LibGUI: Don't require passing a parent to widget constructors

This is a step towards using Core::Object::add<T> more, which takes
care of parenting the newly created child automatically.

Libraries/LibGUI/AbstractButton.h

@@ -60,8 +60,8 @@ public:
     void set_auto_repeat_interval(int interval) { m_auto_repeat_interval = interval; }
 
 protected:
-    explicit AbstractButton(Widget* parent);
-    AbstractButton(const StringView&, Widget* parent);
+    explicit AbstractButton(Widget* parent = nullptr);
+    AbstractButton(const StringView&, Widget* parent = nullptr);
 
     virtual void mousedown_event(MouseEvent&) override;
     virtual void mousemove_event(MouseEvent&) override;

Libraries/LibGUI/AbstractTableView.h

@@ -72,7 +72,7 @@ public:
 
 protected:
     virtual ~AbstractTableView() override;
-    explicit AbstractTableView(Widget* parent);
+    explicit AbstractTableView(Widget* parent = nullptr);
 
     virtual void did_update_model() override;
     virtual void mouseup_event(MouseEvent&) override;

Libraries/LibGUI/AbstractView.h

@@ -73,7 +73,7 @@ public:
     NonnullRefPtr<Gfx::Font> font_for_index(const ModelIndex&) const;
 
 protected:
-    explicit AbstractView(Widget* parent);
+    explicit AbstractView(Widget* parent = nullptr);
     virtual ~AbstractView() override;
 
     virtual void mousedown_event(MouseEvent&) override;

Libraries/LibGUI/Button.h

@@ -62,8 +62,8 @@ public:
     void set_focusable(bool b) { m_focusable = b; }
 
 protected:
-    Button(const StringView& text, Widget* parent);
-    explicit Button(Widget* parent);
+    Button(const StringView& text, Widget* parent = nullptr);
+    explicit Button(Widget* parent = nullptr);
     virtual void paint_event(PaintEvent&) override;
 
 private:

Libraries/LibGUI/CheckBox.h

@@ -38,8 +38,8 @@ public:
     virtual void click() override;
 
 private:
-    CheckBox(const StringView&, Widget* parent);
-    explicit CheckBox(Widget* parent);
+    CheckBox(const StringView&, Widget* parent = nullptr);
+    explicit CheckBox(Widget* parent = nullptr);
 
     // These don't make sense for a check box, so hide them.
     using AbstractButton::auto_repeat_interval;

Libraries/LibGUI/GroupBox.h

@@ -39,8 +39,8 @@ public:
     void set_title(const StringView&);
 
 protected:
-    explicit GroupBox(Widget* parent);
-    GroupBox(const StringView& title, Widget* parent);
+    explicit GroupBox(Widget* parent = nullptr);
+    GroupBox(const StringView& title, Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
 

Libraries/LibGUI/ItemView.h

@@ -48,7 +48,7 @@ public:
     virtual ModelIndex index_at_event_position(const Gfx::Point&) const override;
 
 private:
-    explicit ItemView(Widget* parent);
+    explicit ItemView(Widget* parent = nullptr);
 
     virtual void did_update_model() override;
     virtual void paint_event(PaintEvent&) override;

Libraries/LibGUI/ListView.h

@@ -33,7 +33,7 @@ namespace GUI {
 class ListView : public AbstractView {
     C_OBJECT(ListView)
 public:
-    explicit ListView(Widget* parent);
+    explicit ListView(Widget* parent = nullptr);
     virtual ~ListView() override;
 
     int item_height() const { return 16; }

Libraries/LibGUI/ProgressBar.h

@@ -56,7 +56,7 @@ public:
     void set_format(Format format) { m_format = format; }
 
 protected:
-    explicit ProgressBar(Widget* parent);
+    explicit ProgressBar(Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
 

Libraries/LibGUI/RadioButton.h

@@ -38,8 +38,8 @@ public:
     virtual void click() override;
 
 protected:
-    explicit RadioButton(Widget* parent);
-    explicit RadioButton(const StringView& text, Widget* parent);
+    explicit RadioButton(Widget* parent = nullptr);
+    explicit RadioButton(const StringView& text, Widget* parent = nullptr);
     virtual void paint_event(PaintEvent&) override;
 
 private:

Libraries/LibGUI/ResizeCorner.h

@@ -34,7 +34,7 @@ public:
     virtual ~ResizeCorner() override;
 
 protected:
-    explicit ResizeCorner(Widget* parent);
+    explicit ResizeCorner(Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
     virtual void mousedown_event(MouseEvent&) override;

Libraries/LibGUI/ScrollBar.h

@@ -65,8 +65,8 @@ public:
     };
 
 private:
-    explicit ScrollBar(Widget* parent);
-    explicit ScrollBar(Orientation, Widget* parent);
+    explicit ScrollBar(Widget* parent = nullptr);
+    explicit ScrollBar(Orientation, Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
     virtual void mousedown_event(MouseEvent&) override;

