feat: able to cancel loading at any time & add tons of multithreading bugs

CMakeLists.txt

@@ -53,11 +53,11 @@ target_link_libraries(wallpaper_chooser PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)
 
 target_include_directories(wallpaper_chooser PRIVATE src)
 
-if(NOT ${CMAKE_BUILD_TYPE} STREQUAL "Debug")
+# if(NOT ${CMAKE_BUILD_TYPE} STREQUAL "Debug")
-    target_compile_definitions(wallpaper_chooser PRIVATE
+#     target_compile_definitions(wallpaper_chooser PRIVATE
-        GENERAL_LOGGER_DISABLED
+#         GENERAL_LOGGER_DISABLED
-    )
+#     )
-endif()
+# endif()
 
 # Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
 # If you are developing for iOS or macOS you should consider setting an

src/images_carousel.cpp

@@ -1,17 +1,13 @@
 /*
  * @Author: Uyanide pywang0608@foxmail.com
  * @Date: 2025-08-05 01:22:53
- * @LastEditTime: 2025-08-08 00:43:47
+ * @LastEditTime: 2025-08-08 02:34:24
  * @Description: Animated carousel widget for displaying and selecting images.
  */
 #include "images_carousel.h"
 
+#include <assert.h>
 #include <pthread.h>
-#include <qboxlayout.h>
-#include <qdebug.h>
-#include <qnamespace.h>
-#include <qobject.h>
-#include <qpixmap.h>
 
 #include <QLabel>
 #include <QMetaObject>
@@ -76,7 +72,7 @@ void ImagesCarousel::_onInitImagesLoaded() {
     if (m_loadedImages.isEmpty()) {
         return;
     }
-    _focusCurrImage();
+    focusCurrImage();
 }
 
 ImagesCarousel::~ImagesCarousel() {
@@ -91,8 +87,8 @@ ImagesCarousel::~ImagesCarousel() {
 
 void ImagesCarousel::appendImages(const QStringList& paths) {
     {
-        QMutexLocker locker(&m_imageCountMutex);
+        QMutexLocker locker(&m_countMutex);
-        m_imageCount += paths.size();
+        m_addedImagesCount += paths.size();
     }
     emit loadingStarted(paths.size());
     for (const QString& path : paths) {
@@ -152,14 +148,31 @@ void ImagesCarousel::_insertImage(const ImageData* data) {
 
     emit imageLoaded(m_loadedImages.size());
     {
-        QMutexLocker countLocker(&m_imageCountMutex);
+        QMutexLocker countLocker(&m_countMutex);
-        if (m_loadedImages.size() >= m_imageCount) {
+        if (++m_loadedImagesCount >= m_addedImagesCount) {
-            emit loadingCompleted(m_loadedImages.size());
+            QMutexLocker stopSignLocker(&m_stopSignMutex);
+            if (m_stopSign) {
+                // if all stopped
+                emit stopped();
+            } else {
+                emit loadingCompleted(m_loadedImagesCount);
+            }
         }
     }
 }
 
 void ImageLoader::run() {
+    {
+        QMutexLocker countLocker(&m_carousel->m_countMutex);
+        QMutexLocker stopSignLocker(&m_carousel->m_stopSignMutex);
+        if (m_carousel->m_stopSign) {
+            // if all stopped
+            if (++m_carousel->m_loadedImagesCount == m_carousel->m_addedImagesCount) {
+                emit m_carousel->stopped();
+            }
+            return;
+        }
+    }
     auto data = new ImageData(m_path, m_initWidth, m_initHeight);
     QMetaObject::invokeMethod(m_carousel,
                               "_insertImage",
@@ -183,32 +196,38 @@ ImageData::ImageData(const QString& p, const int initWidth, const int initHeight
 }
 
