Apply the QStaticText text-caching strategy for QML

QML cannot use QStaticText directly as it doesn't support caching a
QTextLayout.  QDeclarativeTextLayout is basically a copy of QStaticText
that adds this support.

Currently this feature is disabled by default (enable with
QML_DISABLE_IMAGE_CACHE=1) while we double check the perf consequences
of this change.

Task-number: QTBUG-14050

5 files changed, 365 insertions, 28 deletions

diff --git a/src/declarative/graphicsitems/graphicsitems.pri b/src/declarative/graphicsitems/graphicsitems.pri
index d420595..ffdeb29 100644
--- a/src/declarative/graphicsitems/graphicsitems.pri
+++ b/src/declarative/graphicsitems/graphicsitems.pri
@@ -49,7 +49,8 @@ HEADERS += \
     $$PWD/qdeclarativelistview_p.h \
     $$PWD/qdeclarativelayoutitem_p.h \
     $$PWD/qdeclarativeitemchangelistener_p.h \
-    $$PWD/qdeclarativegraphicswidget_p.h
+    $$PWD/qdeclarativegraphicswidget_p.h \
+    $$PWD/qdeclarativetextlayout_p.h
 
 SOURCES += \
     $$PWD/qdeclarativeitemsmodule.cpp \
@@ -81,4 +82,6 @@ SOURCES += \
     $$PWD/qdeclarativevisualitemmodel.cpp \
     $$PWD/qdeclarativelistview.cpp \
     $$PWD/qdeclarativelayoutitem.cpp \
-    $$PWD/qdeclarativegraphicswidget.cpp
+    $$PWD/qdeclarativegraphicswidget.cpp \
+    $$PWD/qdeclarativetextlayout.cpp
+
diff --git a/src/declarative/graphicsitems/qdeclarativetext.cpp b/src/declarative/graphicsitems/qdeclarativetext.cpp
index 1f4c1c7..c2dd850 100644
--- a/src/declarative/graphicsitems/qdeclarativetext.cpp
+++ b/src/declarative/graphicsitems/qdeclarativetext.cpp
@@ -82,6 +82,19 @@ private:
     static QSet<QUrl> errors;
 };
 
+DEFINE_BOOL_CONFIG_OPTION(disableImageCache, QML_DISABLE_IMAGE_CACHE);
+
+QDeclarativeTextPrivate::QDeclarativeTextPrivate()
+: color((QRgb)0), style(QDeclarativeText::Normal),
+  hAlign(QDeclarativeText::AlignLeft), vAlign(QDeclarativeText::AlignTop), elideMode(QDeclarativeText::ElideNone),
+  imgDirty(true), dirty(true), richText(false), singleline(false), cache(true), internalWidthUpdate(false), doc(0),
+  format(QDeclarativeText::AutoText), wrapMode(QDeclarativeText::NoWrap)
+{
+    cache = !disableImageCache();
+    QGraphicsItemPrivate::acceptedMouseButtons = Qt::LeftButton;
+    QGraphicsItemPrivate::flags = QGraphicsItemPrivate::flags & ~QGraphicsItem::ItemHasNoContents;
+}
+
 QTextDocumentWithImageResources::QTextDocumentWithImageResources(QDeclarativeText *parent) 
 : QTextDocument(parent), outstanding(0)
 {
@@ -145,7 +158,6 @@ void QTextDocumentWithImageResources::requestFinished()
 void QTextDocumentWithImageResources::setText(const QString &text)
 {
     if (!m_resources.isEmpty()) {
-        qWarning("CLEAR");
         qDeleteAll(m_resources);
         m_resources.clear();
         outstanding = 0;
@@ -792,7 +804,7 @@ void QDeclarativeTextPrivate::updateSize()
 
         //setup instance of QTextLayout for all cases other than richtext
         if (!richText) {
-            size = setupTextLayout(&layout);
+            size = setupTextLayout();
             if (cachedLayoutSize != size) {
                 q->prepareGeometryChange();
                 cachedLayoutSize = size;
@@ -907,10 +919,10 @@ void QDeclarativeTextPrivate::drawOutline(int yOffset)
     imgCache = img;
 }
 
