finish basic work of fit-content

include/nana/deploy.hpp

@@ -19,11 +19,8 @@
 #include <nana/config.hpp>
 #include <nana/stdc++.hpp>
 
-
-#include <stdexcept>
 #include <nana/charset.hpp>
 
-
 namespace nana
 {
 	/// move to *.h ??

include/nana/gui/detail/widget_content_measurer_interface.hpp

@@ -30,11 +30,18 @@ namespace nana
 
 			/// Measures content
 			/**
-			* @param limit_width true if limits the width, false if limits the height.
-			* @param limit_pixels the number of pixels of the limited edge. If this parameter is zero, it is ignored
-			* @return the size of content
-			*/
-			virtual optional<size> measure(graph_reference, bool limit_width, unsigned limit_pixels) const = 0;
+			 * @param graph The graphics for the operation.
+			 * @param limit_pixels The number of pixels of the limited edge. If this parameter is zero, it is ignored.
+			 * @param limit_width True if limits the width, false if limits the height.
+			 * @return the size of content.
+			 */
+			virtual optional<size> measure(graph_reference graph, unsigned limit_pixels, bool limit_width) const = 0;
+
+			/// Returns the extension to the size of widget from content extent
+			/**
+			 * @return the width and height of extension to the widget size.
+			 */
+			virtual size extension() const = 0;
 		};
 	}
 }

include/nana/gui/programming_interface.hpp

@@ -403,6 +403,17 @@ namespace API
 	bool ignore_mouse_focus(window);				///< Determines whether the mouse focus is enabled
 
 	void at_safe_place(window, std::function<void()>);
+
+	/// Returns a widget content extent size
+	/**
+	 * @param wd A handle to a window that returns its content extent size.
+	 * @param limited_px Specifies the max pixels of width or height. If this parameter is zero, this parameter will be ignored.
+	 * @param limit_width Indicates whether the it limits the width or height. If this parameter is *true*, the width is limited.
+	 * If the parameter is *false*, the height is limited. This parameter is ignored if limited_px = 0.
+	 * @return if optional has a value, the first size indicates the content extent, the second size indicates the size of
+	 * widget by the content extent. 
+	 */
+	optional<std::pair<::nana::size, ::nana::size>> content_extent(window wd, unsigned limited_px, bool limit_width);
 }//end namespace API
 
 }//end namespace nana

include/nana/gui/widgets/button.hpp

@@ -59,6 +59,8 @@ namespace nana{
 
 				element::cite_bground cite_{"button"};
 
+				std::unique_ptr<measurer> measurer_;
+
 				struct attr_tag
 				{
 					element_state e_state;