 void ImagesCarousel::focusNextImage() {
-    _unfocusCurrImage();
+    unfocusCurrImage();
     if (m_loadedImages.size() <= 1) return;
     m_currentIndex++;
     if (m_currentIndex >= m_loadedImages.size()) {
         m_currentIndex = 0;
     }
-    _focusCurrImage();
+    focusCurrImage();
 }
 
 void ImagesCarousel::focusPrevImage() {
     if (m_loadedImages.size() <= 1) return;
-    _unfocusCurrImage();
+    unfocusCurrImage();
     m_currentIndex--;
     if (m_currentIndex < 0) {
         m_currentIndex = m_loadedImages.size() - 1;
     }
-    _focusCurrImage();
+    focusCurrImage();
 }
 
-void ImagesCarousel::_unfocusCurrImage() {
+void ImagesCarousel::unfocusCurrImage() {
-    // bound check was (or should) done by caller
+    if (m_currentIndex < 0 || m_currentIndex >= m_loadedImages.size()) {
+        error(QString("Invalid index to unfocus: %1").arg(m_currentIndex));
+        return;
+    }
     m_loadedImages[m_currentIndex]->setFocus(false);
 }
 
-void ImagesCarousel::_focusCurrImage() {
+void ImagesCarousel::focusCurrImage() {
-    // bound check was (or should) done by caller
+    if (m_currentIndex < 0 || m_currentIndex >= m_loadedImages.size()) {
+        error(QString("Invalid index to focus: %1").arg(m_currentIndex));
+        return;
+    }
     m_loadedImages[m_currentIndex]->setFocus(true);
     emit imageFocused(m_loadedImages[m_currentIndex]->getFileFullPath(),
                       m_currentIndex,
@@ -263,19 +282,19 @@ void ImagesCarousel::_onScrollBarValueChanged(int value) {
     if (index == m_currentIndex) {
         return;  // Already focused
     }
-    _unfocusCurrImage();
+    unfocusCurrImage();
     m_currentIndex = index;
-    _focusCurrImage();
+    focusCurrImage();
 }
 
 void ImagesCarousel::_onItemClicked(int index) {
     // if (m_suppressAutoFocus) return;
-    _unfocusCurrImage();
+    unfocusCurrImage();
     m_currentIndex = index;
     if (index < 0 || index >= m_loadedImages.size()) {
         return;  // Out of bounds
     }
-    _focusCurrImage();
+    focusCurrImage();
 }
 
 ImageItem::ImageItem(const ImageData* data,
@@ -288,6 +307,7 @@ ImageItem::ImageItem(const ImageData* data,
       m_data(data),
       m_itemSize(itemWidth, itemHeight),
       m_itemFocusSize(itemFocusWidth, itemFocusHeight) {
+    assert(data != nullptr);
     setScaledContents(true);
     if (data->image.isNull()) {
         setText(":(");
@@ -326,3 +346,8 @@ void ImageItem::setFocus(bool focus) {
             });
     m_scaleAnimation->start();
 }
+
+void ImagesCarousel::onStop() {
+    QMutexLocker locker(&m_stopSignMutex);
+    m_stopSign = true;
+}

src/images_carousel.h

@@ -1,7 +1,7 @@
 /*
  * @Author: Uyanide pywang0608@foxmail.com
  * @Date: 2025-08-05 01:22:53
- * @LastEditTime: 2025-08-07 22:16:37
+ * @LastEditTime: 2025-08-08 02:41:05
  * @Description: Animated carousel widget for displaying and selecting images.
  */
 #ifndef IMAGES_CAROUSEL_H
@@ -44,7 +44,8 @@ struct ImageData {
 };
 
 /**
- * @brief Image label that displays an image
+ * @brief Image label that displays an image,
+ *        which should always be created in the main thread.
  */
 class ImageItem : public QLabel {
     Q_OBJECT
@@ -89,10 +90,13 @@ class ImageItem : public QLabel {
     void clicked(int index);
 };
 