-QSize QDeclarativeTextPrivate::setupTextLayout(QTextLayout *layout)
+QSize QDeclarativeTextPrivate::setupTextLayout()
 {
     Q_Q(QDeclarativeText);
-    layout->setCacheEnabled(true);
+    layout.setCacheEnabled(true);
 
     int height = 0;
     qreal widthUsed = 0;
@@ -920,25 +932,25 @@ QSize QDeclarativeTextPrivate::setupTextLayout(QTextLayout *layout)
     if ((wrapMode != QDeclarativeText::NoWrap || elideMode != QDeclarativeText::ElideNone) && q->widthValid())
         lineWidth = q->width();
 
-    QTextOption textOption = layout->textOption();
+    QTextOption textOption = layout.textOption();
     textOption.setWrapMode(QTextOption::WrapMode(wrapMode));
-    layout->setTextOption(textOption);
+    layout.setTextOption(textOption);
 
-    layout->beginLayout();
+    layout.beginLayout();
 
     while (1) {
-        QTextLine line = layout->createLine();
+        QTextLine line = layout.createLine();
         if (!line.isValid())
             break;
 
         if ((wrapMode != QDeclarativeText::NoWrap || elideMode != QDeclarativeText::ElideNone) && q->widthValid())
             line.setLineWidth(lineWidth);
     }
-    layout->endLayout();
+    layout.endLayout();
 
     int x = 0;
-    for (int i = 0; i < layout->lineCount(); ++i) {
-        QTextLine line = layout->lineAt(i);
+    for (int i = 0; i < layout.lineCount(); ++i) {
+        QTextLine line = layout.lineAt(i);
         widthUsed = qMax(widthUsed, line.naturalTextWidth());
         line.setPosition(QPointF(0, height));
         height += int(line.height());
@@ -1000,7 +1012,7 @@ void QDeclarativeTextPrivate::drawWrappedText(QPainter *p, const QPointF &pos, b
     else
         p->setPen(color);
     p->setFont(font);
-    layout.draw(p, pos);
+    layout.draw(p , pos); 
 }
 
 QPixmap QDeclarativeTextPrivate::richTextImage(bool drawStyle)
diff --git a/src/declarative/graphicsitems/qdeclarativetext_p_p.h b/src/declarative/graphicsitems/qdeclarativetext_p_p.h
index 48552a7..ba1ec78 100644
--- a/src/declarative/graphicsitems/qdeclarativetext_p_p.h
+++ b/src/declarative/graphicsitems/qdeclarativetext_p_p.h
@@ -55,6 +55,7 @@
 
 #include "qdeclarativeitem.h"
 #include "private/qdeclarativeitem_p.h"
+#include "private/qdeclarativetextlayout_p.h"
 
 #include <qdeclarative.h>
 
@@ -65,22 +66,12 @@ QT_BEGIN_NAMESPACE
 class QTextLayout;
 class QTextDocumentWithImageResources;
 
+#define QML_NO_TEXT_CACHE 
 class QDeclarativeTextPrivate : public QDeclarativeItemPrivate
 {
     Q_DECLARE_PUBLIC(QDeclarativeText)
 public:
-    QDeclarativeTextPrivate()
-      : color((QRgb)0), style(QDeclarativeText::Normal),
-        hAlign(QDeclarativeText::AlignLeft), vAlign(QDeclarativeText::AlignTop), elideMode(QDeclarativeText::ElideNone),
-        imgDirty(true), dirty(true), richText(false), singleline(false), cache(true), internalWidthUpdate(false), doc(0),
-        format(QDeclarativeText::AutoText), wrapMode(QDeclarativeText::NoWrap)
-    {
-#if defined(QML_NO_TEXT_CACHE)
-        cache = false;
-#endif
-        QGraphicsItemPrivate::acceptedMouseButtons = Qt::LeftButton;
-        QGraphicsItemPrivate::flags = QGraphicsItemPrivate::flags & ~QGraphicsItem::ItemHasNoContents;
-    }
+    QDeclarativeTextPrivate();
 
     ~QDeclarativeTextPrivate();
 
@@ -101,7 +92,7 @@ public:
     QPixmap wrappedTextImage(bool drawStyle);
     void drawWrappedText(QPainter *p, const QPointF &pos, bool drawStyle);
     QPixmap richTextImage(bool drawStyle);
-    QSize setupTextLayout(QTextLayout *layout);
+    QSize setupTextLayout();
 
