderlines, underlineOffset, underlineThickness);
-
-                        pendingUnderlines.clear();
-
-                        underlineOffset = 0.0;
-                        underlineThickness = 0.0;
-                    }
-
-                    // ### Add pending when overlineOffset/thickness changes to minimize number of
-                    // nodes
-                    if (!pendingOverlines.isEmpty()) {
-                        addTextDecorations(pendingOverlines, overlineOffset, overlineThickness);
-
-                        pendingOverlines.clear();
-
-                        overlineOffset = 0.0;
-                        overlineThickness = 0.0;
-                    }
-
-                    // ### Add pending when overlineOffset/thickness changes to minimize number of
-                    // nodes
-                    if (!pendingStrikeOuts.isEmpty()) {
-                        addTextDecorations(pendingStrikeOuts, strikeOutOffset, strikeOutThickness);
-
-                        pendingStrikeOuts.clear();
-
-                        strikeOutOffset = 0.0;
-                        strikeOutThickness = 0.0;
-                    }
-
-                    // Merge current values with previous. Prefer greatest thickness
-                    QRawFont rawFont = node->glyphRun.rawFont();
-                    if (node->decorations & QQuickTextNode::Underline) {
-                        if (rawFont.lineThickness() > underlineThickness) {
-                            underlineThickness = rawFont.lineThickness();
-                            underlineOffset = rawFont.underlinePosition();
-                        }
-                    }
-
-                    if (node->decorations & QQuickTextNode::Overline) {
-                        overlineOffset = -rawFont.ascent();
-                        overlineThickness = rawFont.lineThickness();
-                    }
-
-                    if (node->decorations & QQuickTextNode::StrikeOut) {
-                        strikeOutThickness = rawFont.lineThickness();
-                        strikeOutOffset = rawFont.ascent() / -3.0;
-                    }
-
-                    currentDecorations = node->decorations;
-                    lastColor = node->color;
-                    lastBackgroundColor = node->backgroundColor;
-                    m_processedNodes.append(*node);
-                }
-            }
-
-            if (!pendingUnderlines.isEmpty())
-                addTextDecorations(pendingUnderlines, underlineOffset, underlineThickness);
-
-            if (!pendingOverlines.isEmpty())
-                addTextDecorations(pendingOverlines, overlineOffset, overlineThickness);
-
-            if (!pendingStrikeOuts.isEmpty())
-                addTextDecorations(pendingStrikeOuts, strikeOutOffset, strikeOutThickness);
-        }
-
-        m_currentLineTree.clear();
-        m_currentLine = QTextLine();
-        m_hasSelection = false;
-    }
-
-    void SelectionEngine::addImage(const QRectF &rect, const QImage &image, qreal ascent,
-                                   BinaryTreeNode::SelectionState selectionState,
-                                   QTextFrameFormat::Position layoutPosition)
-    {
-        QRectF searchRect = rect;
-        if (layoutPosition == QTextFrameFormat::InFlow) {
-            if (m_currentLineTree.isEmpty()) {
-                searchRect.moveTopLeft(m_position + m_currentLine.position());
-            } else {
-                const BinaryTreeNode *lastNode = m_currentLineTree.data() + m_currentLineTree.size() - 1;
-                if (lastNode->glyphRun.isRightToLeft()) {
-                    QPointF lastPos = lastNode->boundingRect.topLeft();
-                    searchRect.moveTopRight(lastPos - QPointF(0, ascent - lastNode->ascent));
-                } else {
-                    QPointF lastPos = lastNode->boundingRect.topRight();
-                    searchRect.moveTopLeft(lastPos - QPointF(0, ascent - lastNode->ascent));
-                }
-            }
-        }
-
-        BinaryTreeNode::insert(&m_currentLineTree, searchRect, image, ascent, selectionState);
-    }
-
-    void SelectionEngine::addTextObject(const QPointF &position, const QTextCharFormat &format,
-                                        BinaryTreeNode::SelectionState selectionState,
-                                        QTextDocument *textDocument, int pos,
