diff --git a/src/gui/CheckListWidget.cxx b/src/gui/CheckListWidget.cxx
index 13afb335a..a42744657 100644
--- a/src/gui/CheckListWidget.cxx
+++ b/src/gui/CheckListWidget.cxx
@@ -143,7 +143,7 @@ Common::Rect CheckListWidget::getEditRect() const
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-bool CheckListWidget::getState(int line)
+bool CheckListWidget::getState(int line) const
 {
   if(line >= 0 && line < int(_stateList.size()))
     return _stateList[line];
diff --git a/src/gui/CheckListWidget.hxx b/src/gui/CheckListWidget.hxx
index 2ebec0d5d..30ccba814 100644
--- a/src/gui/CheckListWidget.hxx
+++ b/src/gui/CheckListWidget.hxx
@@ -39,8 +39,8 @@ class CheckListWidget : public ListWidget
     void setList(const StringList& list, const BoolArray& state);
     void setLine(int line, const string& str, const bool& state);
 
-    bool getState(int line);
-    bool getSelectedState() { return getState(_selectedItem); }
+    bool getState(int line) const;
+    bool getSelectedState() const { return getState(_selectedItem); }
 
   private:
     bool handleEvent(Event::Type e) override;
diff --git a/src/gui/ColorWidget.cxx b/src/gui/ColorWidget.cxx
index 94ef4bbf4..8320c9a88 100644
--- a/src/gui/ColorWidget.cxx
+++ b/src/gui/ColorWidget.cxx
@@ -28,8 +28,8 @@ ColorWidget::ColorWidget(GuiObject* boss, const GUI::Font& font,
                          int x, int y, int w, int h, int cmd, bool framed)
   : Widget(boss, font, x, y, w, h),
     CommandSender(boss),
-    _framed(framed),
-    _cmd(cmd)
+    _framed{framed},
+    _cmd{cmd}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_CLEARBG | Widget::FLAG_RETAIN_FOCUS;
 }
diff --git a/src/gui/Command.hxx b/src/gui/Command.hxx
index 64fab2151..0178670f8 100644
--- a/src/gui/Command.hxx
+++ b/src/gui/Command.hxx
@@ -48,7 +48,7 @@ class CommandSender
   // and add methods addTarget/removeTarget.
   public:
     explicit CommandSender(CommandReceiver* target)
-        : _target(target) { }
+        : _target{target} { }
 
     virtual ~CommandSender() = default;
 
diff --git a/src/gui/ContextMenu.cxx b/src/gui/ContextMenu.cxx
index 2ecf50302..bcf87ca0e 100644
--- a/src/gui/ContextMenu.cxx
+++ b/src/gui/ContextMenu.cxx
@@ -31,9 +31,9 @@ ContextMenu::ContextMenu(GuiObject* boss, const GUI::Font& font,
                          const VariantList& items, int cmd, int width)
   : Dialog(boss->instance(), boss->parent(), font),
     CommandSender(boss),
-    _rowHeight(font.getLineHeight()),
-    _cmd(cmd),
-    _maxWidth(width)
+    _rowHeight{font.getLineHeight()},
+    _cmd{cmd},
+    _maxWidth{width}
 {
   setArrows();
   addItems(items);
diff --git a/src/gui/ContextMenu.hxx b/src/gui/ContextMenu.hxx
index 6807635ba..ab6a0f6ff 100644
--- a/src/gui/ContextMenu.hxx
+++ b/src/gui/ContextMenu.hxx
@@ -130,7 +130,7 @@ class ContextMenu : public Dialog, public CommandSender
     int _id{-1};
 
     uInt32 _xorig{0}, _yorig{0};
-    uInt32 _maxWidth{0};
+    int _maxWidth{0};
 
     int _textOfs{0};
     int _arrowSize{0};
diff --git a/src/gui/DeveloperDialog.hxx b/src/gui/DeveloperDialog.hxx
index fc16e302e..65d057e38 100644
--- a/src/gui/DeveloperDialog.hxx
+++ b/src/gui/DeveloperDialog.hxx
@@ -148,7 +148,7 @@ class DeveloperDialog : public Dialog
     CheckboxWidget*     myGhostReadsTrapWidget{nullptr};
 #endif
 
