GUI: headers: reordering tracks by dragging & dropping

Part of the implementation of #3227.

NEWS.md

@@ -20,6 +20,8 @@
 * MKVToolNix GUI: header editor: a new column has been added to the tree view
   showing the status of the "track enabled" flag. The information is also
   shown on the track overview page on the right. Implements #3228.
+* MKVToolNix GUI: header editor: users can now reorder tracks by dragging &
+  dropping. Implements #3227.
 
 ## Bug fixes
 

src/mkvtoolnix-gui/header_editor/page_model.cpp

@@ -8,6 +8,7 @@
 #include "mkvtoolnix-gui/header_editor/page_base.h"
 #include "mkvtoolnix-gui/header_editor/page_model.h"
 #include "mkvtoolnix-gui/header_editor/top_level_page.h"
+#include "mkvtoolnix-gui/header_editor/track_type_page.h"
 #include "mkvtoolnix-gui/util/model.h"
 
 namespace mtx::gui::HeaderEditor {
@@ -25,6 +26,9 @@ PageModel::~PageModel() {
 PageBase *
 PageModel::selectedPage(QModelIndex const &idx)
   const {
+  if (!idx.isValid())
+    return {};
+
   auto selectedItem = itemFromIndex(idx.sibling(idx.row(), 0));
   if (!selectedItem)
     return {};
@@ -189,20 +193,20 @@ PageModel::canDropMimeData(QMimeData const *data,
   const {
   if (   !data
       || (Qt::MoveAction != action)
-      || !parent.isValid()
       || !m_lastSelectedIdx.isValid()
       || (0 > row))
     return false;
 
   auto draggedPage = selectedPage(m_lastSelectedIdx);
-  if (!draggedPage || !dynamic_cast<AttachedFilePage *>(draggedPage))
-    return false;
+  auto parentPage  = selectedPage(parent);
 
-  auto parentPage = selectedPage(parent);
-  if (!parentPage || !dynamic_cast<AttachmentsPage *>(parentPage))
-    return false;
+  if (dynamic_cast<AttachedFilePage *>(draggedPage))
+    return dynamic_cast<AttachmentsPage *>(parentPage);
 
-  return true;
+  if (dynamic_cast<TrackTypePage *>(draggedPage))
+    return !parentPage && (row > 0) && (row < rowCount());
+
+  return false;
 }
 
 bool
@@ -214,13 +218,30 @@ PageModel::dropMimeData(QMimeData const *data,
   if (!canDropMimeData(data, action, row, column, parent))
     return false;
 
+  auto draggedPage = selectedPage(m_lastSelectedIdx);
+
   auto result = QStandardItemModel::dropMimeData(data, action, row, 0, parent);
 
   Util::requestAllItems(*this);
 
-  Q_EMIT attachmentsReordered();
+  if (dynamic_cast<AttachedFilePage *>(draggedPage))
+    Q_EMIT attachmentsReordered();
+
+  else if (dynamic_cast<TrackTypePage *>(draggedPage))
+    Q_EMIT tracksReordered();
 
   return result;
 }
 
+void
+PageModel::rereadTopLevelPageIndexes() {
+  auto rootItem = invisibleRootItem();
+
+  for (int row = 0, numRows = rootItem->rowCount(); row < numRows; ++row) {
+    auto topLevelItem          = rootItem->child(row);
+    auto pageId                = topLevelItem->data(Util::HeaderEditorPageIdRole).value<int>();
+    m_pages[pageId]->m_pageIdx = topLevelItem->index();
+  }
+}
+
 }

src/mkvtoolnix-gui/header_editor/page_model.h

@@ -48,6 +48,10 @@ public:
 
 Q_SIGNALS:
   void attachmentsReordered();
+  void tracksReordered();
+
+public Q_SLOTS:
+  void rereadTopLevelPageIndexes();
 };
 
 }

src/mkvtoolnix-gui/header_editor/tab.cpp

@@ -93,6 +93,7 @@ Tab::resetData() {
   m_eTracks.reset();
   m_model->reset();
   m_segmentinfoPage = nullptr;
+  m_tracksReordered = false;
 }
 
 void
@@ -196,7 +197,7 @@ Tab::save() {
       tracksModified      = true;
   }
 
-  if (!segmentinfoModified && !tracksModified && !attachmentsModified) {
+  if (!segmentinfoModified && !tracksModified && !attachmentsModified && !m_tracksReordered) {
     Util::MessageBox::information(this)->title(QY("File has not been modified")).text(QY("The header values have not been modified. There is nothing to save.")).exec();
     return;
   }
@@ -226,7 +227,9 @@ Tab::save() {
       }
     }
 
