Add call to new size_changed() method

src/main.cpp

@@ -73,6 +73,7 @@ bool handle_window_resize(const SDL_Event& event, bool quit) {
         cairo_rectangle_t r {0, 0, static_cast<double>(event.window.data1), static_cast<double>(event.window.data2)};
         if (main_saver) {
             main_saver->setup(main_context.get(), r);
+            main_saver->size_changed();
         }
     }
     return quit;