Qt: stop capture syntax worker thread on exit

Instead of creating endless loop and synchronizing using QWaitCondition,
execute the syntax worker check in its thread by emitting signal. The
syntax worker thread affinity is set to worker thread so the slots
handling takes place within the worker thread context.

ui/qt/capture_filter_syntax_worker.cpp

@@ -34,7 +34,7 @@ static QMutex pcap_compile_mtx_;
 #if 0
 #include <QDebug>
 #include <QThread>
-#define DEBUG_SYNTAX_CHECK(state1, state2) qDebug() << "CF state" << QThread::currentThreadId() << state1 << "->" << state2 << ":" << filter_text_ << ":" << filter
+#define DEBUG_SYNTAX_CHECK(state1, state2) qDebug() << "CF state" << QThread::currentThreadId() << state1 << "->" << state2 << ":" << filter
 #define DEBUG_SLEEP_TIME 5000 // ms
 #else
 #define DEBUG_SYNTAX_CHECK(state1, state2)
@@ -44,10 +44,9 @@ static QMutex pcap_compile_mtx_;
 #define DUMMY_SNAPLENGTH                65535
 #define DUMMY_NETMASK                   0xFF000000
 
-void CaptureFilterSyntaxWorker::start() {
+void CaptureFilterSyntaxWorker::checkFilter(const QString filter)
+{
 #ifdef HAVE_LIBPCAP
-    forever {
-        QString filter;
     QSet<gint> active_dlts;
     QSet<guint> active_extcap;
     struct bpf_program fcode;
@@ -56,20 +55,12 @@ void CaptureFilterSyntaxWorker::start() {
     enum SyntaxLineEdit::SyntaxState state = SyntaxLineEdit::Valid;
     QString err_str;
 
-        data_mtx_.lock();
+    DEBUG_SYNTAX_CHECK("received", "?");
-        while (filter_text_.isEmpty()) {
-            data_cond_.wait(&data_mtx_);
-        }
-
-        DEBUG_SYNTAX_CHECK("pending", "unknown");
-        filter = filter_text_;
-        filter_text_ = QString();
-        data_mtx_.unlock();
 
     if (global_capture_opts.num_selected < 1) {
         emit syntaxResult(filter, SyntaxLineEdit::Invalid, QString("No interfaces selected"));
         DEBUG_SYNTAX_CHECK("unknown", "no interfaces");
-            continue;
+        return;
     }
 
     for (guint if_idx = 0; if_idx < global_capture_opts.all_ifaces->len; if_idx++) {
@@ -147,18 +138,6 @@ void CaptureFilterSyntaxWorker::start() {
     emit syntaxResult(filter, state, err_str);
 
     DEBUG_SYNTAX_CHECK("known", "idle");
-    }
-#endif // HAVE_LIBPCAP
-}
-
-void CaptureFilterSyntaxWorker::checkFilter(const QString &filter)
-{
-#ifdef HAVE_LIBPCAP
-    QMutexLocker ml(&data_mtx_);
-    /* Ruthlessly clobber the current state. */
-    filter_text_ = filter;
-    DEBUG_SYNTAX_CHECK("received", "?");
-    data_cond_.wakeOne();
 #else
     emit syntaxResult(filter, SyntaxLineEdit::Deprecated, QString("Syntax checking unavailable"));
 #endif // HAVE_LIBPCAP

ui/qt/capture_filter_syntax_worker.h

@@ -20,15 +20,9 @@ class CaptureFilterSyntaxWorker : public QObject
 
 public:
     CaptureFilterSyntaxWorker(QObject *parent = 0) : QObject(parent) {}
-    void checkFilter(const QString &filter);
 
 public slots:
-    void start();
+    void checkFilter(const QString filter);
-
-private:
-    QMutex data_mtx_;
-    QWaitCondition data_cond_;
-    QString filter_text_;
 
 signals:
     void syntaxResult(QString filter, int state, QString err_msg);

ui/qt/widgets/capture_filter_edit.cpp

@@ -218,21 +218,28 @@ CaptureFilterEdit::CaptureFilterEdit(QWidget *parent, bool plain) :
 #endif
     }
 
-    QThread *syntax_thread = new QThread;
+    syntax_thread_ = new QThread;
     syntax_worker_ = new CaptureFilterSyntaxWorker;
-    syntax_worker_->moveToThread(syntax_thread);
+    syntax_worker_->moveToThread(syntax_thread_);
     connect(wsApp, &WiresharkApplication::appInitialized, this, &CaptureFilterEdit::updateBookmarkMenu);
     connect(wsApp, &WiresharkApplication::captureFilterListChanged, this, &CaptureFilterEdit::updateBookmarkMenu);
-    connect(syntax_thread, &QThread::started, syntax_worker_, &CaptureFilterSyntaxWorker::start);
+    connect(syntax_thread_, &QThread::started, this,
-    connect(syntax_thread, &QThread::started, this,
             static_cast<void (CaptureFilterEdit::*)()>(&CaptureFilterEdit::checkFilter));
     connect(syntax_worker_, &CaptureFilterSyntaxWorker::syntaxResult,
             this, &CaptureFilterEdit::setFilterSyntaxState);
-    connect(syntax_thread, &QThread::finished, syntax_worker_, &CaptureFilterSyntaxWorker::deleteLater);
+    connect(this, &CaptureFilterEdit::captureFilterChanged, syntax_worker_, &CaptureFilterSyntaxWorker::checkFilter);
-    syntax_thread->start();
+    syntax_thread_->start();
     updateBookmarkMenu();
 }
 
+CaptureFilterEdit::~CaptureFilterEdit()
+{
+    syntax_thread_->quit();
+    syntax_thread_->wait();
+    delete syntax_thread_;
+    delete syntax_worker_;
+}
+
 void CaptureFilterEdit::paintEvent(QPaintEvent *evt) {
     SyntaxLineEdit::paintEvent(evt);
 
@@ -366,7 +373,7 @@ void CaptureFilterEdit::checkFilter(const QString& filter)
     if (empty) {
         setFilterSyntaxState(filter, Empty, QString());
     } else {
-        syntax_worker_->checkFilter(filter);
+        emit captureFilterChanged(filter);
     }
 }
 

ui/qt/widgets/capture_filter_edit.h

@@ -24,6 +24,7 @@ class CaptureFilterEdit : public SyntaxLineEdit
     Q_OBJECT
 public:
     explicit CaptureFilterEdit(QWidget *parent = 0, bool plain = false);
+    ~CaptureFilterEdit();
     void setConflict(bool conflict = false);
     // No selections: (QString(), false)
     // Selections, same filter: (filter, false)
@@ -63,11 +64,13 @@ private:
     StockIconToolButton *clear_button_;
     StockIconToolButton *apply_button_;
     CaptureFilterSyntaxWorker *syntax_worker_;
+    QThread *syntax_thread_;
 
     void buildCompletionList(const QString& primitive_word);
 
 signals:
     void captureFilterSyntaxChanged(bool valid);
+    void captureFilterChanged(const QString filter);
     void startCapture();
     void addBookmark(const QString filter);