If the external modification is a deletion, do not ask for reloading.

The behavour when hitting "reload" on a deleted file was also confusing.

src/Buffer.cpp

@@ -379,15 +379,15 @@ public:
 	// Make sure the file monitor monitors the good file.
 	void refreshFileMonitor();
 
-	/// has it been notified of an external modification?
-	bool isExternallyModified() const { return externally_modified_; }
-
 	/// Notify or clear of external modification
-	void fileExternallyModified(bool modified) const;
+	void fileExternallyModified(bool exists) const;
 
 	/// Block notifications of external modifications
 	FileMonitorBlocker blockFileMonitor() { return file_monitor_->block(); }
 
+	/// has been externally modified? Can be reset by the user.
+	mutable bool externally_modified_;
+
 private:
 	/// So we can force access via the accessors.
 	mutable Buffer const * parent_buffer;
@@ -396,9 +396,6 @@ private:
 	int char_count_;
 	int blank_count_;
 
-	/// has been externally modified? Can be reset by the user.
-	mutable bool externally_modified_;
-
 	FileMonitorPtr file_monitor_;
 };
 
@@ -440,9 +437,8 @@ Buffer::Impl::Impl(Buffer * owner, FileName const & file, bool readonly_,
 	  bibfile_cache_valid_(false), cite_labels_valid_(false), preview_error_(false),
 	  inset(0), preview_loader_(0), cloned_buffer_(cloned_buffer),
 	  clone_list_(0), doing_export(false),
-	  tracked_changes_present_(0), parent_buffer(0),
-	  word_count_(0), char_count_(0), blank_count_(0),
-	  externally_modified_(false)
+	  tracked_changes_present_(0), externally_modified_(false), parent_buffer(0),
+	  word_count_(0), char_count_(0), blank_count_(0)
 {
 	refreshFileMonitor();
 	if (!cloned_buffer_) {
@@ -5332,26 +5328,29 @@ void Buffer::Impl::refreshFileMonitor()
 	// The previous file monitor is invalid
 	// This also destroys the previous file monitor and all its connections
 	file_monitor_ = FileSystemWatcher::monitor(filename);
-	fileExternallyModified(false);
 	// file_monitor_ will be destroyed with *this, so it is not going to call a
 	// destroyed object method.
-	file_monitor_->connect([this](){ fileExternallyModified(true); });
+	file_monitor_->connect([this](bool exists) {
+			fileExternallyModified(exists);
+		});
 }
 
 
-void Buffer::Impl::fileExternallyModified(bool modified) const
+void Buffer::Impl::fileExternallyModified(bool const exists) const
 {
-	if (modified) {
-		// prevent false positives, because FileMonitorBlocker is not enough on
-		// OSX.
-		if (filename.exists() && checksum_ == filename.checksum()) {
-			LYXERR(Debug::FILES, "External modification but "
-			       "checksum unchanged: " << filename);
-			return;
-		}
-		lyx_clean = bak_clean = false;
+	// prevent false positives, because FileMonitorBlocker is not enough on
+	// OSX.
+	if (checksum_ == filename.checksum()) {
+		LYXERR(Debug::FILES, "External modification but "
+		       "checksum unchanged: " << filename);
+		return;
 	}
-	externally_modified_ = modified;
+	lyx_clean = bak_clean = false;
+	// If the file has been deleted, only mark the file as dirty since it is
+	// pointless to prompt for reloading. If later a file is moved into this
+	// location, then the externally modified warning will appear then.
+	if (exists)
+			externally_modified_ = true;
 	if (wa_)
 		wa_->updateTitles();
 }
@@ -5359,13 +5358,15 @@ void Buffer::Impl::fileExternallyModified(bool modified) const
 
 bool Buffer::notifiesExternalModification() const
 {
-	return d->isExternallyModified();
+	return d->externally_modified_;
 }
 
 
 void Buffer::clearExternalModification() const
 {
-	d->fileExternallyModified(false);
+	d->externally_modified_ = false;
+	if (d->wa_)
+		d->wa_->updateTitles();
 }
 
 

src/graphics/GraphicsCacheItem.cpp

@@ -220,7 +220,7 @@ void CacheItem::Impl::startMonitor()
 		return;
 	monitor_ = FileSystemWatcher::activeMonitor(filename_);
 	// Disconnected at the same time as this is destroyed.
-	monitor_->connect([=](){ startLoading(); });
+	monitor_->connect([=](bool /* exists */){ startLoading(); });
 }
 
