Implemented a little screenshot tool.

gui/fsm.cpp

@@ -361,6 +361,9 @@ namespace gui {
           case KEY::X:
             event(Event::STAIRS_DOWN);
             break;
+          case KEY::F5:
+            take_screenshot();
+            break;
           default:
             break; // ignored
         }
@@ -519,6 +522,16 @@ namespace gui {
     }
   }
 
+  void FSM::take_screenshot() {
+    auto size = $window.getSize();
+    sf::Texture shot{size};
+    shot.update($window);
+    sf::Image out_img = shot.copyToImage();
+
+    bool worked = out_img.saveToFile("./screenshot.png");
+    dbc::check(worked, "Failed to write screenshot.png");
+  }
+
   void FSM::next_level() {
     $levels.create_level($level.world);
     $level = $levels.next();