-    bool    mySettings;
+    bool    mySettings{false};
     // Emulator sets
     std::array<bool, 2>   myFrameStats;
     std::array<bool, 2>   myDetectedInfo;
diff --git a/src/gui/Dialog.cxx b/src/gui/Dialog.cxx
index 8b052b032..72bdc398a 100644
--- a/src/gui/Dialog.cxx
+++ b/src/gui/Dialog.cxx
@@ -49,8 +49,8 @@
 Dialog::Dialog(OSystem& instance, DialogContainer& parent, const GUI::Font& font,
                const string& title, int x, int y, int w, int h)
   : GuiObject(instance, parent, *this, x, y, w, h),
-    _font(font),
-    _title(title)
+    _font{font},
+    _title{title}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_BORDER | Widget::FLAG_CLEARBG;
   setTitle(title);
diff --git a/src/gui/Dialog.hxx b/src/gui/Dialog.hxx
index 0cc145d55..022334e47 100644
--- a/src/gui/Dialog.hxx
+++ b/src/gui/Dialog.hxx
@@ -213,7 +213,7 @@ class Dialog : public GuiObject
       Widget* widget{nullptr};
       WidgetArray list;
 
-      explicit Focus(Widget* w = nullptr) : widget(w) { }
+      explicit Focus(Widget* w = nullptr) : widget{w} { }
     };
     using FocusList = vector<Focus>;
 
@@ -222,7 +222,7 @@ class Dialog : public GuiObject
       FocusList focus;
       uInt32 currentTab{0};
 
-      explicit TabFocus(TabWidget* w = nullptr) : widget(w) { }
+      explicit TabFocus(TabWidget* w = nullptr) : widget{w} { }
 
       void appendFocusList(WidgetArray& list);
       void saveCurrentFocus(Widget* w);
diff --git a/src/gui/DialogContainer.cxx b/src/gui/DialogContainer.cxx
index 16f32536a..c421cb430 100644
--- a/src/gui/DialogContainer.cxx
+++ b/src/gui/DialogContainer.cxx
@@ -28,7 +28,7 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 DialogContainer::DialogContainer(OSystem& osystem)
-  : myOSystem(osystem)
+  : myOSystem{osystem}
 {
   _DOUBLE_CLICK_DELAY = osystem.settings().getInt("mdouble");
   _REPEAT_INITIAL_DELAY = osystem.settings().getInt("ctrldelay");
diff --git a/src/gui/EventMappingWidget.cxx b/src/gui/EventMappingWidget.cxx
index 0336e4c51..4755c7789 100644
--- a/src/gui/EventMappingWidget.cxx
+++ b/src/gui/EventMappingWidget.cxx
@@ -40,7 +40,7 @@ EventMappingWidget::EventMappingWidget(GuiObject* boss, const GUI::Font& font,
                                        EventMode mode)
   : Widget(boss, font, x, y, w, h),
     CommandSender(boss),
-    myEventMode(mode)
+    myEventMode{mode}
 {
   const int fontHeight   = font.getFontHeight(),
             lineHeight   = font.getLineHeight(),
diff --git a/src/gui/FileListWidget.cxx b/src/gui/FileListWidget.cxx
index 169b9cddb..519c097fa 100644
--- a/src/gui/FileListWidget.cxx
+++ b/src/gui/FileListWidget.cxx
@@ -28,7 +28,7 @@
 FileListWidget::FileListWidget(GuiObject* boss, const GUI::Font& font,
                                int x, int y, int w, int h)
   : StringListWidget(boss, font, x, y, w, h),
-    _filter([](const FilesystemNode& node) { return true; })
+    _filter{[](const FilesystemNode& node) { return true; }}
 {
   // This widget is special, in that it catches signals and redirects them
   setTarget(this);
diff --git a/src/gui/FileListWidget.hxx b/src/gui/FileListWidget.hxx
index 32f6517f7..f60dd97d4 100644
--- a/src/gui/FileListWidget.hxx
+++ b/src/gui/FileListWidget.hxx
@@ -89,7 +89,7 @@ class FileListWidget : public StringListWidget
     const FilesystemNode& currentDir() const { return _node; }
 
     static void setQuickSelectDelay(uInt64 time) { _QUICK_SELECT_DELAY = time; }
-    uInt64 getQuickSelectDelay() { return _QUICK_SELECT_DELAY; }
+    uInt64 getQuickSelectDelay() const { return _QUICK_SELECT_DELAY; }
 
     ProgressDialog& progress();
     void incProgress();
diff --git a/src/gui/Font.cxx b/src/gui/Font.cxx
index e327fa8af..53797d031 100644
--- a/src/gui/Font.cxx
+++ b/src/gui/Font.cxx
@@ -26,7 +26,7 @@ namespace GUI {
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Font::Font(const FontDesc& desc)
-  : myFontDesc(desc)
+  : myFontDesc{desc}
 {
 }
 
diff --git a/src/gui/GuiObject.hxx b/src/gui/GuiObject.hxx
index dd95d62cc..6d69cd04b 100644
--- a/src/gui/GuiObject.hxx
+++ b/src/gui/GuiObject.hxx
@@ -70,10 +70,10 @@ class GuiObject : public CommandReceiver
   public:
     GuiObject(OSystem& osystem, DialogContainer& parent, Dialog& dialog,
               int x, int y, int w, int h)
-      : myOSystem(osystem),
-        myParent(parent),
-        myDialog(dialog),
-        _x(x), _y(y), _w(w), _h(h) { }
+      : myOSystem{osystem},
+        myParent{parent},
+        myDialog{dialog},
+        _x{x}, _y{y}, _w{w}, _h{h} { }
 
