Optimize stringToCMap() usage

CMAP guarantees there is 1:1 mapping between the Unicode code points
array and the glyph indexes array, which means the QString length
always greater than or equal to a sufficient glyph indexes array length.

Simply add some asserts and improve the memory consumption
and the performance where possible.

Change-Id: I0bc8cdba5f86c1c0ba9e79c8d5f96cbe56ec463e
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 5 insertions, 12 deletions

diff --git a/src/gui/text/qrawfont.cpp b/src/gui/text/qrawfont.cpp
index e26f7cdc93..449278df06 100644
--- a/src/gui/text/qrawfont.cpp
+++ b/src/gui/text/qrawfont.cpp
@@ -479,16 +479,8 @@ QVector<quint32> QRawFont::glyphIndexesForString(const QString &text) const
     QGlyphLayout glyphs;
     glyphs.numGlyphs = numGlyphs;
     glyphs.glyphs = glyphIndexes.data();
-    if (!d->fontEngine->stringToCMap(text.data(), text.size(), &glyphs, &numGlyphs, QFontEngine::GlyphIndicesOnly)) {
-        glyphIndexes.resize(numGlyphs);
-
-        glyphs.numGlyphs = numGlyphs;
-        glyphs.glyphs = glyphIndexes.data();
-        if (!d->fontEngine->stringToCMap(text.data(), text.size(), &glyphs, &numGlyphs, QFontEngine::GlyphIndicesOnly)) {
-            Q_ASSERT_X(false, Q_FUNC_INFO, "stringToCMap shouldn't fail twice");
-            return QVector<quint32>();
-        }
-    }
+    if (!d->fontEngine->stringToCMap(text.data(), text.size(), &glyphs, &numGlyphs, QFontEngine::GlyphIndicesOnly))
+        Q_UNREACHABLE();
 
     glyphIndexes.resize(numGlyphs);
     return glyphIndexes;
@@ -565,10 +557,11 @@ bool QRawFont::advancesForGlyphIndexes(const quint32 *glyphIndexes, QPointF *adv
     if (!d->isValid() || numGlyphs <= 0)
         return false;
 
+    QVarLengthArray<QFixed> tmpAdvances(numGlyphs);
+
     QGlyphLayout glyphs;
     glyphs.glyphs = const_cast<glyph_t *>(glyphIndexes);
     glyphs.numGlyphs = numGlyphs;
-    QVarLengthArray<QFixed> tmpAdvances(numGlyphs);
     glyphs.advances = tmpAdvances.data();
 
     bool design = layoutFlags & UseDesignMetrics;
@@ -578,7 +571,7 @@ bool QRawFont::advancesForGlyphIndexes(const quint32 *glyphIndexes, QPointF *adv
         d->fontEngine->doKerning(&glyphs, design ? QFontEngine::DesignMetrics : QFontEngine::ShaperFlag(0));
 
     for (int i=0; i<numGlyphs; ++i)
-        advances[i] = QPointF(glyphs.advances[i].toReal(), 0.0);
+        advances[i] = QPointF(tmpAdvances[i].toReal(), 0.0);
 
     return true;
 }