From 4b88baebec63bbbd98961ec649fe25491f9bbf13 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89milie=20Feral?= <emilie.feral@numworks.com>
Date: Thu, 15 Sep 2016 10:26:35 +0200
Subject: [PATCH] [Escher] Add a magic number to app as poor man's RTTI

Change-Id: If7e907f1187b6b6bda33f89aee4a5dfbd922ed6d
---
 escher/include/escher/app.h | 2 ++
 escher/src/app.cpp          | 1 +
 escher/src/responder.cpp    | 6 +++++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/escher/include/escher/app.h b/escher/include/escher/app.h
index 9afe972ff..ee5a98576 100644
--- a/escher/include/escher/app.h
+++ b/escher/include/escher/app.h
@@ -15,10 +15,12 @@
 
 class App : public Responder {
 public:
+  constexpr static uint8_t Magic = 0xA8;
   App();
   void setWindow(Window * window);
   void focus(Responder * responder);
   void processEvent(Ion::Events::Event event);
+  uint8_t m_magic; // Poor man's RTTI
 protected:
   virtual ViewController * rootViewController() = 0;
 private:
diff --git a/escher/src/app.cpp b/escher/src/app.cpp
index fe8a6c48b..86a062d20 100644
--- a/escher/src/app.cpp
+++ b/escher/src/app.cpp
@@ -5,6 +5,7 @@ extern "C" {
 }
 
 App::App() :
+  m_magic(Magic),
   Responder(nullptr),
   m_focusedResponder(nullptr)
 {
diff --git a/escher/src/responder.cpp b/escher/src/responder.cpp
index 6373a806b..5b867ba72 100644
--- a/escher/src/responder.cpp
+++ b/escher/src/responder.cpp
@@ -1,4 +1,6 @@
 #include <escher/responder.h>
+#include <escher/app.h>
+#include <assert.h>
 
 Responder::Responder(Responder * parentResponder) :
   m_parentResponder(parentResponder)
@@ -29,5 +31,7 @@ App * Responder::app() {
   /* If we used RTTI we could use a dynamic_cast, which would be a lot more
    * safe, as such:
    * return dynamic_cast<App *>(rootResponder); */
-  return (App *)rootResponder;
+   App * result = (App *)rootResponder;
+   assert(result->m_magic == App::Magic); // Poor man's RTTI
+  return result;
 }