-                                        QTextFrameFormat::Position layoutPosition)
-    {
-        QTextObjectInterface *handler = textDocument->documentLayout()->handlerForObject(format.objectType());
-        if (handler != 0) {
-            QImage image;
-            QSizeF size = handler->intrinsicSize(textDocument, pos, format);
-
-            if (format.objectType() == QTextFormat::ImageObject) {
-                QTextImageFormat imageFormat = format.toImageFormat();
-                if (QQuickTextDocumentWithImageResources *imageDoc = qobject_cast<QQuickTextDocumentWithImageResources *>(textDocument)) {
-                    image = imageDoc->image(imageFormat);
-
-                    if (image.isNull())
-                        return;
-                } else {
-                    QTextImageHandler *imageHandler = static_cast<QTextImageHandler *>(handler);
-                    image = imageHandler->image(textDocument, imageFormat);
-                }
-            }
-
-            if (image.isNull()) {
-                image = QImage(size.toSize(), QImage::Format_ARGB32_Premultiplied);
-                image.fill(Qt::transparent);
-                {
-                    QPainter painter(&image);
-                    handler->drawObject(&painter, image.rect(), textDocument, pos, format);
-                }
-            }
-
-            qreal ascent;
-            QFontMetrics m(format.font());
-            switch (format.verticalAlignment())
-            {
-            case QTextCharFormat::AlignMiddle:
-                ascent = size.height() / 2 - 1;
-                break;
-            case QTextCharFormat::AlignBaseline:
-                ascent = size.height() - m.descent() - 1;
-                break;
-            default:
-                ascent = size.height() - 1;
-            }
-
-            addImage(QRectF(position, size), image, ascent, selectionState, layoutPosition);
-        }
-    }
-
-    void SelectionEngine::addUnselectedGlyphs(const QGlyphRun &glyphRun)
-    {
-        BinaryTreeNode::insert(&m_currentLineTree, glyphRun, BinaryTreeNode::Unselected,
-                               QQuickTextNode::NoDecoration, m_textColor, m_backgroundColor, m_position);
-    }
-
-    void SelectionEngine::addSelectedGlyphs(const QGlyphRun &glyphRun)
-    {
-        int currentSize = m_currentLineTree.size();
-        BinaryTreeNode::insert(&m_currentLineTree, glyphRun, BinaryTreeNode::Selected,
-                               QQuickTextNode::NoDecoration, m_textColor, m_backgroundColor, m_position);
-        m_hasSelection = m_hasSelection || m_currentLineTree.size() > currentSize;
-    }
-
-    void SelectionEngine::addGlyphsForRanges(const QVarLengthArray<QTextLayout::FormatRange> &ranges,
-                                             int start, int end,
-                                             int selectionStart, int selectionEnd)
-    {
-        int currentPosition = start;
-        int remainingLength = end - start;
-        for (int j=0; j<ranges.size(); ++j) {
-            const QTextLayout::FormatRange &range = ranges.at(j);
-            if (range.start + range.length >= currentPosition
-                && range.start < currentPosition + remainingLength) {
-
-                if (range.start > currentPosition) {
-                    addGlyphsInRange(currentPosition, range.start - currentPosition,
-                                     QColor(), QColor(), selectionStart, selectionEnd);
-                }
-                int rangeEnd = qMin(range.start + range.length, currentPosition + remainingLength);
-                QColor rangeColor;
-                if (range.format.hasProperty(QTextFormat::ForegroundBrush))
-                    rangeColor = range.format.foreground().color();
-                else if (range.format.isAnchor())
-                    rangeColor = m_anchorColor;
-                QColor rangeBackgroundColor = range.format.hasProperty(QTextFormat::BackgroundBrush)
-                        ? range.format.background().color()
-                        : QColor();
-
-                addGlyphsInRange(range.start, rangeEnd - range.start,
-                                 rangeColor, rangeBackgroundColor,
-                                 selectionStart, selectionEnd);
-
-                currentPosition = range.start + range.length;
-                remainingLength = end - currentPosition;
-