     QString text;
     QFont font;
@@ -121,7 +112,7 @@ public:
     bool cache:1;
     bool internalWidthUpdate:1;
     QTextDocumentWithImageResources *doc;
-    QTextLayout layout;
+    QDeclarativeTextLayout layout;
     QSize cachedLayoutSize;
     QDeclarativeText::TextFormat format;
     QDeclarativeText::WrapMode wrapMode;
diff --git a/src/declarative/graphicsitems/qdeclarativetextlayout.cpp b/src/declarative/graphicsitems/qdeclarativetextlayout.cpp
new file mode 100644
index 0000000..5972f92
--- /dev/null
+++ b/src/declarative/graphicsitems/qdeclarativetextlayout.cpp
@@ -0,0 +1,308 @@
+#include "qdeclarativetextlayout_p.h"
+#include <private/qstatictext_p.h>
+#include <private/qfontengine_p.h>
+#include <private/qtextengine_p.h>
+#include <private/qpainter_p.h>
+#include <private/qpaintengineex_p.h>
+
+class QDeclarativeTextLayoutPrivate
+{
+public:
+    QDeclarativeTextLayoutPrivate() 
+    : cached(false) {}
+
+    QPointF position;
+
+    bool cached;
+    QVector<QStaticTextItem> items;
+    QVector<QFixedPoint> positions;
+    QVector<glyph_t> glyphs;
+    QVector<QChar> chars;
+};
+
+Q_GUI_EXPORT extern int qt_defaultDpiX();
+Q_GUI_EXPORT extern int qt_defaultDpiY();
+
+namespace {
+class DrawTextItemRecorder: public QPaintEngine
+{
+    public:
+        DrawTextItemRecorder(bool untransformedCoordinates, bool useBackendOptimizations)
+            : m_inertText(0), m_dirtyPen(false), m_useBackendOptimizations(useBackendOptimizations),
+            m_untransformedCoordinates(untransformedCoordinates)
+            {
+            }
+
+        virtual void updateState(const QPaintEngineState &newState)
+        {
+            if (newState.state() & QPaintEngine::DirtyPen)
+                m_dirtyPen = true;
+        }
+
+        virtual void drawTextItem(const QPointF &position, const QTextItem &textItem)
+        {
+            int glyphOffset = m_inertText->glyphs.size(); // Store offset into glyph pool
+            int positionOffset = m_inertText->glyphs.size(); // Offset into position pool
+            int charOffset = m_inertText->chars.size();
+
+            const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
+
+            bool needFreshCurrentItem = true;
+            if (!m_inertText->items.isEmpty()) {
+                QStaticTextItem &last = m_inertText->items[m_inertText->items.count() - 1];
+
+                if (last.fontEngine == ti.fontEngine && last.font == ti.font() && 
+                    (!m_dirtyPen || last.color == state->pen().color())) {
+                    needFreshCurrentItem = false;
+
+                    last.numChars += ti.num_chars;
+                    last.numGlyphs += ti.glyphs.numGlyphs;
+
+                }
+            } 
+
+            if (needFreshCurrentItem) {
+                QStaticTextItem currentItem;
+
+                currentItem.fontEngine = ti.fontEngine;
+                currentItem.font = ti.font();
+                currentItem.charOffset = charOffset;
+                currentItem.numChars = ti.num_chars;
+                currentItem.numGlyphs = ti.glyphs.numGlyphs;
+                currentItem.glyphOffset = glyphOffset;
+                currentItem.positionOffset = positionOffset;
+                currentItem.useBackendOptimizations = m_useBackendOptimizations;
+                if (m_dirtyPen)
+                    currentItem.color = state->pen().color();
+
+                m_inertText->items.append(currentItem);
+            }
+
+            QTransform matrix = m_untransformedCoordinates ? QTransform() : state->transform();
+            matrix.translate(position.x(), position.y());
+
+            QVarLengthArray<glyph_t> glyphs;
+            QVarLengthArray<QFixedPoint> positions;
