Save QFont's style name if present

Font style names are quite irregular and the simplistic matching
implemented in QFontDatabase::styleString(const QFont &) is unable to
properly resolve the style name when font is recreated from a string.
This causes the fonts before and after serialization to be considered
different, even though they are not. The from/toString methods were
made to write and respect the exact font style.

[ChangeLog][QtGui][Important Behavior Changes] QFont::toString() and
QFont::key() were modified to save the font's style name if one is
set, invalidating any stored font identifiers. QFont::fromString()
was also adjusted to accommodate the change.

Task-number: QTBUG-54936
Change-Id: Ibc7c54119acdd8f0950d6049cc89f859bf981504
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

2 files changed, 32 insertions, 2 deletions

diff --git a/src/gui/text/qfont.cpp b/src/gui/text/qfont.cpp
index 12631b3a73..0fa32dc56d 100644
--- a/src/gui/text/qfont.cpp
+++ b/src/gui/text/qfont.cpp
@@ -2001,7 +2001,7 @@ QString QFont::key() const
 QString QFont::toString() const
 {
     const QChar comma(QLatin1Char(','));
-    return family() + comma +
+    QString fontDescription = family() + comma +
         QString::number(     pointSizeF()) + comma +
         QString::number(      pixelSize()) + comma +
         QString::number((int) styleHint()) + comma +
@@ -2011,6 +2011,12 @@ QString QFont::toString() const
         QString::number((int) strikeOut()) + comma +
         QString::number((int)fixedPitch()) + comma +
         QString::number((int)   false);
+
+    QString fontStyle = styleName();
+    if (!fontStyle.isEmpty())
+        fontDescription += comma + fontStyle;
+
+    return fontDescription;
 }
 
 /*!
@@ -2054,7 +2060,7 @@ bool QFont::fromString(const QString &descrip)
         setUnderline(l[5].toInt());
         setStrikeOut(l[6].toInt());
         setFixedPitch(l[7].toInt());
-    } else if (count == 10) {
+    } else if (count >= 10) {
         if (l[2].toInt() > 0)
             setPixelSize(l[2].toInt());
         setStyleHint((StyleHint) l[3].toInt());
@@ -2063,7 +2069,10 @@ bool QFont::fromString(const QString &descrip)
         setUnderline(l[6].toInt());
         setStrikeOut(l[7].toInt());
         setFixedPitch(l[8].toInt());
+        if (count == 11)
+            d->request.styleName = l[10].toString();
     }
+
     if (count >= 9 && !d->request.fixedPitch) // assume 'false' fixedPitch equals default
         d->request.ignorePitch = true;
 
diff --git a/tests/auto/gui/text/qfont/tst_qfont.cpp b/tests/auto/gui/text/qfont/tst_qfont.cpp
index 894b197968..ca984a26a5 100644
--- a/tests/auto/gui/text/qfont/tst_qfont.cpp
+++ b/tests/auto/gui/text/qfont/tst_qfont.cpp
@@ -62,6 +62,7 @@ private slots:
     void styleName();
     void defaultFamily_data();
     void defaultFamily();
+    void toAndFromString();
 
     void sharing();
 };
@@ -539,6 +540,26 @@ void tst_QFont::defaultFamily()
     QVERIFY2(isAcceptable, msgNotAcceptableFont(familyForHint, acceptableFamilies));
 }
 
+void tst_QFont::toAndFromString()
+{
+    QFont defaultFont = QGuiApplication::font();
+    QString family = defaultFont.family();
+
+    QFontDatabase fdb;
+    const QStringList stylesList = fdb.styles(family);
+    if (stylesList.size() == 0)
+        QSKIP("Default font doesn't have any styles");
+
+    for (const QString &style : stylesList) {
+        QFont result;
+        QFont initial = fdb.font(family, style, defaultFont.pointSize());
+
+        result.fromString(initial.toString());
+
+        QCOMPARE(result, initial);
+    }
+}
+
 void tst_QFont::sharing()
 {
     // QFontCache references the engineData