+/**
+ * @brief Worker class for loading images in a separate thread.
+ */
 class ImageLoader : public QRunnable {
   public:
     ImageLoader(const QString& path, ImagesCarousel* carousel);
-    void run() override;
+    void run() override;  // friend to ImagesCarousel
 
   private:
     QString m_path;
@@ -126,49 +130,75 @@ class ImagesCarousel : public QWidget {
         return m_loadedImages[m_currentIndex]->getFileFullPath();
     }
 
-    const int m_itemWidth             = 320;
+    // Should always be called in the main thread
-    const int m_itemHeight            = 180;
+    [[nodiscard]] qsizetype getLoadedImagesCount() {
-    const int m_itemFocusWidth        = 480;
+        return m_loadedImages.size();
-    const int m_itemFocusHeight       = 270;
+    }
-    const Config::SortType m_sortType = Config::SortType::None;
+
-    const bool m_sortReverse          = false;
+    [[nodiscard]] qsizetype getAddedImagesCount() {
+        QMutexLocker locker(&m_countMutex);
+        return m_addedImagesCount;
+    }
+
+    // config items
+    const int m_itemWidth;
+    const int m_itemHeight;
+    const int m_itemFocusWidth;
+    const int m_itemFocusHeight;
+    const Config::SortType m_sortType;
+    const bool m_sortReverse;
 
   public slots:
     void focusNextImage();
     void focusPrevImage();
+    void focusCurrImage();
+    void unfocusCurrImage();
+    void onStop();
 
   private slots:
-    void _unfocusCurrImage();
     void _onScrollBarValueChanged(int value);
     void _onItemClicked(int index);
     void _onInitImagesLoaded();
 
   public:
-    void
+    void appendImages(const QStringList& paths);
-    appendImages(const QStringList& paths);
 
   private:
-    void _focusCurrImage();
     Q_INVOKABLE void _insertImage(const ImageData* item);
 
   private:
+    // UI elements
     Ui::ImagesCarousel* ui;
-    QList<ImageItem*> m_loadedImages;
-    int m_currentIndex                    = 0;
-    QPropertyAnimation* m_scrollAnimation = nullptr;
     QHBoxLayout* m_imagesLayout            = nullptr;
-    QMutex m_imageCountMutex;
+    ImagesCarouselScrollArea* m_scrollArea = nullptr;
-    int m_imageCount                       = 0;
+
+    // Items and counters
+    QList<ImageItem*> m_loadedImages;  // m_loadedImages.size() may != m_loadedImagesCount
+    int m_loadedImagesCount = 0;       // increase when _insertImage is called OR ImageLoader::run() is called with m_stopSign as true
+    int m_addedImagesCount  = 0;       // increase when appendImages called
+    QMutex m_countMutex;               // for m_loadedImagesCount and m_addedImagesCount
+    int m_currentIndex = 0;
+
+    // Animations
+    QPropertyAnimation* m_scrollAnimation = nullptr;
+
+    // Auto focusing
     bool m_suppressAutoFocus      = false;
     int m_pendingScrollValue      = 0;
     QTimer* m_scrollDebounceTimer = nullptr;
-    ImagesCarouselScrollArea* m_scrollArea = nullptr;
+
+    // Loading stopped by user
+    QMutex m_stopSignMutex;
+    bool m_stopSign = false;
 
   signals:
     void imageFocused(const QString& path, const int index, const int count);
+
     void loadingStarted(const qsizetype amount);
     void loadingCompleted(const qsizetype amount);
     void imageLoaded(const qsizetype count);
+
+    void stopped();
 };
 
 class ImagesCarouselScrollArea : public QScrollArea {

src/main_window.cpp

@@ -1,7 +1,7 @@
 /*
  * @Author: Uyanide pywang0608@foxmail.com
  * @Date: 2025-08-05 00:37:58
- * @LastEditTime: 2025-08-07 22:15:47
+ * @LastEditTime: 2025-08-08 02:25:20
  * @Description: MainWindow implementation.
  */
 #include "main_window.h"
@@ -33,7 +33,6 @@ MainWindow::~MainWindow() {
 }
 
