feat(library): Add customizable date format option for Library and History

This commit introduces a new user preference to customize how dates are displayed across the Mixxx library and history views. This addresses a common user request for ISO 8601 compliance and regional date format preferences.

Key changes:
- **Core Utility**: Enhanced `datetime.h` with a new `DateFormat` enum and updated helper functions (`formatDate`, `formatDateTime`) to support multiple formats:
  - Native (System Locale)
  - YYYY-MM-DD (ISO 8601)
  - DD/MM/YYYY
  - MM/DD/YYYY
  - YYYY/MM/DD
- **Preferences UI**: Added a new "Date Format" dropdown in the Library Preferences page (`DlgPrefLibrary`), allowing users to easily switch between formats.
- **Backend Storage**: Added `kDateFormatConfigKey` to persist the user's choice in `mixxx.cfg`.
- **Model Integration**: Updated `BaseTrackTableModel` to respect the global date format setting. This ensures that columns like "Date Added" and "Last Played" dynamically update to reflect the user's preference without requiring a restart.
- **History Integration**: The History view's Timestamp column also adheres to the selected format, ensuring consistency across the application.

Validation:
- Tested locally.

Fixes #15327

Author: xARSENICx

src/library/basetracktablemodel.cpp

@@ -114,6 +114,13 @@ void BaseTrackTableModel::setApplyPlayedTrackColor(bool apply) {
     s_bApplyPlayedTrackColor = apply;
 }
 
+mixxx::DateFormat BaseTrackTableModel::s_dateFormat =
+        BaseTrackTableModel::kDateFormatDefault;
+
+void BaseTrackTableModel::setDateFormat(mixxx::DateFormat format) {
+    s_dateFormat = format;
+}
+
 BaseTrackTableModel::BaseTrackTableModel(
         QObject* parent,
         TrackCollectionManager* pTrackCollectionManager,
@@ -688,10 +695,10 @@ QVariant BaseTrackTableModel::roleValue(
             if (field == ColumnCache::COLUMN_PLAYLISTTRACKSTABLE_DATETIMEADDED) {
                 // Timestamp column in history feature:
                 // Use localized date/time format without text: "5/20/98 03:40 AM"
-                return mixxx::displayLocalDateTime(dt);
+                return mixxx::displayLocalDateTime(dt, s_dateFormat);
             }
             // For Date Added, use just the date: "5/20/98"
-            return dt.date();
+            return mixxx::formatDate(dt.date(), s_dateFormat);
         }
         case ColumnCache::COLUMN_LIBRARYTABLE_LAST_PLAYED_AT: {
             QDateTime lastPlayedAt;
@@ -717,7 +724,7 @@ QVariant BaseTrackTableModel::roleValue(
             if (role == Qt::ToolTipRole || role == kDataExportRole) {
                 return dt;
             }
-            return dt.date();
+            return mixxx::formatDate(dt.date(), s_dateFormat);
         }
         case ColumnCache::COLUMN_LIBRARYTABLE_BPM: {
             mixxx::Bpm bpm;

src/library/basetracktablemodel.h

@@ -9,6 +9,7 @@
 #include "library/trackmodel.h"
 #include "track/track_decl.h"
 #include "util/color/colorpalette.h"
+#include "util/datetime.h"
 
 class TrackCollectionManager;
 
@@ -132,6 +133,9 @@ class BaseTrackTableModel : public QAbstractTableModel, public TrackModel {
     static constexpr bool kApplyPlayedTrackColorDefault = true;
     static void setApplyPlayedTrackColor(bool apply);
 
