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include/mainwindow.h

@@ -1,5 +1,8 @@
 #pragma once
 #include <QMainWindow>
+#include <QCloseEvent>
+#include <QSettings>
+#include <QSplitter>
 #include <QThread>
 #include <QTabWidget>
 #include <QSplitter>
@@ -14,6 +17,7 @@
 #include "rawview.h"
 #include "tableview.h"
 #include "tagwidget.h"
+#include "videowidget.h"
 #include "connectdialog.h"
 #include <QSet>
 
@@ -37,21 +41,29 @@ private slots:
     void onTagDetected(const QString &tag, const QString &value);
     void showFormatReference();
     void configureTagFilter();
+    void showAbout();
+
+protected:
+    void closeEvent(QCloseEvent *event) override;
 
 private:
     void setupUi();
     void setupToolBar();
     void setupStatusBar();
     void clearAllViews();
+    void doShutdown();
+    void saveSettings();
+    void restoreSettings();
 
     // Worker & thread
     QThread      *m_thread = nullptr;
     SerialWorker *m_worker = nullptr;
 
     // Views
-    RawView    *m_rawView   = nullptr;
-    TableView  *m_tableView = nullptr;
-    TagWidget  *m_tagWidget = nullptr;
+    RawView     *m_rawView    = nullptr;
+    TableView   *m_tableView  = nullptr;
+    TagWidget   *m_tagWidget  = nullptr;
+    VideoWidget *m_videoWidget= nullptr;
 
     // Status bar widgets
     QLabel *m_portLabel       = nullptr;
@@ -66,6 +78,11 @@ private:
     QAction *m_connectAction    = nullptr;
     QAction *m_disconnectAction = nullptr;
 
+    // Splitters (saved/restored via QSettings)
+    QSplitter       *m_mainSplitter  = nullptr;
+    QSplitter       *m_rightSplitter = nullptr;
+
     SerialConfig    m_lastConfig;
     QSet<QString>   m_suppressedTags;   // tags hidden from Raw view
+    bool            m_shutdownDone = false;
 };

include/v4l2worker.h

@@ -0,0 +1,49 @@
+#pragma once
+#include <QObject>
+#include <QImage>
+#include <QString>
+#include <atomic>
+#include <thread>
+
+class V4l2Worker : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit V4l2Worker(QObject *parent = nullptr);
+    ~V4l2Worker();
+
+public slots:
+    void startCapture(const QString &device, int width = 1920, int height = 1080);
+    void stopCapture();
+
+signals:
+    void newFrame(const QImage &frame);
+    void captureStarted(const QString &device, int width, int height, const QString &format);
+    void captureStopped();
+    void errorOccurred(const QString &message);
+
+private:
+    void stop();           // joins m_captureThread, closes device – safe from any thread
+    void captureLoop();    // runs inside m_captureThread
+    bool openDevice(const QString &device, int width, int height);
+    void closeDevice();
+    bool initMmap();
+    void freeMmap();
+    QImage convertToImage(const void *data, size_t size, int width, int height);
+    QImage yuyv2Rgb(const uchar *src, int width, int height);
+    QImage nv122Rgb(const uchar *src, int width, int height);
+
+    int           m_fd       = -1;
+    int           m_width    = 1920;
+    int           m_height   = 1080;
+    uint32_t      m_pixFmt   = 0;
+
+    static constexpr int MMAP_BUFFERS = 4;
+    struct MmapBuffer { void *start = nullptr; size_t length = 0; };
+    MmapBuffer    m_buffers[MMAP_BUFFERS];
+    int           m_nBuffers = 0;
+
+    std::atomic<bool> m_running{false};
+    std::thread       m_captureThread;   // dedicated capture thread – not the Qt event thread
+};

include/videowidget.h

@@ -0,0 +1,71 @@
+#pragma once
+#include <QWidget>
+#include <QImage>
+#include <QLabel>
+#include <QPushButton>
+#include <QComboBox>
+#include <QHBoxLayout>
+#include <QVBoxLayout>
+#include <QThread>
+#include <QTimer>
+
+#include "v4l2worker.h"
+
+// VideoWidget shows a live preview of a V4L2 capture device.
+// It lives in the right-side panel, below the Tag Monitor.
+// Features:
+//   - Device selector (auto-enumerates /dev/video*)
+//   - Start / Stop capture
+//   - Freeze-frame toggle
+//   - Screenshot (saves current frame as PNG/JPG)
+//   - Frame is scaled to fit the widget while keeping aspect ratio
+class VideoWidget : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit VideoWidget(QWidget *parent = nullptr);
+    ~VideoWidget();
+
+public:
+    // Called by MainWindow::closeEvent to guarantee orderly shutdown before
+    // widget destruction. Safe to call multiple times.
+    void shutdown();
+
+public slots:
+    void onNewFrame(const QImage &frame);
+
+private slots:
+    void onStartStop();
+    void onFreeze(bool frozen);
+    void onScreenshot();
+    void refreshDeviceList();
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+    void resizeEvent(QResizeEvent *event) override;
+
+private:
+    void setupUi();
+    void startCapture();
+    void stopCapture();
+    void updateScaled();
+
+    // Worker
+    QThread     *m_thread = nullptr;
+    V4l2Worker  *m_worker = nullptr;
+
+    // Current frame
+    QImage  m_frame;
+    QImage  m_scaled;
+    bool    m_frozen       = false;
+    bool    m_running      = false;
+    bool    m_shutdownDone = false;
+
+    // UI
+    QComboBox   *m_deviceCombo  = nullptr;
+    QPushButton *m_startBtn     = nullptr;
+    QPushButton *m_freezeBtn    = nullptr;
+    QPushButton *m_screenshotBtn= nullptr;
+    QLabel      *m_infoLabel    = nullptr;
+};