-            } else if (range.start > currentPosition + remainingLength || remainingLength <= 0) {
-                break;
-            }
-        }
-
-        if (remainingLength > 0) {
-            addGlyphsInRange(currentPosition, remainingLength, QColor(), QColor(),
-                             selectionStart, selectionEnd);
-        }
-
-    }
-
-    void SelectionEngine::addGlyphsInRange(int rangeStart, int rangeLength,
-                                           const QColor &color, const QColor &backgroundColor,
-                                           int selectionStart, int selectionEnd)
-    {
-        QColor oldColor;
-        if (color.isValid()) {
-            oldColor = m_textColor;
-            m_textColor = color;
-        }
-
-        QColor oldBackgroundColor = m_backgroundColor;
-        if (backgroundColor.isValid()) {
-            oldBackgroundColor = m_backgroundColor;
-            m_backgroundColor = backgroundColor;
-        }
-
-        bool hasSelection = selectionEnd >= 0
-                         && selectionStart <= selectionEnd;
-
-        QTextLine &line = m_currentLine;
-        int rangeEnd = rangeStart + rangeLength;
-        if (!hasSelection || (selectionStart > rangeEnd || selectionEnd < rangeStart)) {
-            QList<QGlyphRun> glyphRuns = line.glyphRuns(rangeStart, rangeLength);
-            for (int j=0; j<glyphRuns.size(); ++j) {
-                const QGlyphRun &glyphRun = glyphRuns.at(j);
-                addUnselectedGlyphs(glyphRun);
-            }
-        } else {
-            if (rangeStart < selectionStart) {
-                QList<QGlyphRun> glyphRuns = line.glyphRuns(rangeStart,
-                                                            qMin(selectionStart - rangeStart,
-                                                                 rangeLength));
-
-                for (int j=0; j<glyphRuns.size(); ++j) {
-                    const QGlyphRun &glyphRun = glyphRuns.at(j);
-                    addUnselectedGlyphs(glyphRun);
-                }
-            }
-
-            if (rangeEnd > selectionStart) {
-                int start = qMax(selectionStart, rangeStart);
-                int length = qMin(selectionEnd - start + 1, rangeEnd - start);
-                QList<QGlyphRun> glyphRuns = line.glyphRuns(start, length);
-
-                for (int j=0; j<glyphRuns.size(); ++j) {
-                    const QGlyphRun &glyphRun = glyphRuns.at(j);
-                    addSelectedGlyphs(glyphRun);
-                }
-            }
-
-            if (selectionEnd >= rangeStart && selectionEnd < rangeEnd) {
-                QList<QGlyphRun> glyphRuns = line.glyphRuns(selectionEnd + 1, rangeEnd - selectionEnd - 1);
-                for (int j=0; j<glyphRuns.size(); ++j) {
-                    const QGlyphRun &glyphRun = glyphRuns.at(j);
-                    addUnselectedGlyphs(glyphRun);
-                }
-            }
-        }
-
-        if (backgroundColor.isValid())
-            m_backgroundColor = oldBackgroundColor;
-
-        if (oldColor.isValid())
-            m_textColor = oldColor;
-    }
-
-    void SelectionEngine::addBorder(const QRectF &rect, qreal border,
-                                    QTextFrameFormat::BorderStyle borderStyle,
-                                    const QBrush &borderBrush)
-    {
-        QColor color = borderBrush.color();
-
-        // Currently we don't support other styles than solid
-        Q_UNUSED(borderStyle);
-
-        m_backgrounds.append(qMakePair(QRectF(rect.left(), rect.top(), border, rect.height() + border), color));
-        m_backgrounds.append(qMakePair(QRectF(rect.left() + border, rect.top(), rect.width(), border), color));
-        m_backgrounds.append(qMakePair(QRectF(rect.right(), rect.top() + border, border, rect.height() - border), color));
-        m_backgrounds.append(qMakePair(QRectF(rect.left() + border, rect.bottom(), rect.width(), border), color));
-    }
-
-    void SelectionEngine::addFrameDecorations(QTextDocument *document, QTextFrame *frame)
-    {
-        QTextDocumentLayout *documentLayout = qobject_cast<QTextDocumentLayout *>(document->documentLayout());
-        QTextFrameFormat frameFormat = frame->format().toFrameFormat();
-
-        QTextTable *table = qobject_cast<QTextTable *>(frame);
-        QRectF boundingRect = table == 0
-                ? documentLayout->frameBoundingRect(frame)