+    static constexpr mixxx::DateFormat kDateFormatDefault = mixxx::DateFormat::Native;
+    static void setDateFormat(mixxx::DateFormat format);
+
   protected:
     // Build a map from the column names to their indices
     // used by fieldIndex().
@@ -307,4 +311,5 @@ class BaseTrackTableModel : public QAbstractTableModel, public TrackModel {
     static std::optional<ColorPalette> s_keyColorPalette;
 
     static bool s_bApplyPlayedTrackColor;
+    static mixxx::DateFormat s_dateFormat;
 };

src/library/library_prefs.cpp

@@ -114,3 +114,8 @@ const ConfigKey mixxx::library::prefs::kTagFetcherApplyCoverConfigKey =
         ConfigKey{
                 mixxx::library::prefs::kConfigGroup,
                 QStringLiteral("TagFetcherApplyCover")};
+
+const ConfigKey mixxx::library::prefs::kDateFormatConfigKey =
+        ConfigKey{
+                mixxx::library::prefs::kConfigGroup,
+                QStringLiteral("DateFormat")};

src/library/library_prefs.h

@@ -58,6 +58,8 @@ extern const ConfigKey kTagFetcherApplyTagsConfigKey;
 
 extern const ConfigKey kTagFetcherApplyCoverConfigKey;
 
+extern const ConfigKey kDateFormatConfigKey;
+
 } // namespace prefs
 
 } // namespace library

src/preferences/dialog/dlgpreflibrary.cpp

@@ -111,6 +111,21 @@ DlgPrefLibrary::DlgPrefLibrary(
 
     updateSearchLineEditHistoryOptions();
 
+    comboBox_dateFormat->addItem(tr("Native (System Default)"),
+            static_cast<int>(mixxx::DateFormat::Native));
+    comboBox_dateFormat->addItem(tr("YYYY-MM-DD"),
+            static_cast<int>(mixxx::DateFormat::ISO8601));
+    comboBox_dateFormat->addItem(tr("DD/MM/YYYY"),
+            static_cast<int>(mixxx::DateFormat::DayMonthYear));
+    comboBox_dateFormat->addItem(tr("MM/DD/YYYY"),
+            static_cast<int>(mixxx::DateFormat::MonthDayYear));
+    comboBox_dateFormat->addItem(tr("YYYY/MM/DD"),
+            static_cast<int>(mixxx::DateFormat::YearMonthDay));
+    connect(comboBox_dateFormat,
+            QOverload<int>::of(&QComboBox::currentIndexChanged),
+            this,
+            &DlgPrefLibrary::slotDateFormatChanged);
+
     connect(btn_library_font, &QAbstractButton::clicked, this, &DlgPrefLibrary::slotSelectFont);
 
     // TODO(XXX) this string should be extracted from the soundsources
@@ -184,11 +199,12 @@ void DlgPrefLibrary::slotHide() {
     QMessageBox msgBox;
     msgBox.setIcon(QMessageBox::Warning);
     msgBox.setWindowTitle(tr("Music Directory Added"));
-    msgBox.setText(tr("You added one or more music directories. The tracks in "
-                      "these directories won't be available until you rescan "
-                      "your library. Would you like to rescan now?"));
+    msgBox.setText(tr(
+            "You added one or more music directories. The tracks in "
+            "these directories won't be available until you rescan "
+            "your library. Would you like to rescan now?"));
     QPushButton* scanButton = msgBox.addButton(
-        tr("Scan"), QMessageBox::AcceptRole);
+            tr("Scan"), QMessageBox::AcceptRole);
     msgBox.addButton(QMessageBox::Cancel);
     msgBox.setDefaultButton(scanButton);
     msgBox.exec();
@@ -231,7 +247,7 @@ void DlgPrefLibrary::populateDirList() {
     dirList->setModel(&m_dirListModel);
     dirList->setCurrentIndex(m_dirListModel.index(0, 0));
     // reselect index if it still exists
-    for (int i=0 ; i<m_dirListModel.rowCount() ; ++i) {
+    for (int i = 0; i < m_dirListModel.rowCount(); ++i) {
         const QModelIndex index = m_dirListModel.index(i, 0);
         if (index.data().toString() == selected) {
             dirList->setCurrentIndex(index);
@@ -267,6 +283,12 @@ void DlgPrefLibrary::slotResetToDefaults() {
     comboBox_search_bpm_fuzzy_range->setCurrentIndex(
             comboBox_search_bpm_fuzzy_range->findData(kDefaultFuzzyRateRangePercent));
 
