Optimize QStaticText for one line strings

QTextLayout takes a lot of memory. We can get a bigger speed-up and
a more reasonable memory consumption by only supporting the single
line static texts and caching the text items. We need to copy some
structs from the text engine, since this is on the stack.

1 files changed, 69 insertions, 59 deletions

diff --git a/src/gui/text/qstatictext.cpp b/src/gui/text/qstatictext.cpp
index f953d71..90fde9d 100644
--- a/src/gui/text/qstatictext.cpp
+++ b/src/gui/text/qstatictext.cpp
@@ -41,6 +41,7 @@
 
 #include "qstatictext.h"
 #include "qstatictext_p.h"
+#include <private/qtextengine_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -110,13 +111,11 @@ QStaticText::QStaticText()
     \a font and bounded by the given \a maximumSize. If an invalid size is passed for \a maximumSize
     the text will be unbounded.         
 */
-QStaticText::QStaticText(const QString &text, const QFont &font, const QSizeF &sz)
+QStaticText::QStaticText(const QString &text, const QFont &font)
     : d_ptr(new QStaticTextPrivate) 
 {    
-    d_ptr->textLayout->setText(text);
-    d_ptr->textLayout->setFont(font);
-    d_ptr->size = sz;
-
+    d_ptr->text = text;
+    d_ptr->font = font;
     d_ptr->init();
 }
 
@@ -163,9 +162,7 @@ QStaticText &QStaticText::operator=(const QStaticText &other)
 bool QStaticText::operator==(const QStaticText &other) const
 {
     return (d_ptr == other.d_ptr
-        || (d_ptr->textLayout->text() == other.d_ptr->textLayout->text()
-            && d_ptr->textLayout->font() == other.d_ptr->textLayout->font()
-            && d_ptr->size == other.d_ptr->size));
+            || (d_ptr->text == other.d_ptr->text && d_ptr->font == other.d_ptr->font));
 }
 
 /*!
@@ -187,8 +184,7 @@ bool QStaticText::operator!=(const QStaticText &other) const
 void QStaticText::setText(const QString &text) 
 {
     detach();
-
-    d_ptr->textLayout->setText(text);
+    d_ptr->text = text;
     d_ptr->init();
 }
 
@@ -199,7 +195,7 @@ void QStaticText::setText(const QString &text)
 */
 QString QStaticText::text() const 
 {
-    return d_ptr->textLayout->text();
+    return d_ptr->text;
 }
 
 /*!
@@ -212,8 +208,7 @@ QString QStaticText::text() const
 void QStaticText::setFont(const QFont &font)
 {
     detach();
-
-    d_ptr->textLayout->setFont(font);
+    d_ptr->font = font;
     d_ptr->init();
 }
 
@@ -224,33 +219,7 @@ void QStaticText::setFont(const QFont &font)
 */
 QFont QStaticText::font() const
 {
-    return d_ptr->textLayout->font();
-}
-
-/*!
-    Sets the maximum size of the QStaticText to \a maximumSize. If a valid maximum size is set for 
-    the QStaticText, it will be formatted to fit within its width, and clipped by its height.
-
-    \note This function will cause the layout of the text to be recalculated.
-
-    \sa maximumSize()
-*/
-void QStaticText::setMaximumSize(const QSizeF &maximumSize)
-{
-    detach();
-
-    d_ptr->size = maximumSize;
-    d_ptr->init();
-}
-
-/*!
-    Returns the maximum size of the QStaticText.
-
-    \sa setMaximumSize()
-*/
-QSizeF QStaticText::maximumSize() const
-{
-    return d_ptr->size;
+    return d_ptr->font;
 }
 
 QString QStaticText::toString() const
@@ -258,22 +227,24 @@ QString QStaticText::toString() const
     return text();
 }
 