     ~GuiObject() override = default;
 
diff --git a/src/gui/HighScoresDialog.hxx b/src/gui/HighScoresDialog.hxx
index c15105f6f..39ccca335 100644
--- a/src/gui/HighScoresDialog.hxx
+++ b/src/gui/HighScoresDialog.hxx
@@ -35,7 +35,6 @@ class Serializer;
 
 using json = nlohmann::json;
 
-
 /**
   The dialog for displaying high scores in Stella.
 
diff --git a/src/gui/InputDialog.cxx b/src/gui/InputDialog.cxx
index e9bb315c3..2345e3570 100644
--- a/src/gui/InputDialog.cxx
+++ b/src/gui/InputDialog.cxx
@@ -41,8 +41,8 @@
 InputDialog::InputDialog(OSystem& osystem, DialogContainer& parent,
                          const GUI::Font& font, int max_w, int max_h)
   : Dialog(osystem, parent, font, "Input settings"),
-    myMaxWidth(max_w),
-    myMaxHeight(max_h)
+    myMaxWidth{max_w},
+    myMaxHeight{max_h}
 {
   const int lineHeight   = _font.getLineHeight(),
             fontWidth    = _font.getMaxCharWidth(),
diff --git a/src/gui/Launcher.cxx b/src/gui/Launcher.cxx
index 91868282c..81605a703 100644
--- a/src/gui/Launcher.cxx
+++ b/src/gui/Launcher.cxx
@@ -28,7 +28,7 @@
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Launcher::Launcher(OSystem& osystem)
   : DialogContainer(osystem),
-    mySize(myOSystem.settings().getSize("launcherres"))
+    mySize{myOSystem.settings().getSize("launcherres")}
 {
   const Common::Size& d = myOSystem.frameBuffer().desktopSize();
   double overscan = 1 - myOSystem.settings().getInt("tia.fs_overscan") / 100.0;
diff --git a/src/gui/ListWidget.cxx b/src/gui/ListWidget.cxx
index 1cf6c7e0d..a8c0c37da 100644
--- a/src/gui/ListWidget.cxx
+++ b/src/gui/ListWidget.cxx
@@ -28,7 +28,7 @@
 ListWidget::ListWidget(GuiObject* boss, const GUI::Font& font,
                        int x, int y, int w, int h, bool useScrollbar)
   : EditableWidget(boss, font, x, y, 16, 16),
-    _useScrollbar(useScrollbar)
+    _useScrollbar{useScrollbar}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_CLEARBG | Widget::FLAG_RETAIN_FOCUS;
   _bgcolor = kWidColor;
diff --git a/src/gui/MessageBox.cxx b/src/gui/MessageBox.cxx
index d5b5cf11b..ca3913543 100644
--- a/src/gui/MessageBox.cxx
+++ b/src/gui/MessageBox.cxx
@@ -33,8 +33,8 @@ MessageBox::MessageBox(GuiObject* boss, const GUI::Font& font,
                        bool focusOKButton)
   : Dialog(boss->instance(), boss->parent(), font, title, 0, 0, max_w, max_h),
     CommandSender(boss),
-    myOkCmd(okCmd),
-    myCancelCmd(cancelCmd)
+    myOkCmd{okCmd},
+    myCancelCmd{cancelCmd}
 {
   addText(font, text);
 
diff --git a/src/gui/MessageDialog.cxx b/src/gui/MessageDialog.cxx
index ca52c99e6..2c2b19c7d 100644
--- a/src/gui/MessageDialog.cxx
+++ b/src/gui/MessageDialog.cxx
@@ -82,6 +82,7 @@ void MessageDialog::setMessage(const string& title, const string& text, bool yes
   setMessage(title, StringParser(text).stringList(), yesNo);
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 string MessageDialog::myTitle = "";
 StringList MessageDialog::myText;
 bool MessageDialog::myYesNo = false;
diff --git a/src/gui/MessageDialog.hxx b/src/gui/MessageDialog.hxx
index d3c8a8228..6399abafb 100644
--- a/src/gui/MessageDialog.hxx
+++ b/src/gui/MessageDialog.hxx
@@ -26,36 +26,36 @@ class OSystem;
 
 class MessageDialog : public Dialog
 {
-public:
-  MessageDialog(OSystem& osystem, DialogContainer& parent,
-                const GUI::Font& font, int max_w, int max_h);
-  ~MessageDialog() override;
+  public:
+    MessageDialog(OSystem& osystem, DialogContainer& parent,
+                  const GUI::Font& font, int max_w, int max_h);
+    ~MessageDialog() override;
 