+    int defaultDateFormat = static_cast<int>(BaseTrackTableModel::kDateFormatDefault);
+    int dateIndex = comboBox_dateFormat->findData(defaultDateFormat);
+    if (dateIndex != -1) {
+        comboBox_dateFormat->setCurrentIndex(dateIndex);
+    }
+
     checkBox_show_rhythmbox->setChecked(true);
     checkBox_show_banshee->setChecked(true);
     checkBox_show_itunes->setChecked(true);
@@ -297,18 +319,28 @@ void DlgPrefLibrary::slotUpdate() {
             kUseRelativePathOnExportConfigKey, false));
 
     checkBox_show_rhythmbox->setChecked(m_pConfig->getValue(
-            ConfigKey("[Library]","ShowRhythmboxLibrary"), true));
+            ConfigKey("[Library]", "ShowRhythmboxLibrary"), true));
     checkBox_show_banshee->setChecked(m_pConfig->getValue(
-            ConfigKey("[Library]","ShowBansheeLibrary"), true));
+            ConfigKey("[Library]", "ShowBansheeLibrary"), true));
     checkBox_show_itunes->setChecked(m_pConfig->getValue(
-            ConfigKey("[Library]","ShowITunesLibrary"), true));
+            ConfigKey("[Library]", "ShowITunesLibrary"), true));
     checkBox_show_traktor->setChecked(m_pConfig->getValue(
-            ConfigKey("[Library]","ShowTraktorLibrary"), true));
+            ConfigKey("[Library]", "ShowTraktorLibrary"), true));
     checkBox_show_rekordbox->setChecked(m_pConfig->getValue(
-            ConfigKey("[Library]","ShowRekordboxLibrary"), true));
+            ConfigKey("[Library]", "ShowRekordboxLibrary"), true));
     checkBox_show_serato->setChecked(m_pConfig->getValue(
             ConfigKey("[Library]", "ShowSeratoLibrary"), true));
 
+    int dateFormat = m_pConfig->getValue(
+            kDateFormatConfigKey,
+            static_cast<int>(BaseTrackTableModel::kDateFormatDefault));
+    int dateIndex = comboBox_dateFormat->findData(dateFormat);
+    if (dateIndex != -1) {
+        comboBox_dateFormat->setCurrentIndex(dateIndex);
+    }
+    // Ensure the static member is updated on startup/load
+    BaseTrackTableModel::setDateFormat(static_cast<mixxx::DateFormat>(dateFormat));
+
     switch (m_pConfig->getValue<int>(
             kTrackDoubleClickActionConfigKey,
             static_cast<int>(TrackDoubleClickAction::LoadToDeck))) {
@@ -403,9 +435,9 @@ void DlgPrefLibrary::resetLibraryFont() {
 }
 
 void DlgPrefLibrary::slotAddDir() {
-    QString fd = QFileDialog::getExistingDirectory(
-        this, tr("Choose a music directory"),
-        QStandardPaths::writableLocation(QStandardPaths::MusicLocation));
+    QString fd = QFileDialog::getExistingDirectory(this,
+            tr("Choose a music directory"),
+            QStandardPaths::writableLocation(QStandardPaths::MusicLocation));
     if (!fd.isEmpty()) {
         if (m_pLibrary->requestAddDir(fd)) {
             populateDirList();
@@ -423,29 +455,29 @@ void DlgPrefLibrary::slotRemoveDir() {
     removeMsgBox.setWindowTitle(tr("Confirm Directory Removal"));
 
