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Improve the Unicode script itemization implementation 

Make it closer to the Unicode specs (UAX#24):
* Common now inherits the preceding character's script, if any;
* In a combining character sequence, if the base character is
  of Common script, the entire sequence is treated like if it were
  of the first non-Inherited, non-Common script in the sequence.
See http://www.unicode.org/reports/tr24/tr24-21.html for more details.

[ChangeLog][QtGui] Fixed regression in arabic text rendering.

Task-number: QTBUG-28813
Task-number: QTBUG-29930 (related)
Task-number: QTBUG-35836
Change-Id: Id85761965b08ca94c674d5f3613fe58b82b2ce9c
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Reviewed-by: Ahmed Saidi <justroftest@gmail.com>
bb10
Konstantin Ritt 2014-04-10 13:50:53 +03:00 committed by The Qt Project
parent ef77c16cb0
commit 0ec07b68ad
3 changed files with 42 additions and 35 deletions
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38
src/corelib/tools/qunicodetools.cpp
View File

@ -667,7 +667,7 @@ Q_CORE_EXPORT void initCharAttributes(const ushort *string, int length,
// ----------------------------------------------------------------------------
//
// The Unicode script property. See http://www.unicode.org/reports/tr24/ (some very old version)
// The Unicode script property. See http://www.unicode.org/reports/tr24/tr24-21.html
//
// ----------------------------------------------------------------------------
@ -689,15 +689,36 @@ Q_CORE_EXPORT void initScripts(const ushort *string, int length, uchar *scripts)
const QUnicodeTables::Properties *prop = QUnicodeTables::properties(ucs4);
if (Q_LIKELY(prop->script == script || prop->script == QChar::Script_Inherited))
if (Q_LIKELY(prop->script == script || prop->script <= QChar::Script_Inherited))
continue;
// Never break between a combining mark (gc= Mc, Mn or Me) and its base character.
// Thus, a combining mark — whatever its script property value is — should inherit
// the script property value of its base character.
static const int test = (FLAG(QChar::Mark_NonSpacing) | FLAG(QChar::Mark_SpacingCombining) | FLAG(QChar::Mark_Enclosing));
if (Q_UNLIKELY(FLAG(prop->category) & test))
continue;
if (Q_UNLIKELY(FLAG(prop->category) & test)) {
// In cases where the base character itself has the Common script property value,
// and it is followed by one or more combining marks with a specific script property value,
// it may be even better for processing to let the base acquire the script property value
// from the first mark. This approach can be generalized by treating all the characters
// of a combining character sequence as having the script property value
// of the first non-Inherited, non-Common character in the sequence if there is one,
// and otherwise treating all the characters as having the Common script property value.
if (Q_LIKELY(script > QChar::Script_Common || prop->script <= QChar::Script_Common))
continue;
script = QChar::Script(prop->script);
}
if (Q_LIKELY(script != QChar::Script_Common)) {
// override preceding Common-s
while (sor > 0 && scripts[sor - 1] == QChar::Script_Common)
--sor;
} else {
// see if we are inheriting preceding run
if (sor > 0)
script = scripts[sor - 1];
}
while (sor < eor)
scripts[sor++] = script;
@ -705,6 +726,15 @@ Q_CORE_EXPORT void initScripts(const ushort *string, int length, uchar *scripts)
script = prop->script;
}
eor = length;
if (Q_LIKELY(script != QChar::Script_Common)) {
// override preceding Common-s
while (sor > 0 && scripts[sor - 1] == QChar::Script_Common)
--sor;
} else {
// see if we are inheriting preceding run
if (sor > 0)
script = scripts[sor - 1];
}
while (sor < eor)
scripts[sor++] = script;
}

