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

1 files changed, 19 insertions, 0 deletions

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; }");