     removeMsgBox.setText(tr(
-        "Mixxx will no longer watch this directory for new tracks. "
-        "What would you like to do with the tracks from this directory and "
-        "subdirectories?"
-        "<ul>"
-        "<li>Hide all tracks from this directory and subdirectories.</li>"
-        "<li>Delete all metadata for these tracks from Mixxx permanently.</li>"
-        "<li>Leave the tracks unchanged in your library.</li>"
-        "</ul>"
-        "Hiding tracks saves their metadata in case you re-add them in the "
-        "future."));
+            "Mixxx will no longer watch this directory for new tracks. "
+            "What would you like to do with the tracks from this directory and "
+            "subdirectories?"
+            "<ul>"
+            "<li>Hide all tracks from this directory and subdirectories.</li>"
+            "<li>Delete all metadata for these tracks from Mixxx permanently.</li>"
+            "<li>Leave the tracks unchanged in your library.</li>"
+            "</ul>"
+            "Hiding tracks saves their metadata in case you re-add them in the "
+            "future."));
     removeMsgBox.setInformativeText(tr(
-        "Metadata means all track details (artist, title, playcount, etc.) as "
-        "well as beatgrids, hotcues, and loops. This choice only affects the "
-        "Mixxx library. No files on disk will be changed or deleted."));
+            "Metadata means all track details (artist, title, playcount, etc.) as "
+            "well as beatgrids, hotcues, and loops. This choice only affects the "
+            "Mixxx library. No files on disk will be changed or deleted."));
 
     QPushButton* cancelButton =
             removeMsgBox.addButton(QMessageBox::Cancel);
     QPushButton* hideAllButton = removeMsgBox.addButton(
-        tr("Hide Tracks"), QMessageBox::AcceptRole);
+            tr("Hide Tracks"), QMessageBox::AcceptRole);
     QPushButton* deleteAllButton = removeMsgBox.addButton(
-        tr("Delete Track Metadata"), QMessageBox::AcceptRole);
+            tr("Delete Track Metadata"), QMessageBox::AcceptRole);
     QPushButton* leaveUnchangedButton = removeMsgBox.addButton(
-        tr("Leave Tracks Unchanged"), QMessageBox::AcceptRole);
+            tr("Leave Tracks Unchanged"), QMessageBox::AcceptRole);
     Q_UNUSED(leaveUnchangedButton); // Only used in DEBUG_ASSERT
     removeMsgBox.setDefaultButton(cancelButton);
     removeMsgBox.exec();
@@ -487,7 +519,7 @@ void DlgPrefLibrary::slotRelocateDir() {
     }
 
     QString fd = QFileDialog::getExistingDirectory(
-        this, tr("Relink music directory to new location"), startDir);
+            this, tr("Relink music directory to new location"), startDir);
 
     if (!fd.isEmpty() && m_pLibrary->requestRelocateDir(currentFd, fd)) {
         populateDirList();
@@ -541,16 +573,16 @@ void DlgPrefLibrary::slotApply() {
             ConfigValue(checkBox_enable_search_history_shortcuts->isChecked()));
     updateSearchLineEditHistoryOptions();
 
-    m_pConfig->set(ConfigKey("[Library]","ShowRhythmboxLibrary"),
-                ConfigValue((int)checkBox_show_rhythmbox->isChecked()));
-    m_pConfig->set(ConfigKey("[Library]","ShowBansheeLibrary"),
-                ConfigValue((int)checkBox_show_banshee->isChecked()));
-    m_pConfig->set(ConfigKey("[Library]","ShowITunesLibrary"),
-                ConfigValue((int)checkBox_show_itunes->isChecked()));
-    m_pConfig->set(ConfigKey("[Library]","ShowTraktorLibrary"),
-                ConfigValue((int)checkBox_show_traktor->isChecked()));
-    m_pConfig->set(ConfigKey("[Library]","ShowRekordboxLibrary"),
-                ConfigValue((int)checkBox_show_rekordbox->isChecked()));
+    m_pConfig->set(ConfigKey("[Library]", "ShowRhythmboxLibrary"),
+            ConfigValue((int)checkBox_show_rhythmbox->isChecked()));
+    m_pConfig->set(ConfigKey("[Library]", "ShowBansheeLibrary"),
+            ConfigValue((int)checkBox_show_banshee->isChecked()));
+    m_pConfig->set(ConfigKey("[Library]", "ShowITunesLibrary"),
+            ConfigValue((int)checkBox_show_itunes->isChecked()));
+    m_pConfig->set(ConfigKey("[Library]", "ShowTraktorLibrary"),
+            ConfigValue((int)checkBox_show_traktor->isChecked()));
+    m_pConfig->set(ConfigKey("[Library]", "ShowRekordboxLibrary"),
+            ConfigValue((int)checkBox_show_rekordbox->isChecked()));
     m_pConfig->set(ConfigKey("[Library]", "ShowSeratoLibrary"),
             ConfigValue((int)checkBox_show_serato->isChecked()));
 
