QSGDistanceFieldGlyphNode: Use QVarLengthArray to avoid frequent allocation.

This adds a few more text items/frame on my macbook, and more or less halves the
amount of transient 608 byte allocations (42mb -> 25mb).

Change-Id: Ib1a67c8203f777a2f3b790ff3597d1af34eed2dd
Done-with: Gunnar Sletta
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/quick/scenegraph/qsgdistancefieldglyphnode.cpp b/src/quick/scenegraph/qsgdistancefieldglyphnode.cpp
index 7e602fc0bd..4630e45ecf 100644
--- a/src/quick/scenegraph/qsgdistancefieldglyphnode.cpp
+++ b/src/quick/scenegraph/qsgdistancefieldglyphnode.cpp
@@ -200,9 +200,11 @@ void QSGDistanceFieldGlyphNode::updateGeometry()
     const QVector<QPointF> positions = m_glyphs.positions();
     qreal fontPixelSize = m_glyphs.rawFont().pixelSize();
 
-    QVector<QSGGeometry::TexturedPoint2D> vp;
+    // The template parameters here are assuming that most strings are short, 64
+    // characters or less.
+    QVarLengthArray<QSGGeometry::TexturedPoint2D, 256> vp;
     vp.reserve(indexes.size() * 4);
-    QVector<ushort> ip;
+    QVarLengthArray<ushort, 384> ip;
     ip.reserve(indexes.size() * 6);
 
     qreal maxTexMargin = m_glyph_cache->distanceFieldRadius();