Qt: prefer libretro-common file APIs and drop Qt5/Qt6 ladders

Reduces Qt-specific surface and silences three pre-existing
-Wdeprecated-declarations warnings. All changes preserve behaviour
on Qt 5.2 and up (RetroArch's minimum, per qb/config.libs.sh).

* MainWindow::MainWindow:

  Drop dead 'QDir playlistDir(path_dir_playlist)' and the
  path_dir_playlist local that only existed to construct it. Both
  unused since the constructor split. -Wunused-variable did not
  flag the QDir because of its non-trivial constructor.

* MainWindow::setCustomThemeFile:

  Replace QFile open / readAll / close with filestream_read_file
  plus filestream_exists. Same five error paths preserved
  (blank path, missing file, open failure, empty file, success).

* MainWindow::onFileBrowserTreeContextMenuRequested:

  Replace the QDir / dir.exists() existence check with
  path_is_directory(). Removes a Qt5/Qt6 ifdef ladder ('dir =
  string' on Qt5 vs 'dir.setPath(string)' on Qt6) and silences
  the QDir::operator=(QString) deprecation warning. The
  QDir::toNativeSeparators(...) display path stays - that side is
  fine on both Qt 5 and Qt 6.

* LoadCoreWindow::onCoreEnterPressed:

  Replace 'QByteArray::append(QString)' (Qt 5) /
  'QByteArray::append(QString::toStdString())' (Qt 6) ladder with
  'path.toUtf8().constData()' inline. The temporary QByteArray's
  lifetime extends through the loadCore() call so this is safe.
  Silences the QByteArray::append(QString) deprecation warning.

* MainWindow::onPlaylistWidgetContextMenuRequested:

  Replace 'm_listWidget->isItemHidden(item)' (deprecated since
  Qt 4.8) with 'item->isHidden()' (available since Qt 4.x).
  Removes a Qt5/Qt6 ifdef ladder. Silences the
  QListWidget::isItemHidden() deprecation warning.

Tested under Qt 5.15 with -Wdeprecated-declarations enabled; all
four object files (ui_qt, ui_qt_widgets, moc_ui_qt,
moc_ui_qt_widgets) now build with zero warnings.

No behaviour change.

Author: LibretroAdmin

ui/drivers/ui_qt.cpp

@@ -1540,9 +1540,7 @@ MainWindow::MainWindow(QWidget *parent) :
    ,m_itemsCountLabel(new QLabel(this))
 {
    settings_t                   *settings = config_get_ptr();
-   const char *path_dir_playlist          = settings->paths.directory_playlist;
    const char *path_dir_assets            = settings->paths.directory_assets;
-   QDir playlistDir(path_dir_playlist);
    QString                      configDir = QFileInfo(path_get(RARCH_PATH_CONFIG)).dir().absolutePath();
 
    qRegisterMetaType<QPointer<ThumbnailWidget> >("ThumbnailWidget");
@@ -2202,6 +2200,11 @@ const QString& MainWindow::customThemeString() const
 
 bool MainWindow::setCustomThemeFile(QString filePath)
 {
+   QByteArray pathArray;
+   const char *path_data;
+   void   *buf  = NULL;
+   int64_t len  = 0;
+
    if (filePath.isEmpty())
    {
       QMessageBox::critical(this,
@@ -2210,45 +2213,37 @@ bool MainWindow::setCustomThemeFile(QString filePath)
       return false;
    }
 
-   QFile file(filePath);
+   pathArray = filePath.toUtf8();
+   path_data = pathArray.constData();
 
-   if (file.exists())
+   if (!filestream_exists(path_data))
    {
-      bool opened = file.open(QIODevice::ReadOnly);
-
-      if (!opened)
-      {
-         QMessageBox::critical(this,
-               msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_CUSTOM_THEME),
-               msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_FILE_READ_OPEN_FAILED));
-         return false;
-      }
-
-      {
-         QByteArray fileArray = file.readAll();
-         QString fileStr      = QString::fromUtf8(fileArray);
-
-         file.close();
-
-         if (fileStr.isEmpty())
-         {
-            QMessageBox::critical(this,
-                  msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_CUSTOM_THEME),
-                  msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_FILE_IS_EMPTY));
-            return false;
-         }
+      QMessageBox::critical(this,
+            msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_CUSTOM_THEME),
+            msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_FILE_DOES_NOT_EXIST));
+      return false;
+   }
 
