LibGUI: Refactor context menus to be event-driven instead of declarative.

The declarative approach had way too many limitations. This patch adds a
context menu event that can be hooked to prepare a custom context menu on
demand just-in-time. :^)

Applications/VisualBuilder/VBForm.cpp

@@ -35,16 +35,20 @@ VBForm::VBForm(const String& name, GWidget* parent)
     groupbox1->set_rect({ 300, 150, 161, 51 });
     m_widgets.append(move(groupbox1));
 
-    auto context_menu = make<GMenu>("Context menu");
+    m_context_menu = make<GMenu>("Context menu");
-    context_menu->add_action(GAction::create("Move to front", [this] (auto&) {
+    m_context_menu->add_action(GAction::create("Move to front", [this] (auto&) {
         if (m_selected_widget)
             m_selected_widget->gwidget()->move_to_front();
     }));
-    context_menu->add_action(GAction::create("Move to back", [this] (auto&) {
+    m_context_menu->add_action(GAction::create("Move to back", [this] (auto&) {
         if (m_selected_widget)
             m_selected_widget->gwidget()->move_to_back();
     }));
-    set_context_menu(move(context_menu), GWidget::ContextMenuMode::PassthroughMouseEvent);
+}
+
+void VBForm::context_menu_event(GContextMenuEvent& event)
+{
+    m_context_menu->popup(event.screen_position());
 }
 
 void VBForm::insert_widget(VBWidgetType type)

Applications/VisualBuilder/VBForm.h

@@ -31,6 +31,7 @@ protected:
     virtual void mousedown_event(GMouseEvent&) override;
     virtual void mousemove_event(GMouseEvent&) override;
     virtual void mouseup_event(GMouseEvent&) override;
+    virtual void context_menu_event(GContextMenuEvent&) override;
     virtual void keydown_event(GKeyEvent&) override;
 
 private:
@@ -47,4 +48,5 @@ private:
     Rect m_transform_widget_origin_rect;
     Point m_next_insertion_position;
     Direction m_resize_direction { Direction::None };
+    OwnPtr<GMenu> m_context_menu;
 };

LibGUI/GEvent.h

@@ -29,6 +29,7 @@ public:
         FocusIn,
         FocusOut,
         WindowCloseRequest,
+        ContextMenu,
         WM_WindowRemoved,
         WM_WindowStateChanged,
         WM_WindowIconChanged,
@@ -141,6 +142,23 @@ private:
     Size m_size;
 };
 
+class GContextMenuEvent final : public GEvent {
+public:
+    explicit GContextMenuEvent(const Point& position, const Point& screen_position)
+        : GEvent(GEvent::ContextMenu)
+        , m_position(position)
+        , m_screen_position(screen_position)
+    {
+    }
+
+    const Point& position() const { return m_position; }
+    const Point& screen_position() const { return m_screen_position; }
+
+private:
+    Point m_position;
+    Point m_screen_position;
+};
+
 class GShowEvent final : public GEvent {
 public:
     GShowEvent()

LibGUI/GWidget.cpp

@@ -178,18 +178,14 @@ void GWidget::handle_mousedown_event(GMouseEvent& event)
 {
     if (accepts_focus())
         set_focus(true);
-    if (event.button() == GMouseButton::Right) {
-        if (m_context_menu) {
-            if (m_context_menu_mode == ContextMenuMode::PassthroughMouseEvent)
-                mousedown_event(event);
-            m_context_menu->popup(screen_relative_rect().location().translated(event.position()));
-            return;
-        }
-    }
     // FIXME: Maybe the click clock should be per-button.
     if (!m_click_clock.is_valid())
         m_click_clock.start();
     mousedown_event(event);
+    if (event.button() == GMouseButton::Right) {
+        GContextMenuEvent c_event(event.position(), screen_relative_rect().location().translated(event.position()));
+        context_menu_event(c_event);
+    }
 }
 
 void GWidget::handle_enter_event(CEvent& event)
@@ -253,6 +249,10 @@ void GWidget::mousemove_event(GMouseEvent&)
 {
 }
 
+void GWidget::context_menu_event(GContextMenuEvent&)
+{
+}
+
 void GWidget::focusin_event(CEvent&)
 {
 }
@@ -437,14 +437,6 @@ void GWidget::set_enabled(bool enabled)
     update();
 }
 
-void GWidget::set_context_menu(OwnPtr<GMenu>&& context_menu, ContextMenuMode mode)
-{
-    // FIXME: Support switching context menus.
-    ASSERT(!m_context_menu);
-    m_context_menu = move(context_menu);
-    m_context_menu_mode = mode;
-}
-
 void GWidget::move_to_front()
 {
     auto* parent = parent_widget();

LibGUI/GWidget.h

@@ -42,11 +42,6 @@ public:
     bool is_enabled() const { return m_enabled; }
     void set_enabled(bool);
 
-    enum class ContextMenuMode { SwallowMouseEvent, PassthroughMouseEvent };
-
-    const GMenu* context_menu() const { return m_context_menu.ptr(); }
-    void set_context_menu(OwnPtr<GMenu>&&, ContextMenuMode = ContextMenuMode::SwallowMouseEvent);
-
     virtual void event(CEvent&) override;
     virtual void paint_event(GPaintEvent&);
     virtual void resize_event(GResizeEvent&);
@@ -59,6 +54,7 @@ public:
     virtual void mouseup_event(GMouseEvent&);
     virtual void click_event(GMouseEvent&);
     virtual void doubleclick_event(GMouseEvent&);
+    virtual void context_menu_event(GContextMenuEvent&);
     virtual void focusin_event(CEvent&);
     virtual void focusout_event(CEvent&);
     virtual void enter_event(CEvent&);
@@ -206,6 +202,4 @@ private:
     bool m_enabled { true };
 
     CElapsedTimer m_click_clock;
-    OwnPtr<GMenu> m_context_menu;
-    ContextMenuMode m_context_menu_mode { ContextMenuMode::SwallowMouseEvent };
 };