Merge bitcoin-core/gui#881: Move FreespaceChecker class into its own module

3a03f07560 qt: Avoid header circular dependency (Anthony Towns)
25884bd896 qt, refactor: Move `FreespaceChecker` class into its own module (Hennadii Stepanov)

Pull request description:

  For some reason, the MOC compiler in older versions of Qt 6 fails to parse `qt/intro.cpp`, as noted in [this comment](https://github.com/bitcoin/bitcoin/pull/32998#issuecomment-3082011233).

  This PR proposes a move-only refactoring to simplify the source structure by eliminating the need for the inline `#include <qt/intro.moc>`, thereby effectively working around the issue.

  Required for https://github.com/bitcoin/bitcoin/pull/32998.

ACKs for top commit:
  ajtowns:
    ACK 3a03f07560

Tree-SHA512: 4a7261f04fff9bd8edd4dc2df619c90e06417e19da672dd688a917cd0b9a324a6db7185a47c48f0385713b5e6c45d2204bef58cbe6c77299386136ed5682bd8d

src/qt/CMakeLists.txt

@@ -75,6 +75,8 @@ add_library(bitcoinqt STATIC EXCLUDE_FROM_ALL
   clientmodel.h
   csvmodelwriter.cpp
   csvmodelwriter.h
+  freespacechecker.cpp
+  freespacechecker.h
   guiutil.cpp
   guiutil.h
   initexecutor.cpp

src/qt/freespacechecker.cpp

@@ -0,0 +1,58 @@
+// Copyright (c) 2011-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <qt/freespacechecker.h>
+
+#include <qt/guiutil.h>
+#include <util/fs.h>
+
+#include <QDir>
+#include <QString>
+
+#include <cstdint>
+
+void FreespaceChecker::check()
+{
+    QString dataDirStr = intro->getPathToCheck();
+    fs::path dataDir = GUIUtil::QStringToPath(dataDirStr);
+    uint64_t freeBytesAvailable = 0;
+    int replyStatus = ST_OK;
+    QString replyMessage = tr("A new data directory will be created.");
+
+    /* Find first parent that exists, so that fs::space does not fail */
+    fs::path parentDir = dataDir;
+    fs::path parentDirOld = fs::path();
+    while(parentDir.has_parent_path() && !fs::exists(parentDir))
+    {
+        parentDir = parentDir.parent_path();
+
+        /* Check if we make any progress, break if not to prevent an infinite loop here */
+        if (parentDirOld == parentDir)
+            break;
+
+        parentDirOld = parentDir;
+    }
+
+    try {
+        freeBytesAvailable = fs::space(parentDir).available;
+        if(fs::exists(dataDir))
+        {
+            if(fs::is_directory(dataDir))
+            {
+                QString separator = "<code>" + QDir::toNativeSeparators("/") + tr("name") + "</code>";
+                replyStatus = ST_OK;
+                replyMessage = tr("Directory already exists. Add %1 if you intend to create a new directory here.").arg(separator);
+            } else {
+                replyStatus = ST_ERROR;
+                replyMessage = tr("Path already exists, and is not a directory.");
+            }
+        }
+    } catch (const fs::filesystem_error&)
+    {
+        /* Parent directory does not exist or is not accessible */
+        replyStatus = ST_ERROR;
+        replyMessage = tr("Cannot create data directory here.");
+    }
+    Q_EMIT reply(replyStatus, replyMessage, freeBytesAvailable);
+}

src/qt/freespacechecker.h

@@ -0,0 +1,50 @@
+// Copyright (c) 2011-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_QT_FREESPACECHECKER_H
+#define BITCOIN_QT_FREESPACECHECKER_H
+
+#include <QObject>
+#include <QString>
+#include <QtGlobal>
+
+/* Check free space asynchronously to prevent hanging the UI thread.
+
+   Up to one request to check a path is in flight to this thread; when the check()
+   function runs, the current path is requested from the associated Intro object.
+   The reply is sent back through a signal.
+
+   This ensures that no queue of checking requests is built up while the user is
+   still entering the path, and that always the most recently entered path is checked as
+   soon as the thread becomes available.
+*/
+class FreespaceChecker : public QObject
+{
+    Q_OBJECT
+
+public:
+    class PathQuery
+    {
+    public:
+        virtual QString getPathToCheck() = 0;
+    };
+
+    explicit FreespaceChecker(PathQuery* intro) : intro{intro} {}
+
+    enum Status {
+        ST_OK,
+        ST_ERROR
+    };
+
+public Q_SLOTS:
+    void check();
+
+Q_SIGNALS:
+    void reply(int status, const QString &message, quint64 available);
+
+private:
+    PathQuery* intro;
+};
+
+#endif // BITCOIN_QT_FREESPACECHECKER_H

src/qt/intro.cpp

@@ -1,4 +1,4 @@
-// Copyright (c) 2011-2022 The Bitcoin Core developers
+// Copyright (c) 2011-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -10,6 +10,7 @@
 #include <util/chaintype.h>
 #include <util/fs.h>
 
