Optimize QStaticText for space

By caching the results of getGlyphPositions() we can make a code path
in the critical paint engines which is optimal both in space and speed.
The engines where speed is of less importance (pdf engine etc.) which
may need more information, we choose the slower code path of drawText()
which lays out the text again. We should have optimal paths in raster,
vg and GL2 paint engines. The others are less important. Memory
consumption of static text is now 14 bytes per glyph, 8 bytes per item
and a static overhead of 40 bytes per QStaticText object.

2 files changed, 53 insertions, 78 deletions

diff --git a/src/gui/text/qstatictext.cpp b/src/gui/text/qstatictext.cpp
index 70e1c47..c43eeb0 100644
--- a/src/gui/text/qstatictext.cpp
+++ b/src/gui/text/qstatictext.cpp
@@ -262,7 +262,7 @@ bool QStaticText::isEmpty() const
 }
 
 QStaticTextPrivate::QStaticTextPrivate()
-        : glyphLayoutMemory(0), logClusterMemory(0), items(0), itemPositions(0), itemCount(0)
+        : items(0), itemCount(0)
 {
     ref = 1;    
 }
@@ -278,10 +278,7 @@ QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)
 
 QStaticTextPrivate::~QStaticTextPrivate()
 {
-    delete[] glyphLayoutMemory;
-    delete[] logClusterMemory;    
-    delete[] items;
-    delete[] itemPositions;
+    delete[] items;    
 }
 
 QStaticTextPrivate *QStaticTextPrivate::get(const QStaticText *q)
@@ -298,43 +295,37 @@ namespace {
     class DrawTextItemRecorder: public QPaintEngine
     {
     public:
-        DrawTextItemRecorder(int expectedItemCount, int expectedGlyphCount,
-                             QTextItemInt *items,
-                             QPointF *positions,
-                             char *glyphLayoutMemory,
-                             unsigned short *logClusterMemory)
+        DrawTextItemRecorder(int expectedItemCount, QStaticTextItem *items)
                 : m_items(items),
-                  m_positions(positions),
-                  m_glyphLayoutMemory(glyphLayoutMemory),
-                  m_logClusterMemory(logClusterMemory),
-                  m_glyphLayoutMemoryOffset(0),
-                  m_logClusterMemoryOffset(0),
                   m_expectedItemCount(expectedItemCount),
-                  m_expectedGlyphCount(expectedGlyphCount),
-                  m_glyphCount(0),
                   m_itemCount(0)
         {
         }
 
         virtual void drawTextItem(const QPointF &p, const QTextItem &textItem)
         {
-            const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
-
+            const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);          
+            
+            Q_ASSERT(m_expectedItemCount < 0 || m_itemCount < m_expectedItemCount);
             m_itemCount++;
-            m_glyphCount += ti.glyphs.numGlyphs;
 
-            Q_ASSERT(m_expectedItemCount < 0 || m_itemCount <= m_expectedItemCount);
-            Q_ASSERT(m_expectedGlyphCount < 0 || m_glyphCount <= m_expectedGlyphCount);
-
-            if (m_items == 0 || m_glyphLayoutMemory == 0 || m_logClusterMemory == 0 || m_positions == 0)
+            if (m_items == 0)
                 return;
 
-            m_items[m_itemCount - 1] = ti.clone(m_glyphLayoutMemory + m_glyphLayoutMemoryOffset,
-                                                m_logClusterMemory + m_logClusterMemoryOffset);
-            m_positions[m_itemCount - 1] = p;
+            QStaticTextItem *currentItem = (m_items + (m_itemCount - 1));
+            currentItem->fontEngine = ti.fontEngine;
+            currentItem->chars = ti.chars;
+            currentItem->numChars = ti.num_chars;
+            ti.fontEngine->getGlyphPositions(ti.glyphs, QTransform(), ti.flags, currentItem->glyphs,
+                                             currentItem->glyphPositions);
+
+            QFixed fx = QFixed::fromReal(p.x());
+            QFixed fy = QFixed::fromReal(p.y());
 
-            m_glyphLayoutMemoryOffset += QGlyphLayout::spaceNeededForGlyphLayout(ti.glyphs.numGlyphs);
-            m_logClusterMemoryOffset += ti.glyphs.numGlyphs;
+            for (int i=0; i<currentItem->glyphPositions.size(); ++i) {
+                currentItem->glyphPositions[i].x += fx;
+                currentItem->glyphPositions[i].y += fy;
+            }
         }                
 
