From 5f253838910b7483fb3a83cbeae533a36289ccea Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Sun, 9 Feb 2025 20:31:58 -0500
Subject: [PATCH] Added a small micro example of the problem with SFML's use of
 const on drawable virtual functions which shows the _real_ reason they did
 this is because of a poor design decision to make both Drawable and
 RenderTarget equally in charge of drawing the other. AKA the 'Deadly Embrace'
 design flaw.

---
 meson.build              |  4 ++++
 sfml-const/constness.cpp | 24 ++++++++++++++++++++++++
 sfml-const/constness.hpp | 18 ++++++++++++++++++
 3 files changed, 46 insertions(+)
 create mode 100644 sfml-const/constness.cpp
 create mode 100644 sfml-const/constness.hpp

diff --git a/meson.build b/meson.build
index 80ce1c4..10b19e6 100644
--- a/meson.build
+++ b/meson.build
@@ -49,3 +49,7 @@ executable('rvo_test', [
   ],
   override_options: exe_defaults,
   dependencies: dependencies)
+
+executable('constness', 'sfml-const/constness.cpp',
+  override_options: exe_defaults,
+  dependencies: dependencies)
diff --git a/sfml-const/constness.cpp b/sfml-const/constness.cpp
new file mode 100644
index 0000000..9d88955
--- /dev/null
+++ b/sfml-const/constness.cpp
@@ -0,0 +1,24 @@
+#include <iostream>
+#include "constness.hpp"
+
+using std::cout;
+
+void RenderTarget::draw(const Drawable& drawable) {
+  drawable.draw(*this);
+}
+
+void Shape::draw(const RenderTarget& target) const {
+  cout << "shape draw\n";
+}
+
+using std::cout;
+
+int main() {
+
+  RenderTarget target;
+  Shape shape;
+
+  target.draw(shape);
+
+  return 0;
+}
diff --git a/sfml-const/constness.hpp b/sfml-const/constness.hpp
new file mode 100644
index 0000000..2ced61c
--- /dev/null
+++ b/sfml-const/constness.hpp
@@ -0,0 +1,18 @@
+#pragma once
+
+class Drawable;
+
+class RenderTarget {
+  public:
+    void draw(const Drawable& drawable);
+};
+
+class Drawable {
+  public:
+    virtual void draw(const RenderTarget& target) const = 0;
+};
+
+class Shape : public Drawable {
+  public:
+  void draw(const RenderTarget& target) const override;
+};