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A basic justification algorithm for HarfBuzz-NG 

This does mostly the same HB-old did, except of non-BMP codepoints
support and better handling of space and punctuation characters.

Change-Id: Iaf8565a35f27d5f4837128cec345eff3d9d2bdf0
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
bb10
Konstantin Ritt 2014-07-17 08:32:18 +03:00
parent 8b4635d895
commit dc4dfe4ffa
1 changed files with 80 additions and 0 deletions
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80
src/gui/text/qtextengine.cpp
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@ -837,6 +837,81 @@ enum JustificationClass {
Justification_Arabic_Kashida = 13 // User-inserted Kashida(U+0640)
};
#ifdef QT_ENABLE_HARFBUZZ_NG
/*
Adds an inter character justification opportunity after the number or letter
character and a space justification opportunity after the space character.
*/
static inline void qt_getDefaultJustificationOpportunities(const ushort *string, int length, QGlyphLayout g, ushort *log_clusters, int spaceAs)
{
int str_pos = 0;
while (str_pos < length) {
int glyph_pos = log_clusters[str_pos];
Q_ASSERT(glyph_pos < g.numGlyphs && g.attributes[glyph_pos].clusterStart);
uint ucs4 = string[str_pos];
if (QChar::isHighSurrogate(ucs4) && str_pos + 1 < length) {
ushort low = string[str_pos + 1];
if (QChar::isLowSurrogate(low)) {
++str_pos;
ucs4 = QChar::surrogateToUcs4(ucs4, low);
}
}
// skip whole cluster
do {
++str_pos;
} while (str_pos < length && log_clusters[str_pos] == glyph_pos);
do {
++glyph_pos;
} while (glyph_pos < g.numGlyphs && !g.attributes[glyph_pos].clusterStart);
--glyph_pos;
// justification opportunity at the end of cluster
if (Q_LIKELY(QChar::isLetterOrNumber(ucs4)))
g.attributes[glyph_pos].justification = Justification_Character;
else if (Q_LIKELY(QChar::isSpace(ucs4)))
g.attributes[glyph_pos].justification = spaceAs;
}
}
static inline void qt_getJustificationOpportunities(const ushort *string, int length, const QScriptItem &si, QGlyphLayout g, ushort *log_clusters)
{
Q_ASSERT(length > 0 && g.numGlyphs > 0);
for (int glyph_pos = 0; glyph_pos < g.numGlyphs; ++glyph_pos)
g.attributes[glyph_pos].justification = Justification_Prohibited;
int spaceAs;
switch (si.analysis.script) {
case QChar::Script_Nko:
case QChar::Script_Mandaic:
case QChar::Script_Mongolian:
case QChar::Script_PhagsPa:
// same as default but inter character justification takes precedence
spaceAs = Justification_Arabic_Space;
break;
case QChar::Script_Hiragana:
case QChar::Script_Katakana:
case QChar::Script_Han:
// same as default but inter character justification is the only option
spaceAs = Justification_Character;
break;
default:
spaceAs = Justification_Space;
break;
}
qt_getDefaultJustificationOpportunities(string, length, g, log_clusters, spaceAs);
}
#endif // QT_ENABLE_HARFBUZZ_NG
// shape all the items that intersect with the line, taking tab widths into account to find out what text actually fits in the line.
void QTextEngine::shapeLine(const QScriptLine &line)
@ -997,6 +1072,11 @@ void QTextEngine::shapeText(int item) const
QGlyphLayout glyphs = shapedGlyphs(&si);
#ifdef QT_ENABLE_HARFBUZZ_NG
if (useHarfbuzzNG)
qt_getJustificationOpportunities(string, itemLength, si, glyphs, logClusters(&si));
#endif
if (letterSpacing != 0) {
for (int i = 1; i < si.num_glyphs; ++i) {
if (glyphs.attributes[i].clusterStart) {