refactor(ui): remove unused tree view stubs

* Remove dead context-menu compression wiring and empty handler to cut
  unused UI paths
* Drop a no-op paint override to simplify event flow
* Remove an unused helper for resolving target directory index to reduce
  API surface
* Expand widget documentation to clarify intent and maintenance

Author: saturneric

src/ui/widgets/FilePage.h

@@ -1,3 +1,31 @@
+/**
+ * Copyright (C) 2021-2024 Saturneric <eric@bktus.com>
+ *
+ * This file is part of GpgFrontend.
+ *
+ * GpgFrontend is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GpgFrontend is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GpgFrontend. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * The initial version of the source code is inherited from
+ * the gpg4usb project, which is under GPL-3.0-or-later.
+ *
+ * All the source code of GpgFrontend was modified and released by
+ * Saturneric <eric@bktus.com> starting on May 12, 2021.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ */
+
 #pragma once
 
 #include "ui/widgets/InfoBoardWidget.h"

src/ui/widgets/FileTreeView.cpp

@@ -542,8 +542,6 @@ void FileTreeView::slot_create_popup_menu() {
       new QAction(QIcon::fromTheme(QStringLiteral("archive-insert")),
                   tr("Compress..."), this);
   action_compress_files_->setVisible(false);
-  connect(action_compress_files_, &QAction::triggered, this,
-          &FileTreeView::slot_compress_files);
 
   action_copy_path_ = new QAction(QIcon::fromTheme(QStringLiteral("edit-copy")),
                                   tr("Copy Path"), this);
@@ -679,17 +677,6 @@ void FileTreeView::slot_calculate_hash() {
       });
 }
 
-void FileTreeView::slot_compress_files() {}
-
-void FileTreeView::paintEvent(QPaintEvent* event) {
-  QTreeView::paintEvent(event);
-
-  // if (!initial_resize_done_) {
-  //   slot_adjust_column_widths();
-  //   initial_resize_done_ = true;
-  // }
-}
-
 void FileTreeView::mousePressEvent(QMouseEvent* event) {
 #if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
   auto pos = event->position().toPoint();
@@ -783,21 +770,6 @@ void FileTreeView::SetPath(const QString& target_path) {
   }
 }
 
-auto FileTreeView::current_target_directory_index() const -> QModelIndex {
-  auto index = currentIndex();
-
-  if (!index.isValid()) {
-    return rootIndex();
-  }
-
-  const auto info = dir_model_->fileInfo(index);
-  if (info.isDir()) {
-    return index;
-  }
-
-  return index.parent().isValid() ? index.parent() : rootIndex();
-}
-
 auto FileTreeView::current_target_directory_path() const -> QString {
   auto index = currentIndex();