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Fix artihmetic exception when using non-scalable fonts 

For non-scalable fonts, the units_per_EM in FreeType is
documented to be undefined and will default to 0, which means
that any division by it will cause an exception.

The emSquareSize() function already checks if the font is scalable
and returns y_ppem if not, so lets use it instead in all locations
where we're not already sure the font is scalable.

[ChangeLog][Text][Freetype] Fixed a divide-by-zero exception
when accessing bitmap fonts.

Change-Id: I8839d4c83047fb3f6bb4d69af0258e94a258a4d9
Task-number: QTBUG-45963
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
bb10
Eskil Abrahamsen Blomfeldt 2016-01-26 14:45:46 +01:00
parent ba7f76dea0
commit a67a905190
1 changed files with 3 additions and 3 deletions
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6
src/gui/text/qfontengine_ft.cpp
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@ -1255,7 +1255,7 @@ QFixed QFontEngineFT::xHeight() const
TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
if (os2 && os2->sxHeight) {
lockFace();
QFixed answer = QFixed(os2->sxHeight*freetype->face->size->metrics.y_ppem)/freetype->face->units_per_EM;
QFixed answer = QFixed(os2->sxHeight * freetype->face->size->metrics.y_ppem) / emSquareSize();
unlockFace();
return answer;
}
@ -1267,7 +1267,7 @@ QFixed QFontEngineFT::averageCharWidth() const
TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
if (os2 && os2->xAvgCharWidth) {
lockFace();
QFixed answer = QFixed(os2->xAvgCharWidth*freetype->face->size->metrics.x_ppem)/freetype->face->units_per_EM;
QFixed answer = QFixed(os2->xAvgCharWidth * freetype->face->size->metrics.x_ppem) / emSquareSize();
unlockFace();
return answer;
}
@ -1295,7 +1295,7 @@ void QFontEngineFT::doKerning(QGlyphLayout *g, QFontEngine::ShaperFlags flags) c
kerning_pairs_loaded = true;
lockFace();
if (freetype->face->size->metrics.x_ppem != 0) {
QFixed scalingFactor(freetype->face->units_per_EM/freetype->face->size->metrics.x_ppem);
QFixed scalingFactor = emSquareSize() / QFixed(freetype->face->size->metrics.x_ppem);
unlockFace();
const_cast<QFontEngineFT *>(this)->loadKerningPairs(scalingFactor);
} else {