diff --git a/include/nana/gui/detail/window_manager.hpp b/include/nana/gui/detail/window_manager.hpp
index 965be995..d3468483 100644
--- a/include/nana/gui/detail/window_manager.hpp
+++ b/include/nana/gui/detail/window_manager.hpp
@@ -104,13 +104,13 @@ namespace detail
 
 		//destroy_handle
 		//@brief:	Delete window handle, the handle type must be a root and a frame.
+
+		// Deletes a window whose category type is a root type or a frame type.
 		void destroy_handle(core_window_t*);
 
 		void default_icon(const paint::image& _small_icon, const paint::image& big_icon);
 		void icon(core_window_t*, const paint::image& small_icon, const paint::image& big_icon);
 
-		//show
-		//@brief: show or hide a window
 		bool show(core_window_t* wd, bool visible);
 
 		core_window_t* find_window(native_window_type root, int x, int y);
@@ -139,10 +139,10 @@ namespace detail
 		core_window_t* set_focus(core_window_t*, bool root_has_been_focused, arg_focus::reason);
 
 		core_window_t* capture_redirect(core_window_t*);
-		void capture_ignore_children(bool ignore);
+
 		bool capture_window_entered(int root_x, int root_y, bool& prev);
 		core_window_t * capture_window() const;
-		core_window_t* capture_window(core_window_t*, bool value);
+		void capture_window(core_window_t*, bool capture, bool ignore_children_if_captured);
 
 		void enable_tabstop(core_window_t*);
 		core_window_t* tabstop(core_window_t*, bool forward) const;	//forward means move to next in logic.
diff --git a/include/nana/gui/programming_interface.hpp b/include/nana/gui/programming_interface.hpp
index 03138a04..85196997 100644
--- a/include/nana/gui/programming_interface.hpp
+++ b/include/nana/gui/programming_interface.hpp
@@ -268,10 +268,13 @@ namespace API
 	 */
 	void lazy_refresh();
 
-	/**	@brief:	calls refresh() of a widget's drawer. if currently state is lazy_refresh, Nana.GUI may paste the drawing on the window after an event processing.
-	 *	@param window: specify a window to be refreshed.
+
+	/// Refresh the window and display it immediately calling the refresh function of its drawer_trigger.
+	/*
+	 * The drawer::refresh() will be called. If the currently state is lazy_refrsh, the window is delayed to update the graphics until an event is finished.
+	 * @param window_handle A handle to the window to be refreshed.
 	 */
-	void refresh_window(window);           ///< Refreshs the window and display it immediately calling the refresh method of its drawer_trigger..
+	void refresh_window(window window_handle);
 	void refresh_window_tree(window);      ///< Refreshs the specified window and all it’s children windows, then display it immediately
 	void update_window(window);            ///< Copies the off-screen buffer to the screen for immediate display.
 
@@ -294,8 +297,20 @@ namespace API
 	void focus_window(window);
 
 	window	capture_window();
-	window	capture_window(window, bool);         ///< Enables or disables the window to grab the mouse input
-	void	capture_ignore_children(bool ignore); ///< Enables or disables the captured window whether redirects the mouse input to its children if the mouse is over its children.
+
+	/// Enables a window to grab the mouse input.
+	/**
+	 * @param window_handle A handle to a window to grab the mouse input.
+	 * @param ignore_children Indicates whether to redirect the mouse input to its children if the mouse pointer is over its children.
+	 */
+	void set_capture(window window_handle, bool ignore_children);
+	
+	/// Disable a window to grab the mouse input.
+	/**
+	 * @param window handle A handle to a window to release grab of mouse input.
+	 */
+	void release_capture(window window_handle);
+
 	void modal_window(window);                    ///< Blocks the routine til the specified window is closed.
 	void wait_for(window);
 
@@ -316,10 +331,25 @@ namespace API
 	void caret_visible(window, bool is_show);
 	bool caret_visible(window);
 
-	void tabstop(window);                       ///< Sets the window that owns the tabstop.
-            /// treu: The focus is not to be changed when Tab key is pressed, and a key_char event with tab will be generated.
-	void eat_tabstop(window, bool);
-	window move_tabstop(window, bool next);     ///< Sets the focus to the window which tabstop is near to the specified window.
+	/// Enables that the user can give input focus to the specified window using TAB key.
+	void tabstop(window);
+
+	/// Enables or disables a window to receive a key_char event for pressing TAB key.
+	/*
+	 * @param window_handle A handle to the window to catch TAB key through key_char event.
+	 * @param enable Indicates whether to enable or disable catch of TAB key. If this parameter is *true*, the window is
+	 * received a key_char when pressing TAB key, and the input focus is not changed. If this parameter is *false*, the
+	 * input focus is changed to the next tabstop window.
+	 */
+	void eat_tabstop(window window_handle, bool enable);
+
+	/// Sets the input focus to the window which the tabstop is near to the specified window.
+	/*
+	 * @param window_handle A handle to the window.
+	 * @param forward Indicates whether forward or backward window to be given the input focus.
+	 * @return A handle to the window which to be given the input focus.
+	 */
+	window move_tabstop(window window_handle, bool forward);
 