 void MainWindow::_setupUI() {
-
     // create images carousel
     m_carousel = new ImagesCarousel(
         m_config.getStyleConfig(),
@@ -44,6 +43,14 @@ void MainWindow::_setupUI() {
             &ImagesCarousel::imageFocused,
             this,
             &MainWindow::_onImageFocused);
+    connect(this, &MainWindow::stop, m_carousel, &ImagesCarousel::onStop);
+    connect(m_carousel, &ImagesCarousel::stopped, this,
+            // &MainWindow::close); // instead of closing, we just stop the loading
+            [this]() {
+                _onLoadingCompleted(m_carousel->getLoadedImagesCount());
+                m_carousel->focusCurrImage(); },
+            // ensure this is called in the main thread
+            Qt::QueuedConnection);
     m_carouselIndex = ui->stackedWidget->addWidget(m_carousel);
 
     // create loading indicator
@@ -85,6 +92,10 @@ void MainWindow::keyPressEvent(QKeyEvent *event) {
         onCancel();
     } else if (event->key() == Qt::Key_Return || event->key() == Qt::Key_Enter) {
         onConfirm();
+    }
+    // if loadingScreen is enabled and loading is in progress, ignore other keys
+    else if (!m_config.getStyleConfig().noLoadingScreen && m_isLoading) {
+        event->ignore();
     } else if (event->key() == Qt::Key_Space || event->key() == Qt::Key_Tab || event->key() == Qt::Key_Right) {
         m_carousel->focusNextImage();
     } else if (event->key() == Qt::Key_Left) {
@@ -105,6 +116,10 @@ void MainWindow::wheelEvent(QWheelEvent *event) {
 }
 
 void MainWindow::onConfirm() {
+    if (m_isLoading) {
+        warn("Loading is still in progress, please wait until it finishes.");
+        return;
+    }
     close();
     const auto path = m_carousel->getCurrentImagePath();
     if (path.isEmpty()) {
@@ -129,7 +144,12 @@ void MainWindow::onConfirm() {
 }
 
 void MainWindow::onCancel() {
+    if (m_isLoading) {
+        warn("Loading stopped by user, waiting all threads to finish...");
+        emit stop();
+    } else {
         close();
+    }
 }
 
 void MainWindow::_onImageFocused(const QString &path, const int index, const int count) {
@@ -137,6 +157,7 @@ void MainWindow::_onImageFocused(const QString &path, const int index, const int
 }
 
 void MainWindow::_onLoadingStarted(const qsizetype amount) {
+    m_isLoading = true;
     if (m_config.getStyleConfig().noLoadingScreen) {
         return;
     }
@@ -145,5 +166,7 @@ void MainWindow::_onLoadingStarted(const qsizetype amount) {
 }
 
 void MainWindow::_onLoadingCompleted(const qsizetype amount) {
+    info(QString("Loading completed, loaded %1 images").arg(amount));
     ui->stackedWidget->setCurrentIndex(m_carouselIndex);
+    m_isLoading = false;
 }

src/main_window.h

@@ -1,7 +1,7 @@
 /*
  * @Author: Uyanide pywang0608@foxmail.com
  * @Date: 2025-08-05 00:37:58
- * @LastEditTime: 2025-08-07 01:08:12
+ * @LastEditTime: 2025-08-08 02:11:57
  * @Description: MainWindow implementation.
  */
 #ifndef MAINWINDOW_H
@@ -50,5 +50,9 @@ class MainWindow : public QMainWindow {
     LoadingIndicator *m_loadingIndicator = nullptr;
     int m_carouselIndex, m_loadingIndicatorIndex;
     const Config &m_config;
+    bool m_isLoading = false;
+
+  signals:
+    void stop();
 };
 #endif  // MAINWINDOW_H