-QStaticTextPrivate::QStaticTextPrivate()
-    : textLayout(new QTextLayout())
+QStaticTextPrivate::QStaticTextPrivate() : glyphLayoutMemory(0), logClusterMemory(0)
 {
-    ref = 1;
+    ref = 1;    
 }
 
-QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)    
+QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)
 {
     ref = 1;
-    textLayout = new QTextLayout(other.textLayout->text(), other.textLayout->font());
-    size = other.size;    
+    text = other.text;
+    font = other.font;
+    init();
 }
 
 QStaticTextPrivate::~QStaticTextPrivate()
 {
-    delete textLayout;
+    delete glyphLayoutMemory;
+    delete logClusterMemory;
+    qDeleteAll(items);
 }
 
 QStaticTextPrivate *QStaticTextPrivate::get(const QStaticText *q)
@@ -283,22 +254,61 @@ QStaticTextPrivate *QStaticTextPrivate::get(const QStaticText *q)
 
 void QStaticTextPrivate::init()
 {
-    Q_ASSERT(textLayout != 0);
-    textLayout->setCacheEnabled(true);
+    delete glyphLayoutMemory;
+    delete logClusterMemory;
+    qDeleteAll(items);
+
+    QStackTextEngine engine = QStackTextEngine(text, font);
+    engine.itemize();
+
+    engine.option.setTextDirection(QApplication::layoutDirection());
+    QScriptLine line;
+    line.length = text.length();
+    engine.shapeLine(line);
+
+    int nItems = engine.layoutData->items.size();
+    QVarLengthArray<int> visualOrder(nItems);
+    QVarLengthArray<uchar> levels(nItems);
+    for (int i = 0; i < nItems; ++i)
+        levels[i] = engine.layoutData->items[i].analysis.bidiLevel;
+    QTextEngine::bidiReorder(nItems, levels.data(), visualOrder.data());
+
+    int numGlyphs = engine.layoutData->glyphLayout.numGlyphs;
+    glyphLayoutMemory = new char[QGlyphLayout::spaceNeededForGlyphLayout(numGlyphs)];
+    logClusterMemory = new unsigned short[numGlyphs];
+
+    char *currentGlyphLayout = glyphLayoutMemory;
+    unsigned short *currentLogCluster = logClusterMemory;
+    for (int i = 0; i < nItems; ++i) {
+        int item = visualOrder[i];
+        const QScriptItem &si = engine.layoutData->items.at(item);
+
+        QFont f = engine.font(si);
+        if (si.analysis.flags >= QScriptAnalysis::TabOrObject) {
+            QTextItemInt *gf = new QTextItemInt(si, &f);
+            gf->width = si.width;
+            items.append(gf);
+            continue;
+        }
 
-    QFontMetrics fontMetrics(textLayout->font());
+        QTextItemInt *gf = new QTextItemInt(si, &f);
 
-    textLayout->beginLayout();
-    int h = size.isValid() ? 0 : -fontMetrics.ascent();
+        QGlyphLayout l = engine.shapedGlyphs(&si);
+        gf->glyphs = l.clone(currentGlyphLayout);
+        currentGlyphLayout += QGlyphLayout::spaceNeededForGlyphLayout(l.numGlyphs);
 
-    QTextLine line;
-    qreal lineWidth = size.isValid() ? size.width() : fontMetrics.width(textLayout->text());
-    while ((line = textLayout->createLine()).isValid()) {
-        line.setLineWidth(lineWidth);
-        line.setPosition(QPointF(0, h));
-        h += line.height();
+        gf->chars = text.unicode() + si.position;
+        gf->num_chars = engine.length(item);
+        gf->width = si.width;
+
+        memmove(currentLogCluster, engine.logClusters(&si), sizeof(unsigned short) * l.numGlyphs);
+        gf->logClusters = currentLogCluster;
+        currentLogCluster += l.numGlyphs;
+
+        items.append(gf);
     }
-    textLayout->endLayout();
+
+    items.squeeze();
 }
 
 QT_END_NAMESPACE