+            ti.fontEngine->getGlyphPositions(ti.glyphs, matrix, ti.flags, glyphs, positions);
+
+            int size = glyphs.size();
+            Q_ASSERT(size == ti.glyphs.numGlyphs);
+            Q_ASSERT(size == positions.size());
+
+            m_inertText->glyphs.resize(m_inertText->glyphs.size() + size);
+            m_inertText->positions.resize(m_inertText->glyphs.size());
+            m_inertText->chars.resize(m_inertText->chars.size() + ti.num_chars);
+
+            glyph_t *glyphsDestination = m_inertText->glyphs.data() + glyphOffset;
+            qMemCopy(glyphsDestination, glyphs.constData(), sizeof(glyph_t) * ti.glyphs.numGlyphs);
+
+            QFixedPoint *positionsDestination = m_inertText->positions.data() + positionOffset;
+            qMemCopy(positionsDestination, positions.constData(), sizeof(QFixedPoint) * ti.glyphs.numGlyphs);
+
+            QChar *charsDestination = m_inertText->chars.data() + charOffset;
+            qMemCopy(charsDestination, ti.chars, sizeof(QChar) * ti.num_chars);
+
+        }
+
+        virtual void drawPolygon(const QPointF *, int , PolygonDrawMode )
+        {
+            /* intentionally empty */
+        }
+
+        virtual bool begin(QPaintDevice *)  { return true; }
+        virtual bool end() { return true; }
+        virtual void drawPixmap(const QRectF &, const QPixmap &, const QRectF &) {}
+        virtual Type type() const
+        {
+            return User;
+        }
+
+        void begin(QDeclarativeTextLayoutPrivate *t) {
+            m_inertText = t;
+            m_dirtyPen = false;
+        }
+
+    private:
+        QDeclarativeTextLayoutPrivate *m_inertText;
+
+        bool m_dirtyPen;
+        bool m_useBackendOptimizations;
+        bool m_untransformedCoordinates;
+};
+
+class DrawTextItemDevice: public QPaintDevice
+{
+    public:
+        DrawTextItemDevice(bool untransformedCoordinates, bool useBackendOptimizations)
+        {
+            m_paintEngine = new DrawTextItemRecorder(untransformedCoordinates,
+                    useBackendOptimizations);
+        }
+
+        ~DrawTextItemDevice()
+        {
+            delete m_paintEngine;
+        }
+
+        void begin(QDeclarativeTextLayoutPrivate *t) {
+            m_paintEngine->begin(t);
+        }
+
+        int metric(PaintDeviceMetric m) const
+        {
+            int val;
+            switch (m) {
+            case PdmWidth:
+            case PdmHeight:
+            case PdmWidthMM:
+            case PdmHeightMM:
+                val = 0;
+                break;
+            case PdmDpiX:
+            case PdmPhysicalDpiX:
+                val = qt_defaultDpiX();
+                break;
+            case PdmDpiY:
+            case PdmPhysicalDpiY:
+                val = qt_defaultDpiY();
+                break;
+            case PdmNumColors:
+                val = 16777216;
+                break;
+            case PdmDepth:
+                val = 24;
+                break;
+            default:
+                val = 0;
+                qWarning("DrawTextItemDevice::metric: Invalid metric command");
+            }
+            return val;
+        }
+
+        virtual QPaintEngine *paintEngine() const
+        {
+            return m_paintEngine;
+        }
+
+    private:
+        DrawTextItemRecorder *m_paintEngine;
+};
+
+struct InertTextPainter {
+    InertTextPainter()
+    : device(true, true), painter(&device) {}
+
+    DrawTextItemDevice device;
+    QPainter painter;
+};
+}
+
+Q_GLOBAL_STATIC(InertTextPainter, inertTextPainter);
+
+/*!
+\class QDeclarativeTextLayout
+\brief The QDeclarativeTextLayout class is a version of QStaticText that works with QTextLayouts.
+\internal
+
+This class is basically a copy of the QStaticText code, but it is adapted to source its text from
+QTextLayout.
