feat(translate): keep translated subtitles next to the video so they load on reopen (#14)

Co-authored-by: Tri Vo Khac <git@trivk.dev>

src/mpv/mpvitem.cpp

@@ -7,6 +7,7 @@
 
 #include <QDir>
 #include <QFile>
+#include <QFileInfo>
 #include <QLocale>
 #include <QSaveFile>
 #include <QStandardPaths>
@@ -44,6 +45,38 @@ QList<TrackSelection::Track> selectionTracks(const QVariantList &tracks)
     return result;
 }
 
+QString subtitlePath(const QVariantList &tracks, int id)
+{
+    for (const QVariant &entry : tracks) {
+        const QVariantMap track = entry.toMap();
+        if (track.value(QStringLiteral("id")).toInt() == id) {
+            return track.value(QStringLiteral("externalFilename")).toString();
+        }
+    }
+    return {};
+}
+
+int subtitleIdForPath(const QVariantList &tracks, const QString &path)
+{
+    if (path.isEmpty()) {
+        return 0;
+    }
+    for (const QVariant &entry : tracks) {
+        const QVariantMap track = entry.toMap();
+        if (track.value(QStringLiteral("externalFilename")).toString() == path) {
+            return track.value(QStringLiteral("id")).toInt();
+        }
+    }
+    return 0;
+}
+
+// "movie.abc123.vi.srt" -> "vi", the way mpv tags subtitles it finds next to a video.
+QString filenameLanguage(const QString &path)
+{
+    const QStringList parts = QFileInfo(path).completeBaseName().split(QLatin1Char('.'));
+    return parts.size() > 1 ? parts.constLast() : QString();
+}
+
 QString trackLanguage(const QVariantList &tracks, int id)
 {
     for (const QVariant &entry : tracks) {
@@ -112,7 +145,7 @@ MpvItem::MpvItem(QQuickItem *parent)
         // Before the first file, so its options apply from the start.
         applyUserConfig();
         if (m_pendingUrl.isValid()) {
-            loadFile(std::exchange(m_pendingUrl, {}));
+            loadFile(std::exchange(m_pendingUrl, {}), QString(m_openingTranslatedPath), QString(m_openingTranslatedTitle));
         }
     });
 }
@@ -156,12 +189,18 @@ bool MpvItem::isFileLoaded() const
     return m_fileLoaded;
 }
 
-void MpvItem::loadFile(const QUrl &url)
+void MpvItem::loadFile(const QUrl &url, const QString &translatedSubtitle, const QString &translatedTitle)
 {
     if (!url.isValid()) {
         return;
     }
 
+    m_translatedPaths.clear();
+    m_openingTranslatedPath = translatedSubtitle;
+    m_openingTranslatedTitle = translatedTitle;
+    if (!translatedSubtitle.isEmpty()) {
+        m_translatedPaths.append(translatedSubtitle);
+    }
     m_currentUrl = url;
     Q_EMIT currentUrlChanged();
 
@@ -355,6 +394,9 @@ void MpvItem::showTranslatedSubtitleFile(const QUrl &url, const QString &title)
         return;
     }
     const QString path = localPathOrUrl(url);
+    if (!m_translatedPaths.contains(path)) {
+        m_translatedPaths.append(path);
+    }
     for (const QVariant &entry : std::as_const(m_subtitleTracks)) {
         const QVariantMap track = entry.toMap();
         if (track.value(QStringLiteral("externalFilename")).toString() == path) {
@@ -370,11 +412,22 @@ void MpvItem::showTranslatedSubtitleFile(const QUrl &url, const QString &title)
 
 int MpvItem::translationSourceId() const
 {
+    QVariantList sources;
+    for (const QVariant &entry : std::as_const(m_subtitleTracks)) {
+        if (!isTranslatedSubtitle(entry.toMap().value(QStringLiteral("id")).toInt())) {
+            sources.append(entry);
+        }
+    }
     // English first: it is the usual original, and dubbed releases often default to
     // subtitles translated from it.
-    return TrackSelection::pickTranslationSource(selectionTracks(m_subtitleTracks),
+    return TrackSelection::pickTranslationSource(selectionTracks(sources),
                                                  {QStringLiteral("en"), trackLanguage(m_audioTracks, m_audioId)},
-                                                 m_subtitleId);
+                                                 isTranslatedSubtitle(m_subtitleId) ? 0 : m_subtitleId);
+}
+
+bool MpvItem::isTranslatedSubtitle(int id) const
+{
+    return id > 0 && m_translatedPaths.contains(subtitlePath(m_subtitleTracks, id));
 }
 
 void MpvItem::selectInitialTracks()
@@ -382,6 +435,16 @@ void MpvItem::selectInitialTracks()
     // The observed track-list may still describe the previous file; read it directly.
     updateTracks(getProperty(QStringLiteral("track-list")).toList());
 
+    // mpv finds a translation next to the video by itself (sub-auto); one kept in the
+    // cache is added here, before choosing, so it can be chosen.
+    const QString translated = std::exchange(m_openingTranslatedPath, {});
+    int translationId = subtitleIdForPath(m_subtitleTracks, translated);
+    if (!translated.isEmpty() && translationId == 0 && QFileInfo::exists(translated)) {
+        commandBlocking(QStringList{QStringLiteral("sub-add"), translated, QStringLiteral("auto"), m_openingTranslatedTitle, filenameLanguage(translated)});
+        updateTracks(getProperty(QStringLiteral("track-list")).toList());
+        translationId = subtitleIdForPath(m_subtitleTracks, translated);
+    }
+
     const int audioId = TrackSelection::pickAudio(selectionTracks(m_audioTracks), m_preferredAudioLanguages, m_audioId);
     if (audioId != m_audioId) {
         setAudioId(audioId);
@@ -393,7 +456,8 @@ void MpvItem::selectInitialTracks()
                                                         m_preferredSubtitleLanguages,
                                                         fallbackLanguages,
                                                         m_subtitleId,
-                                                        m_autoSelectSubtitle);
+                                                        m_autoSelectSubtitle,
+                                                        translationId);
     if (subtitleId != m_subtitleId) {
         setSubtitleId(subtitleId);
     }