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, 2 insertions, 5 deletions

diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index 2944130eaa..1fc044aa44 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -5845,11 +5845,8 @@ void QPainter::drawText(const QPointF &p, const QString &str, int tf, int justif
         int numGlyphs = len;
         QVarLengthGlyphLayoutArray glyphs(len);
         QFontEngine *fontEngine = d->state->font.d->engineForScript(QChar::Script_Common);
-        if (!fontEngine->stringToCMap(str.data(), len, &glyphs, &numGlyphs, 0)) {
-            glyphs.resize(numGlyphs);
-            if (!fontEngine->stringToCMap(str.data(), len, &glyphs, &numGlyphs, 0))
-                Q_ASSERT_X(false, Q_FUNC_INFO, "stringToCMap shouldn't fail twice");
-        }
+        if (!fontEngine->stringToCMap(str.data(), len, &glyphs, &numGlyphs, 0))
+            Q_UNREACHABLE();
 
         QTextItemInt gf(glyphs, &d->state->font, str.data(), len, fontEngine);
         drawTextItem(p, gf);