Merge bitcoin-core/gui#658: Intro: Never change the prune checkbox after the user has touched it

bee0ffbecf4f95b65f4084893924a1ab250ca77c GUI/Intro: Never change the prune checkbox after the user has touched it (Luke Dashjr)
420a983e25d2f3ac3cc4d537bf223682be651604 Bugfix: GUI/Intro: Disable GUI prune option if -prune is set, regardless of set value (Luke Dashjr)

Pull request description:

  Re-PR from https://github.com/bitcoin/bitcoin/pull/18729

  Now includes a bugfix too (`-prune=2+` disabled the checkbox, but `-prune=0/1` did not; this behaviour is necessary since `-prune` overrides GUI settings)

ACKs for top commit:
  hebasto:
    ACK bee0ffbecf4f95b65f4084893924a1ab250ca77c, both commits are improvements of the current behaviour. Tested on Ubuntu 23.10.

Tree-SHA512: 8eb7d90af37deb30fe226179db3bc9df8ab59e4f3218c8e447ed31fc9ddc81ac1a1629da63347518587a56a4c8558b05cf7ec474024c5f5dfc6d49d6ff0eb0cc

2 files changed, 6 insertions, 3 deletions

diff --git a/src/qt/intro.cpp b/src/qt/intro.cpp
index f86b167076..5371dbaa30 100644
--- a/src/qt/intro.cpp
+++ b/src/qt/intro.cpp
@@ -142,8 +142,9 @@ Intro::Intro(QWidget *parent, int64_t blockchain_size_gb, int64_t chain_state_si
 
     const int min_prune_target_GB = std::ceil(MIN_DISK_SPACE_FOR_BLOCK_FILES / 1e9);
     ui->pruneGB->setRange(min_prune_target_GB, std::numeric_limits<int>::max());
-    if (gArgs.GetIntArg("-prune", 0) > 1) { // -prune=1 means enabled, above that it's a size in MiB
-        ui->prune->setChecked(true);
+    if (gArgs.IsArgSet("-prune")) {
+        m_prune_checkbox_is_default = false;
+        ui->prune->setChecked(gArgs.GetIntArg("-prune", 0) >= 1);
         ui->prune->setEnabled(false);
     }
     ui->pruneGB->setValue(m_prune_target_gb);
@@ -152,6 +153,7 @@ Intro::Intro(QWidget *parent, int64_t blockchain_size_gb, int64_t chain_state_si
     UpdatePruneLabels(ui->prune->isChecked());
 
     connect(ui->prune, &QCheckBox::toggled, [this](bool prune_checked) {
+        m_prune_checkbox_is_default = false;
         UpdatePruneLabels(prune_checked);
         UpdateFreeSpaceLabel();
     });
@@ -287,7 +289,7 @@ void Intro::setStatus(int status, const QString &message, quint64 bytesAvailable
         ui->freeSpace->setText("");
     } else {
         m_bytes_available = bytesAvailable;
-        if (ui->prune->isEnabled() && !(gArgs.IsArgSet("-prune") && gArgs.GetIntArg("-prune", 0) == 0)) {
+        if (ui->prune->isEnabled() && m_prune_checkbox_is_default) {
             ui->prune->setChecked(m_bytes_available < (m_blockchain_size_gb + m_chain_state_size_gb + 10) * GB_BYTES);
         }
         UpdateFreeSpaceLabel();
diff --git a/src/qt/intro.h b/src/qt/intro.h
index 900c657b27..7b34c73b02 100644
--- a/src/qt/intro.h
+++ b/src/qt/intro.h
@@ -64,6 +64,7 @@ private Q_SLOTS:
 
 private:
     Ui::Intro *ui;
+    bool m_prune_checkbox_is_default{true};
     QThread* thread{nullptr};
     QMutex mutex;
     bool signalled{false};