-                : documentLayout->tableBoundingRect(table);
-
-        QBrush bg = frame->frameFormat().background();
-        if (bg.style() != Qt::NoBrush)
-            m_backgrounds.append(qMakePair(boundingRect, bg.color()));
-
-        if (!frameFormat.hasProperty(QTextFormat::FrameBorder))
-            return;
-
-        qreal borderWidth = frameFormat.border();
-        if (qFuzzyIsNull(borderWidth))
-            return;
-
-        QBrush borderBrush = frameFormat.borderBrush();
-        QTextFrameFormat::BorderStyle borderStyle = frameFormat.borderStyle();
-        if (borderStyle == QTextFrameFormat::BorderStyle_None)
-            return;
-
-        addBorder(boundingRect.adjusted(frameFormat.leftMargin(), frameFormat.topMargin(),
-                                        -frameFormat.rightMargin(), -frameFormat.bottomMargin()),
-                  borderWidth, borderStyle, borderBrush);
-        if (table != 0) {
-            int rows = table->rows();
-            int columns = table->columns();
-
-            for (int row=0; row<rows; ++row) {
-                for (int column=0; column<columns; ++column) {
-                    QTextTableCell cell = table->cellAt(row, column);
-
-                    QRectF cellRect = documentLayout->tableCellBoundingRect(table, cell);
-                    addBorder(cellRect.adjusted(-borderWidth, -borderWidth, 0, 0), borderWidth,
-                              borderStyle, borderBrush);
-                }
-            }
-        }
-    }
-
-    void SelectionEngine::addToSceneGraph(QQuickTextNode *parentNode,
-                                          QQuickText::TextStyle style,
-                                          const QColor &styleColor)
-    {
-        if (m_currentLine.isValid())
-            processCurrentLine();
-
-
-        for (int i=0; i<m_backgrounds.size(); ++i) {
-            const QRectF &rect = m_backgrounds.at(i).first;
-            const QColor &color = m_backgrounds.at(i).second;
-
-            parentNode->appendChildNode(new QSGSimpleRectNode(rect, color));
-        }
-
-        // First, prepend all selection rectangles to the tree
-        for (int i=0; i<m_selectionRects.size(); ++i) {
-            const QRectF &rect = m_selectionRects.at(i);
-
-            parentNode->appendChildNode(new QSGSimpleRectNode(rect, m_selectionColor));
-        }
-
-        // Finally, add decorations for each node to the tree.
-        for (int i=0; i<m_lines.size(); ++i) {
-            const TextDecoration &textDecoration = m_lines.at(i);
-
-            QColor color = textDecoration.selectionState == BinaryTreeNode::Selected
-                    ? m_selectedTextColor
-                    : textDecoration.color;
-
-            parentNode->appendChildNode(new QSGSimpleRectNode(textDecoration.rect, color));
-        }
-
-        // Then, go through all the nodes for all lines and combine all QGlyphRuns with a common
-        // font, selection state and clip node.
-        typedef QPair<QFontEngine *, QPair<QQuickDefaultClipNode *, QPair<QRgb, int> > > KeyType;
-        QHash<KeyType, BinaryTreeNode *> map;
-        QList<BinaryTreeNode *> nodes;
-        for (int i=0; i<m_processedNodes.size(); ++i) {
-            BinaryTreeNode *node = m_processedNodes.data() + i;
-
-            if (node->image.isNull()) {
-                QGlyphRun glyphRun = node->glyphRun;
-                QRawFont rawFont = glyphRun.rawFont();
-                QRawFontPrivate *rawFontD = QRawFontPrivate::get(rawFont);
-
-                QFontEngine *fontEngine = rawFontD->fontEngine;
-
-                KeyType key(qMakePair(fontEngine,
-                                      qMakePair(node->clipNode,
-                                                qMakePair(node->color.rgba(), int(node->selectionState)))));
-
-                BinaryTreeNode *otherNode = map.value(key, 0);
-                if (otherNode != 0) {
-                    QGlyphRun &otherGlyphRun = otherNode->glyphRun;
-
-                    QVector<quint32> otherGlyphIndexes = otherGlyphRun.glyphIndexes();
-                    QVector<QPointF> otherGlyphPositions = otherGlyphRun.positions();
-
-                    otherGlyphIndexes += glyphRun.glyphIndexes();
-
-                    QVector<QPointF> glyphPositions = glyphRun.positions();
-                    for (int j=0; j<glyphPositions.size(); ++j) {
-                        otherGlyphPositions += glyphPositions.at(j) + (node->position - otherNode->position);
