Always update QPalette resolve mask, regardless of QBrush change

56bd1b76d2e81c58a80bf6b5d74219c6b1ab8499 changed the update
resolve mask behavior in QPalette to avoid detaching brush data
when modifying the resolve mask if the brush value is not changed.

But this behavior broke compatibility, it introduced unknown risks, and
we cannot ensure that other code in Qt does not depend on the old
behavior.

We both need to ensure that we don't detach when the value is not
changed, and ensure that the resolveMask is always updated regardless
of whether the value changes, so we need to split them up and
independently share the brush data.

QFont will update its corresponding resolveMask even if the value has
not changed, so it is better to correct this behavior so that QPalette
and QFont are consistent.

[ChangeLog][QtGui][QPalette] Always update resolve mask in
QPalette::setBrush, even if the value of brush has not changed.

Fixes: QTBUG-98762
Pick-to: 6.4 6.3 6.2
Change-Id: Ib845361b30f21c3d78c16ced923c1678b12e05ac
Reviewed-by: JiDe Zhang <[email protected]>
Reviewed-by: Shawn Rutledge <[email protected]>
Reviewed-by: Volker Hilsheimer <[email protected]>

2 files changed, 37 insertions, 23 deletions

diff --git a/src/gui/kernel/qpalette.cpp b/src/gui/kernel/qpalette.cpp
index 311658d26ce..ea876d935ee 100644
--- a/src/gui/kernel/qpalette.cpp
+++ b/src/gui/kernel/qpalette.cpp
@@ -33,12 +33,25 @@ static_assert(bitPosition(QPalette::ColorGroup(QPalette::NColorGroups - 1),
 class QPalettePrivate
 {
 public:
-    QPalettePrivate() : ref(1), ser_no(qt_palette_count++), detach_no(0) { }
+    class Data : public QSharedData {
+    public:
+        Data() : ser_no(qt_palette_count++) { }
+
+        QBrush br[QPalette::NColorGroups][QPalette::NColorRoles];
+        const int ser_no;
+    };
+
+    QPalettePrivate(const QExplicitlySharedDataPointer<Data> &data)
+        : ref(1), detach_no(0), data(data)
+    { }
+    QPalettePrivate()
+        : QPalettePrivate(QExplicitlySharedDataPointer<Data>(new Data))
+    { }
+
     QAtomicInt ref;
-    QBrush br[QPalette::NColorGroups][QPalette::NColorRoles];
     QPalette::ResolveMask resolveMask = {0};
-    int ser_no;
     int detach_no;
+    QExplicitlySharedDataPointer<Data> data;
 };
 
 static QColor qt_mix_colors(QColor a, QColor b)
@@ -710,7 +723,7 @@ const QBrush &QPalette::brush(ColorGroup gr, ColorRole cr) const
             gr = Active;
         }
     }
-    return d->br[gr][cr];
+    return d->data->br[gr][cr];
 }
 
 /*!
@@ -748,11 +761,18 @@ void QPalette::setBrush(ColorGroup cg, ColorRole cr, const QBrush &b)
         cg = Active;
     }
 
-    if (d->br[cg][cr] != b) {
+    const auto newResolveMask = d->resolveMask | ResolveMask(1) << bitPosition(cg, cr);
+    const auto valueChanged = d->data->br[cg][cr] != b;
+
+    if (valueChanged) {
+        detach();
+        d->data.detach();
+        d->data->br[cg][cr] = b;
+    } else if (d->resolveMask != newResolveMask) {
         detach();
-        d->br[cg][cr] = b;
-        d->resolveMask |= ResolveMask(1) << bitPosition(cg, cr);
     }
+
+    d->resolveMask = newResolveMask;
 }
 