 

src/insets/RenderPreview.cpp

@@ -304,7 +304,7 @@ void RenderMonitoredPreview::startMonitoring() const
 {
 	if (!monitoring()) {
 		monitor_ = FileSystemWatcher::activeMonitor(filename_);
-		monitor_->connect(changed_);
+		monitor_->connect([this](bool /* exists */){ changed_(); });
 	}
 }
 

src/support/FileMonitor.cpp

@@ -118,31 +118,37 @@ FileMonitorGuard::~FileMonitorGuard()
 }
 
 
-void FileMonitorGuard::refresh()
+void FileMonitorGuard::refresh(bool const emit)
 {
 	if (filename_.empty())
 		return;
 	QString const qfilename = toqstr(filename_);
-	if(!qwatcher_->files().contains(qfilename)) {
-		bool exists = QFile(qfilename).exists();
+	if (!qwatcher_->files().contains(qfilename)) {
+		bool const existed = exists_;
+		exists_ = QFile(qfilename).exists();
 #if (QT_VERSION >= 0x050000)
-		if (!exists || !qwatcher_->addPath(qfilename))
+		if (exists_ && !qwatcher_->addPath(qfilename))
 #else
 		auto add_path = [&]() {
 			qwatcher_->addPath(qfilename);
 			return qwatcher_->files().contains(qfilename);
 		};
-		if (!exists || !add_path())
+		if (exists_ && !add_path())
 #endif
 		{
-			if (exists)
-				LYXERR(Debug::FILES,
-				       "Could not add path to QFileSystemWatcher: "
-				       << filename_);
-			QTimer::singleShot(2000, this, SLOT(refresh()));
-		} else if (exists && !exists_)
-			Q_EMIT fileChanged();
-		setExists(exists);
+			LYXERR(Debug::FILES,
+			       "Could not add path to QFileSystemWatcher: " << filename_);
+			QTimer::singleShot(5000, this, SLOT(refresh()));
+		} else {
+			if (!exists_)
+				// The standard way to overwrite a file is to delete it and
+				// create a new file with the same name. Therefore if the file
+				// has just been deleted, it is smart to check not too long
+				// after whether it has been recreated.
+			    QTimer::singleShot(existed ? 100 : 2000, this, SLOT(refresh()));
+			if (existed != exists_ && emit)
+				Q_EMIT fileChanged(exists_);
+		}
 	}
 }
 
@@ -150,11 +156,12 @@ void FileMonitorGuard::refresh()
 void FileMonitorGuard::notifyChange(QString const & path)
 {
 	if (path == toqstr(filename_)) {
-		Q_EMIT fileChanged();
 		// If the file has been modified by delete-move, we are notified of the
 		// deletion but we no longer track the file. See
 		// <https://bugreports.qt.io/browse/QTBUG-46483> (not a bug).
-		refresh();
+		// Therefore we must refresh.
+		refresh(false);
+		Q_EMIT fileChanged(exists_);
 	}
 }
 
@@ -162,17 +169,15 @@ void FileMonitorGuard::notifyChange(QString const & path)
 FileMonitor::FileMonitor(std::shared_ptr<FileMonitorGuard> monitor)
 	: monitor_(monitor)
 {
-	QObject::connect(monitor_.get(), SIGNAL(fileChanged()),
-	                 this, SLOT(changed()));
+	connectToFileMonitorGuard();
 	refresh();
 }
 
 
-void FileMonitor::reconnectToFileMonitorGuard()
+void FileMonitor::connectToFileMonitorGuard()
 {
-	monitor_->setExists(true);
-	QObject::connect(monitor_.get(), SIGNAL(fileChanged()),
-	                 this, SLOT(changed()));
+	QObject::connect(monitor_.get(), SIGNAL(fileChanged(bool)),
+	                 this, SLOT(changed(bool)));
 }
 
 
@@ -185,15 +190,15 @@ signals2::connection FileMonitor::connect(slot const & slot)
 void FileMonitor::disconnect()
 {
 	fileChanged_.disconnect_all_slots();
-	QObject::disconnect(this, SIGNAL(fileChanged()));
+	QObject::disconnect(this, SIGNAL(fileChanged(bool)));
 }
 
 
-void FileMonitor::changed()
+void FileMonitor::changed(bool const exists)
 {
 	// emit boost signal
-	fileChanged_();
-	Q_EMIT fileChanged();
+	fileChanged_(exists);
+	Q_EMIT fileChanged(exists);
 }
 
 
@@ -210,8 +215,8 @@ FileMonitorBlocker FileMonitor::block(int delay)
 FileMonitorBlockerGuard::FileMonitorBlockerGuard(FileMonitor * monitor)
 	: monitor_(monitor), delay_(0)
 {
-	QObject::disconnect(monitor->monitor_.get(), SIGNAL(fileChanged()),
-	                    monitor, SLOT(changed()));
+	QObject::disconnect(monitor->monitor_.get(), SIGNAL(fileChanged(bool)),
+	                    monitor, SLOT(changed(bool)));
 }
 