Libraries/LibGUI/ScrollableWidget.h

@@ -71,7 +71,7 @@ public:
     Gfx::Point to_widget_position(const Gfx::Point& content_position) const;
 
 protected:
-    explicit ScrollableWidget(Widget* parent);
+    explicit ScrollableWidget(Widget* parent = nullptr);
     virtual void custom_layout() override;
     virtual void resize_event(ResizeEvent&) override;
     virtual void mousewheel_event(MouseEvent&) override;

Libraries/LibGUI/Slider.h

@@ -106,7 +106,7 @@ public:
     virtual ~VerticalSlider() override {}
 
 private:
-    explicit VerticalSlider(Widget* parent)
+    explicit VerticalSlider(Widget* parent = nullptr)
         : Slider(Orientation::Vertical, parent)
     {
     }
@@ -118,7 +118,7 @@ public:
     virtual ~HorizontalSlider() override {}
 
 private:
-    explicit HorizontalSlider(Widget* parent)
+    explicit HorizontalSlider(Widget* parent = nullptr)
         : Slider(Orientation::Horizontal, parent)
     {
     }

Libraries/LibGUI/Splitter.h

@@ -36,7 +36,7 @@ public:
     virtual ~Splitter() override;
 
 protected:
-    Splitter(Gfx::Orientation, Widget* parent);
+    Splitter(Gfx::Orientation, Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
     virtual void resize_event(ResizeEvent&) override;
@@ -68,7 +68,7 @@ public:
     virtual ~VerticalSplitter() override {}
 
 private:
-    explicit VerticalSplitter(Widget* parent)
+    explicit VerticalSplitter(Widget* parent = nullptr)
         : Splitter(Gfx::Orientation::Vertical, parent)
     {
     }
@@ -80,7 +80,7 @@ public:
     virtual ~HorizontalSplitter() override {}
 
 private:
-    explicit HorizontalSplitter(Widget* parent)
+    explicit HorizontalSplitter(Widget* parent = nullptr)
         : Splitter(Gfx::Orientation::Horizontal, parent)
     {
     }

Libraries/LibGUI/StackWidget.h

@@ -42,7 +42,7 @@ public:
     Function<void(Widget*)> on_active_widget_change;
 
 protected:
-    explicit StackWidget(Widget* parent);
+    explicit StackWidget(Widget* parent = nullptr);
     virtual void child_event(Core::ChildEvent&) override;
     virtual void resize_event(ResizeEvent&) override;
 

Libraries/LibGUI/StatusBar.h

@@ -41,8 +41,8 @@ public:
     void set_text(int index, const StringView&);
 
 protected:
-    explicit StatusBar(Widget* parent);
-    explicit StatusBar(int label_count, Widget* parent);
+    explicit StatusBar(Widget* parent = nullptr);
+    explicit StatusBar(int label_count, Widget* parent = nullptr);
     virtual void paint_event(PaintEvent&) override;
 
 private:

Libraries/LibGUI/TabWidget.h

@@ -38,7 +38,7 @@ public:
         Bottom,
     };
 
-    explicit TabWidget(Widget* parent);
+    explicit TabWidget(Widget* parent = nullptr);
     virtual ~TabWidget() override;
 
     TabPosition tab_position() const { return m_tab_position; }

Libraries/LibGUI/TableView.h

@@ -36,7 +36,7 @@ public:
     virtual ~TableView() override;
 
 protected:
-    explicit TableView(Widget* parent);
+    explicit TableView(Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
 };

Libraries/LibGUI/TextBox.h

@@ -33,7 +33,7 @@ namespace GUI {
 class TextBox : public TextEditor {
     C_OBJECT(TextBox)
 public:
-    explicit TextBox(Widget* parent);
+    explicit TextBox(Widget* parent = nullptr);
     virtual ~TextBox() override;
 };
 

Libraries/LibGUI/TextEditor.h

@@ -130,8 +130,8 @@ public:
     void set_syntax_highlighter(OwnPtr<SyntaxHighlighter>);
 
 protected:
-    explicit TextEditor(Widget* parent);
-    explicit TextEditor(Type, Widget* parent);
+    explicit TextEditor(Widget* parent = nullptr);
+    explicit TextEditor(Type, Widget* parent = nullptr);
 
     virtual void did_change_font() override;
     virtual void paint_event(PaintEvent&) override;

Libraries/LibGUI/ToolBar.h

@@ -43,8 +43,8 @@ public:
     void set_has_frame(bool has_frame) { m_has_frame = has_frame; }
 
 protected:
-    explicit ToolBar(Widget* parent);
-    explicit ToolBar(Orientation, int button_size, Widget* parent);
+    explicit ToolBar(Widget* parent = nullptr);
+    explicit ToolBar(Orientation, int button_size, Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
 

Libraries/LibGUI/TreeView.h

@@ -41,7 +41,7 @@ public:
     virtual int item_count() const override;
 
 protected:
-    explicit TreeView(Widget*);
+    explicit TreeView(Widget* parent = nullptr);
 
     virtual void paint_event(PaintEvent&) override;
     virtual void doubleclick_event(MouseEvent&) override;