From 27f6f37b336c3fcdc73e307ffc7e843a50142ef7 Mon Sep 17 00:00:00 2001
From: Callum Carmicheal <callumcarmicheal@gmail.com>
Date: Sat, 17 Aug 2019 04:18:05 +0100
Subject: [PATCH] Adding dukglue_register_function_property

A helper function to allow the use of dukglue on Objects instead of the Global namespace.

Example code usage:

```cpp
int math_add(int x, int y) {
    printf("Example function called\n");
    return x + y;
}

void CreateTheObject(duk_context *ctx) {
    // 1. Create a new object
    // 2. Register the function as a property on the object
    // 3. Store the object as global
    duk_push_object(ctx);
    dukglue_register_function_property(ctx, &math_add, "add");
    duk_put_global_string(ctx, "Math");
}

void CreateTheObjectWithIndex(duk_context *ctx) {
    // 1. Create a new object
    // 2. Register the function as a property on the object
    // 3. Store the object as global
    duk_idx_t mathObjectIdx = duk_push_object(ctx);

    // lets say for what ever reason there are more values on the stack
    for(int x = 0; x < 3; x++)
        duk_push_null(ctx);

    // We will now register the function to the original stack object's index (mathObjectIdx)
    dukglue_register_function_property(ctx, &math_add, mathObjectIdx, "add");
    duk_put_global_string(ctx, "Math");

    // Clean up the nulls (only in the example)
    for(int x = 0; x < 3; x++)
        duk_pop(ctx);
}

int PlayerOnHit(int currentHealth) {
    return currentHealth--;
}

void AppendToObject(duk_context *ctx) {
    // 1. Find the global object "Player"
    // 2. Register the function as a property
    // 3. Remove "Game" from the stack
    duk_get_global_string(ctx, "Game");
    dukglue_register_function_property(ctx, &PlayerOnHit, "OnHit");
    duk_pop(ctx);
}
```
---
 include/dukglue/register_function.h | 32 +++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/include/dukglue/register_function.h b/include/dukglue/register_function.h
index 77e83aa..fba9091 100644
--- a/include/dukglue/register_function.h
+++ b/include/dukglue/register_function.h
@@ -33,3 +33,35 @@ void dukglue_register_function(duk_context* ctx, RetType(*funcToCall)(Ts...), co
 
 	duk_put_global_string(ctx, name);
 }
+
+
+// Register a function as a property to a object.
+// Simply does the same as the above but replaces duk_put_global_string with duk_put_prop_string
+template<typename RetType, typename... Ts>
+void dukglue_register_function_property(duk_context* ctx, RetType(*funcToCall)(Ts...), const char* name)
+{
+	duk_c_function evalFunc = dukglue::detail::FuncInfoHolder<RetType, Ts...>::FuncRuntime::call_native_function;
+
+	duk_push_c_function(ctx, evalFunc, sizeof...(Ts));
+
+  static_assert(sizeof(RetType(*)(Ts...)) == sizeof(void*), "Function pointer and data pointer are different sizes");
+	duk_push_pointer(ctx, reinterpret_cast<void*>(funcToCall));
+	duk_put_prop_string(ctx, -2, "\xFF" "func_ptr");
+	
+	duk_put_prop_string(ctx, -2, name);
+}
+
+// Register a function as a property to a object using the objects index.
+template<typename RetType, typename... Ts>
+void dukglue_register_function_property(duk_context* ctx, RetType(*funcToCall)(Ts...), duk_idx_t objectIdx, const char* name)
+{
+	duk_c_function evalFunc = dukglue::detail::FuncInfoHolder<RetType, Ts...>::FuncRuntime::call_native_function;
+
+	duk_push_c_function(ctx, evalFunc, sizeof...(Ts));
+
+  static_assert(sizeof(RetType(*)(Ts...)) == sizeof(void*), "Function pointer and data pointer are different sizes");
+	duk_push_pointer(ctx, reinterpret_cast<void*>(funcToCall));
+	duk_put_prop_string(ctx, -2, "\xFF" "func_ptr");
+	
+	duk_put_prop_string(ctx, objectIdx, name);
+}