Save settings in Qt convention, delete all children in destructors (bug #45366) * QUnixTerminalImpl.cpp (QUnixTerminalImpl::~QUnixTerminalImpl): Delete dynamic objects pointed to by m_terminal (TerminalModel), m_kpty (KPty) and m_terminalView (TerminalView). (bug fix) * files-dock-widget.cc: (files_dock_widget::~files_dock_widget): Rename to save_settings. Return if variable 'settings' is not valid object pointer. (files_dock_widget::save_settings): Added. Similar code as destructor was. Call base class octave_dock_widget::save_settings at end of routine. * files-dock-widget.h: (files_dock_widget::~files_dock_widget): Provide empty destructor. (files_dock_widget::save_settings): Added, public slot. * find-files-dialog.cc: (find_files_dialog::~find_files_dialog): Moved most of the code, except the statement deleting the directory iterator, to new routine save_settings. (find_files_dialog::save_settings): Added. Large portion of the code that was in the destructor. Return immediately if variable 'settings' is not valid object pointer. * find-files-dialog.h: (find_files_dialog::save_settings): Added, public slot. * history-dock-widget.cc: (history_dock_widget::~history_dock_widget): Rename to save_settings. Return if variable 'settings' is not valid object pointer. (history_dock_widget::save_settings): Similar code as destructor was. Call base class octave_dock_widget::save_settings at end of routine. * history-dock-widget.h: (history_dock_widget::~history_dock_widget): Provide empty destructor. (history_dock_widget::save_settings): Added, public slot. * main-window.cc (main_window::prepare_to_exit): If find_files_dlg is valid, call the object's save_settings routine. (main_window::construct): Connect appropriate slot of all objects that must save_settings information to the qApp aboutToQuit signal. (Except for find_files_dlg, see above.) At end of this sequence, connect aboutToQuit to the shortcut_manager and resource_manager function that deletes instance. * octave-dock-widget.cc: (octave_dock_widget::~octave_dock_widget): Rename to save_settings. Return if variable 'settings' is not valid object pointer. (octave_dock_widget::save_settings): Similar code as destructor was. * octave-dock-widget.h: (octave_dock_widget::~octave_dock_widget): Provide empty destructor. (octave_dock_widget::save_settings): Added, public slot. * octave-qt-link.cc (octave_qt_link::do_prompt_new_edit_file): Check that 'settings' pointer is valid before using. * resource-manager.cc: Remove "singleton-cleanup.h" header reference. (resource_manager::instance_ok): Do not add cleanup_instance to worker thread's exit cleanup procedure. * resource-manager.h (resource_manager::instance) Change variable to public for connecting. (resource_manager::cleanup_instance) Change to a public slot for connecting to qApp aboutToQuit signal. (resource_manager::resource_manager): Remove an unused variation of the constructor. (resource_manager::operator =) Removed. * settings-dialog.cc: Add QMessageBox to header file list. (settings_dialog::settings_dialog): If QSettings pointer settings is not valid return immediately. (settings_dialog::show_tab): Condition setting the current index on pointer 'settings' being valid. (settings_dialog::write_changed_settings): Remove FIXME comment. If the settings are not valid, display a dialog about missing file and return. * shortcut-manager.cc: Remove "singleton-cleanup.h" header reference. (shortcut_manager::instance_ok): Do not add cleanup_instance to worker thread's exit cleanup procedure. * shortcut-manager.h (shortcut_manager::instance) Change variable to public for connecting. (shortcut_manager::cleanup_instance) Change to a public slot for connecting to qApp aboutToQuit signal. (shortcut_manager::shortcut_manager): Remove an unused variation of the constructor. (shortcut_manager::operator =) Removed. * terminal-dock-widget.cc (terminal_dock_widget::~terminal_dock_widget): Added. Delete QTerminal terminal. (bug fix) * terminal-dock-widget.h (terminal_dock_widget::~terminal_dock_widget): Added. * workspace-view.cc: (workspace_view::workspace_view): Place code hunk using QSettings pointer 'settings' within a conditional block. (workspace_view::~workspace_view): Rename to save_settings. Return if variable 'settings' is not valid object pointer. (workspace_view::save_settings): Almost same code as destructor was. Call base class octave_dock_widget::save_settings at end of routine. * workspace-view.h: (workspace_view::~workspace_view): Provide empty destructor. (workspace_view::save_settings): Added, public slot.