QStyleHelper::uniqueName(): Improve palette pixmap cache key

Use QDataStream to obtain cache key for a palettes that are different
from the default QPalette. This results in unique keys for palettes
created from QStyleSheetStyle's render rules.

Task-number: QTBUG-56743
Change-Id: Icbfe165f705ef3e1c9e88cfc9dca88ff1d1e81e6
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

1 files changed, 21 insertions, 1 deletions

diff --git a/src/widgets/styles/qstylehelper.cpp b/src/widgets/styles/qstylehelper.cpp
index 6602b58a9d..960695e9df 100644
--- a/src/widgets/styles/qstylehelper.cpp
+++ b/src/widgets/styles/qstylehelper.cpp
@@ -43,6 +43,8 @@
 
 #include "qstylehelper_p.h"
 #include <qstringbuilder.h>
+#include <qdatastream.h>
+#include <qcryptographichash.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -56,7 +58,6 @@ QString uniqueName(const QString &key, const QStyleOption *option, const QSize &
     QString tmp = key % HexString<uint>(option->state)
                       % HexString<uint>(option->direction)
                       % HexString<uint>(complexOption ? uint(complexOption->activeSubControls) : 0u)
-                      % HexString<quint64>(option->palette.cacheKey())
                       % HexString<uint>(size.width())
                       % HexString<uint>(size.height());
 
@@ -67,6 +68,25 @@ QString uniqueName(const QString &key, const QStyleOption *option, const QSize &
                   % QLatin1Char(spinBox->frame ? '1' : '0'); ;
     }
 #endif // QT_NO_SPINBOX
+
+    // QTBUG-56743, try to create a palette cache key reflecting the value,
+    // as leaks may occur in conjunction with QStyleSheetStyle/QRenderRule modifying
+    // palettes when using QPalette::cacheKey()
+    if (option->palette != QGuiApplication::palette()) {
+        tmp.append(QLatin1Char('P'));
+#ifndef QT_NO_DATASTREAM
+        QByteArray key;
+        key.reserve(5120); // Observed 5040B for a serialized palette on 64bit
+        {
+            QDataStream str(&key, QIODevice::WriteOnly);
+            str << option->palette;
+        }
+        const QByteArray sha1 = QCryptographicHash::hash(key, QCryptographicHash::Sha1).toHex();
+        tmp.append(QString::fromLatin1(sha1));
+#else // QT_NO_DATASTREAM
+        tmp.append(QString::number(option->palette.cacheKey(), 16));
+#endif // !QT_NO_DATASTREAM
+    }
     return tmp;
 }