-  // Define the message displayed
-  void setMessage(const string& title, const string& text, bool yesNo = false);
-  void setMessage(const string& title, const StringList& text, bool yesNo = false);
-  bool confirmed() { return myConfirmed; }
+    // Define the message displayed
+    void setMessage(const string& title, const string& text, bool yesNo = false);
+    void setMessage(const string& title, const StringList& text, bool yesNo = false);
+    bool confirmed() { return myConfirmed; }
 
-protected:
-  void loadConfig() override;
-  void handleCommand(CommandSender* sender, int cmd, int data, int id) override;
+  protected:
+    void loadConfig() override;
+    void handleCommand(CommandSender* sender, int cmd, int data, int id) override;
 
-private:
-  static string myTitle;
-  static StringList myText;
-  static bool myYesNo;
-  static bool myConfirmed;
+  private:
+    static string myTitle;
+    static StringList myText;
+    static bool myYesNo;
+    static bool myConfirmed;
 
-  // Show a message
-  GUI::MessageBox* myMsg{nullptr};
+    // Show a message
+    GUI::MessageBox* myMsg{nullptr};
 
-private:
-  // Following constructors and assignment operators not supported
-  MessageDialog() = delete;
-  MessageDialog(const MessageDialog&) = delete;
-  MessageDialog(MessageDialog&&) = delete;
-  MessageDialog& operator=(const MessageDialog&) = delete;
-  MessageDialog& operator=(MessageDialog&&) = delete;
+  private:
+    // Following constructors and assignment operators not supported
+    MessageDialog() = delete;
+    MessageDialog(const MessageDialog&) = delete;
+    MessageDialog(MessageDialog&&) = delete;
+    MessageDialog& operator=(const MessageDialog&) = delete;
+    MessageDialog& operator=(MessageDialog&&) = delete;
 };
 
 #endif
diff --git a/src/gui/OptionsDialog.cxx b/src/gui/OptionsDialog.cxx
index 865103822..b2dc3b083 100644
--- a/src/gui/OptionsDialog.cxx
+++ b/src/gui/OptionsDialog.cxx
@@ -49,8 +49,8 @@
 OptionsDialog::OptionsDialog(OSystem& osystem, DialogContainer& parent,
                              GuiObject* boss, int max_w, int max_h, Menu::AppMode mode)
   : Dialog(osystem, parent, osystem.frameBuffer().font(), "Options"),
-    myBoss(boss),
-    myMode(mode)
+    myBoss{boss},
+    myMode{mode}
 {
   // do not show basic settings options in debugger
   bool minSettings = osystem.settings().getBool("minimal_ui") && mode != Menu::AppMode::debugger;
diff --git a/src/gui/OptionsDialog.hxx b/src/gui/OptionsDialog.hxx
index bd13c3f37..ea0f38935 100644
--- a/src/gui/OptionsDialog.hxx
+++ b/src/gui/OptionsDialog.hxx
@@ -71,7 +71,7 @@ class OptionsDialog : public Dialog
     ButtonWidget* myGameInfoButton{nullptr};
     ButtonWidget* myCheatCodeButton{nullptr};
 
-    GuiObject* myBoss;
+    GuiObject* myBoss{nullptr};
     // Indicates if this dialog is used for global (vs. in-game) settings
     Menu::AppMode myMode{Menu::AppMode::emulator};
 