-                    }
-
-                    otherGlyphRun.setGlyphIndexes(otherGlyphIndexes);
-                    otherGlyphRun.setPositions(otherGlyphPositions);
-
-                } else {
-                    map.insert(key, node);
-                    nodes.append(node);
-                }
-            } else {
-                parentNode->addImage(node->boundingRect, node->image);
-                if (node->selectionState == BinaryTreeNode::Selected) {
-                    QColor color = m_selectionColor;
-                    color.setAlpha(128);
-                    parentNode->appendChildNode(new QSGSimpleRectNode(node->boundingRect, color));
-                }
-            }
-        }
-
-        // ...and add clip nodes and glyphs to tree.
-        foreach (const BinaryTreeNode *node, nodes) {
-
-            QQuickDefaultClipNode *clipNode = node->clipNode;
-            if (clipNode != 0 && clipNode->parent() == 0 )
-                parentNode->appendChildNode(clipNode);
-
-            QColor color = node->selectionState == BinaryTreeNode::Selected
-                    ? m_selectedTextColor
-                    : node->color;
-
-            parentNode->addGlyphs(node->position, node->glyphRun, color, style, styleColor, clipNode);
-        }
-    }
-}
-
-void QQuickTextNode::mergeFormats(QTextLayout *textLayout,
-                               QVarLengthArray<QTextLayout::FormatRange> *mergedFormats)
+void QQuickTextNode::initEngine(const QColor& textColor, const QColor& selectedTextColor, const QColor& selectionColor, const QColor& anchorColor)
 {
-    Q_ASSERT(mergedFormats != 0);
-    if (textLayout == 0)
-        return;
-
-    QList<QTextLayout::FormatRange> additionalFormats = textLayout->additionalFormats();
-    for (int i=0; i<additionalFormats.size(); ++i) {
-        QTextLayout::FormatRange additionalFormat = additionalFormats.at(i);
-        if (additionalFormat.format.hasProperty(QTextFormat::ForegroundBrush)
-         || additionalFormat.format.hasProperty(QTextFormat::BackgroundBrush)
-         || additionalFormat.format.isAnchor()) {
-            // Merge overlapping formats
-            if (!mergedFormats->isEmpty()) {
-                QTextLayout::FormatRange *lastFormat = mergedFormats->data() + mergedFormats->size() - 1;
-
-                if (additionalFormat.start < lastFormat->start + lastFormat->length) {
-                    QTextLayout::FormatRange *mergedRange = 0;
-
-                    int length = additionalFormat.length;
-                    if (additionalFormat.start > lastFormat->start) {
-                        lastFormat->length = additionalFormat.start - lastFormat->start;
-                        length -= lastFormat->length;
-
-                        mergedFormats->append(QTextLayout::FormatRange());
-                        mergedRange = mergedFormats->data() + mergedFormats->size() - 1;
-                        lastFormat = mergedFormats->data() + mergedFormats->size() - 2;
-                    } else {
-                        mergedRange = lastFormat;
-                    }
-
-                    mergedRange->format = lastFormat->format;
-                    mergedRange->format.merge(additionalFormat.format);
-                    mergedRange->start = additionalFormat.start;
-
-                    int end = qMin(additionalFormat.start + additionalFormat.length,
-                                   lastFormat->start + lastFormat->length);
-
-                    mergedRange->length = end - mergedRange->start;
-                    length -= mergedRange->length;
-
-                    additionalFormat.start = end;
-                    additionalFormat.length = length;
-                }
-            }
-
-            if (additionalFormat.length > 0)
-                mergedFormats->append(additionalFormat);
-        }
-    }
-
-}
-
-namespace {
-
-    class ProtectedLayoutAccessor: public QAbstractTextDocumentLayout
-    {
-    public:
-        inline QTextCharFormat formatAccessor(int pos)
-        {
-            return format(pos);
-        }
-    };
-
+    m_engine.reset(new QQuickTextNodeEngine);
+    m_engine->m_hasContents = false;
+    m_engine->setTextColor(textColor);
+    m_engine->setSelectedTextColor(selectedTextColor);
+    m_engine->setSelectionColor(selectionColor);
+    m_engine->setAnchorColor(anchorColor);
 }
 
