qml: show option for single server in ServerConfig

electrum/gui/qml/components/ServerConfigDialog.qml

@@ -44,6 +44,9 @@ ElDialog {
             onClicked: {
                 Config.autoConnect = serverconfig.auto_connect
                 Network.server = serverconfig.address
+                Network.oneServer = serverconfig.auto_connect
+                    ? false
+                    : serverconfig.one_server
                 rootItem.close()
             }
         }

electrum/gui/qml/components/controls/ServerConfig.qml

@@ -12,6 +12,7 @@ Item {
     property bool showAutoselectServer: true
     property alias auto_connect: auto_server_cb.checked
     property alias address: address_tf.text
+    property alias one_server: one_server_cb.checked
 
     implicitHeight: rootLayout.height
 
@@ -26,7 +27,7 @@ Item {
             id: auto_server_cb
             visible: showAutoselectServer
             text: qsTr('Select server automatically')
-            checked: true
+            checked: !showAutoselectServer
         }
 
         Label {
@@ -45,6 +46,22 @@ Item {
             }
         }
 
+        RowLayout {
+            Layout.fillWidth: true
+            visible: !auto_server_cb.checked && address_tf.text
+
+            CheckBox {
+                id: one_server_cb
+                Layout.fillWidth: true
+                text: qsTr('One server')
+            }
+
+            HelpButton {
+                heading: qsTr('One server')
+                helptext: qsTr('Connect only to a single Electrum Server. This can help with privacy, but at the cost of detecting lagging and forks')
+            }
+        }
+
         ColumnLayout {
             Heading {
                 text: qsTr('Servers')
@@ -96,6 +113,7 @@ Item {
     Component.onCompleted: {
         root.auto_connect = Config.autoConnectDefined ? Config.autoConnect : false
         root.address = Network.server
+        one_server_cb.checked = Network.oneServer
         // TODO: initial setup should not connect already, is Network.server defined?
     }
 }

electrum/gui/qml/components/wizard/WCServerConfig.qml

@@ -12,6 +12,7 @@ WizardComponent {
     function apply() {
         wizard_data['autoconnect'] = sc.address.trim() == ""
         wizard_data['server'] = sc.address
+        wizard_data['one_server'] = sc.one_server
     }
 
     ColumnLayout {

electrum/gui/qml/qenetwork.py

@@ -269,6 +269,18 @@ def proxy(self, proxy_settings):
     def isProxyTor(self):
         return bool(self.network.is_proxy_tor)
 
+    @pyqtProperty(bool, notify=statusChanged)
+    def oneServer(self):
+        return self.network.oneserver
+
+    @oneServer.setter
+    def oneServer(self, one_server: bool):
+        if one_server != self.network.oneserver:
+            net_params = self.network.get_parameters()
+            net_params = net_params._replace(oneserver=one_server)
+            self.network.run_from_another_thread(self.network.set_parameters(net_params))
+            self.statusChanged.emit()
+
     @pyqtProperty('QVariant', notify=feeHistogramUpdated)
     def feeHistogram(self):
         return self._fee_histogram

electrum/gui/qt/wizard/server_connect.py

@@ -110,3 +110,4 @@ def __init__(self, parent, wizard):
     def apply(self):
         self.wizard_data['autoconnect'] = self.sw.server_e.text().strip() == ''
         self.wizard_data['server'] = self.sw.server_e.text()
+        self.wizard_data['one_server'] = self.wizard.config.NETWORK_ONESERVER

electrum/network.py

@@ -517,6 +517,13 @@ def get_parameters(self) -> NetworkParameters:
     def _init_parameters_from_config(self) -> None:
         dns_hacks.configure_dns_resolver()
         self.auto_connect = self.config.NETWORK_AUTO_CONNECT
+        if self.auto_connect and self.config.NETWORK_ONESERVER:
+            # enabling both oneserver and auto_connect doesn't really make sense
+            # assume oneserver is enabled for privacy reasons, disable auto_connect and assume server is unpredictable
+            self.logger.warning(f'both "oneserver" and "auto_connect" options enabled, disabling "auto_connect" and resetting "server".')
+            self.config.NETWORK_SERVER = ""  # let _set_default_server set harmless default (localhost)
+            self.auto_connect = False
+
         self._set_default_server()
         self._set_proxy(deserialize_proxy(self.config.NETWORK_PROXY, self.config.NETWORK_PROXY_USER,
                                           self.config.NETWORK_PROXY_PASSWORD))
@@ -639,7 +646,12 @@ def _set_default_server(self) -> None:
                 self.logger.warning(f'failed to parse server-string ({server!r}); falling back to localhost:1:s.')
                 self.default_server = ServerAddr.from_str("localhost:1:s")
         else:
-            self.default_server = pick_random_server(allowed_protocols=self._allowed_protocols)
+            # if oneserver is enabled but no server specified then don't pick a random server
+            if self.config.NETWORK_ONESERVER:
+                self.logger.warning(f'"oneserver" option enabled, but no "server" defined; falling back to localhost:1:s.')
+                self.default_server = ServerAddr.from_str("localhost:1:s")
+            else:
+                self.default_server = pick_random_server(allowed_protocols=self._allowed_protocols)
         assert isinstance(self.default_server, ServerAddr), f"invalid type for default_server: {self.default_server!r}"
 
     def _set_proxy(self, proxy: Optional[dict]):
@@ -684,6 +696,7 @@ async def set_parameters(self, net_params: NetworkParameters):
                 int(proxy['port'])
         except Exception:
             return
+
         self.config.NETWORK_AUTO_CONNECT = net_params.auto_connect
         self.config.NETWORK_ONESERVER = net_params.oneserver
         self.config.NETWORK_PROXY = proxy_str

electrum/wizard.py

@@ -704,14 +704,15 @@ def do_configure_server(self, wizard_data: dict):
         self._logger.debug(f'configuring server: {wizard_data!r}')
         net_params = self._daemon.network.get_parameters()
         server = ''
+        oneserver = wizard_data.get('one_server', False)
         if not wizard_data['autoconnect']:
             try:
                 server = ServerAddr.from_str_with_inference(wizard_data['server'])
                 if not server:
                     raise Exception('failed to parse server %s' % wizard_data['server'])
             except Exception:
                 return
-        net_params = net_params._replace(server=server, auto_connect=wizard_data['autoconnect'])
+        net_params = net_params._replace(server=server, auto_connect=wizard_data['autoconnect'], oneserver=oneserver)
         self._daemon.network.run_from_another_thread(self._daemon.network.set_parameters(net_params))
 
     def do_configure_autoconnect(self, wizard_data: dict):