 /*!
@@ -793,11 +813,7 @@ bool QPalette::isBrushSet(ColorGroup cg, ColorRole cr) const
 void QPalette::detach()
 {
     if (d->ref.loadRelaxed() != 1) {
-        QPalettePrivate *x = new QPalettePrivate;
-        for(int grp = 0; grp < (int)NColorGroups; grp++) {
-            for(int role = 0; role < (int)NColorRoles; role++)
-                x->br[grp][role] = d->br[grp][role];
-        }
+        QPalettePrivate *x = new QPalettePrivate(d->data);
         x->resolveMask = d->resolveMask;
         if (!d->ref.deref())
             delete d;
@@ -829,11 +845,11 @@ void QPalette::detach()
 */
 bool QPalette::operator==(const QPalette &p) const
 {
-    if (isCopyOf(p))
+    if (isCopyOf(p) || d->data == p.d->data)
         return true;
     for(int grp = 0; grp < (int)NColorGroups; grp++) {
         for(int role = 0; role < (int)NColorRoles; role++) {
-            if (d->br[grp][role] != p.d->br[grp][role])
+            if (d->data->br[grp][role] != p.d->data->br[grp][role])
                 return false;
         }
     }
@@ -867,7 +883,7 @@ bool QPalette::isEqual(QPalette::ColorGroup group1, QPalette::ColorGroup group2)
     if (group1 == group2)
         return true;
     for(int role = 0; role < (int)NColorRoles; role++) {
-        if (d->br[group1][role] != d->br[group2][role])
+        if (d->data->br[group1][role] != d->data->br[group2][role])
                 return false;
     }
     return true;
@@ -882,7 +898,7 @@ bool QPalette::isEqual(QPalette::ColorGroup group1, QPalette::ColorGroup group2)
 */
 qint64 QPalette::cacheKey() const
 {
-    return (((qint64) d->ser_no) << 32) | ((qint64) (d->detach_no));
+    return (((qint64) d->data->ser_no) << 32) | ((qint64) (d->detach_no));
 }
 
 static constexpr QPalette::ResolveMask allResolveMask()
@@ -918,7 +934,8 @@ QPalette QPalette::resolve(const QPalette &other) const
     for (int role = 0; role < int(NColorRoles); ++role) {
         for (int grp = 0; grp < int(NColorGroups); ++grp) {
             if (!(d->resolveMask & (ResolveMask(1) << bitPosition(ColorGroup(grp), ColorRole(role))))) {
-                palette.d->br[grp][role] = other.d->br[grp][role];
+                palette.d->data.detach();
+                palette.d->data->br[grp][role] = other.d->data->br[grp][role];
             }
         }
     }
@@ -981,7 +998,7 @@ QDataStream &operator<<(QDataStream &s, const QPalette &p)
         if (s.version() == 1) {
             // Qt 1.x
             for (int i = 0; i < NumOldRoles; ++i)
-                s << p.d->br[grp][oldRoles[i]].color();
+                s << p.d->data->br[grp][oldRoles[i]].color();
         } else {
             int max = (int)QPalette::NColorRoles;
             if (s.version() <= QDataStream::Qt_2_1)
@@ -991,7 +1008,7 @@ QDataStream &operator<<(QDataStream &s, const QPalette &p)
             else if (s.version() <= QDataStream::Qt_5_11)
                 max = QPalette::ToolTipText + 1;
             for (int r = 0; r < max; r++)
-                s << p.d->br[grp][r];
+                s << p.d->data->br[grp][r];
         }
     }
     return s;
diff --git a/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp b/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp
index 22aaaecf19a..cdb68175981 100644
--- a/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp
+++ b/tests/auto/gui/kernel/qpalette/tst_qpalette.cpp
@@ -190,9 +190,6 @@ void tst_QPalette::setBrush()
 
     const QPalette pp = p;
     QVERIFY(pp.isCopyOf(p));
-    // Setting the same brush won't detach
-    p.setBrush(QPalette::Disabled, QPalette::Button, Qt::green);
-    QVERIFY(pp.isCopyOf(p));
 }
 
 void tst_QPalette::isBrushSet()
@@ -217,7 +214,7 @@ void tst_QPalette::isBrushSet()
     QVERIFY(!p2.isBrushSet(QPalette::Active, QPalette::Dark));
     p2.setBrush(QPalette::Active, QPalette::Dark, p2.brush(QPalette::Active, QPalette::Dark));
     QVERIFY(!p3.isBrushSet(QPalette::Active, QPalette::Dark));
-    QVERIFY(!p2.isBrushSet(QPalette::Active, QPalette::Dark));
+    QVERIFY(p2.isBrushSet(QPalette::Active, QPalette::Dark));
 }
 
 void tst_QPalette::setAllPossibleBrushes()