diff --git a/src/gui/PopUpWidget.cxx b/src/gui/PopUpWidget.cxx
index ab9560ed8..762ce3bf8 100644
--- a/src/gui/PopUpWidget.cxx
+++ b/src/gui/PopUpWidget.cxx
@@ -29,8 +29,8 @@ PopUpWidget::PopUpWidget(GuiObject* boss, const GUI::Font& font,
                          int x, int y, int w, int h, const VariantList& list,
                          const string& label, int labelWidth, int cmd)
   : EditableWidget(boss, font, x, y - 1, w, h + 2),
-    _label(label),
-    _labelWidth(labelWidth)
+    _label{label},
+    _labelWidth{labelWidth}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_RETAIN_FOCUS
     | Widget::FLAG_TRACK_MOUSE;
diff --git a/src/gui/ProgressDialog.cxx b/src/gui/ProgressDialog.cxx
index 80aafc8c4..235e24f6c 100644
--- a/src/gui/ProgressDialog.cxx
+++ b/src/gui/ProgressDialog.cxx
@@ -30,7 +30,7 @@
 ProgressDialog::ProgressDialog(GuiObject* boss, const GUI::Font& font,
                                const string& message)
   : Dialog(boss->instance(), boss->parent()),
-    myFont(font)
+    myFont{font}
 {
   const int fontWidth  = font.getMaxCharWidth(),
             fontHeight = font.getFontHeight(),
diff --git a/src/gui/QuadTariDialog.cxx b/src/gui/QuadTariDialog.cxx
index b4d1891ef..4b0ef8ead 100644
--- a/src/gui/QuadTariDialog.cxx
+++ b/src/gui/QuadTariDialog.cxx
@@ -29,7 +29,7 @@
 QuadTariDialog::QuadTariDialog(GuiObject* boss, const GUI::Font& font, int max_w, int max_h,
                                Properties& properties)
   : Dialog(boss->instance(), boss->parent(), font, "QuadTari controllers", 0, 0, max_w, max_h),
-    myGameProperties(properties)
+    myGameProperties{properties}
 {
   const int lineHeight = font.getLineHeight(),
     fontHeight = font.getFontHeight(),
diff --git a/src/gui/RadioButtonWidget.cxx b/src/gui/RadioButtonWidget.cxx
index 658859b97..7c3b8b16d 100644
--- a/src/gui/RadioButtonWidget.cxx
+++ b/src/gui/RadioButtonWidget.cxx
@@ -221,8 +221,8 @@ RadioButtonWidget::RadioButtonWidget(GuiObject* boss, const GUI::Font& font,
                                      int x, int y, const string& label,
                                      RadioButtonGroup* group, int cmd)
   : CheckboxWidget(boss, font, x, y, label, cmd),
-    myGroup(group),
-    _buttonSize(buttonSize(font)) // 14 | 22
+    myGroup{group},
+    _buttonSize{buttonSize(font)} // 14 | 22
 {
   _flags = Widget::FLAG_ENABLED;
   _bgcolor = _bgcolorhi = kWidColor;
diff --git a/src/gui/RadioButtonWidget.hxx b/src/gui/RadioButtonWidget.hxx
index 8003a8627..52a81bb99 100644
--- a/src/gui/RadioButtonWidget.hxx
+++ b/src/gui/RadioButtonWidget.hxx
@@ -40,7 +40,7 @@ class RadioButtonWidget : public CheckboxWidget
   protected:
     void setFill(FillType type);
     void drawWidget(bool hilite) override;
-    static int buttonSize(const GUI::Font& font)
+    static uInt32 buttonSize(const GUI::Font& font)
     {
       return font.getFontHeight() < 24 ? 14 : 22; // box is square
     }
diff --git a/src/gui/RomAuditDialog.cxx b/src/gui/RomAuditDialog.cxx
index a95e4fce5..65b4d0c33 100644
--- a/src/gui/RomAuditDialog.cxx
+++ b/src/gui/RomAuditDialog.cxx
@@ -37,9 +37,9 @@
 RomAuditDialog::RomAuditDialog(OSystem& osystem, DialogContainer& parent,
                                const GUI::Font& font, int max_w, int max_h)
   : Dialog(osystem, parent, font, "Audit ROMs"),
-    myFont(font),
-    myMaxWidth(max_w),
-    myMaxHeight(max_h)
+    myFont{font},
+    myMaxWidth{max_w},
+    myMaxHeight{max_h}
 {
   const int lineHeight   = font.getLineHeight(),
             fontWidth    = font.getMaxCharWidth(),
diff --git a/src/gui/RomInfoWidget.cxx b/src/gui/RomInfoWidget.cxx
index 4cf7f4d33..11eddc6e5 100644
--- a/src/gui/RomInfoWidget.cxx
+++ b/src/gui/RomInfoWidget.cxx
@@ -37,7 +37,7 @@ RomInfoWidget::RomInfoWidget(GuiObject* boss, const GUI::Font& font,
                              int x, int y, int w, int h,
                              const Common::Size& imgSize)
   : Widget(boss, font, x, y, w, h),
-    myAvail(imgSize)
+    myAvail{imgSize}
 {
   _flags = Widget::FLAG_ENABLED;
   _bgcolor = kDlgColor;
diff --git a/src/gui/SnapshotDialog.cxx b/src/gui/SnapshotDialog.cxx
index 792d7af7f..80af8ec1d 100644
--- a/src/gui/SnapshotDialog.cxx
+++ b/src/gui/SnapshotDialog.cxx
@@ -29,7 +29,7 @@
 SnapshotDialog::SnapshotDialog(OSystem& osystem, DialogContainer& parent,
                                const GUI::Font& font, int max_w, int max_h)
   : Dialog(osystem, parent, font, "Snapshot settings"),
-    myFont(font)
+    myFont{font}
 {
   const int lineHeight   = font.getLineHeight(),
             fontHeight   = _font.getFontHeight(),
diff --git a/src/gui/StellaSettingsDialog.cxx b/src/gui/StellaSettingsDialog.cxx
index 06ff03b3e..5236735f0 100644
--- a/src/gui/StellaSettingsDialog.cxx
+++ b/src/gui/StellaSettingsDialog.cxx
@@ -32,7 +32,7 @@
 StellaSettingsDialog::StellaSettingsDialog(OSystem& osystem, DialogContainer& parent,
   int max_w, int max_h, Menu::AppMode mode)
   : Dialog(osystem, parent, osystem.frameBuffer().font(), "Basic settings"),
-    myMode(mode)
+    myMode{mode}
 {
   const int buttonHeight = _font.getLineHeight() + _font.getLineHeight() / 5,
     lineHeight = _font.getLineHeight(),
diff --git a/src/gui/StringListWidget.cxx b/src/gui/StringListWidget.cxx
index b94d1b5c4..5371947c5 100644
--- a/src/gui/StringListWidget.cxx
+++ b/src/gui/StringListWidget.cxx
@@ -27,7 +27,7 @@ StringListWidget::StringListWidget(GuiObject* boss, const GUI::Font& font,
                                    int x, int y, int w, int h, bool hilite,
                                    bool useScrollbar)
   : ListWidget(boss, font, x, y, w, h, useScrollbar),
-    _hilite(hilite)
+    _hilite{hilite}
 {
   _bgcolorlo = kDlgColor;
 
