--- a/ui/downloader.cpp	Wed Sep 10 11:05:34 2014 +0200
+++ b/ui/downloader.cpp	Wed Sep 10 11:06:49 2014 +0200
@@ -74,13 +74,14 @@
 /* Set up Proxy support. */
     QSettings settings;
     QString settingsProxy = settings.value("ProxyURL").toString();
-    if (settingsProxy.isEmpty()) {
+    bool useProxy = settings.value("UseProxy", false).toBool();
+    if (useProxy && settingsProxy.isEmpty()) {
         QByteArray envProxy = qgetenv("http_proxy");
         if (envProxy.size()) {
             settingsProxy = QString::fromLocal8Bit(envProxy);
         }
     }
-    if (!settingsProxy.isEmpty()) {
+    if (useProxy && !settingsProxy.isEmpty()) {
         mSSLConnection->setProxy(QUrl(settingsProxy));
     }
 #else

--- a/ui/proxysettingsdlg.cpp	Wed Sep 10 11:05:34 2014 +0200
+++ b/ui/proxysettingsdlg.cpp	Wed Sep 10 11:06:49 2014 +0200
@@ -16,6 +16,7 @@
 #include <QDebug>
 #include <QIcon>
 #include <QPixmap>
+#include <QCheckBox>
 
 #include "proxysettingsdlg.h"
 
@@ -36,7 +37,7 @@
 
     QLabel *explanation = new QLabel(tr("Please enter the proxy server to use in the field below.") +
         " " + tr("The URL can follow the scheme:") + "<br/>" + 
-        tr("&lt;username&gt;:&lt;password&gt;@&lt;hostname&gt;:&lt;port&gt;") +
+        tr("[&lt;username&gt;:&lt;password&gt;]@&lt;hostname&gt;[:&lt;port&gt;]") +
         "<br/></br/>");
     explanation->setTextFormat(Qt::RichText);
     explanation->setWordWrap(true);
@@ -44,9 +45,18 @@
     iconTextLayout->addWidget(explanation);
     mainLayout->addLayout(iconTextLayout);
 
+    bool useProxy = settings.value("UseProxy", false).toBool();
+    mCheckBox = new QCheckBox(tr("Use Proxy Server"));
+    mCheckBox->setTristate(false);
+    mCheckBox->setCheckState(useProxy ? Qt::Checked : Qt::Unchecked);
+
+    mainLayout->addWidget(mCheckBox);
+
     mProxyURL = new QLineEdit(settings.value("ProxyURL").toString());
     QLabel *proxyLabel = new QLabel(tr("Proxy Server:"));
     proxyLabel->setBuddy(mProxyURL);
+    mProxyURL->setReadOnly(!useProxy);
+    mProxyURL->setEnabled(useProxy);
 
     labelLineLayout->addWidget(proxyLabel);
     labelLineLayout->addWidget(mProxyURL);
@@ -61,6 +71,7 @@
     connect(mSaveButton, SIGNAL(clicked()), this, SLOT(save()));
     connect(mProxyURL, SIGNAL(textChanged(const QString &)),
             this, SLOT(checkCanSave(const QString&)));
+    connect(mCheckBox, SIGNAL(stateChanged(int)), this, SLOT(checkCanEdit(int)));
 
     mainLayout->addLayout(labelLineLayout);
     mainLayout->addLayout(okCancelLayout);
@@ -69,12 +80,19 @@
 }
 
 void ProxySettingsDlg::checkCanSave(const QString &val) {
-    mSaveButton->setEnabled(val.isEmpty() || QUrl(val).isValid());
+    mSaveButton->setEnabled(mCheckBox->checkState() == Qt::Unchecked ||
+        QUrl(val).isValid());
+}
+
+void ProxySettingsDlg::checkCanEdit(int state) {
+    mProxyURL->setReadOnly(state != Qt::Checked);
+    mProxyURL->setEnabled(state == Qt::Checked);
 }
 
 void ProxySettingsDlg::save() {
     QSettings settings;
     settings.setValue("ProxyURL", mProxyURL->text());
+    settings.setValue("UseProxy", mCheckBox->checkState() == Qt::Checked);
     settings.sync();
     accept();
 }

--- a/ui/proxysettingsdlg.h	Wed Sep 10 11:05:34 2014 +0200
+++ b/ui/proxysettingsdlg.h	Wed Sep 10 11:06:49 2014 +0200
@@ -12,6 +12,7 @@
 
 class QLineEdit;
 class QPushButton;
+class QCheckBox;
 
 /** 
  * @file proxysettingsdlg.h
@@ -32,9 +33,13 @@
     /** @brief save the contents of mProxyURL in the settings. */
     void save();
 
+    /** @brief make the URL editiable depending on UseProxy setting. */
+    void checkCanEdit(int state);
+
 private:
     QLineEdit *mProxyURL;
     QPushButton *mSaveButton;
+    QCheckBox *mCheckBox;
 };
 
 #endif // PROXYSETTINGSDLG_H