Merge #13043: [qt] OptionsDialog: add prune setting

cbede7dbfde83d53ef38d257e9940af5f163b03c [qt] OptionsDialog: add prune setting (Sjors Provoost)

Pull request description:

  The default suggested value is 2 GB. Minimum is 1 GB (550 MB rounded up).

  When the user toggles this setting, a strong warning appears that undoing requires re-downloading the chain:

  <img width="478" alt="schermafbeelding 2018-05-15 om 12 35 24" src="https://user-images.githubusercontent.com/10217/40051858-7939cc20-583c-11e8-9120-327a75376732.png">

  Tooltip points out that actual disk usage can be higher. It's a bit vague on the "advanced features", because I'm assuming anyone who needs to use `-rescan` and `-txindex` will read the documentation, and a more detailed text would needlessly confuse everyone else.

  <img width="450" alt="schermafbeelding 2018-05-15 om 12 33 51" src="https://user-images.githubusercontent.com/10217/40051791-49d6156a-583c-11e8-97b9-7de6dfd8c481.png">

  The UI uses gigabytes for readability and easy of use. There is also no manual pruning UI (`prune=1`). The user will have to use `bitcoin.conf` for those things.

  Fixes #6461. When combined with #13029 the user, after pruning their node, can safely reset settings and/or use bitcoind without having to edit `bitcoin.conf`. However I don't think that's an essential prerequisite.

Tree-SHA512: e17aff276d7235fbd40796adb6431d430620788a753ee13bc064abd35d2edc4280a3d3cddc18e42b4e00edff13ed18fd4f2a966c6f0b43b689afd13673e0c4bf

5 files changed, 113 insertions, 2 deletions

diff --git a/src/qt/forms/optionsdialog.ui b/src/qt/forms/optionsdialog.ui
index a3721991ee..8f34e6bc82 100644
--- a/src/qt/forms/optionsdialog.ui
+++ b/src/qt/forms/optionsdialog.ui
@@ -38,6 +38,69 @@
         </widget>
        </item>
        <item>
+        <spacer name="horizontalSpacer_0_Main">
+         <property name="orientation">
+          <enum>Qt::Horizontal</enum>
+         </property>
+         <property name="sizeHint" stdset="0">
+          <size>
+           <width>40</width>
+           <height>5</height>
+          </size>
+         </property>
+        </spacer>
+       </item>
+       <item>
+       <layout class="QHBoxLayout" name="horizontalLayout_Main_Prune">
+        <item>
+         <widget class="QCheckBox" name="prune">
+          <property name="toolTip">
+           <string>Disables some advanced features but all blocks will still be fully validated. Reverting this setting requires re-downloading the entire blockchain. Actual disk usage may be somewhat higher.</string>
+          </property>
+          <property name="text">
+           <string>Prune &amp;block storage to</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSpinBox" name="pruneSize"/>
+        </item>
+         <item>
+          <widget class="QLabel" name="pruneSizeUnitLabel">
+           <property name="text">
+            <string>GB</string>
+           </property>
+           <property name="textFormat">
+            <enum>Qt::PlainText</enum>
+           </property>
+          </widget>
+         </item>
+         <item>
+          <spacer name="horizontalSpacer_Main_Prune">
+           <property name="orientation">
+            <enum>Qt::Horizontal</enum>
+           </property>
+           <property name="sizeHint" stdset="0">
+            <size>
+             <width>40</width>
+             <height>20</height>
+            </size>
+           </property>
+          </spacer>
+         </item>
+        </layout>
+       </item>
+       <item>
+        <widget class="QLabel" name="pruneWarning">
+         <property name="text">
+          <string>Reverting this setting requires re-downloading the entire blockchain.</string>
+         </property>
+         <property name="textFormat">
+          <enum>Qt::PlainText</enum>
+         </property>
+        </widget>
+       </item>
+       <item>
         <layout class="QHBoxLayout" name="horizontalLayout_2_Main">
          <item>
           <widget class="QLabel" name="databaseCacheLabel">
@@ -81,7 +144,7 @@
         </layout>
        </item>
        <item>
-        <layout class="QHBoxLayout" name="horizontalLayout_3_Main">
+        <layout class="QHBoxLayout" name="horizontalLayout_Main_VerifyLabel">
          <item>
           <widget class="QLabel" name="threadsScriptVerifLabel">
            <property name="text">
@@ -103,7 +166,7 @@
           </widget>
          </item>
          <item>
-          <spacer name="horizontalSpacer_3_Main">
+          <spacer name="horizontalSpacer_Main_Threads">
            <property name="orientation">
             <enum>Qt::Horizontal</enum>
            </property>
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index c0ddb89b40..108aa4f99c 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -36,8 +36,17 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
     /* Main elements init */
     ui->databaseCache->setMinimum(nMinDbCache);
     ui->databaseCache->setMaximum(nMaxDbCache);
+    static const uint64_t GiB = 1024 * 1024 * 1024;
+    static const uint64_t nMinDiskSpace = MIN_DISK_SPACE_FOR_BLOCK_FILES / GiB +
+                          (MIN_DISK_SPACE_FOR_BLOCK_FILES % GiB) ? 1 : 0;
+    ui->pruneSize->setMinimum(nMinDiskSpace);
     ui->threadsScriptVerif->setMinimum(-GetNumCores());
     ui->threadsScriptVerif->setMaximum(MAX_SCRIPTCHECK_THREADS);
+    ui->pruneWarning->setVisible(false);
+    ui->pruneWarning->setStyleSheet("QLabel { color: red; }");
+
+    ui->pruneSize->setEnabled(false);
+    connect(ui->prune, SIGNAL(toggled(bool)), ui->pruneSize, SLOT(setEnabled(bool)));
 
