refactor: use extensible design for fetching playlist from single file

CMakeLists.txt

@@ -53,7 +53,9 @@ set (PPIC_CPP_FILES
     app/exiv2wrapper.cpp
     app/playlistmanager.cpp
     app/fileopeneventhandler.cpp
-    app/winplaylistpatch.cpp
+    app/playlistscout.cpp
+    app/playlistscouts/qtscout.cpp
+    app/playlistscouts/explorerscout.cpp
 )
 
 set (PPIC_HEADER_FILES
@@ -71,7 +73,9 @@ set (PPIC_HEADER_FILES
     app/exiv2wrapper.h
     app/playlistmanager.h
     app/fileopeneventhandler.h
-    app/winplaylistpatch.h
+    app/playlistscout.h
+    app/playlistscouts/qtscout.h
+    app/playlistscouts/explorerscout.h
 )
 
 set (PPIC_UI_FILES

app/playlistmanager.cpp

@@ -3,7 +3,7 @@
 // SPDX-License-Identifier: MIT
 
 #include "playlistmanager.h"
-#include "winplaylistpatch.h"
+#include "playlistscout.h"
 
 #include <QCollator>
 #include <QDir>
@@ -72,50 +72,14 @@ bool PlaylistManager::loadSingleFilePlaylist(const QUrl& url) {
     if (!checkUrl(url))
         return false;
 
-    QList<QUrl> playlist;
-    std::optional<qsizetype> idx = std::nullopt;
-
-#ifdef Q_OS_WIN
-    // In Windows, Qt approach can not aware Windows Explorer custom sort order.
-    // So we need to try using Win32 functions for fetching it at first
-    if (!WinPlaylistPatch::loadSingleFilePlaylist(url, m_allowedSuffixes, playlist, idx)) {
-#endif // Q_OS_WIN
-
-        // If Windows approach is failed or we are not in Windows,
-        // use Qt way to process it.
-
-        QFileInfo info(url.toLocalFile());
-        QDir dir(info.path());
-        QString currentFileName = info.fileName();
-
-        QStringList entryList = dir.entryList(
-            m_allowedSuffixes, QDir::Files | QDir::NoSymLinks, QDir::NoSort);
-
-        QCollator collator;
-        collator.setNumericMode(true);
-
-        std::sort(entryList.begin(), entryList.end(), collator);
-
-        playlist.clear();
-        idx = std::nullopt;
-        for (qsizetype i = 0; i < entryList.count(); i++) {
-            const QString &fileName = entryList.at(i);
-            const QString &oneEntry = dir.absoluteFilePath(fileName);
-            const QUrl &url = QUrl::fromLocalFile(oneEntry);
-            if (!checkUrl(url)) {
+    // Scout playlist by given file
+    auto scoutResult = PlaylistScout::scout(url, m_allowedSuffixes);
+    if (!scoutResult.has_value()) {
         return false;
     }
-            playlist.append(url);
-            if (fileName == currentFileName) {
-                idx = i;
-            }
-        }
 
-#ifdef Q_OS_WIN
-    }
-#endif // Q_OS_WIN
-
-    setPlaylist(std::move(playlist), idx);
+    // Setup playlist with index
+    setPlaylist(std::move(scoutResult->playlist), scoutResult->indexHint);
     return true;
 }
 

app/playlistscout.cpp

@@ -0,0 +1,25 @@
+// SPDX-FileCopyrightText: 2026 yyc12345 <yyc12321@outlook.com>
+//
+// SPDX-License-Identifier: MIT
+
+#include "playlistscout.h"
+
+#include "playlistscouts/qtscout.h"
+#include "playlistscouts/explorerscout.h"
+
+std::optional<PlaylistScout::ScoutResult> PlaylistScout::scout(
+    const QUrl &url, const QStringList &allowedSuffixes) {
+
+#ifdef Q_OS_WIN
+    // In Windows, Qt approach can not aware Windows Explorer custom sort order.
+    // So we need to try using Win32 functions for fetching it at first.
+    if (auto rv = PlaylistScout::Explorer::scout(url, allowedSuffixes); rv.has_value()) {
+        return rv;
+    }
+#endif // Q_OS_WIN
+
+    // TODO: We may add macOS Finder, KDE Dolphin and etc supports in future.
+
+    // Qt way is the last fallback.
+    return PlaylistScout::Qt::scout(url, allowedSuffixes);
+}

app/playlistscout.h

@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: 2026 yyc12345 <yyc12321@outlook.com>
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <QUrl>
+#include <QStringList>
+#include <QList>
+#include <optional>
+
+namespace PlaylistScout {
+    /// The result of scout
+    struct ScoutResult {
+        /// The final fetched playlist (it can be empty).
+        /// Each item must be a QUrl pointing to a local file.
+        QList<QUrl> playlist;
+        /// The index of given file located in playlist.
+        /// Nullopt if it is not presented in playlist.
+        std::optional<qsizetype> indexHint;
+    };
+
+    /// @brief Scout available image files in given file's parent dir with given allowed suffixes.
+    /// @param[in] url The path to file whose parent dir is our target dir for finding image files.
+    /// @param[in] allowedSuffixes 
+    /// Each items in this list is a wildcard pattern for matching allowed file name, like \c *.png .
+    /// The fetched item will be preserved if its name matching any of them.
+    /// If this list is empty, there is no restrictions for finding files.
+    /// @return Scout result if success, otherwise nullopt.
+    std::optional<ScoutResult> scout(const QUrl &url, const QStringList &allowedSuffixes);
+}

app/playlistscouts/explorerscout.cpp

@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: MIT
 
-#include "winplaylistpatch.h"
+#include "explorerscout.h"
 
