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Fix QTextEngine regression with large-ish texts

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Change 997fd3b88ede8078af286da6ecc197e83a8cbb46 fixed integer overflows
with huge texts. This was done by using qsizetype for size calculations
instead of int. However, that change introduced a serious regression
due to an itermediate imultiplication result being "promoted" to unsigned,
and therefore a negative value being converted to a large positive.
The solution is to make sure all values in the expression are signed.

Fixes: QTBUG-123339
Task-number: QTBUG-119611
Change-Id: I3f9189f77b383c6103cf5b35981cdb607b065f6f
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
(cherry picked from commit 7a84c58f55ab56c5d77be80e43783d0b5302a749)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Paul Olav Tvete 2024-03-15 15:28:26 +01:00 committed by Qt Cherry-pick Bot
parent 32ce7fa8d2
commit c9b5b40d14
3 changed files with 28 additions and 7 deletions
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7
src/gui/text/qtextengine.cpp
View File

@ -2658,9 +2658,10 @@ QTextEngine::LayoutData::LayoutData(const QString &str, void **stack_memory, qsi
{
allocated = _allocated;
qsizetype space_charAttributes = sizeof(QCharAttributes) * string.size() / sizeof(void*) + 1;
qsizetype space_logClusters = sizeof(unsigned short) * string.size() / sizeof(void*) + 1;
available_glyphs = (allocated - space_charAttributes - space_logClusters) * sizeof(void*) / QGlyphLayout::SpaceNeeded;
constexpr qsizetype voidSize = sizeof(void*);
qsizetype space_charAttributes = sizeof(QCharAttributes) * string.size() / voidSize + 1;
qsizetype space_logClusters = sizeof(unsigned short) * string.size() / voidSize + 1;
available_glyphs = (allocated - space_charAttributes - space_logClusters) * voidSize / QGlyphLayout::SpaceNeeded;
if (available_glyphs < str.size()) {
// need to allocate on the heap

6
src/gui/text/qtextengine_p.h
View File

@ -159,10 +159,8 @@ Q_DECLARE_TYPEINFO(QGlyphAttributes, Q_PRIMITIVE_TYPE);
struct QGlyphLayout
{
enum {
SpaceNeeded = sizeof(glyph_t) + sizeof(QFixed) + sizeof(QFixedPoint)
+ sizeof(QGlyphAttributes) + sizeof(QGlyphJustification)
};
static constexpr qsizetype SpaceNeeded = sizeof(glyph_t) + sizeof(QFixed) + sizeof(QFixedPoint)
+ sizeof(QGlyphAttributes) + sizeof(QGlyphJustification);
// init to 0 not needed, done when shaping
QFixedPoint *offsets; // 8 bytes per element

22
tests/auto/gui/text/qfontmetrics/tst_qfontmetrics.cpp
View File

@ -34,6 +34,8 @@ private slots:
void zeroWidthMetrics();
void verticalMetrics_data();
void verticalMetrics();
void largeText_data();
void largeText(); // QTBUG-123339
};
void tst_QFontMetrics::same()
@ -388,5 +390,25 @@ void tst_QFontMetrics::verticalMetrics()
QVERIFY(fm.ascent() != 0 || fm.descent() != 0);
}
void tst_QFontMetrics::largeText_data()
{
QTest::addColumn<qsizetype>("size");
for (int i = 1; i < 20; ++i) {
qsizetype size = qsizetype(1) << i;
QByteArray rowText = QByteArray::number(size);
QTest::newRow(rowText.constData()) << size;
}
}
void tst_QFontMetrics::largeText()
{
QFont font;
QFontMetrics fm(font);
QFETCH(qsizetype, size);
QString string(size, QLatin1Char('A'));
QRect boundingRect = fm.boundingRect(string);
QVERIFY(boundingRect.isValid());
}
QTEST_MAIN(tst_QFontMetrics)
#include "tst_qfontmetrics.moc"