Do not force a direction before we know it

WebCore does not calculate the text direction when calculating widths
the best we can do here is let the shaper guess the direction. Forcing
it to the default LTR breaks HarfbuzzNG on Arabic scripts.

Since the default HarfBuzz engine changed in 5.4, this was a regression
from 5.3.

See also https://bugs.webkit.org/show_bug.cgi?id=101440

Task-number: QTBUG-41450
Change-Id: Ia324c8e5ebd1744ce2dfaea94d5046ef1f77b483
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>

1 files changed, 9 insertions, 7 deletions

diff --git a/Source/WebCore/platform/graphics/qt/FontQt.cpp b/Source/WebCore/platform/graphics/qt/FontQt.cpp
index 3eead7e70..ab11c5199 100644
--- a/Source/WebCore/platform/graphics/qt/FontQt.cpp
+++ b/Source/WebCore/platform/graphics/qt/FontQt.cpp
@@ -59,9 +59,11 @@ static const QString fromRawDataWithoutRef(const String& string, int start = 0,
     return QString::fromRawData(reinterpret_cast<const QChar*>(string.characters() + start), len);
 }
 
-static QTextLine setupLayout(QTextLayout* layout, const TextRun& style)
+static QTextLine setupLayout(QTextLayout* layout, const TextRun& style, bool shouldSetDirection)
 {
-    int flags = style.rtl() ? Qt::TextForceRightToLeft : Qt::TextForceLeftToRight;
+    int flags = 0;
+    if (shouldSetDirection || style.directionalOverride())
+        flags |= style.rtl() ? Qt::TextForceRightToLeft : Qt::TextForceLeftToRight;
     if (style.expansion())
         flags |= Qt::TextJustificationForced;
     layout->setCacheEnabled(true);
@@ -187,7 +189,7 @@ public:
         m_layout.setText(string);
         m_layout.setRawFont(font.rawFont());
         font.initFormatForTextLayout(&m_layout, run);
-        m_line = setupLayout(&m_layout, run);
+        m_line = setupLayout(&m_layout, run, false);
     }
 
     float width(unsigned from, unsigned len, HashSet<const SimpleFontData*>* fallbackFonts)
@@ -239,7 +241,7 @@ void Font::drawComplexText(GraphicsContext* ctx, const TextRun& run, const Float
     QTextLayout layout(string);
     layout.setRawFont(rawFont());
     initFormatForTextLayout(&layout, run);
-    QTextLine line = setupLayout(&layout, run);
+    QTextLine line = setupLayout(&layout, run, true);
     const QPointF adjustedPoint(point.x(), point.y() - line.ascent());
 
     QList<QGlyphRun> runs = line.glyphRuns(from, to - from);
@@ -263,7 +265,7 @@ float Font::floatWidthForComplexText(const TextRun& run, HashSet<const SimpleFon
     QTextLayout layout(string);
     layout.setRawFont(rawFont());
     initFormatForTextLayout(&layout, run);
-    QTextLine line = setupLayout(&layout, run);
+    QTextLine line = setupLayout(&layout, run, false);
     float x1 = line.cursorToX(0);
     float x2 = line.cursorToX(run.length());
     float width = qAbs(x2 - x1);
@@ -279,7 +281,7 @@ int Font::offsetForPositionForComplexText(const TextRun& run, float position, bo
     QTextLayout layout(string);
     layout.setRawFont(rawFont());
     initFormatForTextLayout(&layout, run);
-    QTextLine line = setupLayout(&layout, run);
+    QTextLine line = setupLayout(&layout, run, false);
     return line.xToCursor(position);
 }
 
@@ -291,7 +293,7 @@ FloatRect Font::selectionRectForComplexText(const TextRun& run, const FloatPoint
     QTextLayout layout(string);
     layout.setRawFont(rawFont());
     initFormatForTextLayout(&layout, run);
-    QTextLine line = setupLayout(&layout, run);
+    QTextLine line = setupLayout(&layout, run, false);
 
     float x1 = line.cursorToX(from);
     float x2 = line.cursorToX(to);