Update max write cache size to 2048MB and set it to automatic by default (closes #148)

src/preferences/advancedsettings.h

@@ -55,6 +55,8 @@ public:
     horizontalHeader()->setStretchLastSection(true);
     verticalHeader()->setVisible(false);
     setRowCount(ROW_COUNT);
+    // Signals
+    connect(&spin_cache, SIGNAL(valueChanged(int)), SLOT(updateCacheSpinSuffix(int)));
     // Load settings
     loadAdvancedSettings();
   }
@@ -151,13 +153,22 @@ private:
   }
 
 private slots:
-  void loadAdvancedSettings() {
+  void updateCacheSpinSuffix(int value)
+  {
+    if (value <= 0)
+      spin_cache.setSuffix(tr(" (auto)"));
+    else
+      spin_cache.setSuffix(tr(" MiB"));
+  }
+
+  void loadAdvancedSettings()
+  {
     const Preferences pref;
     // Disk write cache
-    spin_cache.setMinimum(1);
-    spin_cache.setMaximum(200);
+    spin_cache.setMinimum(0);
+    spin_cache.setMaximum(2048);
     spin_cache.setValue(pref.diskCacheSize());
-    spin_cache.setSuffix(tr(" MiB"));
+    updateCacheSpinSuffix(spin_cache.value());
     setRow(DISK_CACHE, tr("Disk write cache size"), &spin_cache);
     // Outgoing port Min
     outgoing_ports_min.setMinimum(0);

src/preferences/preferences.h

@@ -927,11 +927,11 @@ public:
   }
 
   uint diskCacheSize() const {
-    return value(QString::fromUtf8("Preferences/Downloads/DiskCache"), 16).toUInt();
+    return value(QString::fromUtf8("Preferences/Downloads/DiskWriteCacheSize"), 0).toUInt();
   }
 
   void setDiskCacheSize(uint size) {
-    setValue(QString::fromUtf8("Preferences/Downloads/DiskCache"), size);
+    setValue(QString::fromUtf8("Preferences/Downloads/DiskWriteCacheSize"), size);
   }
 
   uint outgoingPortsMin() const {

src/qtlibtorrent/qbtsession.cpp

@@ -402,7 +402,8 @@ void QBtSession::configureSession() {
   sessionSettings.announce_to_all_trackers = announce_to_all;
   sessionSettings.announce_to_all_tiers = announce_to_all;
   sessionSettings.auto_scrape_min_interval = 900; // 15 minutes
-  sessionSettings.cache_size = pref.diskCacheSize()*64;
+  int cache_size = pref.diskCacheSize();
+  sessionSettings.cache_size = cache_size ? pref.diskCacheSize() * 64 : -1;
   qDebug() << "Using a disk cache size of" << pref.diskCacheSize() << "MiB";
   // Disable OS cache to avoid memory problems (uTorrent behavior)
 #ifdef Q_WS_WIN