use individual local gui_settings objects Previously, we created a single gui_settings object (derived from QSettings) and accessed it from the resource_manager object. That design is not necessary and is not the way QSettings was designed to be used. Instead of managing a single object, we should be using individual QSettings objects where needed. Each individual QSettings object manages thread-safe access to a single global collection of settings. The Qt docs say that operations on QSettings are not thread safe, but that means that you can't create a QSettings object in one thread and use it in another without some locking. I'm not sure whether we were doing that correctly, but with this change it no longer matters. Each QSettings object does perform locking when reading or writing the underlying global data. * resource-manager.h, resource-manager.cc (resource_manager::m_settings): Delete data member. (resource_manager::get_settings): Delete. * annotation-dialog.cc, QTerminal.cc, QTerminal.h, command-widget.cc, command-widget.h, community-news.cc, dialog.cc, documentation-bookmarks.cc, documentation-bookmarks.h, documentation-dock-widget.cc, documentation-dock-widget.h, documentation.cc, documentation.h, dw-main-window.cc, dw-main-window.h, external-editor-interface.cc, files-dock-widget.cc, files-dock-widget.h, find-files-dialog.cc, history-dock-widget.cc, history-dock-widget.h, file-editor-interface.h, file-editor-tab.cc, file-editor-tab.h, file-editor.cc, file-editor.h, find-dialog.cc, octave-qscintilla.cc, main-window.cc, main-window.h, news-reader.cc, octave-dock-widget.cc, octave-dock-widget.h, qt-interpreter-events.cc, qt-interpreter-events.h, release-notes.cc, resource-manager.cc, resource-manager.h, set-path-dialog.cc, settings-dialog.cc, settings-dialog.h, shortcut-manager.cc, shortcut-manager.h, terminal-dock-widget.cc, terminal-dock-widget.h, variable-editor.cc, variable-editor.h, welcome-wizard.cc, workspace-model.cc, workspace-model.h, workspace-view.cc: Use local gui_settings objects instead of accessing a pointer to a single gui_settings object owned by the resource_manager object.

////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2011-2022 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave 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.
//
// Octave 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 Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if ! defined (octave_documentation_dock_widget_h)
#define octave_documentation_dock_widget_h 1

#include "documentation.h"
#include "octave-dock-widget.h"

namespace octave
{
  class base_qobject;

  class documentation_dock_widget : public octave_dock_widget
  {
    Q_OBJECT

  public:

    documentation_dock_widget (QWidget *parent, base_qobject& oct_qobj);

    ~documentation_dock_widget (void) = default;

  public slots:

    void notice_settings (void);
    void save_settings (void);

    void copyClipboard (void);
    void pasteClipboard (void);
    void selectAll (void);

    void showDoc (const QString& name);
    void registerDoc (const QString& name);
    void unregisterDoc (const QString& name);

  private:

    documentation *m_docs;
  };
}

#endif