QTextFormatCollection: replace copy ctor and op= with clear()

operator=, which was only used for clearing, wasn't clearing the hash.
This led to a mismatch between the vector and the hash (given that the hash
points into the vector).

Spotted by interrupting kmail in gdb, and it was in this code
iterating over a 2000 entries hash (the first vector entries not matching
the hash, this code keep appending new entries for the same formats).

This fixes QTBUG-8862 again, the initial fix having been accidentally
reverted in 467b15a.

Change-Id: Ia34b3d002a0199e1930431a4bbdb2ec981ed4ffc
Task-number: QTBUG-8862
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/gui/text/qtextdocument_p.cpp

@@ -265,7 +265,7 @@ void QTextDocumentPrivate::clear()
         unreachableCharacterCount = 0;
         modifiedState = 0;
         modified = false;
-        formats = QTextFormatCollection();
+        formats.clear();
         int len = fragments.length();
         fragments.clear();
         blocks.clear();

src/gui/text/qtextformat.cpp

@@ -3371,24 +3371,17 @@ QTextTableCellFormat::QTextTableCellFormat(const QTextFormat &fmt)
 
 // ------------------------------------------------------
 
-
-QTextFormatCollection::QTextFormatCollection(const QTextFormatCollection &rhs)
-{
-    formats = rhs.formats;
-    objFormats = rhs.objFormats;
-}
-
-QTextFormatCollection &QTextFormatCollection::operator=(const QTextFormatCollection &rhs)
-{
-    formats = rhs.formats;
-    objFormats = rhs.objFormats;
-    return *this;
-}
-
 QTextFormatCollection::~QTextFormatCollection()
 {
 }
 
+void QTextFormatCollection::clear()
+{
+    formats.clear();
+    objFormats.clear();
+    hashes.clear();
+}
+
 int QTextFormatCollection::indexForFormat(const QTextFormat &format)
 {
     uint hash = getHash(format.d, format.format_type);

src/gui/text/qtextformat_p.h

@@ -63,8 +63,7 @@ public:
     QTextFormatCollection() {}
     ~QTextFormatCollection();
 
-    QTextFormatCollection(const QTextFormatCollection &rhs);
-    QTextFormatCollection &operator=(const QTextFormatCollection &rhs);
+    void clear();
 
     inline QTextFormat objectFormat(int objectIndex) const
     { return format(objectFormatIndex(objectIndex)); }
@@ -104,6 +103,8 @@ public:
 
 private:
     QFont defaultFnt;
+
+    Q_DISABLE_COPY(QTextFormatCollection)
 };
 
 QT_END_NAMESPACE

tests/auto/gui/text/qtextformat/tst_qtextformat.cpp

@@ -60,6 +60,7 @@ private slots:
     void setFont();
     void setFont_collection_data();
     void setFont_collection();
+    void clearCollection();
 };
 
 /*! \internal
@@ -640,5 +641,32 @@ void tst_QTextFormat::setFont_collection()
     }
 }
 
+void tst_QTextFormat::clearCollection()
+{
+    QTextFormatCollection collection;
+    QFont f;
+    f.setUnderline(true);
+    collection.setDefaultFont(f);
+    QTextCharFormat charFormat;
+    charFormat.setFontStyleHint(QFont::SansSerif);
+    int formatIndex = collection.indexForFormat(charFormat);
+    QCOMPARE(formatIndex, 0);
+    QTextCharFormat charFormat2;
+    charFormat2.setUnderlineStyle(QTextCharFormat::SingleUnderline);
+    int formatIndex2 = collection.indexForFormat(charFormat2);
+    QCOMPARE(formatIndex2, 1);
+    QCOMPARE(collection.formats.count(), 2);
+    QCOMPARE(collection.hashes.count(), 2);
+    QCOMPARE(collection.defaultFont(), f);
+
+    collection.clear();
+    QCOMPARE(collection.formats.count(), 0);
+    QCOMPARE(collection.hashes.count(), 0);
+    QCOMPARE(collection.indexForFormat(charFormat2), 0);
+    QCOMPARE(collection.formats.count(), 1);
+    QCOMPARE(collection.hashes.count(), 1);
+    QCOMPARE(collection.defaultFont(), f); // kept, QTextDocument::clear or setPlainText should not reset the font set by setDefaultFont
+}
+
 QTEST_MAIN(tst_QTextFormat)
 #include "tst_qtextformat.moc"