diff --git a/src/gui/TabWidget.hxx b/src/gui/TabWidget.hxx
index d2ca4305c..fa33c06c1 100644
--- a/src/gui/TabWidget.hxx
+++ b/src/gui/TabWidget.hxx
@@ -83,7 +83,7 @@ class TabWidget : public Widget, public CommandSender
 
       explicit Tab(const string& t, int tw = NO_WIDTH,
           Widget* first = nullptr, Widget* parent = nullptr, bool e = true)
-        : title(t), firstWidget(first), parentWidget(parent), enabled(e), tabWidth(tw) { }
+        : title{t}, firstWidget{first}, parentWidget{parent}, enabled{e}, tabWidth{tw} { }
     };
     using TabList = vector<Tab>;
 
diff --git a/src/gui/TimeLineWidget.cxx b/src/gui/TimeLineWidget.cxx
index 5f6e0e687..3018bb40c 100644
--- a/src/gui/TimeLineWidget.cxx
+++ b/src/gui/TimeLineWidget.cxx
@@ -33,7 +33,7 @@ TimeLineWidget::TimeLineWidget(GuiObject* boss, const GUI::Font& font,
                                int x, int y, int w, int h,
                                const string& label, uInt32 labelWidth, int cmd)
   : ButtonWidget(boss, font, x, y, w, h, label, cmd),
-    _labelWidth(labelWidth)
+    _labelWidth{labelWidth}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_TRACK_MOUSE
     | Widget::FLAG_CLEARBG | Widget::FLAG_NOBG;
@@ -205,13 +205,13 @@ void TimeLineWidget::drawWidget(bool hilite)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-uInt32 TimeLineWidget::valueToPos(uInt32 value)
+uInt32 TimeLineWidget::valueToPos(uInt32 value) const
 {
   return _stepValue[BSPF::clamp(value, _valueMin, _valueMax)];
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-uInt32 TimeLineWidget::posToValue(uInt32 pos)
+uInt32 TimeLineWidget::posToValue(uInt32 pos) const
 {
   // Find the interval in which 'pos' falls, and then the endpoint which
   // it is closest to
diff --git a/src/gui/TimeLineWidget.hxx b/src/gui/TimeLineWidget.hxx
index 5518fac20..e0cdd8980 100644
--- a/src/gui/TimeLineWidget.hxx
+++ b/src/gui/TimeLineWidget.hxx
@@ -49,8 +49,8 @@ class TimeLineWidget : public ButtonWidget
 
     void drawWidget(bool hilite) override;
 
-    uInt32 valueToPos(uInt32 value);
-    uInt32 posToValue(uInt32 pos);
+    uInt32 valueToPos(uInt32 value) const;
+    uInt32 posToValue(uInt32 pos) const;
 