 
@@ -229,7 +234,7 @@ FileMonitorBlockerGuard::~FileMonitorBlockerGuard()
 	// from QFileSystemWatcher that we meant to ignore are not going to be
 	// treated immediately, so we must yield to give us the opportunity to
 	// ignore them.
-	QTimer::singleShot(delay_, monitor_, SLOT(reconnectToFileMonitorGuard()));
+	QTimer::singleShot(delay_, monitor_, SLOT(connectToFileMonitorGuard()));
 }
 
 
@@ -238,8 +243,9 @@ ActiveFileMonitor::ActiveFileMonitor(std::shared_ptr<FileMonitorGuard> monitor,
 	: FileMonitor(monitor), filename_(filename), interval_(interval),
 	  timestamp_(0), checksum_(0), cooldown_(true)
 {
-	QObject::connect(this, SIGNAL(fileChanged()), this, SLOT(setCooldown()));
+	QObject::connect(this, SIGNAL(fileChanged(bool)), this, SLOT(setCooldown()));
 	QTimer::singleShot(interval_, this, SLOT(clearCooldown()));
+	filename_.refresh();
 	if (!filename_.exists())
 		return;
 	timestamp_ = filename_.lastModified();
@@ -254,7 +260,9 @@ void ActiveFileMonitor::checkModified()
 
 	cooldown_ = true;
 	bool changed = false;
-	if (!filename_.exists()) {
+	filename_.refresh();
+	bool exists = filename_.exists();
+	if (!exists) {
 		changed = timestamp_ || checksum_;
 		timestamp_ = 0;
 		checksum_ = 0;
@@ -272,7 +280,7 @@ void ActiveFileMonitor::checkModified()
 		}
 	}
 	if (changed)
-		FileMonitor::changed();
+		FileMonitor::changed(exists);
 	QTimer::singleShot(interval_, this, SLOT(clearCooldown()));
 }
 

src/support/FileMonitor.h

@@ -108,18 +108,16 @@ public:
 	~FileMonitorGuard();
 	/// absolute path being tracked
 	std::string const & filename() { return filename_; }
-	/// if false, emit fileChanged() when we notice the existence of the file
-	void setExists(bool exists) { exists_ = exists; }
 
 public Q_SLOTS:
 	/// Make sure it is being monitored, after e.g. a deletion. See
 	/// <https://bugreports.qt.io/browse/QTBUG-46483>. This is called
 	/// automatically.
-	void refresh();
+	void refresh(bool emit = true);
 
 Q_SIGNALS:
 	/// Connect to this to be notified when the file changes
-	void fileChanged() const;
+	void fileChanged(bool exists) const;
 
 private Q_SLOTS:
 	/// Receive notifications from the QFileSystemWatcher
@@ -128,6 +126,7 @@ private Q_SLOTS:
 private:
 	std::string const filename_;
 	QFileSystemWatcher * qwatcher_;
+	/// for emitting fileChanged() when the file is created or deleted
 	bool exists_;
 };
 
@@ -157,7 +156,7 @@ class FileMonitor : public QObject
 public:
 	FileMonitor(std::shared_ptr<FileMonitorGuard> monitor);
 
-	typedef signals2::signal<void()> sig;
+	typedef signals2::signal<void(bool)> sig;
 	typedef sig::slot_type slot;
 	/// Connect and you'll be informed when the file has changed.
 	signals2::connection connect(slot const &);
@@ -177,7 +176,7 @@ public:
 	/// inotify backend (e.g. Linux); for OSX (kqueue), a value of 100ms is
 	/// unsufficient and more tests need to be done in combination with
 	/// flushing/syncing to disk in order to understand how to catch one's own
-	/// operations reliably. No feedback from Windows yet. See
+	/// operations reliably. No feedback about Windows. See
 	/// <https://www.mail-archive.com/lyx-devel@lists.lyx.org/msg200252.html>.
 	FileMonitorBlocker block(int delay = 0);
 	/// Make sure the good file is being monitored, after e.g. a move or a
@@ -187,13 +186,13 @@ public:
 
 Q_SIGNALS:
 	/// Connect to this to be notified when the file changes
-	void fileChanged() const;
+	void fileChanged(bool exists) const;
 
 protected Q_SLOTS:
 	/// Receive notifications from the FileMonitorGuard
-	void changed();
+	void changed(bool exists);
 	///
-	void reconnectToFileMonitorGuard();
+	void connectToFileMonitorGuard();
 
 private:
 	/// boost signal