Add preset load callback to playlist library

src/playlist/PlaylistCWrapper.cpp

@@ -103,6 +103,13 @@ void PlaylistCWrapper::SetPresetSwitchFailedCallback(projectm_playlist_preset_sw
 }
 
 
+void PlaylistCWrapper::SetPresetLoadCallback(projectm_playlist_preset_load_event callback, void* userData)
+{
+    m_presetLoadEventCallback = callback;
+    m_presetLoadEventUserData = userData;
+}
+
+
 void PlaylistCWrapper::PlayPresetIndex(uint32_t index, bool hardCut, bool resetFailureCount)
 {
     m_hardCutRequested = hardCut;
@@ -117,8 +124,22 @@ void PlaylistCWrapper::PlayPresetIndex(uint32_t index, bool hardCut, bool resetF
             return;
         }
 
-        projectm_load_preset_file(m_projectMInstance,
-                                  playlistItems.at(index).Filename().c_str(), !hardCut);
+        const auto& filename = playlistItems.at(index).Filename();
+
+        // If a preset load callback is set, give the application a chance to handle loading
+        if (m_presetLoadEventCallback != nullptr)
+        {
+            if (m_presetLoadEventCallback(index, filename.c_str(), hardCut, m_presetLoadEventUserData))
+            {
+                // Application handled the load - return without further action.
+                // The app is responsible for calling projectm_load_preset_file/data,
+                // handling errors, and firing the switched event when ready.
+                return;
+            }
+        }
+
+        // Default behavior: load from filesystem
+        projectm_load_preset_file(m_projectMInstance, filename.c_str(), !hardCut);
 
         if (!m_lastPresetSwitchFailed)
         {
@@ -249,6 +270,15 @@ void projectm_playlist_set_preset_switch_failed_event_callback(projectm_playlist
 }
 
 
+void projectm_playlist_set_preset_load_event_callback(projectm_playlist_handle instance,
+                                                      projectm_playlist_preset_load_event callback,
+                                                      void* user_data)
+{
+    auto* playlist = playlist_handle_to_instance(instance);
+    playlist->SetPresetLoadCallback(callback, user_data);
+}
+
+
 void projectm_playlist_connect(projectm_playlist_handle instance, projectm_handle projectm_instance)
 {
     auto* playlist = playlist_handle_to_instance(instance);

src/playlist/PlaylistCWrapper.hpp

@@ -82,6 +82,14 @@ class PlaylistCWrapper : public Playlist
     virtual void SetPresetSwitchFailedCallback(projectm_playlist_preset_switch_failed_event callback,
                                                void* userData);
 
+    /**
+     * @brief Sets the preset load callback.
+     * @param callback The callback pointer.
+     * @param userData The callback context data.
+     */
+    virtual void SetPresetLoadCallback(projectm_playlist_preset_load_event callback,
+                                       void* userData);
+
     /**
      * @brief Sets the last navigation direction used to switch a preset.
      * This is used when retrying on a failed preset load, keeping the same direction/logic as in the original switch.
@@ -111,6 +119,9 @@ class PlaylistCWrapper : public Playlist
     projectm_playlist_preset_switch_failed_event m_presetSwitchFailedEventCallback{nullptr}; //!< Preset switch failed callback pointer set by the application.
     void* m_presetSwitchFailedEventUserData{nullptr};                                        //!< Context data pointer set by the application.
 
+    projectm_playlist_preset_load_event m_presetLoadEventCallback{nullptr}; //!< Preset load callback pointer set by the application.
+    void* m_presetLoadEventUserData{nullptr};                               //!< Context data pointer set by the application.
+
     NavigationDirection m_lastNavigationDirection{NavigationDirection::Next}; //!< Last direction used to switch a preset.
 };
 

src/playlist/api/projectM-4/playlist_callbacks.h

@@ -69,6 +69,42 @@ typedef void (*projectm_playlist_preset_switched_event)(bool is_hard_cut, unsign
 typedef void (*projectm_playlist_preset_switch_failed_event)(const char* preset_filename,
                                                              const char* message, void* user_data);
 
+/**
+ * @brief Callback function that is executed when the playlist wants to load a preset.
+ *
+ * This callback allows applications to handle preset loading themselves instead of
+ * letting the playlist library load presets from the filesystem. This is useful for:
+ * - Loading presets from archives (e.g., ZIP files)
+ * - Loading presets from network sources (e.g., HTTP)
+ * - Custom preset storage solutions
+ *
+ * When this callback is set and returns true, the playlist library will NOT attempt
+ * to load the preset file itself and will return immediately without firing any events.
+ * The application takes full responsibility for:
+ * - Calling projectm_load_preset_file() or projectm_load_preset_data() with the preset content
+ * - Handling any loading errors
+ * - Firing the preset_switched_event callback when the preset is ready (if desired)
+ *
+ * Note: If implementing asynchronous loading, the application must complete the load and
+ * fire the preset_switched_event callback itself after the async operation completes.
+ *
+ * If the callback returns false or is not set, the playlist library will use the
+ * default behavior of loading the preset from the filesystem.
+ *
+ * @note The filename pointer is only valid inside the callback. Make a copy if it needs
+ *       to be retained for later use.
+ * @note Do not call any playlist preset-switching functions from within this callback.
+ * @param index The playlist index of the preset to be loaded.
+ * @param filename The preset filename/URL at this index. Can be used as a key or path.
+ * @param hard_cut True if this should be a hard cut, false for a smooth transition.
+ * @param user_data A user-defined data pointer that was provided when registering the callback,
+ *                  e.g. context information.
+ * @return True if the application handles preset loading, false to use default behavior.
+ * @since 4.2.0
+ */
+typedef bool (*projectm_playlist_preset_load_event)(unsigned int index, const char* filename,
+                                                    bool hard_cut, void* user_data);
+
 
 /**
  * @brief Sets a callback function that will be called when a preset changes.
@@ -105,6 +141,25 @@ PROJECTM_PLAYLIST_EXPORT void projectm_playlist_set_preset_switch_failed_event_c
                                                                                         projectm_playlist_preset_switch_failed_event callback,
                                                                                         void* user_data);
 
+/**
+ * @brief Sets a callback function that will be called when the playlist wants to load a preset.
+ *
+ * This allows applications to handle preset loading themselves, e.g., from archives,
+ * network sources, or using custom storage. When set, this callback is called before
+ * the playlist library attempts to load a preset file.
+ *
+ * Only one callback can be registered per playlist instance. To remove the callback, use NULL.
+ *
+ * @param instance The playlist manager instance.
+ * @param callback A pointer to the callback function.
+ * @param user_data A pointer to any data that will be sent back in the callback, e.g. context
+ *                  information.
+ * @since 4.2.0
+ */
+PROJECTM_PLAYLIST_EXPORT void projectm_playlist_set_preset_load_event_callback(projectm_playlist_handle instance,
+                                                                               projectm_playlist_preset_load_event callback,
+                                                                               void* user_data);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif