feat(group): Add .empty class to empty groups

include/group.hpp

@@ -26,6 +26,7 @@ class Group : public AModule {
   bool is_first_widget = true;
   bool is_drawer = false;
   bool click_to_reveal = false;
+  bool empty_if_drawer_empty = false;
   std::string add_class_to_drawer_children;
   bool handleMouseEnter(GdkEventCrossing* const& ev) override;
   bool handleMouseLeave(GdkEventCrossing* const& ev) override;

man/waybar.5.scd.in

@@ -374,6 +374,11 @@ A group may hide all but one element, showing them only on mouse hover. In order
 	Defines the direction of the transition animation. If true, the hidden elements will slide from left to right. If false, they will slide from right to left.
 	When the bar is vertical, it reads as top-to-bottom.
 
+*empty-if-drawer-empty*: ++
+	typeof: bool ++
+	default: false ++
+	Defines whether the group should be assigned the "empty" CSS class when all modules inside the drawer are hidden or missing. If false, the group will not receive the "empty" class as long as the leader module remains visible. This allows users to dynamically style or hide the entire group using CSS when its drawer contents are unavailable.
+
 ```
 "group/power": {
     "orientation": "inherit",
@@ -390,6 +395,19 @@ A group may hide all but one element, showing them only on mouse hover. In order
     ]
 },
 ```
+To hide the power group if it is empty, apply to #power and all its children:
+```
+#power.empty,
+#power.empty * {
+    min-width: 0px;
+    min-height: 0px;
+    padding: 0px;
+    margin: 0px;
+    border: none;
+    font-size: 0px;
+    opacity: 0;
+}
+```
 
 # SUPPORTED MODULES
 

src/group.cpp

@@ -30,6 +30,7 @@ Group::Group(const std::string& name, const std::string& id, const Json::Value&
       box{vertical ? Gtk::ORIENTATION_VERTICAL : Gtk::ORIENTATION_HORIZONTAL, 0},
       revealer_box{vertical ? Gtk::ORIENTATION_VERTICAL : Gtk::ORIENTATION_HORIZONTAL, 0} {
   box.set_name(name_);
+  box.get_style_context()->add_class("empty");
   if (!id.empty()) {
     box.get_style_context()->add_class(id);
   }
@@ -67,6 +68,9 @@ Group::Group(const std::string& name, const std::string& id, const Json::Value&
     const bool start_expanded =
         (drawer_config["start-expanded"].isBool() ? drawer_config["start-expanded"].asBool()
                                                   : false);
+    empty_if_drawer_empty = (drawer_config["empty-if-drawer-empty"].isBool()
+                                 ? drawer_config["empty-if-drawer-empty"].asBool()
+                                 : false);
 
     auto transition_type = getPreferredTransitionType(vertical);
 
@@ -129,7 +133,44 @@ bool Group::handleToggle(GdkEventButton* const& e) {
 }
 
 auto Group::update() -> void {
-  // noop
+  bool has_visible_child = false;
+  bool has_visible_drawer_child = false;
+
+  if (is_drawer) {
+    for (auto* rev_child : revealer_box.get_children()) {
+      if (rev_child->get_visible()) {
+        has_visible_drawer_child = true;
+        break;
+      }
+    }
+  }
+
+  if (is_drawer && empty_if_drawer_empty) {
+    has_visible_child = has_visible_drawer_child;
+  } else {
+    for (auto* child : box.get_children()) {
+      if (child == &revealer) {
+        if (has_visible_drawer_child) {
+          has_visible_child = true;
+          break;
+        }
+      } else if (child->get_visible()) {
+        has_visible_child = true;
+        break;
+      }
+    }
+  }
+
+  auto style = box.get_style_context();
+  if (has_visible_child) {
+    if (style->has_class("empty")) {
+      style->remove_class("empty");
+    }
+  } else {
+    if (!style->has_class("empty")) {
+      style->add_class("empty");
+    }
+  }
 }
 
 bool Group::handleScroll(GdkEventScroll* e) {
@@ -147,6 +188,8 @@ void Group::addWidget(Gtk::Widget& widget) {
   }
 
   is_first_widget = false;
+  widget.property_visible().signal_changed().connect(sigc::mem_fun(*this, &Group::update));
+  update();
 }
 
 Group::operator Gtk::Widget&() { return event_box_; }