-         setCustomThemeString(fileStr);
-      }
+   if (!filestream_read_file(path_data, &buf, &len))
+   {
+      QMessageBox::critical(this,
+            msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_CUSTOM_THEME),
+            msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_FILE_READ_OPEN_FAILED));
+      return false;
    }
-   else
+
+   if (len <= 0)
    {
+      free(buf);
       QMessageBox::critical(this,
             msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_CUSTOM_THEME),
-            msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_FILE_DOES_NOT_EXIST));
+            msg_hash_to_str(MENU_ENUM_LABEL_VALUE_QT_FILE_IS_EMPTY));
       return false;
    }
 
+   setCustomThemeString(QString::fromUtf8(static_cast<const char*>(buf),
+            static_cast<int>(len)));
+   free(buf);
    return true;
 }
 
@@ -2327,28 +2322,24 @@ bool MainWindow::showMessageBox(QString msg, MessageBoxType msgType,
 void MainWindow::onFileBrowserTreeContextMenuRequested(const QPoint&)
 {
 #ifdef HAVE_LIBRETRODB
-   QDir dir;
-   QByteArray dirArray;
    QPointer<QAction> action;
    QList<QAction*> actions;
    QScopedPointer<QAction> scanAction;
    QString currentDirString      = QDir::toNativeSeparators(
          m_dirModel->filePath(m_dirTree->currentIndex()));
    settings_t *settings          = config_get_ptr();
-   const char *fullpath          = NULL;
    const char *path_dir_playlist = settings->paths.directory_playlist;
    const char *path_content_db   = settings->paths.path_content_database;
+   QByteArray dirArray;
+   const char *fullpath          = NULL;
 
    if (currentDirString.isEmpty())
       return;
 
-#if (QT_VERSION > QT_VERSION_CHECK(6, 0, 0))
-   dir.setPath(currentDirString);
-#else
-   dir = currentDirString;
-#endif
+   dirArray = currentDirString.toUtf8();
+   fullpath = dirArray.constData();
 
-   if (!dir.exists())
+   if (!path_is_directory(fullpath))
       return;
 
    /* Default NULL parameter for parent wasn't added until 5.7 */
@@ -2360,9 +2351,6 @@ void MainWindow::onFileBrowserTreeContextMenuRequested(const QPoint&)
    if (!(action = QMenu::exec(actions, QCursor::pos(), NULL, m_dirTree)))
       return;
 
-   dirArray = currentDirString.toUtf8();
-   fullpath = dirArray.constData();
-
    task_push_dbscan(
          path_dir_playlist,
          path_content_db,
@@ -5426,22 +5414,13 @@ void LoadCoreWindow::loadCore(const char *path)
 
 void LoadCoreWindow::onCoreEnterPressed()
 {
-   QByteArray pathArray;
-   const char               *pathData = NULL;
    QTableWidgetItem *selectedCoreItem =
       m_table->item(m_table->currentRow(), CORE_NAME_COLUMN);
    QVariantHash                  hash = selectedCoreItem->data(
          Qt::UserRole).toHash();
    QString                       path = hash["path"].toString();
 
-#if (QT_VERSION > QT_VERSION_CHECK(6, 0, 0))
-   pathArray.append(path.toStdString());
-#else
-   pathArray.append(path);
-#endif
-   pathData                           = pathArray.constData();
-
-   loadCore(pathData);
+   loadCore(path.toUtf8().constData());
 }
 
 void LoadCoreWindow::onLoadCustomCoreClicked()

ui/drivers/ui_qt_widgets.cpp

@@ -8024,13 +8024,8 @@ void MainWindow::onPlaylistWidgetContextMenuRequested(const QPoint&)
    for (j = 0; j < m_listWidget->count(); j++)
    {
       QListWidgetItem *item = m_listWidget->item(j);
-#if (QT_VERSION > QT_VERSION_CHECK(6, 0, 0))
-      bool           hidden = item->isHidden();
-#else
-      bool           hidden = m_listWidget->isItemHidden(item);
-#endif
 
-      if (hidden)
+      if (item->isHidden())
       {
          QAction *action = hiddenPlaylistsMenu->addAction(item->text());
          action->setProperty("row", j);