@@ -587,14 +619,14 @@ void DlgPrefLibrary::slotApply() {
     QFont font = m_pLibrary->getTrackTableFont();
     if (m_originalTrackTableFont != font) {
         m_pConfig->set(ConfigKey("[Library]", "Font"),
-                       ConfigValue(font.toString()));
+                ConfigValue(font.toString()));
         m_originalTrackTableFont = font;
     }
 
     int rowHeight = spinBox_row_height->value();
     if (m_iOriginalTrackTableRowHeight != rowHeight) {
-        m_pConfig->set(ConfigKey("[Library]","RowHeight"),
-                       ConfigValue(rowHeight));
+        m_pConfig->set(ConfigKey("[Library]", "RowHeight"),
+                ConfigValue(rowHeight));
         m_iOriginalTrackTableRowHeight = rowHeight;
     }
 
@@ -660,8 +692,10 @@ void DlgPrefLibrary::setLibraryFont(const QFont& font) {
 void DlgPrefLibrary::slotSelectFont() {
     // False if the user cancels font selection.
     bool ok = false;
-    QFont font = QFontDialog::getFont(&ok, m_pLibrary->getTrackTableFont(),
-                                      this, tr("Select Library Font"));
+    QFont font = QFontDialog::getFont(&ok,
+            m_pLibrary->getTrackTableFont(),
+            this,
+            tr("Select Library Font"));
     if (ok) {
         setLibraryFont(font);
     }
@@ -712,3 +746,10 @@ void DlgPrefLibrary::setSeratoMetadataEnabled(bool shouldSyncTrackMetadata) {
         checkBox_serato_metadata_export->setChecked(false);
     }
 }
+
+void DlgPrefLibrary::slotDateFormatChanged(int index) {
+    int formatInt = comboBox_dateFormat->itemData(index).toInt();
+    mixxx::DateFormat format = static_cast<mixxx::DateFormat>(formatInt);
+    m_pConfig->setValue(kDateFormatConfigKey, formatInt);
+    BaseTrackTableModel::setDateFormat(format);
+}

src/preferences/dialog/dlgpreflibrary.h

@@ -13,7 +13,7 @@
 class QWidget;
 class ControlProxy;
 
-class DlgPrefLibrary : public DlgPreferencePage, public Ui::DlgPrefLibraryDlg  {
+class DlgPrefLibrary : public DlgPreferencePage, public Ui::DlgPrefLibraryDlg {
     Q_OBJECT
   public:
     enum class TrackDoubleClickAction : int {
@@ -67,6 +67,7 @@ class DlgPrefLibrary : public DlgPreferencePage, public Ui::DlgPrefLibraryDlg  {
     void slotBpmRangeSelected(int index);
     void slotBpmColumnPrecisionChanged(int bpmPrecision);
     void slotSeratoMetadataExportClicked(bool);
+    void slotDateFormatChanged(int index);
 
   private:
     void populateDirList();

src/preferences/dialog/dlgpreflibrarydlg.ui

@@ -298,6 +298,20 @@
        </widget>
       </item>
 
+      <item row="11" column="0">
+       <widget class="QLabel" name="label_dateFormat">
+        <property name="text">
+         <string>Date Format:</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignLeft|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="11" column="1" colspan="2">
+       <widget class="QComboBox" name="comboBox_dateFormat"/>
+      </item>
+
      </layout>
     </widget>
    </item><!-- Track Table View -->
@@ -695,6 +709,7 @@
   <tabstop>btn_library_font</tabstop>
   <tabstop>spinbox_bpm_precision</tabstop>
   <tabstop>checkbox_played_track_color</tabstop>
+  <tabstop>comboBox_dateFormat</tabstop>
   <tabstop>spinBox_search_debouncing_timeout</tabstop>
   <tabstop>checkBox_enable_search_completions</tabstop>
   <tabstop>checkBox_enable_search_history_shortcuts</tabstop>