[Mono-dev] Func parameter in embedded mono

[Robert Jordan]

Hi,

On 28.03.2018 15:36, pierre wrote:
> I am looking for info on how I can setup a callback in an embedded mono?
> 
> so, I can define in C#, something like:
> 
> Class Widget {
> 
>    private IntPtr _native;
> 
>    [MethodImplAttribute(MethodImplOptions.InternalCall)]
> 
>    static extern private void mono_set_callback(IntPtr widget, 
> Func<Widget, Bool> callback);
> 
>    public void setCallback(Func<Widget, Bool>callback)
> 
>    {
> 
>      mono_set_callback(_native, callback);
> 
>    }
> 
> }
> 
> Is that correct?
> 
> what will be my C function?
> 
> void mono_set_callback(mono_widget_object *widget, ???? *callback) { ... }
> 
> and how can I call the callback from C? There is mono_runtime_invoke but 
> it need an object (or NULL if static) and a method...
> 

The callback argument is a MonoObject* because it's a delegate.
It already encapsulates the "this" pointer.

Example:

gint32 static_handle

void mono_set_callback(mono_widget_object *widget, MonoObject *callback)
{
     /* keep delegate alive! */
     static_handle = mono_gchandle_new (callback, FALSE);
}

void invoke_callback (...)
{
     /* get object from handle */
     MonoObject *del = mono_gchandle_get_target (static_handle);
     MonoMethod *invoke = mono_get_delegate_invoke (
         mono_object_get_class (del));

     mono_runtime_invoke(invoke, del, ...)
}


Robert