Add "Save Database As..." action

The feature is implemented using the SQLite backup API.

https://sqlite.org/backup.html

This allows saving in-memory databases and saving database files to another
file name.

src/MainWindow.cpp

@@ -687,6 +687,30 @@ void MainWindow::refreshTableBrowsers(bool force_refresh)
     QApplication::restoreOverrideCursor();
 }
 
+bool MainWindow::fileSaveAs() {
+
+    QString fileName =  FileDialog::getSaveFileName(
+                    OpenDatabaseFile,
+                    this,
+                    tr("Choose a database file to save under"),
+                    FileDialog::getSqlDatabaseFileFilter()
+                    );
+    // catch situation where user has canceled file selection from dialog
+    if(!fileName.isEmpty()) {
+        bool result = db.saveAs(fileName.toStdString());
+        if(result) {
+            setCurrentFile(fileName);
+            addToRecentFilesMenu(fileName);
+        } else {
+            QMessageBox::warning(this, QApplication::applicationName(),
+                                 tr("Error while saving the database to the new file."));
+        }
+        return result;
+    } else {
+        return false;
+    }
+}
+
 bool MainWindow::fileClose()
 {
     // Stop any running SQL statements before closing the database
@@ -1415,6 +1439,9 @@ void MainWindow::dbState(bool dirty)
 {
     ui->fileSaveAction->setEnabled(dirty);
     ui->fileRevertAction->setEnabled(dirty);
+    // Unfortunately, sqlite does not allow to backup the DB while there are pending savepoints,
+    // so we cannot "Save As" when the DB is dirty.
+    ui->fileSaveAsAction->setEnabled(!dirty);
 }
 
 void MainWindow::fileSave()
@@ -1824,6 +1851,7 @@ void MainWindow::activateFields(bool enable)
     bool tempDb = db.currentFile() == ":memory:";
 
     ui->fileCloseAction->setEnabled(enable);
+    ui->fileSaveAsAction->setEnabled(enable);
     ui->fileAttachAction->setEnabled(enable);
     ui->fileCompactAction->setEnabled(enable && write);
     ui->fileExportJsonAction->setEnabled(enable);

src/MainWindow.h

@@ -167,6 +167,7 @@ private slots:
     void fileNewInMemoryDatabase();
     void refreshTableBrowsers(bool force_refresh = false);
     bool fileClose();
+    bool fileSaveAs();
     void createTable();
     void createIndex();
     void compact();

src/MainWindow.ui

@@ -785,6 +785,7 @@ You can drag SQL statements from an object row and drop them into other applicat
     <addaction name="fileOpenReadOnlyAction"/>
     <addaction name="fileAttachAction"/>
     <addaction name="fileRecentFiles"/>
+    <addaction name="fileSaveAsAction"/>
     <addaction name="fileCloseAction"/>
     <addaction name="separator"/>
     <addaction name="fileSaveAction"/>
@@ -2240,6 +2241,21 @@ You can drag SQL statements from the Schema column and drop them into the SQL ed
     <string>This shows the number of rows for each table and view in the database.</string>
    </property>
   </action>
+  <action name="fileSaveAsAction">
+   <property name="enabled">
+    <bool>false</bool>
+   </property>
+   <property name="icon">
+    <iconset resource="icons/icons.qrc">
+     <normaloff>:/icons/db_save</normaloff>:/icons/db_save</iconset>
+   </property>
+   <property name="text">
+    <string>Save Database &amp;As...</string>
+   </property>
+   <property name="toolTip">
+    <string>Save the current database as a different file</string>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>
@@ -2350,6 +2366,22 @@ You can drag SQL statements from the Schema column and drop them into the SQL ed
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>fileSaveAsAction</sender>
+   <signal>triggered()</signal>
+   <receiver>MainWindow</receiver>
+   <slot>fileSaveAs()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>-1</x>
+     <y>-1</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>399</x>
+     <y>299</y>
+    </hint>
+   </hints>
+  </connection>
   <connection>
    <sender>fileCompactAction</sender>
    <signal>triggered()</signal>

src/sqlitedb.cpp

@@ -755,6 +755,62 @@ bool DBBrowserDB::close()
     return true;
 }
 
+bool DBBrowserDB::saveAs(const std::string& filename) {
+    int rc;
+    sqlite3_backup *pBackup;
+    sqlite3 *pTo;
+
+    if(!_db)
+        return false;
+
+    waitForDbRelease();
+
+    // Open the database file identified by filename. Exit early if this fails
+    // for any reason.
+    rc = sqlite3_open(filename.c_str(), &pTo);
+    if(rc!=SQLITE_OK) {
+        qWarning() << tr("Cannot open destination file: '%1'").arg(filename.c_str());
+        return false;
+    } else {
+        // Set up the backup procedure to copy from the "main" database of
+        // connection _db to the main database of connection pTo.
+        // If something goes wrong, pBackup will be set to nullptr and an error
+        // code and message left in connection pTo.
+        //
+        // If the backup object is successfully created, call backup_step()
+        // to copy data from _db to pTo. Then call backup_finish()
+        // to release resources associated with the pBackup object.  If an
+        // error occurred, then an error code and message will be left in
+        // connection pTo. If no error occurred, then the error code belonging
+        // to pTo is set to SQLITE_OK.
+        //
+        pBackup = sqlite3_backup_init(pTo, "main", _db, "main");
+        if(pBackup == nullptr) {
+            qWarning() << tr("Cannot backup to file: '%1'. Message: %2").arg(filename.c_str()).arg(sqlite3_errmsg(pTo));
+            sqlite3_close(pTo);
+            return false;
+        } else {
+            sqlite3_backup_step(pBackup, -1);
+            sqlite3_backup_finish(pBackup);
+        }
+        rc = sqlite3_errcode(pTo);
+    }
+
+    if(rc == SQLITE_OK) {
+        // Close current database and set backup as current
+        sqlite3_close(_db);
+        _db = pTo;
+        curDBFilename = QString::fromStdString(filename);
+
+        return true;
+    } else {
+        qWarning() << tr("Cannot backup to file: '%1'. Message: %2").arg(filename.c_str()).arg(sqlite3_errmsg(pTo));
+        // Close failed database connection.
+        sqlite3_close(pTo);
+        return false;
+    }
+}
+
 DBBrowserDB::db_pointer_type DBBrowserDB::get(const QString& user, bool force_wait)
 {
     if(!_db)

src/sqlitedb.h

@@ -80,6 +80,7 @@ public:
     bool detach(const std::string& attached_as);
     bool create ( const QString & db);
     bool close();
+    bool saveAs(const std::string& filename);
 
     // This returns the SQLite version as well as the SQLCipher if DB4S is compiled with encryption support
     static void getSqliteVersion(QString& sqlite, QString& sqlcipher);