 
@@ -347,40 +338,23 @@ namespace {
             return User;
         }
 
-        int glyphCount() const
-        {
-            return m_glyphCount;
-        }
-
         int itemCount() const
         {
             return m_itemCount;
         }
 
     private:
-        QTextItemInt *m_items;
-        char *m_glyphLayoutMemory;
-        unsigned short *m_logClusterMemory;
-        QPointF *m_positions;
-
-        int m_glyphLayoutMemoryOffset;
-        int m_logClusterMemoryOffset;
-        int m_expectedGlyphCount;
-        int m_expectedItemCount;
-        int m_glyphCount;
+        QStaticTextItem *m_items;
         int m_itemCount;
+        int m_expectedItemCount;
     };
 
     class DrawTextItemDevice: public QPaintDevice
     {
     public:
-        DrawTextItemDevice(int expectedItemCount = -1, int expectedGlyphCount = -1,
-                           QTextItemInt *items = 0, QPointF *positions = 0,
-                           char *glyphLayoutMemory = 0, unsigned short *logClusterMemory = 0)
+        DrawTextItemDevice(int expectedItemCount = -1,  QStaticTextItem *items = 0)
         {
-            m_paintEngine = new DrawTextItemRecorder(expectedItemCount, expectedGlyphCount,
-                                                     items, positions,glyphLayoutMemory,
-                                                     logClusterMemory);
+            m_paintEngine = new DrawTextItemRecorder(expectedItemCount, items);
         }
 
         ~DrawTextItemDevice()
@@ -424,11 +398,6 @@ namespace {
             return m_paintEngine;
         }
 
-        int glyphCount() const
-        {
-            return m_paintEngine->glyphCount();
-        }
-
         int itemCount() const
         {
             return m_paintEngine->itemCount();
@@ -438,17 +407,13 @@ namespace {
 
     private:
         DrawTextItemRecorder *m_paintEngine;
-        QRectF brect;
     };
 
 }
 
 void QStaticTextPrivate::init()
 {
-    delete[] glyphLayoutMemory;
-    delete[] logClusterMemory;
     delete[] items;
-    delete[] itemPositions;
 
     // Draw once to count number of items and glyphs, so that we can use as little memory
     // as possible to store the data
@@ -464,16 +429,10 @@ void QStaticTextPrivate::init()
     }
 
     itemCount = counterDevice.itemCount();
-    items = new QTextItemInt[itemCount];
-    itemPositions = new QPointF[itemCount];
-
-    int glyphCount = counterDevice.glyphCount();
-    glyphLayoutMemory = new char[QGlyphLayout::spaceNeededForGlyphLayout(glyphCount)];
-    logClusterMemory = new unsigned short[glyphCount];
+    items = new QStaticTextItem[itemCount];
 
     // Draw again to actually record the items and glyphs
-    DrawTextItemDevice recorderDevice(itemCount, glyphCount, items, itemPositions,
-                                      glyphLayoutMemory, logClusterMemory);
+    DrawTextItemDevice recorderDevice(itemCount, items);
     {
         QPainter painter(&recorderDevice);
         painter.setFont(font);
diff --git a/src/gui/text/qstatictext_p.h b/src/gui/text/qstatictext_p.h
index f5fd8d3..2a8d23a 100644
--- a/src/gui/text/qstatictext_p.h
+++ b/src/gui/text/qstatictext_p.h
@@ -54,8 +54,26 @@
 //
 
 #include <private/qtextengine_p.h>
+#include <private/qfontengine_p.h>
 
-QT_BEGIN_NAMESPACE              
+QT_BEGIN_NAMESPACE
+
+class QStaticTextItem
+{
+public:    
+    QStaticTextItem() : chars(0), numChars(0), fontEngine(0) {}
+
+    QVarLengthArray<QFixedPoint> glyphPositions; // 8 bytes per glyph
+    QVarLengthArray<glyph_t> glyphs;             // 4 bytes per glyph
+    const QChar *chars;                          // 2 bytes per glyph
+                                                 // =================
+                                                 // 14 bytes per glyph
+
+    int numChars;                                // 4 bytes per item
+    QFontEngine *fontEngine;                     // 4 bytes per item
+                                                 // ================
+                                                 // 8 bytes per item
+};
 
 class QStaticText;
 class QStaticTextPrivate
@@ -67,19 +85,17 @@ public:
 
     void init();
 
-    QAtomicInt ref;
+    QAtomicInt ref;          // 4 bytes per text
 
-    QString text;
-    QFont font;
-    QSizeF size;
+    QString text;            // 4 bytes per text
+    QFont font;              // 8 bytes per text
+    QSizeF size;             // 16 bytes per text
 
-    QTextItemInt *items;
-    QPointF *itemPositions;
-    int itemCount;
+    QStaticTextItem *items;  // 4 bytes per text
+    int itemCount;           // 4 bytes per text
+                             // ================
+                             // 40 bytes per text
 
-    char *glyphLayoutMemory;
-    unsigned short *logClusterMemory;
-    
     static QStaticTextPrivate *get(const QStaticText *q);
 };