     /* Network elements init */
 #ifndef USE_UPNP
@@ -157,6 +166,9 @@ void OptionsDialog::setModel(OptionsModel *_model)
     /* warn when one of the following settings changes by user action (placed here so init via mapper doesn't trigger them) */
 
     /* Main */
+    connect(ui->prune, SIGNAL(clicked(bool)), this, SLOT(showRestartWarning()));
+    connect(ui->prune, SIGNAL(clicked(bool)), this, SLOT(togglePruneWarning(bool)));
+    connect(ui->pruneSize, SIGNAL(valueChanged(int)), this, SLOT(showRestartWarning()));
     connect(ui->databaseCache, SIGNAL(valueChanged(int)), this, SLOT(showRestartWarning()));
     connect(ui->threadsScriptVerif, SIGNAL(valueChanged(int)), this, SLOT(showRestartWarning()));
     /* Wallet */
@@ -176,6 +188,8 @@ void OptionsDialog::setMapper()
     mapper->addMapping(ui->bitcoinAtStartup, OptionsModel::StartAtStartup);
     mapper->addMapping(ui->threadsScriptVerif, OptionsModel::ThreadsScriptVerif);
     mapper->addMapping(ui->databaseCache, OptionsModel::DatabaseCache);
+    mapper->addMapping(ui->prune, OptionsModel::Prune);
+    mapper->addMapping(ui->pruneSize, OptionsModel::PruneSize);
 
     /* Wallet */
     mapper->addMapping(ui->spendZeroConfChange, OptionsModel::SpendZeroConfChange);
@@ -266,6 +280,11 @@ void OptionsDialog::on_hideTrayIcon_stateChanged(int fState)
     }
 }
 
+void OptionsDialog::togglePruneWarning(bool enabled)
+{
+    ui->pruneWarning->setVisible(!ui->pruneWarning->isVisible());
+}
+
 void OptionsDialog::showRestartWarning(bool fPersistent)
 {
     ui->statusLabel->setStyleSheet("QLabel { color: red; }");
diff --git a/src/qt/optionsdialog.h b/src/qt/optionsdialog.h
index faf9ff8959..5aad484ce7 100644
--- a/src/qt/optionsdialog.h
+++ b/src/qt/optionsdialog.h
@@ -53,6 +53,7 @@ private Q_SLOTS:
     
     void on_hideTrayIcon_stateChanged(int fState);
 
+    void togglePruneWarning(bool enabled);
     void showRestartWarning(bool fPersistent = false);
     void clearStatusLabel();
     void updateProxyValidationState();
diff --git a/src/qt/optionsmodel.cpp b/src/qt/optionsmodel.cpp
index cae9dace4c..31a85f4e23 100644
--- a/src/qt/optionsmodel.cpp
+++ b/src/qt/optionsmodel.cpp
@@ -88,6 +88,16 @@ void OptionsModel::Init(bool resetSettings)
     // by command-line and show this in the UI.
 
     // Main
+    if (!settings.contains("bPrune"))
+        settings.setValue("bPrune", false);
+    if (!settings.contains("nPruneSize"))
+        settings.setValue("nPruneSize", 2);
+    // Convert prune size to MB:
+    const uint64_t nPruneSizeMB = settings.value("nPruneSize").toInt() * 1000;
+    if (!m_node.softSetArg("-prune", settings.value("bPrune").toBool() ? std::to_string(nPruneSizeMB) : "0")) {
+      addOverriddenOption("-prune");
+    }
+
     if (!settings.contains("nDatabaseCache"))
         settings.setValue("nDatabaseCache", (qint64)nDefaultDbCache);
     if (!m_node.softSetArg("-dbcache", settings.value("nDatabaseCache").toString().toStdString()))
@@ -281,6 +291,10 @@ QVariant OptionsModel::data(const QModelIndex & index, int role) const
             return settings.value("language");
         case CoinControlFeatures:
             return fCoinControlFeatures;
+        case Prune:
+            return settings.value("bPrune");
+        case PruneSize:
+            return settings.value("nPruneSize");
         case DatabaseCache:
             return settings.value("nDatabaseCache");
         case ThreadsScriptVerif:
@@ -405,6 +419,18 @@ bool OptionsModel::setData(const QModelIndex & index, const QVariant & value, in
             settings.setValue("fCoinControlFeatures", fCoinControlFeatures);
             Q_EMIT coinControlFeaturesChanged(fCoinControlFeatures);
             break;
+        case Prune:
+            if (settings.value("bPrune") != value) {
+                settings.setValue("bPrune", value);
+                setRestartRequired(true);
+            }
+            break;
+        case PruneSize:
+            if (settings.value("nPruneSize") != value) {
+                settings.setValue("nPruneSize", value);
+                setRestartRequired(true);
+            }
+            break;
         case DatabaseCache:
             if (settings.value("nDatabaseCache") != value) {
                 settings.setValue("nDatabaseCache", value);
diff --git a/src/qt/optionsmodel.h b/src/qt/optionsmodel.h
index fc1d119a71..2777cbeaf2 100644
--- a/src/qt/optionsmodel.h
+++ b/src/qt/optionsmodel.h
@@ -50,6 +50,8 @@ public:
         Language,               // QString
         CoinControlFeatures,    // bool
         ThreadsScriptVerif,     // int
+        Prune,                  // bool
+        PruneSize,              // int
         DatabaseCache,          // int
         SpendZeroConfChange,    // bool
         Listen,                 // bool