 	/// Sets the window active state. If a window active state is false, the window will not obtain the focus when a mouse clicks on it wich will be obteined by take_if_has_active_false.
 	void take_active(window, bool has_active, window take_if_has_active_false);
@@ -349,6 +379,7 @@ namespace API
 
 	void at_safe_place(window, std::function<void()>);
 }//end namespace API
+
 }//end namespace nana
 
 #endif
diff --git a/include/nana/gui/widgets/scroll.hpp b/include/nana/gui/widgets/scroll.hpp
index 1cf5bb83..00107b5f 100644
--- a/include/nana/gui/widgets/scroll.hpp
+++ b/include/nana/gui/widgets/scroll.hpp
@@ -262,7 +262,7 @@ namespace nana
 							timer_.start();
 							break;
 						case buttons::scroll:
-							API::capture_window(widget_->handle(), true);
+							widget_->set_capture(true);
 							metrics_.scroll_mouse_offset = (Vertical ? arg.pos.y : arg.pos.x) - metrics_.scroll_pos;
 							break;
 						case buttons::forward:
@@ -286,7 +286,7 @@ namespace nana
 				{
 					timer_.stop();
 
-					API::capture_window(widget_->handle(), false);
+					widget_->release_capture();
 
 					metrics_.pressed = false;
 					metrics_.what = drawer_.what(graph, arg.pos);
diff --git a/include/nana/gui/widgets/widget.hpp b/include/nana/gui/widgets/widget.hpp
index cfc174f7..14b6f2bd 100644
--- a/include/nana/gui/widgets/widget.hpp
+++ b/include/nana/gui/widgets/widget.hpp
@@ -78,6 +78,15 @@ namespace nana
 
 		nana::size size() const;
 		void size(const nana::size&);
+
+		/// Enables the widget to grab the mouse input.
+		/*
+		 * @param ignore_children Indicates whether to redirect the mouse input to its children if the mouse pointer is over its children.
+		 */
+		void set_capture(bool ignore_children);
+
+		/// Disables the widget to grab the mouse input.
+		void release_capture();
 		
 		point pos() const;
 		void move(int x, int y);
diff --git a/source/gui/detail/bedrock_pi.cpp b/source/gui/detail/bedrock_pi.cpp
index 928c422a..d705261c 100644
--- a/source/gui/detail/bedrock_pi.cpp
+++ b/source/gui/detail/bedrock_pi.cpp
@@ -310,7 +310,7 @@ namespace nana
 				return (is_keyboard_condition ? (pi_data_->menu.has_keyboard ? pi_data_->menu.window : nullptr) : pi_data_->menu.window);
 			}
 
-			return 0;
+			return nullptr;
 		}
 
 		native_window_type bedrock::get_menu()
diff --git a/source/gui/detail/window_manager.cpp b/source/gui/detail/window_manager.cpp
index 39e88c87..29e7b97a 100644
--- a/source/gui/detail/window_manager.cpp
+++ b/source/gui/detail/window_manager.cpp
@@ -455,8 +455,6 @@ namespace detail
 			update(parent, false, false, &update_area);
 		}
 
-		//destroy_handle
-		//@brief:	Delete window handle, the handle type must be a root and a frame.
 		void window_manager::destroy_handle(core_window_t* wd)
 		{
 			//Thread-Safe Required!
@@ -975,7 +973,7 @@ namespace detail
 			//A fix by Katsuhisa Yuasa
 			//The menubar token window will be redirected to the prev focus window when the new
 			//focus window is a menubar.
-			//The focus window will be restore to the prev focus which losts the focus becuase of
+			//The focus window will be restored to the prev focus which losts the focus becuase of
 			//memberbar. 
 			if (prev_focus && (wd == wd->root_widget->other.attribute.root->menubar))
 				wd = prev_focus;
@@ -998,11 +996,6 @@ namespace detail
 			return attr_.capture.window;
 		}
 