   protected:
     uInt32  _value{0};
diff --git a/src/gui/TimeMachine.cxx b/src/gui/TimeMachine.cxx
index 1dad57152..033aed076 100644
--- a/src/gui/TimeMachine.cxx
+++ b/src/gui/TimeMachine.cxx
@@ -23,7 +23,7 @@
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 TimeMachine::TimeMachine(OSystem& osystem)
   : DialogContainer(osystem),
-    myWidth(FBMinimum::Width)
+    myWidth{FBMinimum::Width}
 {
   myBaseDialog = new TimeMachineDialog(myOSystem, *this, myWidth);
 }
diff --git a/src/gui/TimeMachineDialog.cxx b/src/gui/TimeMachineDialog.cxx
index 594ed5036..c0ca3d299 100644
--- a/src/gui/TimeMachineDialog.cxx
+++ b/src/gui/TimeMachineDialog.cxx
@@ -495,7 +495,7 @@ void TimeMachineDialog::initBar()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-string TimeMachineDialog::getTimeString(uInt64 cycles)
+string TimeMachineDialog::getTimeString(uInt64 cycles) const
 {
   const Int32 scanlines = std::max<Int32>(instance().console().tia().scanlinesLastFrame(), 240);
   const bool isNTSC = scanlines <= 287;
diff --git a/src/gui/TimeMachineDialog.hxx b/src/gui/TimeMachineDialog.hxx
index 1d15d6b15..b9fe118fd 100644
--- a/src/gui/TimeMachineDialog.hxx
+++ b/src/gui/TimeMachineDialog.hxx
@@ -33,7 +33,7 @@ class TimeMachineDialog : public Dialog
 
     /** set/get number of winds when entering the dialog */
     void setEnterWinds(Int32 numWinds) { _enterWinds = numWinds; }
-    Int32 getEnterWinds() { return _enterWinds; }
+    Int32 getEnterWinds() const { return _enterWinds; }
 
   private:
     void loadConfig() override;
@@ -48,7 +48,7 @@ class TimeMachineDialog : public Dialog
     void setPosition() override;
 
     /** convert cycles into time */
-    string getTimeString(uInt64 cycles);
+    string getTimeString(uInt64 cycles) const;
     /** re/unwind and update display */
     void handleWinds(Int32 numWinds = 0);
     /** toggle Time Machine mode */
diff --git a/src/gui/ToolTip.cxx b/src/gui/ToolTip.cxx
index c2f7b7656..88e5915bd 100644
--- a/src/gui/ToolTip.cxx
+++ b/src/gui/ToolTip.cxx
@@ -27,7 +27,7 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 ToolTip::ToolTip(Dialog& dialog, const GUI::Font& font)
-  : myDialog(dialog)
+  : myDialog{dialog}
 {
   myScale = myDialog.instance().frameBuffer().hidpiScaleFactor();
 
@@ -179,5 +179,5 @@ void ToolTip::show(const string& tip)
 void ToolTip::render()
 {
   if(myTipShown)
-    mySurface->render(); 
+    mySurface->render();
 }
diff --git a/src/gui/UIDialog.cxx b/src/gui/UIDialog.cxx
index 11a9e0308..beb6f576d 100644
--- a/src/gui/UIDialog.cxx
+++ b/src/gui/UIDialog.cxx
@@ -42,8 +42,8 @@ UIDialog::UIDialog(OSystem& osystem, DialogContainer& parent,
                    const GUI::Font& font, GuiObject* boss, int max_w, int max_h)
   : Dialog(osystem, parent, font, "User interface settings"),
     CommandSender(boss),
-    myFont(font),
-    myIsGlobal(boss != nullptr)
+    myFont{font},
+    myIsGlobal{boss != nullptr}
 {
   const GUI::Font& ifont = instance().frameBuffer().infoFont();
   const int lineHeight   = font.getLineHeight(),
diff --git a/src/gui/UndoHandler.cxx b/src/gui/UndoHandler.cxx
index f8eeb0c48..4246d2f7f 100644
--- a/src/gui/UndoHandler.cxx
+++ b/src/gui/UndoHandler.cxx
@@ -19,7 +19,7 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 UndoHandler::UndoHandler(size_t size)
-  : mySize(size)
+  : mySize{size}
 {
   reset();
 }
diff --git a/src/gui/VideoAudioDialog.hxx b/src/gui/VideoAudioDialog.hxx
index f0d376140..25a78baa5 100644
--- a/src/gui/VideoAudioDialog.hxx
+++ b/src/gui/VideoAudioDialog.hxx
@@ -66,7 +66,7 @@ class VideoAudioDialog : public Dialog
     void updateSettingsWithPreset(AudioSettings&);
 
   private:
-    TabWidget* myTab;
+    TabWidget* myTab{nullptr};
 
