LibGUI+WindowServer: Flash menubar menu when using a keyboard shortcut

Briefly flash the menubar menu containing the keyboard shortcut action
to give the user immediate visual feedback on their interaction with the
system.

Userland/Services/WindowServer/ClientConnection.cpp

@@ -192,6 +192,40 @@ void ClientConnection::update_menu_item(i32 menu_id, i32 identifier, [[maybe_unu
         menu_item->set_checked(checked);
 }
 
+void ClientConnection::flash_menubar_menu(i32 window_id, i32 menu_id)
+{
+    auto itw = m_windows.find(window_id);
+    if (itw == m_windows.end()) {
+        did_misbehave("FlashMenubarMenu: Bad window ID");
+        return;
+    }
+    auto& window = *(*itw).value;
+
+    auto itm = m_menus.find(menu_id);
+    if (itm == m_menus.end()) {
+        did_misbehave("FlashMenubarMenu: Bad menu ID");
+        return;
+    }
+    auto& menu = *(*itm).value;
+
+    if (window.menubar().flash_menu(&menu)) {
+        window.frame().invalidate_menubar();
+
+        if (m_flashed_menu_timer && m_flashed_menu_timer->is_active()) {
+            m_flashed_menu_timer->on_timeout();
+            m_flashed_menu_timer->stop();
+        }
+
+        m_flashed_menu_timer = Core::Timer::create_single_shot(75, [&window] {
+            window.menubar().flash_menu(nullptr);
+            window.frame().invalidate_menubar();
+        });
+        m_flashed_menu_timer->start();
+    } else if (m_flashed_menu_timer) {
+        m_flashed_menu_timer->restart();
+    }
+}
+
 void ClientConnection::add_menu_separator(i32 menu_id)
 {
     auto it = m_menus.find(menu_id);

Userland/Services/WindowServer/ClientConnection.h

@@ -97,6 +97,7 @@ private:
     virtual void add_menu_item(i32, i32, i32, String const&, bool, bool, bool, bool, String const&, Gfx::ShareableBitmap const&, bool) override;
     virtual void add_menu_separator(i32) override;
     virtual void update_menu_item(i32, i32, i32, String const&, bool, bool, bool, bool, String const&) override;
+    virtual void flash_menubar_menu(i32, i32) override;
     virtual void create_window(i32, Gfx::IntRect const&, bool, bool, bool, bool, bool,
         bool, bool, bool, bool, bool, float, float, Gfx::IntSize const&, Gfx::IntSize const&, Gfx::IntSize const&,
         Optional<Gfx::IntSize> const&, i32, String const&, i32, Gfx::IntRect const&) override;
@@ -178,6 +179,7 @@ private:
     HashMap<int, NonnullRefPtr<Window>> m_windows;
     HashMap<int, NonnullRefPtr<Menu>> m_menus;
 
+    RefPtr<Core::Timer> m_flashed_menu_timer;
     RefPtr<Core::Timer> m_ping_timer;
 
     bool m_has_display_link { false };

Userland/Services/WindowServer/Menubar.h

@@ -23,6 +23,26 @@ public:
         layout_menu(menu, window_rect);
     }
 
+    bool flash_menu(Menu* flashed_submenu)
+    {
+        Menu* const old_flashed_menu = m_flashed_menu;
+        m_flashed_menu = nullptr;
+
+        if (flashed_submenu) {
+            for_each_menu([&](Menu& menu) {
+                if ((&menu) == flashed_submenu || menu.is_menu_ancestor_of(*flashed_submenu)) {
+                    m_flashed_menu = &menu;
+                    return IterationDecision::Break;
+                }
+                return IterationDecision::Continue;
+            });
+        }
+
+        return (old_flashed_menu != m_flashed_menu);
+    }
+
+    Menu* flashed_menu() const { return m_flashed_menu; }
+
     bool has_menus()
     {
         return !m_menus.is_empty();
@@ -40,6 +60,7 @@ private:
     void layout_menu(Menu&, Gfx::IntRect window_rect);
 
     Vector<Menu&> m_menus;
+    Menu* m_flashed_menu { nullptr };
 
     // FIXME: This doesn't support removing menus from a menubar or inserting a
     //        menu in the middle.

Userland/Services/WindowServer/WindowFrame.cpp

@@ -264,8 +264,15 @@ void WindowFrame::paint_menubar(Gfx::Painter& painter)
     painter.translate(menubar_rect.location());
 
     m_window.menubar().for_each_menu([&](Menu& menu) {
+        bool paint_as_flashed = ((&menu) == m_window.menubar().flashed_menu());
+        if (paint_as_flashed) {
+            auto flashed_rect = menu.rect_in_window_menubar();
+            flashed_rect.shrink(2, 2);
+            painter.fill_rect(flashed_rect, palette.selection());
+        }
+
         auto text_rect = menu.rect_in_window_menubar();
-        Color text_color = palette.window_text();
+        Color text_color = (paint_as_flashed ? palette.selection_text() : palette.window_text());
         auto is_open = menu.is_open();
         if (is_open)
             text_rect.translate_by(1, 1);

Userland/Services/WindowServer/WindowServer.ipc

@@ -24,6 +24,7 @@ endpoint WindowServer
     add_menu_separator(i32 menu_id) =|
 
     update_menu_item(i32 menu_id, i32 identifier, i32 submenu_id, [UTF8] String text, bool enabled, bool checkable, bool checked, bool is_default, [UTF8] String shortcut) =|
+    flash_menubar_menu(i32 window_id, i32 menu_id) =|
 
     create_window(
         i32 window_id,