QQuickText: Don't store node engine per node.

Since these are only used during one particular phase of dealing with text, it
is extremely wasteful to heap allocate them and keep them around for the entire
lifetime of the node (~3kb of total allocation _each_ according to OS X).

Removing these cuts around 100mb of transient allocations off the qmlbench text
creation benchmark (and takes the total allocations during a test run from
~496 MB to ~389 MB). It also improves the approximate throughput for creation
of text items by ~5%.

Change-Id: I45c8a50879ed545da1fb13ab3c2c5d857b112cf7
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

1 files changed, 22 insertions, 23 deletions

diff --git a/src/quick/items/qquicktextnode.cpp b/src/quick/items/qquicktextnode.cpp
index 010a443d18..d40dedd798 100644
--- a/src/quick/items/qquicktextnode.cpp
+++ b/src/quick/items/qquicktextnode.cpp
@@ -186,17 +186,6 @@ void QQuickTextNode::clearCursor()
     m_cursorNode = 0;
 }
 
-void QQuickTextNode::initEngine(const QColor& textColor, const QColor& selectedTextColor, const QColor& selectionColor, const QColor& anchorColor, const QPointF &position)
-{
-    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);
-    m_engine->setPosition(position);
-}
-
 void QQuickTextNode::addRectangleNode(const QRectF &rect, const QColor &color)
 {
     QSGRenderContext *sg = QQuickItemPrivate::get(m_ownerElement)->sceneGraphRenderContext();
@@ -224,7 +213,12 @@ void QQuickTextNode::addTextDocument(const QPointF &position, QTextDocument *tex
                                   const QColor &selectionColor, const QColor &selectedTextColor,
                                   int selectionStart, int selectionEnd)
 {
-    initEngine(textColor, selectedTextColor, selectionColor, anchorColor);
+    QQuickTextNodeEngine engine;
+    engine.setTextColor(textColor);
+    engine.setSelectedTextColor(selectedTextColor);
+    engine.setSelectionColor(selectionColor);
+    engine.setAnchorColor(anchorColor);
+    engine.setPosition(position);
 
     QList<QTextFrame *> frames;
     frames.append(textDocument->rootFrame());
@@ -232,7 +226,7 @@ void QQuickTextNode::addTextDocument(const QPointF &position, QTextDocument *tex
         QTextFrame *textFrame = frames.takeFirst();
         frames.append(textFrame->childFrames());
 
-        m_engine->addFrameDecorations(textDocument, textFrame);
+        engine.addFrameDecorations(textDocument, textFrame);
 
         if (textFrame->firstPosition() > textFrame->lastPosition()
          && textFrame->frameFormat().position() != QTextFrameFormat::InFlow) {
@@ -242,23 +236,23 @@ void QQuickTextNode::addTextDocument(const QPointF &position, QTextDocument *tex
             QRectF rect = a->frameBoundingRect(textFrame);
 
             QTextBlock block = textFrame->firstCursorPosition().block();
-            m_engine->setCurrentLine(block.layout()->lineForTextPosition(pos - block.position()));
-            m_engine->addTextObject(rect.topLeft(), format, QQuickTextNodeEngine::Unselected, textDocument,
+            engine.setCurrentLine(block.layout()->lineForTextPosition(pos - block.position()));
+            engine.addTextObject(rect.topLeft(), format, QQuickTextNodeEngine::Unselected, textDocument,
                                  pos, textFrame->frameFormat().position());
         } else {
             QTextFrame::iterator it = textFrame->begin();
 
             while (!it.atEnd()) {
-                Q_ASSERT(!m_engine->currentLine().isValid());
+                Q_ASSERT(!engine.currentLine().isValid());
 
                 QTextBlock block = it.currentBlock();
-                m_engine->addTextBlock(textDocument, block, position, textColor, anchorColor, selectionStart, selectionEnd);
+                engine.addTextBlock(textDocument, block, position, textColor, anchorColor, selectionStart, selectionEnd);
                 ++it;
             }
         }
     }
 
-    m_engine->addToSceneGraph(this, style, styleColor);
+    engine.addToSceneGraph(this, style, styleColor);
 }
 
 void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLayout, const QColor &color,
@@ -268,7 +262,12 @@ void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLay
                                 int selectionStart, int selectionEnd,
                                 int lineStart, int lineCount)
 {
-    initEngine(color, selectedTextColor, selectionColor, anchorColor, position);
+    QQuickTextNodeEngine engine;
+    engine.setTextColor(color);
+    engine.setSelectedTextColor(selectedTextColor);
+    engine.setSelectionColor(selectionColor);
+    engine.setAnchorColor(anchorColor);
+    engine.setPosition(position);
 
 #ifndef QT_NO_IM
     int preeditLength = textLayout->preeditAreaText().length();
@@ -276,7 +275,7 @@ void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLay
 #endif
 
     QVarLengthArray<QTextLayout::FormatRange> colorChanges;
-    m_engine->mergeFormats(textLayout, &colorChanges);
+    engine.mergeFormats(textLayout, &colorChanges);
 
     lineCount = lineCount >= 0
             ? qMin(lineStart + lineCount, textLayout->lineCount())
@@ -297,11 +296,11 @@ void QQuickTextNode::addTextLayout(const QPointF &position, QTextLayout *textLay
         }
 #endif
 
-        m_engine->setCurrentLine(line);
-        m_engine->addGlyphsForRanges(colorChanges, start, end, selectionStart, selectionEnd);
+        engine.setCurrentLine(line);
+        engine.addGlyphsForRanges(colorChanges, start, end, selectionStart, selectionEnd);
     }
 
-    m_engine->addToSceneGraph(this, style, styleColor);
+    engine.addToSceneGraph(this, style, styleColor);
 }
 
 void QQuickTextNode::deleteContent()