+
+It is also considerably faster to create a QDeclarativeTextLayout than a QStaticText because it uses 
+a single, shared QPainter instance.  QStaticText by comparison creates a new QPainter per instance.
+As a consequence this means that QDeclarativeTextLayout is not re-enterant.  Adding a lock around 
+the shared painter solves this, and only introduces a minor performance penalty, but is unnecessary 
+for QDeclarativeTextLayout's current use (QDeclarativeText is already tied to the GUI thread).
+*/
+
+QDeclarativeTextLayout::QDeclarativeTextLayout()
+: d(0)
+{
+}
+
+QDeclarativeTextLayout::QDeclarativeTextLayout(const QString &text)
+: QTextLayout(text), d(0)
+{
+}
+
+QDeclarativeTextLayout::~QDeclarativeTextLayout()
+{
+    if (d) delete d;
+}
+
+void QDeclarativeTextLayout::beginLayout()
+{
+    if (d && d->cached) {
+        d->cached = false;
+        d->items.clear();
+        d->positions.clear();
+        d->glyphs.clear();
+        d->chars.clear();
+        d->position = QPointF();
+    }
+    QTextLayout::beginLayout();
+}
+
+void QDeclarativeTextLayout::prepare()
+{
+    if (!d || !d->cached) {
+
+        if (!d)  
+            d = new QDeclarativeTextLayoutPrivate;
+
+        InertTextPainter *itp = inertTextPainter();
+        itp->device.begin(d);
+        QTextLayout::draw(&itp->painter, QPointF(0, 0));
+
+        glyph_t *glyphPool = d->glyphs.data();
+        QFixedPoint *positionPool = d->positions.data();
+        QChar *charPool = d->chars.data();
+
+        int itemCount = d->items.count();
+        for (int ii = 0; ii < itemCount; ++ii) {
+            QStaticTextItem &item = d->items[ii];
+            item.glyphs = glyphPool + item.glyphOffset;
+            item.glyphPositions = positionPool + item.positionOffset;
+            item.chars = charPool + item.charOffset;
+        }
+
+        d->cached = true;
+    }
+}
+
+void QDeclarativeTextLayout::draw(QPainter *painter, const QPointF &p)
+{
+    QPainterPrivate *priv = QPainterPrivate::get(painter);
+
+    if (!priv->extended) {
+        QTextLayout::draw(painter, p);
+        return;
+    }
+
+    prepare();
+
+    int itemCount = d->items.count();
+
+    if (p != d->position) {
+        QFixed fx = QFixed::fromReal(p.x());
+        QFixed fy = QFixed::fromReal(p.y());
+        QFixed oldX = QFixed::fromReal(d->position.x());
+        QFixed oldY = QFixed::fromReal(d->position.y());
+        for (int item = 0; item < itemCount; ++item) {
+            QStaticTextItem &textItem = d->items[item];
+
+            for (int ii = 0; ii < textItem.numGlyphs; ++ii) {
+                textItem.glyphPositions[ii].x += fx - oldX;
+                textItem.glyphPositions[ii].y += fy - oldY;
+            }
+            textItem.userDataNeedsUpdate = true;
+        }
+
+        d->position = p;
+    }
+
+    for (int ii = 0; ii < itemCount; ++ii) {
+        QStaticTextItem &item = d->items[ii];
+        priv->extended->drawStaticTextItem(&item);
+    }
+}
+
diff --git a/src/declarative/graphicsitems/qdeclarativetextlayout_p.h b/src/declarative/graphicsitems/qdeclarativetextlayout_p.h
new file mode 100644
index 0000000..1a4473d
--- /dev/null
+++ b/src/declarative/graphicsitems/qdeclarativetextlayout_p.h
@@ -0,0 +1,23 @@
+#ifndef QDECLARATIVETEXTLAYOUT_P_H
+#define QDECLARATIVETEXTLAYOUT_P_H
+
+#include <QtGui/qtextlayout.h>
+
+class QDeclarativeTextLayoutPrivate;
+class QDeclarativeTextLayout : public QTextLayout
+{
+public:
+    QDeclarativeTextLayout();
+    QDeclarativeTextLayout(const QString &);
+    ~QDeclarativeTextLayout();
+
+    void beginLayout();
+
+    void prepare();
+    void draw(QPainter *, const QPointF & = QPointF());
+
+private:
+    QDeclarativeTextLayoutPrivate *d;
+};
+
+#endif // QDECLARATIVETEXTLAYOUT_P_H