 void QQuickTextNode::addImage(const QRectF &rect, const QImage &image)
@@ -1118,11 +205,7 @@ void QQuickTextNode::addTextDocument(const QPointF &position, QTextDocument *tex
                                   const QColor &selectionColor, const QColor &selectedTextColor,
                                   int selectionStart, int selectionEnd)
 {
-    SelectionEngine engine;
-    engine.setTextColor(textColor);
-    engine.setSelectedTextColor(selectedTextColor);
-    engine.setSelectionColor(selectionColor);
-    engine.setAnchorColor(anchorColor);
+    initEngine(textColor, selectedTextColor, selectionColor, anchorColor);
 
     QList<QTextFrame *> frames;
     frames.append(textDocument->rootFrame());
@@ -1130,7 +213,7 @@ void QQuickTextNode::addTextDocument(const QPointF &position, QTextDocument *tex
         QTextFrame *textFrame = frames.takeFirst();
         frames.append(textFrame->childFrames());
 
-        engine.addFrameDecorations(textDocument, textFrame);
+        m_engine->addFrameDecorations(textDocument, textFrame);
 
         if (textFrame->firstPosition() > textFrame->lastPosition()
          && textFrame->frameFormat().position() != QTextFrameFormat::InFlow) {
@@ -1140,160 +223,23 @@ void QQuickTextNode::addTextDocument(const QPointF &position, QTextDocument *tex
             QRectF rect = a->frameBoundingRect(textFrame);
 
