Retain bidirectional marks when eliding text

When the text contains unicode markers for bidirectional
text, these will not affect the width of the text, but they
might affects its layout. Thus, we need to retain these
markers in the elided text to avoid the layout of the string
changing when its allocated width changes.

Task-number: QTBUG-3768
Change-Id: I3866c32cd1dcd5fff2b8fa5b25ae89e551531a97
Reviewed-by: Jiang Jiang <jiang.jiang@nokia.com>

1 files changed, 44 insertions, 2 deletions

diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index ec7dc57314..9848898d66 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -2329,6 +2329,42 @@ static inline bool prevCharJoins(const QString &string, int pos)
     return (joining == QChar::Dual || joining == QChar::Center);
 }
 
+static bool isRetainableControlCode(const QChar &c)
+{
+    return (c.unicode() == 0x202a       // LRE
+            || c.unicode() == 0x202b    // LRE
+            || c.unicode() == 0x202c    // PDF
+            || c.unicode() == 0x202d    // LRO
+            || c.unicode() == 0x202e    // RLO
+            || c.unicode() == 0x200e    // LRM
+            || c.unicode() == 0x200f);  // RLM
+}
+
+static QString stringMidRetainingBidiCC(const QString &string,
+                                        const QString &ellidePrefix,
+                                        const QString &ellideSuffix,
+                                        int subStringFrom,
+                                        int subStringTo,
+                                        int midStart,
+                                        int midLength)
+{
+    QString prefix;
+    for (int i=subStringFrom; i<midStart; ++i) {
+        QChar c = string.at(i);
+        if (isRetainableControlCode(c))
+            prefix += c;
+    }
+
+    QString suffix;
+    for (int i=midStart + midLength; i<subStringTo; ++i) {
+        QChar c = string.at(i);
+        if (isRetainableControlCode(c))
+            suffix += c;
+    }
+
+    return prefix + ellidePrefix + string.mid(midStart, midLength) + ellideSuffix + suffix;
+}
+
 QString QTextEngine::elidedText(Qt::TextElideMode mode, const QFixed &width, int flags, int from, int count) const
 {
 //    qDebug() << "elidedText; available width" << width.toReal() << "text width:" << this->width(0, layoutData->string.length()).toReal();
@@ -2440,7 +2476,10 @@ QString QTextEngine::elidedText(Qt::TextElideMode mode, const QFixed &width, int
         if (nextCharJoins(layoutData->string, pos))
             ellipsisText.prepend(QChar(0x200d) /* ZWJ */);
 
-        return layoutData->string.mid(from, pos - from) + ellipsisText;
+        return stringMidRetainingBidiCC(layoutData->string,
+                                        QString(), ellipsisText,
+                                        from, to,
+                                        from, pos - from);
     } else if (mode == Qt::ElideLeft) {
         QFixed currentWidth;
         int pos;
@@ -2460,7 +2499,10 @@ QString QTextEngine::elidedText(Qt::TextElideMode mode, const QFixed &width, int
         if (prevCharJoins(layoutData->string, pos))
             ellipsisText.append(QChar(0x200d) /* ZWJ */);
 
-        return ellipsisText + layoutData->string.mid(pos, to - pos);
+        return stringMidRetainingBidiCC(layoutData->string,
+                                        ellipsisText, QString(),
+                                        from, to,
+                                        pos, to - pos);
     } else if (mode == Qt::ElideMiddle) {
         QFixed leftWidth;
         QFixed rightWidth;