-		void window_manager::capture_ignore_children(bool ignore)
-		{
-			attr_.capture.ignore_children = ignore;
-		}
-
 		bool window_manager::capture_window_entered(int root_x, int root_y, bool& prev)
 		{
 			if(attr_.capture.window)
@@ -1023,19 +1016,15 @@ namespace detail
 			return attr_.capture.window;
 		}
 
-		//capture_window
-		//@brief:	set a window that always captures the mouse event if it is not in the range of window
-		//@return:	this function dose return the previous captured window. If the wnd set captured twice,
-		//			the return value is NULL
-		window_manager::core_window_t* window_manager::capture_window(core_window_t* wd, bool value)
+		void window_manager::capture_window(core_window_t* wd, bool captured, bool ignore_children)
 		{
 			if (!this->available(wd))
-				return nullptr;
+				return;
 
 			nana::point pos = native_interface::cursor_position();
 			auto & attr_cap = attr_.capture.history;
 
-			if(value)
+			if (captured)
 			{
 				if(wd != attr_.capture.window)
 				{
@@ -1045,19 +1034,17 @@ namespace detail
 					if (impl_->wd_register.available(wd))
 					{
 						wd->flags.captured = true;
-						native_interface::capture_window(wd->root, value);
-						auto prev = attr_.capture.window;
-						if(prev && (prev != wd))
-							attr_cap.emplace_back(prev, attr_.capture.ignore_children);
+						native_interface::capture_window(wd->root, captured);
+
+						if (attr_.capture.window)
+							attr_cap.emplace_back(attr_.capture.window, attr_.capture.ignore_children);
 
 						attr_.capture.window = wd;
-						attr_.capture.ignore_children = true;
+						attr_.capture.ignore_children = ignore_children;
 						native_interface::calc_window_point(wd->root, pos);
 						attr_.capture.inside = _m_effective(wd, pos);
-						return prev;
 					}
 				}
-				return attr_.capture.window;
 			}
 			else if(wd == attr_.capture.window)
 			{
@@ -1092,10 +1079,7 @@ namespace detail
 						break;
 					}
 				}
-
-				return attr_.capture.window;
 			}
-			return wd;
 		}
 
 		//enable_tabstop
@@ -1356,7 +1340,7 @@ namespace detail
 				if (established)
 				{
 					if (check_tree(wd, attr_.capture.window))
-						capture_window(attr_.capture.window, false);
+						capture_window(attr_.capture.window, false, false);	//The 3rd parameter is ignored
 
 					if (root_attr->focus && check_tree(wd, root_attr->focus))
 						root_attr->focus = nullptr;
@@ -1369,7 +1353,7 @@ namespace detail
 				else
 				{
 					if (wd == attr_.capture.window)
-						capture_window(attr_.capture.window, false);
+						capture_window(attr_.capture.window, false, false);	//The 3rd parameter is ignored.
 
 					if (root_attr->focus == wd)
 						root_attr->focus = nullptr;
diff --git a/source/gui/dragger.cpp b/source/gui/dragger.cpp
index 43a56ba2..459d9833 100644
--- a/source/gui/dragger.cpp
+++ b/source/gui/dragger.cpp
@@ -47,7 +47,7 @@ namespace nana
 				API::umake_event(t.over);
 				API::umake_event(t.release);
 				API::umake_event(t.destroy);
-				API::capture_window(t.wd, false);
+				API::release_capture(t.wd);
 			}
 		}
 
@@ -87,7 +87,8 @@ namespace nana
 				{
 				case event_code::mouse_down:
 					dragging_ = true;
-					API::capture_window(arg.window_handle, true);
+					API::set_capture(arg.window_handle, true);
+
 					origin_ = API::cursor_position();
 					for (auto & t : targets_)
 					{
@@ -133,7 +134,8 @@ namespace nana
 					}
 					break;
 				case event_code::mouse_up:
-					API::capture_window(arg.window_handle, false);
+					API::release_capture(arg.window_handle);
+
 					dragging_ = false;
 					break;
 				default:
@@ -151,7 +153,7 @@ namespace nana
 					if (i->wd == arg.window_handle)
 					{
 						triggers_.erase(i);
-						API::capture_window(arg.window_handle, false);
+						API::release_capture(arg.window_handle);
 						return;
 					}
 				}
diff --git a/source/gui/place.cpp b/source/gui/place.cpp
index d0796c90..48ba39bc 100644
--- a/source/gui/place.cpp
+++ b/source/gui/place.cpp
@@ -1775,7 +1775,8 @@ namespace nana
 
 						bool is_vert = _m_is_vert(dir_);
 