             QTextBlock block = textFrame->firstCursorPosition().block();
-            engine.setCurrentLine(block.layout()->lineForTextPosition(pos - block.position()));
-            engine.addTextObject(rect.topLeft(), format, BinaryTreeNode::Unselected, textDocument,
+            m_engine->setCurrentLine(block.layout()->lineForTextPosition(pos - block.position()));
+            m_engine->addTextObject(rect.topLeft(), format, QQuickTextNodeEngine::Unselected, textDocument,
                                  pos, textFrame->frameFormat().position());
         } else {
             QTextFrame::iterator it = textFrame->begin();
 
             while (!it.atEnd()) {
-                Q_ASSERT(!engine.currentLine().isValid());
+                Q_ASSERT(!m_engine->currentLine().isValid());
 
                 QTextBlock block = it.currentBlock();
-#ifndef QT_NO_IM
-                int preeditLength = block.isValid() ? block.layout()->preeditAreaText().length() : 0;
-                int preeditPosition = block.isValid() ? block.layout()->preeditAreaPosition() : -1;
-#endif
-
-                QVarLengthArray<QTextLayout::FormatRange> colorChanges;
-                mergeFormats(block.layout(), &colorChanges);
-
-                QPointF blockPosition = textDocument->documentLayout()->blockBoundingRect(block).topLeft() + position;
-                if (QTextList *textList = block.textList()) {
-                    QPointF pos = blockPosition;
-                    QTextLayout *layout = block.layout();
-                    if (layout->lineCount() > 0) {
-                        QTextLine firstLine = layout->lineAt(0);
-                        Q_ASSERT(firstLine.isValid());
-
-                        engine.setCurrentLine(firstLine);
-
-                        QRectF textRect = firstLine.naturalTextRect();
-                        pos += textRect.topLeft();
-                        if (block.textDirection() == Qt::RightToLeft)
-                            pos.rx() += textRect.width();
-
-                        const QTextCharFormat charFormat = block.charFormat();
-                        QFont font(charFormat.font());
-                        QFontMetricsF fontMetrics(font);
-                        QTextListFormat listFormat = textList->format();
-
-                        QString listItemBullet;
-                        switch (listFormat.style()) {
-                        case QTextListFormat::ListCircle:
-                            listItemBullet = QChar(0x25E6); // White bullet
-                            break;
-                        case QTextListFormat::ListSquare:
-                            listItemBullet = QChar(0x25AA); // Black small square
-                            break;
-                        case QTextListFormat::ListDecimal:
-                        case QTextListFormat::ListLowerAlpha:
-                        case QTextListFormat::ListUpperAlpha:
-                        case QTextListFormat::ListLowerRoman:
-                        case QTextListFormat::ListUpperRoman:
-                            listItemBullet = textList->itemText(block);
-                            break;
-                        default:
-                            listItemBullet = QChar(0x2022); // Black bullet
-                            break;
-                        };
-
-                        QSizeF size(fontMetrics.width(listItemBullet), fontMetrics.height());
-                        qreal xoff = fontMetrics.width(QLatin1Char(' '));
-                        if (block.textDirection() == Qt::LeftToRight)
-                            xoff = -xoff - size.width();
-                        engine.setPosition(pos + QPointF(xoff, 0));
-
-                        QTextLayout layout;
-                        layout.setFont(font);
-                        layout.setText(listItemBullet); // Bullet
-                        layout.beginLayout();
-                        QTextLine line = layout.createLine();
-                        line.setPosition(QPointF(0, 0));
-                        layout.endLayout();
-
-                        QList<QGlyphRun> glyphRuns = layout.glyphRuns();
-                        for (int i=0; i<glyphRuns.size(); ++i)
-                            engine.addUnselectedGlyphs(glyphRuns.at(i));
-                    }
-                }
-
-                int textPos = block.position();
-                QTextBlock::iterator blockIterator = block.begin();
-
-                while (!blockIterator.atEnd()) {
-                    QTextFragment fragment = blockIterator.fragment();
-                    QString text = fragment.text();
-                    if (text.isEmpty())
-                        continue;
-
-                    QTextCharFormat charFormat = fragment.charFormat();
-                    engine.setPosition(blockPosition);
-                    if (text.contains(QChar::ObjectReplacementCharacter)) {
-                        QTextFrame *frame = qobject_cast<QTextFrame *>(textDocument->objectForFormat(charFormat));
-                        if (frame && frame->frameFormat().position() == QTextFrameFormat::InFlow) {
-                            int blockRelativePosition = textPos - block.position();
-                            QTextLine line = block.layout()->lineForTextPosition(blockRelativePosition);
-                            if (!engine.currentLine().isValid()
-                                    || line.lineNumber() != engine.currentLine().lineNumber()) {
-                                engine.setCurrentLine(line);
-                            }
-
-                            BinaryTreeNode::SelectionState selectionState =
-                                    (selectionStart < textPos + text.length()
-                                     && selectionEnd >= textPos)
-                                    ? BinaryTreeNode::Selected
-                                    : BinaryTreeNode::Unselected;
-
-                            engine.addTextObject(QPointF(), charFormat, selectionState, textDocument, textPos);
-                        }
-                        textPos += text.length();
-                    } else {
-                        if (charFormat.foreground().style() != Qt::NoBrush)
-                            engine.setTextColor(charFormat.foreground().color());
-                        else if (charFormat.isAnchor())
-                            engine.setTextColor(anchorColor);
-                        else
-                            engine.setTextColor(textColor);
-
-                        int fragmentEnd = textPos + fragment.length();
-#ifndef QT_NO_IM
-                        if (preeditPosition >= 0
-                         && preeditPosition >= textPos
-                         && preeditPosition <= fragmentEnd) {
-                            fragmentEnd += preeditLength;
-                        }
-#endif
-
-                        textPos = engine.addText(block, charFormat, textColor, colorChanges, textPos, fragmentEnd,
-                                       selectionStart, selectionEnd);
-                    }
-
-                    ++blockIterator;
-                }
-
-#ifndef QT_NO_IM
-                if (preeditLength >= 0 && textPos <= block.position() + preeditPosition) {
-                    engine.setPosition(blockPosition);
-                    textPos = block.position() + preeditPosition;
-                    QTextLine line = block.layout()->lineForTextPosition(preeditPosition);
-                    if (!engine.currentLine().isValid()
-                            || line.lineNumber() != engine.currentLine().lineNumber()) {
-                        engine.setCurrentLine(line);
-                    }
-                    textPos = engine.addText(block, block.charFormat(), textColor, colorChanges,
-                                             textPos, textPos + preeditLength,
-                                             selectionStart, selectionEnd);
-                }
-#endif
-
-                engine.setCurrentLine(QTextLine()); // Reset current line because the text layout changed
+                m_engine->addTextBlock(textDocument, block, position, textColor, anchorColor, selectionStart, selectionEnd);
                 ++it;
             }
         }
     }
 