 #ifdef Q_OS_WIN
 
@@ -242,9 +242,9 @@ static ComPtr<IFolderView2> FindLiveFolderView(const QString& targetFolderPath)
     return nullptr;
 }
 
-bool WinPlaylistPatch::loadSingleFilePlaylist(
-    const QUrl &url, const QStringList &allowedSuffixes, QList<QUrl> &playlist,
-    std::optional<qsizetype> &indexHint) {
+std::optional<PlaylistScout::ScoutResult> PlaylistScout::Explorer::scout(
+    const QUrl &url, const QStringList &allowedSuffixes) {
+    PlaylistScout::ScoutResult rv;
 
     QFileInfo info(url.toLocalFile());
     QString folderPath = info.path();
@@ -263,14 +263,14 @@ bool WinPlaylistPatch::loadSingleFilePlaylist(
     ComGuard comGuard;
     if (!comGuard.IsInitialized()) {
         ReportError("COM initialization failed");
-        return false;
+        return std::nullopt;
     }
 
     // Find a live Explorer window that is currently displaying the target folder.
     ComPtr<IFolderView2> folderView2 = FindLiveFolderView(folderPath);
     if (!folderView2) {
         ReportError("No open Explorer window matches the folder: " + folderPath);
-        return false;
+        return std::nullopt;
     }
 
     // Get items already sorted in Explorer's view order, as an IShellItemArray.
@@ -279,7 +279,7 @@ bool WinPlaylistPatch::loadSingleFilePlaylist(
     if (FAILED(folderView2->Items(SVGIO_ALLVIEW | SVGIO_FLAG_VIEWORDER,
             IID_PPV_ARGS(itemArray.GetAddressOf())))) {
         ReportError("IFolderView2::Items(SVGIO_ALLVIEW | SVGIO_FLAG_VIEWORDER) failed");
-        return false;
+        return std::nullopt;
     }
 
     DWORD itemCount = 0;
@@ -320,13 +320,13 @@ bool WinPlaylistPatch::loadSingleFilePlaylist(
             continue;
         }
 
-        playlist.append(QUrl::fromLocalFile(filePath));
+        rv.playlist.append(QUrl::fromLocalFile(filePath));
         if (fileName == currentFileName) {
-            indexHint = playlist.size() - 1;
+            rv.indexHint = rv.playlist.size() - 1;
         }
     }
 
-    return true;
+    return rv;
 }
 
 #endif // Q_OS_WIN

app/playlistscouts/explorerscout.h

@@ -0,0 +1,16 @@
+// SPDX-FileCopyrightText: 2026 yyc12345 <yyc12321@outlook.com>
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include "../playlistscout.h"
+#include <QtSystemDetection>
+
+#ifdef Q_OS_WIN
+
+namespace PlaylistScout::Explorer {
+    std::optional<ScoutResult> scout(const QUrl &url, const QStringList &allowedSuffixes);
+}
+
+#endif // Q_OS_WIN

app/playlistscouts/qtscout.cpp

@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: 2025 Gary Wang <git@blumia.net>
+// SPDX-FileCopyrightText: 2026 yyc12345 <yyc12321@outlook.com>
+//
+// SPDX-License-Identifier: MIT
+
+#include "qtscout.h"
+
+#include <QFileInfo>
+#include <QDir>
+#include <QCollator>
+
+std::optional<PlaylistScout::ScoutResult> PlaylistScout::Qt::scout(
+    const QUrl &url, const QStringList &allowedSuffixes) {
+    PlaylistScout::ScoutResult rv;
+
+    QFileInfo info(url.toLocalFile());
+    QDir dir(info.path());
+    QString currentFileName = info.fileName();
+
+    QStringList entryList = dir.entryList(
+        allowedSuffixes, QDir::Files | QDir::NoSymLinks, QDir::NoSort);
+
+    QCollator collator;
+    collator.setNumericMode(true);
+
+    std::sort(entryList.begin(), entryList.end(), collator);
+
+    for (qsizetype i = 0; i < entryList.count(); i++) {
+        const QString &fileName = entryList.at(i);
+        const QString &oneEntry = dir.absoluteFilePath(fileName);
+        const QUrl &url = QUrl::fromLocalFile(oneEntry);
+
+        rv.playlist.append(url);
+        if (fileName == currentFileName) {
+            rv.indexHint = i;
+        }
+    }
+
+    return rv;
+}

app/playlistscouts/qtscout.h

@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: 2026 yyc12345 <yyc12321@outlook.com>
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include "../playlistscout.h"
+
+namespace PlaylistScout::Qt {
+    std::optional<ScoutResult> scout(const QUrl &url, const QStringList &allowedSuffixes);
+}

app/winplaylistpatch.h

@@ -1,21 +0,0 @@
-// SPDX-FileCopyrightText: 2026 yyc12345 <yyc12321@outlook.com>
-//
-// SPDX-License-Identifier: MIT
-
-#pragma once
-
-#include <QtSystemDetection>
-
-#ifdef Q_OS_WIN
-
-#include <QUrl>
-class WinPlaylistPatch
-{
-public:
-    static bool loadSingleFilePlaylist(const QUrl &url,
-                                       const QStringList &allowedSuffixes,
-                                       QList<QUrl> &playlist,
-                                       std::optional<qsizetype> &indexHint);
-};
-
-#endif // Q_OS_WIN