SDLPP: add collider IDs

sdlpp/sdlpp_renderer.cpp

@@ -22,6 +22,13 @@ Vec2D< int > Renderer::getDimensions() const {
     SDL_GetRendererOutputSize( renderer, &width, &height );
     return { width, height };
 }
+Vec2D< double > Renderer::getDoubleDimensions() const {
+    auto dimensions = getDimensions();
+    double smaller = dimensions.getX() < dimensions.getY() ? dimensions.getX()
+                                                           : dimensions.getY();
+    return { static_cast< double >( dimensions.getX() ) / smaller,
+             static_cast< double >( dimensions.getY() ) / smaller };
+}
 int Renderer::getWidth() const {
     return getDimensions().getX();
 }