17
src/gui/text/qtextengine.cpp
View File

@ -122,20 +122,9 @@ private:
return;
const int end = start + length;
for (int i = start + 1; i < end; ++i) {
// According to the unicode spec we should be treating characters in the Common script
// (punctuation, spaces, etc) as being the same script as the surrounding text for the
// purpose of splitting up text. This is important because, for example, a fullstop
// (0x2E) can be used to indicate an abbreviation and so must be treated as part of a
// word. Thus it must be passed along with the word in languages that have to calculate
// word breaks. For example the thai word "ครม." has no word breaks but the word "ครม"
// does.
// Unfortuntely because we split up the strings for both wordwrapping and for setting
// the font and because Japanese and Chinese are also aliases of the script "Common",
// doing this would break too many things. So instead we only pass the full stop
// along, and nothing else.
if (m_analysis[i].bidiLevel == m_analysis[start].bidiLevel
&& m_analysis[i].flags == m_analysis[start].flags
&& (m_analysis[i].script == m_analysis[start].script || m_string[i] == QLatin1Char('.'))
&& m_analysis[i].script == m_analysis[start].script
&& m_analysis[i].flags < QScriptAnalysis::SpaceTabOrObject
&& i - start < MaxItemLength)
continue;
@ -1515,26 +1504,22 @@ void QTextEngine::itemize() const
while (uc < e) {
switch (*uc) {
case QChar::ObjectReplacementCharacter:
analysis->script = QChar::Script_Common;
analysis->flags = QScriptAnalysis::Object;
break;
case QChar::LineSeparator:
if (analysis->bidiLevel % 2)
--analysis->bidiLevel;
analysis->script = QChar::Script_Common;
analysis->flags = QScriptAnalysis::LineOrParagraphSeparator;
if (option.flags() & QTextOption::ShowLineAndParagraphSeparators)
*const_cast<ushort*>(uc) = 0x21B5; // visual line separator
break;
case QChar::Tabulation:
analysis->script = QChar::Script_Common;
analysis->flags = QScriptAnalysis::Tab;
analysis->bidiLevel = control.baseLevel();
break;
case QChar::Space:
case QChar::Nbsp:
if (option.flags() & QTextOption::ShowTabsAndSpaces) {
analysis->script = QChar::Script_Common;
analysis->flags = QScriptAnalysis::Space;
analysis->bidiLevel = control.baseLevel();
break;

22
tests/auto/gui/text/qtextscriptengine/tst_qtextscriptengine.cpp
View File

@ -1258,29 +1258,21 @@ void tst_QTextScriptEngine::thaiWithZWJ()
QTextLayout layout(s, font);
QTextEngine *e = layout.engine();
e->itemize();
QCOMPARE(e->layoutData->items.size(), 11);
QCOMPARE(e->layoutData->items.size(), 3);
for (int item = 0; item < e->layoutData->items.size(); ++item)
e->shape(item);
QCOMPARE(e->layoutData->items[0].num_glyphs, ushort(7)); // Thai: The ZWJ and ZWNJ characters are inherited, so should be part of the thai script
QCOMPARE(e->layoutData->items[1].num_glyphs, ushort(1)); // Common: The smart quotes cannot be handled by thai, so should be a separate item
QCOMPARE(e->layoutData->items[2].num_glyphs, ushort(1)); // Thai: Thai character
QCOMPARE(e->layoutData->items[3].num_glyphs, ushort(1)); // Common: Ellipsis
QCOMPARE(e->layoutData->items[4].num_glyphs, ushort(1)); // Thai: Thai character
QCOMPARE(e->layoutData->items[5].num_glyphs, ushort(1)); // Common: Smart quote
QCOMPARE(e->layoutData->items[6].num_glyphs, ushort(1)); // Thai: Thai character
QCOMPARE(e->layoutData->items[7].num_glyphs, ushort(1)); // Common: \xA0 = non-breaking space. Could be useful to have in thai, but not currently implemented
QCOMPARE(e->layoutData->items[8].num_glyphs, ushort(1)); // Thai: Thai character
QCOMPARE(e->layoutData->items[9].num_glyphs, ushort(1)); // Japanese: Kanji for tree
QCOMPARE(e->layoutData->items[10].num_glyphs, ushort(2)); // Thai: Thai character followed by superscript "a" which is of inherited type
QCOMPARE(e->layoutData->items[0].num_glyphs, ushort(15)); // Thai: The ZWJ and ZWNJ characters are inherited, so should be part of the thai script
QCOMPARE(e->layoutData->items[1].num_glyphs, ushort(1)); // Han: Kanji for tree
QCOMPARE(e->layoutData->items[2].num_glyphs, ushort(2)); // Thai: Thai character followed by superscript "a" which is of inherited type
//A quick sanity check - check all the characters are individual clusters
unsigned short *logClusters = e->layoutData->logClustersPtr;
for (int i = 0; i < 7; i++)
for (int i = 0; i <= 14; i++)
QCOMPARE(logClusters[i], ushort(i));
for (int i = 0; i < 10; i++)
QCOMPARE(logClusters[i+7], ushort(0));
QCOMPARE(logClusters[15], ushort(0));
QCOMPARE(logClusters[16], ushort(0));
#ifndef Q_OS_MAC
// ### Result differs for HarfBuzz-NG
QCOMPARE(logClusters[17], ushort(1));