From 31244327f25883cc7a1de06a833255ed2b8747d0 Mon Sep 17 00:00:00 2001
From: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date: Tue, 22 Sep 2020 12:33:31 +0200
Subject: [PATCH] mutex added when accessing the cache

---
 src/graphic/QskGraphicProvider.cpp | 31 ++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/graphic/QskGraphicProvider.cpp b/src/graphic/QskGraphicProvider.cpp
index 04436d97..40afd672 100644
--- a/src/graphic/QskGraphicProvider.cpp
+++ b/src/graphic/QskGraphicProvider.cpp
@@ -7,6 +7,7 @@
 #include "QskGraphic.h"
 #include "QskSetup.h"
 
+#include <qmutex.h>
 #include <qcache.h>
 #include <qdebug.h>
 #include <qurl.h>
@@ -16,6 +17,7 @@ class QskGraphicProvider::PrivateData
   public:
     // caching of graphics
     QCache< QString, const QskGraphic > cache;
+    QMutex mutex;
 };
 
 QskGraphicProvider::QskGraphicProvider( QObject* parent )
@@ -33,34 +35,55 @@ void QskGraphicProvider::setCacheSize( int size )
     if ( size < 0 )
         size = 0;
 
+    QMutexLocker locker( &m_data->mutex );
     m_data->cache.setMaxCost( size );
 }
 
 int QskGraphicProvider::cacheSize() const
 {
+    QMutexLocker locker( &m_data->mutex );
     return m_data->cache.maxCost();
 }
 
 void QskGraphicProvider::clearCache()
 {
+    QMutexLocker locker( &m_data->mutex );
     m_data->cache.clear();
 }
 
 const QskGraphic* QskGraphicProvider::requestGraphic( const QString& id ) const
 {
-    const QskGraphic* graphic = m_data->cache.object( id );
+    const QskGraphic* graphic = nullptr;
+
+    {
+        QMutexLocker locker( &m_data->mutex );
+        graphic = m_data->cache.object( id );
+    }
 
     if ( graphic == nullptr )
     {
         graphic = loadGraphic( id );
+
         if ( graphic == nullptr )
         {
             qWarning() << "QskGraphicProvider: can't load" << id;
             return nullptr;
-        }
+        }        
 
-        const int cost = 1; // TODO ...
-        m_data->cache.insert( id, graphic, cost );
+        {
+            QMutexLocker locker( &m_data->mutex );
+
+            if( auto cached = m_data->cache.object( id ) )
+            {
+                delete graphic;
+                graphic = cached;
+            }
+            else
+            {
+                const int cost = 1; // TODO ...
+                m_data->cache.insert( id, graphic, cost );
+            }
+        }
     }
 
     return graphic;