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.

--- a/libgui/src/settings-dialog.h	Fri Dec 02 15:51:44 2022 -0500
+++ b/libgui/src/settings-dialog.h	Fri Dec 02 14:23:53 2022 -0500
@@ -33,7 +33,6 @@
 
 #include "color-picker.h"
 #include "gui-preferences-ed.h"
-#include "gui-settings.h"
 #include "ui-settings-dialog.h"
 
 class QsciLexer;
@@ -84,21 +83,21 @@
   private:
 
 #if defined (HAVE_QSCINTILLA)
-    void update_lexer (QsciLexer *lexer, gui_settings *settings, int mode, int def = 0);
-    void get_lexer_settings (QsciLexer *lexer, gui_settings *settings);
-    void write_lexer_settings (QsciLexer *lexer, gui_settings *settings);
+    void update_lexer (QsciLexer *lexer, int mode, int def = 0);
+    void get_lexer_settings (QsciLexer *lexer);
+    void write_lexer_settings (QsciLexer *lexer);
 #endif
 
     void write_changed_settings (bool closing);
 
-    void read_workspace_colors (gui_settings *settings);
-    void write_workspace_colors (gui_settings *settings);
+    void read_workspace_colors (void);
+    void write_workspace_colors (void);
 
-    void read_terminal_colors (gui_settings *settings);
-    void write_terminal_colors (gui_settings *settings);
+    void read_terminal_colors (void);
+    void write_terminal_colors (void);
 
-    void read_varedit_colors (gui_settings *settings);
-    void write_varedit_colors (gui_settings *settings);
+    void read_varedit_colors (void);
+    void write_varedit_colors (void);
 
     base_qobject& m_octave_qobj;