Expose topShownLayer from LayerStackWidget/LaayerManager.

ui/layers/layer_manager.cpp

@@ -59,6 +59,10 @@ bool LayerManager::setFocus() {
 	return true;
 }
 
+const LayerWidget *LayerManager::topShownLayer() const {
+	return _layer ? _layer->topShownLayer() : nullptr;
+}
+
 void LayerManager::ensureLayerCreated() {
 	if (_layer) {
 		return;

ui/layers/layer_manager.h

@@ -36,6 +36,8 @@ public:
 	void raise();
 	bool setFocus();
 
+	const LayerWidget *topShownLayer() const;
+
 private:
 	void ensureLayerCreated();
 	void destroyLayer();

ui/layers/layer_widget.cpp

@@ -458,6 +458,17 @@ bool LayerStackWidget::layerShown() const {
 	return _specialLayer || currentLayer() || _mainMenu;
 }
 
+const LayerWidget *LayerStackWidget::topShownLayer() const {
+	if (const auto result = currentLayer()) {
+		return result;
+	} else if (const auto special = _specialLayer.data()) {
+		return special;
+	} else if (const auto menu = _mainMenu.data()) {
+		return menu;
+	}
+	return nullptr;
+}
+
 void LayerStackWidget::setStyleOverrides(
 		const style::Box *boxSt,
 		const style::Box *layerSt) {

ui/layers/layer_widget.h

@@ -144,6 +144,7 @@ public:
 		const ::Window::SectionShow &params);
 
 	bool layerShown() const;
+	const LayerWidget *topShownLayer() const;
 
 	~LayerStackWidget();