-    if (ok && tracksModified && m_eTracks) {
+    if (ok && m_eTracks && (tracksModified || m_tracksReordered)) {
+      updateTracksElementToMatchTrackOrder();
+
       auto result = m_analyzer->update_element(m_eTracks, true);
       if (kax_analyzer_c::uer_success != result) {
         Util::KaxAnalyzer::displayUpdateElementResult(this, result, QY("Saving the modified track headers failed."));
@@ -314,6 +317,13 @@ Tab::setupUi() {
   connect(m_replaceAttachmentContentAction,          &QAction::triggered,                              [this]() { replaceAttachmentContent(false); });
   connect(m_replaceAttachmentContentSetValuesAction, &QAction::triggered,                              [this]() { replaceAttachmentContent(true); });
   connect(m_model,                                   &PageModel::attachmentsReordered,                 [this]() { m_attachmentsPage->rereadChildren(*m_model); });
+  connect(m_model,                                   &PageModel::tracksReordered,                      this, &Tab::handleReorderedTracks);
+}
+
+void
+Tab::handleReorderedTracks() {
+  m_tracksReordered = true;
+  m_model->rereadTopLevelPageIndexes();
 }
 
 void
@@ -874,13 +884,15 @@ Tab::isClosingOrReloadingOkIfModified(ModifiedConfirmationMode mode) {
     return true;
 
   auto modifiedPage = hasBeenModified();
-  if (!modifiedPage)
+  if (!modifiedPage && !m_tracksReordered)
     return true;
 
   auto tool = MainWindow::headerEditorTool();
   MainWindow::get()->switchToTool(tool);
   tool->showTab(*this);
-  focusPage(modifiedPage);
+
+  if (modifiedPage)
+    focusPage(modifiedPage);
 
   auto closing  = mode == ModifiedConfirmationMode::Closing;
   auto text     = closing ? QY("The file \"%1\" has been modified. Do you really want to close? All changes will be lost.")
@@ -898,4 +910,15 @@ Tab::isClosingOrReloadingOkIfModified(ModifiedConfirmationMode mode) {
   return answer == QMessageBox::Yes;
 }
 
+void
+Tab::updateTracksElementToMatchTrackOrder() {
+  auto &tracks = static_cast<libebml::EbmlMaster &>(*m_eTracks);
+
+  RemoveChildren<libmatroska::KaxTrackEntry>(tracks);
+
+  for (auto page : m_model->topLevelPages())
+    if (dynamic_cast<TrackTypePage *>(page))
+      tracks.PushElement(static_cast<TrackTypePage &>(*page).m_master);
+}
+
 }

src/mkvtoolnix-gui/header_editor/tab.h

@@ -45,7 +45,7 @@ protected:
   PageModel *m_model;
   PageBase *m_segmentinfoPage{};
   AttachmentsPage *m_attachmentsPage{};
-  bool m_ignoreSelectionChanges{};
+  bool m_ignoreSelectionChanges{}, m_tracksReordered{};
 
   QMenu *m_treeContextMenu;
   QAction *m_expandAllAction, *m_collapseAllAction, *m_addAttachmentsAction, *m_removeAttachmentAction, *m_removeAllAttachmentsAction, *m_saveAttachmentContentAction;
@@ -86,6 +86,7 @@ public Q_SLOTS:
   virtual void replaceAttachmentContent(bool deriveNameAndMimeType);
   virtual void handleDroppedFiles(QStringList const &fileNames, Qt::MouseButtons mouseButtons);
   virtual void focusPage(PageBase *page);
+  virtual void handleReorderedTracks();
 
 protected:
   void setupUi();
@@ -107,6 +108,8 @@ protected:
   void pruneEmptyMastersForTrack(TrackTypePage &page);
   void pruneEmptyMastersForAllTracks();
 
+  void updateTracksElementToMatchTrackOrder();
+
 public:
   static memory_cptr readFileData(QWidget *parent, QString const &fileName);
 };