-						API::capture_window(this->handle(), true);
+						this->set_capture(true);
+
 						auto basepos = API::cursor_position();
 						base_pos_.x = (is_vert ? basepos.y : basepos.x);
 
@@ -1838,7 +1839,7 @@ namespace nana
 						dock_dv_->collocate(wd);
 					}
 					else
-						API::capture_window(this->handle(), false);	//release mouse button
+						this->release_capture();
 				};
 
 				auto & evt = this->events();
diff --git a/source/gui/place_parts.hpp b/source/gui/place_parts.hpp
index 1d21d600..8cd0e418 100644
--- a/source/gui/place_parts.hpp
+++ b/source/gui/place_parts.hpp
@@ -240,7 +240,7 @@ namespace nana
 							moves_.started = true;
 							moves_.start_pos = API::cursor_position();
 							moves_.start_container_pos = (floating() ? container_->pos() : this->pos());
-							API::capture_window(caption_, true);
+							caption_.set_capture(true);
 						}
 					}
 					else if (event_code::mouse_move == arg.evt_code)
@@ -266,7 +266,7 @@ namespace nana
 						if ((::nana::mouse::left_button == arg.button) && moves_.started)
 						{
 							moves_.started = false;
-							API::capture_window(caption_, false);
+							caption_.release_capture();
 							notifier_->notify_move_stopped();
 						}
 					}
@@ -345,7 +345,7 @@ namespace nana
 				if (container_)
 					return;
 
-				API::capture_window(caption_, false);
+				caption_.release_capture();
 
 				rectangle r{ pos() + move_pos, size() };
 				container_.reset(new form(host_window_, r.pare_off(-1), form::appear::bald<form::appear::sizable>()));
@@ -364,14 +364,15 @@ namespace nana
 				});
 
 				container_->show();
-				API::capture_window(caption_, true);
+				caption_.set_capture(true);
 
 				notifier_->notify_float();
 			}
 
 			void dock()
 			{
-				API::capture_window(caption_, false);
+				caption_.release_capture();
+
 				API::set_parent_window(handle(), host_window_);
 				container_.reset();
 				notifier_->notify_dock();
diff --git a/source/gui/programming_interface.cpp b/source/gui/programming_interface.cpp
index a13e81cd..75f34ebe 100644
--- a/source/gui/programming_interface.cpp
+++ b/source/gui/programming_interface.cpp
@@ -937,16 +937,15 @@ namespace API
 		return reinterpret_cast<window>(restrict::wd_manager().capture_window());
 	}
 
-	window capture_window(window wd, bool value)
+	void set_capture(window wd, bool ignore_children)
 	{
-		return reinterpret_cast<window>(
-					restrict::wd_manager().capture_window(reinterpret_cast<basic_window*>(wd), value)
-		);
+		restrict::wd_manager().capture_window(reinterpret_cast<basic_window*>(wd), true, ignore_children);
 	}
 
-	void capture_ignore_children(bool ignore)
+	void release_capture(window wd)
 	{
-		restrict::wd_manager().capture_ignore_children(ignore);
+		//The 3rd parameter is useless when the 2nd parameter is false.
+		restrict::wd_manager().capture_window(reinterpret_cast<basic_window*>(wd), false, false);
 	}
 
 	void modal_window(window wd)
diff --git a/source/gui/widgets/button.cpp b/source/gui/widgets/button.cpp
index 1b7aa835..ec0b6e85 100644
--- a/source/gui/widgets/button.cpp
+++ b/source/gui/widgets/button.cpp
@@ -321,11 +321,12 @@ namespace nana{	namespace drawerbase
 