     // General options
     PopUpWidget*      myRenderer{nullptr};
diff --git a/src/gui/Widget.cxx b/src/gui/Widget.cxx
index 7f605a6ea..4e11b59ff 100644
--- a/src/gui/Widget.cxx
+++ b/src/gui/Widget.cxx
@@ -32,8 +32,8 @@
 Widget::Widget(GuiObject* boss, const GUI::Font& font,
                int x, int y, int w, int h)
   : GuiObject(boss->instance(), boss->parent(), boss->dialog(), x, y, w, h),
-    _boss(boss),
-    _font(font)
+    _boss{boss},
+    _font{font}
 {
   // Insert into the widget list of the boss
   _next = _boss->_firstWidget;
@@ -395,8 +395,8 @@ StaticTextWidget::StaticTextWidget(GuiObject* boss, const GUI::Font& font,
                                    const string& text, TextAlign align,
                                    ColorId shadowColor)
   : Widget(boss, font, x, y, w, h),
-    _label(text),
-    _align(align)
+    _label{text},
+    _align{align}
 {
   _flags = Widget::FLAG_ENABLED | FLAG_CLEARBG;
 
@@ -464,8 +464,8 @@ ButtonWidget::ButtonWidget(GuiObject* boss, const GUI::Font& font,
                            const string& label, int cmd, bool repeat)
   : StaticTextWidget(boss, font, x, y, w, h, label, TextAlign::Center),
     CommandSender(boss),
-    _cmd(cmd),
-    _repeat(repeat)
+    _cmd{cmd},
+    _repeat{repeat}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_CLEARBG;
   _bgcolor = kBtnColor;
@@ -739,11 +739,11 @@ SliderWidget::SliderWidget(GuiObject* boss, const GUI::Font& font,
                            int valueLabelWidth, const string& valueUnit, int valueLabelGap,
                            bool forceLabelSign)
   : ButtonWidget(boss, font, x, y, w, h, label, cmd),
-    _labelWidth(labelWidth),
-    _valueUnit(valueUnit),
-    _valueLabelGap(valueLabelGap),
-    _valueLabelWidth(valueLabelWidth),
-    _forceLabelSign(forceLabelSign)
+    _labelWidth{labelWidth},
+    _valueUnit{valueUnit},
+    _valueLabelGap{valueLabelGap},
+    _valueLabelWidth{valueLabelWidth},
+    _forceLabelSign{forceLabelSign}
 {
   _flags = Widget::FLAG_ENABLED | Widget::FLAG_TRACK_MOUSE | Widget::FLAG_CLEARBG;
   _bgcolor = kDlgColor;
diff --git a/src/libretro/FBSurfaceLIBRETRO.hxx b/src/libretro/FBSurfaceLIBRETRO.hxx
index 7578ca658..b00fea94d 100644
--- a/src/libretro/FBSurfaceLIBRETRO.hxx
+++ b/src/libretro/FBSurfaceLIBRETRO.hxx
@@ -64,7 +64,7 @@ class FBSurfaceLIBRETRO : public FBSurface
     void applyAttributes() override { }
 
   private:
-    uInt32 myWidth, myHeight;
+    uInt32 myWidth{0}, myHeight{0};
     unique_ptr<uInt32[]> myPixelData;
     Common::Rect mySrcGUIR, myDstGUIR;
 
diff --git a/src/libretro/StellaLIBRETRO.hxx b/src/libretro/StellaLIBRETRO.hxx
index d4ae39c87..3b76a93e3 100644
--- a/src/libretro/StellaLIBRETRO.hxx
+++ b/src/libretro/StellaLIBRETRO.hxx
@@ -43,7 +43,7 @@ class StellaLIBRETRO
     StellaLIBRETRO();
 
   public:
-    OSystemLIBRETRO& osystem() { return *myOSystem; }
+    OSystemLIBRETRO& osystem() const { return *myOSystem; }
 
     bool create(bool logging);
     void destroy();
diff --git a/src/unix/FSNodePOSIX.cxx b/src/unix/FSNodePOSIX.cxx
index c49d7d1ce..1ef2b684b 100644
--- a/src/unix/FSNodePOSIX.cxx
+++ b/src/unix/FSNodePOSIX.cxx
@@ -25,8 +25,8 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 FilesystemNodePOSIX::FilesystemNodePOSIX()
-  : _path(ROOT_DIR),
-    _displayName(_path)
+  : _path{ROOT_DIR},
+    _displayName{_path}
 {
 }
 
diff --git a/src/windows/FSNodeWINDOWS.cxx b/src/windows/FSNodeWINDOWS.cxx
index 82182fe83..179476b27 100644
--- a/src/windows/FSNodeWINDOWS.cxx
+++ b/src/windows/FSNodeWINDOWS.cxx
@@ -175,7 +175,7 @@ FilesystemNodeWINDOWS::FilesystemNodeWINDOWS()
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 FilesystemNodeWINDOWS::FilesystemNodeWINDOWS(const string& p)
-  : _path(p.length() > 0 ? p : "~")  // Default to home directory
+  : _path{p.length() > 0 ? p : "~"}  // Default to home directory
 {
   // Expand '~' to the users 'home' directory
   if(_path[0] == '~')