Add a clear function to the window.

Also clear the window in the constructor.

src/sdl/window.cpp

@@ -54,6 +54,8 @@ twindow::twindow(const std::string& title,
 	}
 
 	pixel_format_ = info.texture_formats[0];
+
+	clear();
 }
 
 twindow::~twindow()
@@ -73,6 +75,14 @@ void twindow::full_screen()
 	/** @todo Implement. */
 }
 
+void twindow::clear()
+{
+	if(SDL_RenderClear(*this) != 0) {
+		throw texception("Failed to clear the SDL_Renderer object.",
+						 true);
+	}
+}
+
 void twindow::render()
 {
 	SDL_RenderPresent(*this);

src/sdl/window.hpp

@@ -98,6 +98,9 @@ class twindow : private boost::noncopyable
 	 */
 	void full_screen();
 
+	/** Clears the contents of the window. */
+	void clear();
+
 	/** Renders the contents of the window. */
 	void render();