add new features to listbox

a method to enable/disable the number of items
methods about expanding category
methods about category icons

include/nana/gui/widgets/listbox.hpp

@@ -1052,6 +1052,19 @@ namespace nana
 				cat_proxy & select(bool);
 				bool selected() const;
 
+				/// Enables/disables the number of items in the category to be displayed behind the category title
+				cat_proxy& display_number(bool display);
+
+				/// Determines whether the category is expanded.
+				bool expanded() const;
+
+				/// Expands/collapses the category
+				/**
+				 * @param expand Indicates whether to expand or collapse the category. If this parameter is true, it expands the category. If the parameter is false, it collapses the category.
+				 * @return the reference of *this.
+				 */
+				cat_proxy& expanded(bool expand);
+
 				/// Behavior of a container
 				void push_back(std::string text_utf8);
 
@@ -1484,6 +1497,22 @@ the nana::detail::basic_window member pointer scheme
 		void enable_single(bool for_selection, bool category_limited);
 		void disable_single(bool for_selection);
 		export_options& def_export_options();
+
+
+		/// Sets a renderer for category icon
+		/**
+		 * @param icon_renderer The renderer of category icon
+		 * @return the reference of *this.
+		 */
+		listbox& category_icon(std::function<void(paint::graphics& graph, const rectangle& rt_icon, bool expanded)> icon_renderer);
+
+		/// Sets category icons
+		/**
+		 * @param img_expanded An icon displayed in front of category title when the category is expanded.
+		 * @param img_collapsed An icon displayed in front of category title when the category is collapsed.
+		 * @return the reference of *this.
+		 */
+		listbox& category_icon(const paint::image& img_expanded, const paint::image&& img_collapsed);
 	private:
 		drawerbase::listbox::essence & _m_ess() const;
 		nana::any* _m_anyobj(size_type cat, size_type index, bool allocate_if_empty) const override;

source/gui/widgets/listbox.cpp

@@ -659,7 +659,8 @@ namespace nana
 
 				std::unique_ptr<model_interface> model_ptr;
 
-				bool expand{true};
+				bool expand{ true };
+				bool display_number{ true };
 
 				//A cat may have a key object to identify the category
 				std::shared_ptr<nana::detail::key_interface> key_ptr;
@@ -1938,6 +1939,8 @@ namespace nana
 
 				std::unique_ptr<widgets::skeletons::content_view> content_view;
 
+				std::function<void(paint::graphics&, const rectangle&, bool)> ctg_icon_renderer;	///< Renderer for the category icon
+
 				struct mouse_selection_part
 				{
 					bool	started{ false };
@@ -3544,27 +3547,36 @@ namespace nana
 
 					color txt_color{ static_cast<color_rgb>(0x3399) };
 
-					facade<element::arrow> arrow("double");
+					//Area of category icon
-					arrow.direction(categ.expand ? ::nana::direction::north : ::nana::direction::south);
+					rectangle rt_ctg_icon{ x + 5, y + static_cast<int>(item_height - 16) / 2, 16, 16 };
-					arrow.draw(	*graph, {}, txt_color,
+
-								{ x + 5, y + static_cast<int>(item_height - 16) / 2, 16, 16 },
+					if (essence_->ctg_icon_renderer)
-								element_state::normal);
+					{
+						essence_->ctg_icon_renderer(*graph, rt_ctg_icon, categ.expand);
+					}
+					else
+					{
+						facade<element::arrow> arrow("double");
+						arrow.direction(categ.expand ? ::nana::direction::south : ::nana::direction::east);
+						arrow.draw(*graph, {}, txt_color, rt_ctg_icon, element_state::normal);
+					}
 
 					graph->string({ x + 20, y + txtoff }, categ.text, txt_color);
 
-					native_string_type str = to_nstring('(' + std::to_string(categ.items.size()) + ')');
+					auto text_px = graph->text_extent_size(categ.text).width;
-
+					if (categ.display_number)
-					auto text_s = graph->text_extent_size(categ.text).width;
-					auto extend_text_w = text_s + graph->text_extent_size(str).width;
-
-					graph->string({ x + 25 + static_cast<int>(text_s), y + txtoff }, str);
-
-					if (35 + extend_text_w < width)
 					{
-						::nana::point pos{ x + 30 + static_cast<int>(extend_text_w), y + static_cast<int>(item_height) / 2 };
+						//Display the number of items in the category
+						native_string_type str = to_nstring('(' + std::to_string(categ.items.size()) + ')');
+						graph->string({ x + 25 + static_cast<int>(text_px), y + txtoff }, str);
+						text_px += graph->text_extent_size(str).width;
+					}
 
-						graph->line(pos, { x + static_cast<int>(width) - 5, pos.y },
+					if (35 + text_px < width)
-									txt_color);
+					{
+						::nana::point pos{ x + 30 + static_cast<int>(text_px), y + static_cast<int>(item_height) / 2 };
+
+						graph->line(pos, { x + static_cast<int>(width) - 5, pos.y }, txt_color);
 					}
 
 					//Draw selecting inner rectangle
@@ -4814,6 +4826,32 @@ namespace nana
                     return true;
                 }
 
+				cat_proxy& cat_proxy::display_number(bool display)
+				{
+					if (cat_->display_number != display)
+					{
+						cat_->display_number = display;
+						ess_->update();
+					}
+					return *this;
+				}
+
+				bool cat_proxy::expanded() const
+				{
+					return cat_->expand;
+				}
+
+				cat_proxy& cat_proxy::expanded(bool expand)
+				{
+					//The first category isn't allowed to be collapsed
+					if ((expand != cat_->expand) && pos_)
+					{
+						cat_->expand = expand;
+						ess_->update();
+					}
+					return *this;
+				}
+
 				auto cat_proxy::columns() const -> size_type
 				{
 					return ess_->header.cont().size();
@@ -5585,6 +5623,32 @@ namespace nana
 			return _m_ess().def_exp_options;
         }
 
+		listbox& listbox::category_icon(std::function<void(paint::graphics& graph, const rectangle& rt_icon, bool expanded)> icon_renderer)
+		{
+			_m_ess().ctg_icon_renderer.swap(icon_renderer);
+			_m_ess().update();
+			return *this;
+		}
+
+		listbox& listbox::category_icon(const paint::image& img_expanded, const paint::image&& img_collapsed)
+		{
+			_m_ess().ctg_icon_renderer = [img_expanded, img_collapsed](paint::graphics& graph, const rectangle& rt_icon, bool expanded)
+			{
+				if (expanded)
+				{
+					img_expanded.stretch(rectangle{ img_expanded.size() }, graph, rt_icon);
+				}
+				else
+				{
+					img_collapsed.stretch(rectangle{ img_collapsed.size() }, graph, rt_icon);
+				}
+			};
+
+			_m_ess().update();
+			return *this;
+		}
+
+
 		drawerbase::listbox::essence & listbox::_m_ess() const
 		{
 			return get_drawer_trigger().ess();