+#include <qt/freespacechecker.h>
 #include <qt/guiconstants.h>
 #include <qt/guiutil.h>
 #include <qt/optionsmodel.h>
@@ -25,90 +26,6 @@
 
 #include <cmath>
 
-/* Check free space asynchronously to prevent hanging the UI thread.
-
-   Up to one request to check a path is in flight to this thread; when the check()
-   function runs, the current path is requested from the associated Intro object.
-   The reply is sent back through a signal.
-
-   This ensures that no queue of checking requests is built up while the user is
-   still entering the path, and that always the most recently entered path is checked as
-   soon as the thread becomes available.
-*/
-class FreespaceChecker : public QObject
-{
-    Q_OBJECT
-
-public:
-    explicit FreespaceChecker(Intro *intro);
-
-    enum Status {
-        ST_OK,
-        ST_ERROR
-    };
-
-public Q_SLOTS:
-    void check();
-
-Q_SIGNALS:
-    void reply(int status, const QString &message, quint64 available);
-
-private:
-    Intro *intro;
-};
-
-#include <qt/intro.moc>
-
-FreespaceChecker::FreespaceChecker(Intro *_intro)
-{
-    this->intro = _intro;
-}
-
-void FreespaceChecker::check()
-{
-    QString dataDirStr = intro->getPathToCheck();
-    fs::path dataDir = GUIUtil::QStringToPath(dataDirStr);
-    uint64_t freeBytesAvailable = 0;
-    int replyStatus = ST_OK;
-    QString replyMessage = tr("A new data directory will be created.");
-
-    /* Find first parent that exists, so that fs::space does not fail */
-    fs::path parentDir = dataDir;
-    fs::path parentDirOld = fs::path();
-    while(parentDir.has_parent_path() && !fs::exists(parentDir))
-    {
-        parentDir = parentDir.parent_path();
-
-        /* Check if we make any progress, break if not to prevent an infinite loop here */
-        if (parentDirOld == parentDir)
-            break;
-
-        parentDirOld = parentDir;
-    }
-
-    try {
-        freeBytesAvailable = fs::space(parentDir).available;
-        if(fs::exists(dataDir))
-        {
-            if(fs::is_directory(dataDir))
-            {
-                QString separator = "<code>" + QDir::toNativeSeparators("/") + tr("name") + "</code>";
-                replyStatus = ST_OK;
-                replyMessage = tr("Directory already exists. Add %1 if you intend to create a new directory here.").arg(separator);
-            } else {
-                replyStatus = ST_ERROR;
-                replyMessage = tr("Path already exists, and is not a directory.");
-            }
-        }
-    } catch (const fs::filesystem_error&)
-    {
-        /* Parent directory does not exist or is not accessible */
-        replyStatus = ST_ERROR;
-        replyMessage = tr("Cannot create data directory here.");
-    }
-    Q_EMIT reply(replyStatus, replyMessage, freeBytesAvailable);
-}
-
 namespace {
 //! Return pruning size that will be used if automatic pruning is enabled.
 int GetPruneTargetGB()

src/qt/intro.h

@@ -1,18 +1,18 @@
-// Copyright (c) 2011-2021 The Bitcoin Core developers
+// Copyright (c) 2011-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_QT_INTRO_H
 #define BITCOIN_QT_INTRO_H
 
+#include <qt/freespacechecker.h>
+
 #include <QDialog>
 #include <QMutex>
 #include <QThread>
 
 static const bool DEFAULT_CHOOSE_DATADIR = false;
 
-class FreespaceChecker;
-
 namespace interfaces {
     class Node;
 }
@@ -25,7 +25,7 @@ namespace Ui {
   Allows the user to choose a data directory,
   in which the wallet and block chain will be stored.
  */
-class Intro : public QDialog
+class Intro : public QDialog, public FreespaceChecker::PathQuery
 {
     Q_OBJECT
 
@@ -78,7 +78,7 @@ private:
 
     void startThread();
     void checkPath(const QString &dataDir);
-    QString getPathToCheck();
+    QString getPathToCheck() override;
     void UpdatePruneLabels(bool prune_checked);
     void UpdateFreeSpaceLabel();