 				attr_.e_state = element_state::pressed;
 				attr_.keep_pressed = true;
-				API::capture_window(*wdg_, true);
+				wdg_->set_capture(true);
 			}
 			else
 			{
-				API::capture_window(*wdg_, false);
+				wdg_->release_capture();
+
 				attr_.keep_pressed = false;
 				if (attr_.enable_pushed && (false == attr_.pushed))
 				{
diff --git a/source/gui/widgets/float_listbox.cpp b/source/gui/widgets/float_listbox.cpp
index d2591ac0..c51c8342 100644
--- a/source/gui/widgets/float_listbox.cpp
+++ b/source/gui/widgets/float_listbox.cpp
@@ -469,8 +469,8 @@ namespace nana
 		float_listbox::float_listbox(window wd, const rectangle & r, bool is_ignore_first_mouse_up)
 			:base_type(wd, false, r, appear::bald<appear::floating, appear::no_activate>())
 		{
-			API::capture_window(handle(), true);
-			API::capture_ignore_children(false);
+			this->set_capture(false);
+
 			API::take_active(handle(), false, parent());
 			auto & impl = get_drawer_trigger().get_drawer_impl();
 			impl.clear_state();
diff --git a/source/gui/widgets/listbox.cpp b/source/gui/widgets/listbox.cpp
index 007615cd..030283ad 100644
--- a/source/gui/widgets/listbox.cpp
+++ b/source/gui/widgets/listbox.cpp
@@ -3343,7 +3343,8 @@ namespace nana
 							nana::point pos = arg.pos;
 							essence_->widget_to_header(pos);
 							drawer_header_->grab(pos, true);
-							API::capture_window(essence_->lister.wd_ptr()->handle(), true);
+							essence_->lister.wd_ptr()->set_capture(true);
+
 							update = 2;
 						}
 					}
@@ -3535,7 +3536,7 @@ namespace nana
 						drawer_header_->grab(pos, false);
 						refresh(graph);
 						API::lazy_refresh();
-						API::capture_window(essence_->lister.wd_ptr()->handle(), false);
+						essence_->lister.wd_ptr()->release_capture();
 					}
 				}
 
diff --git a/source/gui/widgets/skeletons/text_editor.cpp b/source/gui/widgets/skeletons/text_editor.cpp
index 3c372903..747e29a9 100644
--- a/source/gui/widgets/skeletons/text_editor.cpp
+++ b/source/gui/widgets/skeletons/text_editor.cpp
@@ -1719,7 +1719,7 @@ namespace nana{	namespace widgets
 
 				if (::nana::mouse::left_button == arg.button)
 				{
-					API::capture_window(window_, true);
+					API::set_capture(window_, true);
 					text_area_.captured = true;
 
 					//Set caret pos by screen point and get the caret pos.
@@ -1764,7 +1764,8 @@ namespace nana{	namespace widgets
 				}
 				select_.dragged = false;
 
-				API::capture_window(window_, false);
+				API::release_capture(window_);
+
 				text_area_.captured = false;
 				if (hit_text_area(arg.pos) == false)
 					API::window_cursor(window_, nana::cursor::arrow);
diff --git a/source/gui/widgets/slider.cpp b/source/gui/widgets/slider.cpp
index 45fbd122..38ba84e7 100644
--- a/source/gui/widgets/slider.cpp
+++ b/source/gui/widgets/slider.cpp
@@ -263,14 +263,15 @@ namespace nana
 					slider_state_.trace = slider_state_.TraceCapture;
 					slider_state_.snap_pos = static_cast<int>(attr_.pos);
 					slider_state_.refpos = pos;
-					API::capture_window(other_.wd, true);
+					API::set_capture(other_.wd, true);
 				}
 
 				bool release_slider()
 				{
 					if(slider_state_.trace == slider_state_.TraceCapture)
 					{
-						API::capture_window(other_.wd, false);
+						API::release_capture(other_.wd);
+
 						if(other_.wd != API::find_window(API::cursor_position()))
 						{
 							slider_state_.trace = slider_state_.TraceNone;
diff --git a/source/gui/widgets/spinbox.cpp b/source/gui/widgets/spinbox.cpp
index 90397d41..427dc47d 100644
--- a/source/gui/widgets/spinbox.cpp
+++ b/source/gui/widgets/spinbox.cpp
@@ -351,7 +351,8 @@ namespace nana
 				{
 					if (!pressed)
 					{
-						API::capture_window(editor_->window_handle(), false);
+						API::release_capture(editor_->window_handle());
+
 						timer_.stop();
 						timer_.interval(600);
 					}
@@ -361,7 +362,7 @@ namespace nana
 						//Spins the value when mouse button is released
 						if (pressed)
 						{
-							API::capture_window(editor_->window_handle(), true);
+							API::set_capture(editor_->window_handle(), true);
 							range_->spin(buttons::increase == spin_stated_);
 							reset_text();
 							timer_.start();
diff --git a/source/gui/widgets/widget.cpp b/source/gui/widgets/widget.cpp
index 1169e59e..ac50687b 100644
--- a/source/gui/widgets/widget.cpp
+++ b/source/gui/widgets/widget.cpp
@@ -183,6 +183,16 @@ namespace nana
 			_m_size(sz);
 		}
 
+		void widget::set_capture(bool ignore_children)
+		{
+			API::set_capture(*this, ignore_children);
+		}
+
+		void widget::release_capture()
+		{
+			API::release_capture(*this);
+		}
+
 		nana::point widget::pos() const
 		{
 			return API::window_position(handle());