Merge #17696: qt: Force set nPruneSize in QSettings after the intro dialog

af112ab qt: Rename SetPrune() to InitializePruneSetting() (Hennadii Stepanov)
b0bfbe5 refactor: Drop `bool force' parameter (Hennadii Stepanov)
68c9bbe qt: Force set nPruneSize in QSettings after intro (Hennadii Stepanov)
a82bd8f util: Replace magics with DEFAULT_PRUNE_TARGET_GB (Hennadii Stepanov)

Pull request description:

  On master (5622d8f), having `QSettings` set already
  ```
  $ grep nPruneSize ~/.config/Bitcoin/Bitcoin-Qt-testnet.conf
  nPruneSize=6
  ```

  enabling prune option in the intro dialog

  ```
  $ ./src/qt/bitcoin-qt -choosedatadir -testnet
  ```
  ![DeepinScreenshot_select-area_20191208120425](https://user-images.githubusercontent.com/32963518/70388183-eed68580-19b6-11ea-9aa1-f9ad9aaa68a6.png)

  has no effect:
  ```
  $ grep Prune ~/.bitcoin/testnet3/debug.log
  2019-12-08T10:04:41Z Prune configured to target 5722 MiB on disk for block and undo files.
  ```

  ---

  With this PR:
  ```
  $ grep Prune ~/.bitcoin/testnet3/debug.log
  2019-12-08T10:20:35Z Prune configured to target 1907 MiB on disk for block and undo files.
  ```

  This PR has been split of #17453 (the first two commits) as it fixes an orthogonal bug.

  Refs:
  - bitcoin/bitcoin#17453 (comment)
  - bitcoin/bitcoin#17453 (comment)

ACKs for top commit:
  Sjors:
    Code review re-ACK af112ab
  ryanofsky:
    Code review ACK af112ab. Just suggested changes since last review (thanks!)
  promag:
    Tested ACK af112ab. Latest suggestions and changes look good to me.

Tree-SHA512: 8ddad34b30dcc2cdcad6678ba8a0b36fa176e4e3465862ef6eee9be0f98d8146705138c9c7995dd8c0990af41078ca743fef1a90ed9240081f052f32ddec72b9

Author: fanquake

src/qt/bitcoin.cpp

@@ -281,8 +281,11 @@ void BitcoinApplication::parameterSetup()
     m_node.initParameterInteraction();
 }
 
-void BitcoinApplication::SetPrune(bool prune, bool force) {
-     optionsModel->SetPrune(prune, force);
+void BitcoinApplication::InitializePruneSetting(bool prune)
+{
+    // If prune is set, intentionally override existing prune size with
+    // the default size since this is called when choosing a new datadir.
+    optionsModel->SetPruneTargetGB(prune ? DEFAULT_PRUNE_TARGET_GB : 0, true);
 }
 
 void BitcoinApplication::requestInitialize()
@@ -562,7 +565,7 @@ int GuiMain(int argc, char* argv[])
 
     if (did_show_intro) {
         // Store intro dialog settings other than datadir (network specific)
-        app.SetPrune(prune, true);
+        app.InitializePruneSetting(prune);
     }
 
     if (gArgs.GetBoolArg("-splash", DEFAULT_SPLASHSCREEN) && !gArgs.GetBoolArg("-min", false))

src/qt/bitcoin.h

@@ -67,8 +67,8 @@ class BitcoinApplication: public QApplication
     void parameterSetup();
     /// Create options model
     void createOptionsModel(bool resetSettings);
-    /// Update prune value
-    void SetPrune(bool prune, bool force = false);
+    /// Initialize prune setting
+    void InitializePruneSetting(bool prune);
     /// Create main window
     void createWindow(const NetworkStyle *networkStyle);
     /// Create splash screen

src/qt/guiconstants.h

@@ -51,4 +51,7 @@ static const int TOOLTIP_WRAP_THRESHOLD = 80;
 /* One gigabyte (GB) in bytes */
 static constexpr uint64_t GB_BYTES{1000000000};
 
+// Default prune target displayed in GUI.
+static constexpr int DEFAULT_PRUNE_TARGET_GB{2};
+
 #endif // BITCOIN_QT_GUICONSTANTS_H

src/qt/intro.cpp

@@ -135,7 +135,7 @@ Intro::Intro(QWidget *parent, uint64_t blockchain_size, uint64_t chain_state_siz
         ui->prune->setChecked(true);
         ui->prune->setEnabled(false);
     }
-    ui->prune->setText(tr("Discard blocks after verification, except most recent %1 GB (prune)").arg(pruneTarget ? pruneTarget / 1000 : 2));
+    ui->prune->setText(tr("Discard blocks after verification, except most recent %1 GB (prune)").arg(pruneTarget ? pruneTarget / 1000 : DEFAULT_PRUNE_TARGET_GB));
     requiredSpace = m_blockchain_size;
     QString storageRequiresMsg = tr("At least %1 GB of data will be stored in this directory, and it will grow over time.");
     if (pruneTarget) {

src/qt/optionsmodel.cpp

@@ -91,8 +91,8 @@ void OptionsModel::Init(bool resetSettings)
     if (!settings.contains("bPrune"))
         settings.setValue("bPrune", false);
     if (!settings.contains("nPruneSize"))
-        settings.setValue("nPruneSize", 2);
-    SetPrune(settings.value("bPrune").toBool());
+        settings.setValue("nPruneSize", DEFAULT_PRUNE_TARGET_GB);
+    SetPruneEnabled(settings.value("bPrune").toBool());
 
     if (!settings.contains("nDatabaseCache"))
         settings.setValue("nDatabaseCache", (qint64)nDefaultDbCache);
@@ -236,7 +236,7 @@ static const QString GetDefaultProxyAddress()
     return QString("%1:%2").arg(DEFAULT_GUI_PROXY_HOST).arg(DEFAULT_GUI_PROXY_PORT);
 }
 
-void OptionsModel::SetPrune(bool prune, bool force)
+void OptionsModel::SetPruneEnabled(bool prune, bool force)
 {
     QSettings settings;
     settings.setValue("bPrune", prune);
@@ -252,6 +252,16 @@ void OptionsModel::SetPrune(bool prune, bool force)
     }
 }
 
+void OptionsModel::SetPruneTargetGB(int prune_target_gb, bool force)
+{
+    const bool prune = prune_target_gb > 0;
+    if (prune) {
+        QSettings settings;
+        settings.setValue("nPruneSize", prune_target_gb);
+    }
+    SetPruneEnabled(prune, force);
+}
+
 // read QSettings values and return them
 QVariant OptionsModel::data(const QModelIndex & index, int role) const
 {

src/qt/optionsmodel.h

@@ -73,7 +73,8 @@ class OptionsModel : public QAbstractListModel
     const QString& getOverriddenByCommandLine() { return strOverriddenByCommandLine; }
 
     /* Explicit setters */
-    void SetPrune(bool prune, bool force = false);
+    void SetPruneEnabled(bool prune, bool force = false);
+    void SetPruneTargetGB(int prune_target_gb, bool force = false);
 
     /* Restart flag helper */
     void setRestartRequired(bool fRequired);