-    engine.addToSceneGraph(this, style, styleColor);
+    m_engine->addToSceneGraph(this, style, styleColor);
 }
 
 void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLayout, const QColor &color,
@@ -1303,12 +249,7 @@ void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLay
                                 int selectionStart, int selectionEnd,
                                 int lineStart, int lineCount)
 {
-    SelectionEngine engine;
-    engine.setTextColor(color);
-    engine.setSelectedTextColor(selectedTextColor);
-    engine.setSelectionColor(selectionColor);
-    engine.setAnchorColor(anchorColor);
-    engine.setPosition(position);
+    initEngine(color, selectedTextColor, selectionColor, anchorColor);
 
 #ifndef QT_NO_IM
     int preeditLength = textLayout->preeditAreaText().length();
@@ -1316,7 +257,7 @@ void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLay
 #endif
 
     QVarLengthArray<QTextLayout::FormatRange> colorChanges;
-    mergeFormats(textLayout, &colorChanges);
+    m_engine->mergeFormats(textLayout, &colorChanges);
 
     lineCount = lineCount >= 0
             ? qMin(lineStart + lineCount, textLayout->lineCount())
@@ -1337,11 +278,11 @@ void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLay
         }
 #endif
 
-        engine.setCurrentLine(line);
-        engine.addGlyphsForRanges(colorChanges, start, end, selectionStart, selectionEnd);
+        m_engine->setCurrentLine(line);
+        m_engine->addGlyphsForRanges(colorChanges, start, end, selectionStart, selectionEnd);
     }
 
-    engine.addToSceneGraph(this, style, styleColor);
+    m_engine->addToSceneGraph(this, style, styleColor);
 }
 
 void QQuickTextNode::deleteContent()