• "deed" <none none.none> Sep 28 2012
• "Jesse Phillips" <Jessekphillips+D gmail.com> Sep 28 2012
• "Maxim Fomin" <maxim maxim-fomin.ru> Sep 28 2012
• Andrej Mitrovic <andrej.mitrovich gmail.com> Sep 28 2012
• "deed" <none none.none> Sep 30 2012

"deed" <none none.none> writes:

Hi

I am trying to register a class member function as 
wc.lpfnWndProc, but get the error message "cannot implicitly 
convert expression (&this.WndProc) of type extern (Windows) int 
delegate(...) to extern (Windows) int function(...).

I have:

extern (Windows)
class App
{
     HRESULT initialize(HINSTANCE hInstance, int iCmdShow)
     {
         WNDCLASS wc;
         ...
         wc.lpfnWndProc = &wndProc;
         ...
     }

     HRESULT wndProc(HWND hwnd, UINT message, WPARAM wParam, 
LPARAM lParam)
     {
         switch (message)
         {
             ...
         }
     }
     ...
}


(Defining wndProc as a global function works, but is not what I 
want to do...)
What is the issue here and how do I make it work?

"Jesse Phillips" <Jessekphillips+D gmail.com> writes:

On Friday, 28 September 2012 at 17:53:59 UTC, deed wrote:

 (Defining wndProc as a global function works, but is not what I 
 want to do...)
 What is the issue here and how do I make it work?


You are interfacing with C, which does not support functions with 
state (delegate). You must pass it a function, and while you can 
get at the function pointer of a delegate this is unsafe.

You make it work by providing a function and not a delegate. I do 
not know how to wrap a delegate to make that work.

"Maxim Fomin" <maxim maxim-fomin.ru> writes:

On Friday, 28 September 2012 at 17:53:59 UTC, deed wrote:
 Hi

 I am trying to register a class member function as 
 wc.lpfnWndProc, but get the error message "cannot implicitly 
 convert expression (&this.WndProc) of type extern (Windows) int 
 delegate(...) to extern (Windows) int function(...).

 I have:

 extern (Windows)
 class App
 {
     HRESULT initialize(HINSTANCE hInstance, int iCmdShow)
     {
         WNDCLASS wc;
         ...
         wc.lpfnWndProc = &wndProc;
         ...
     }

     HRESULT wndProc(HWND hwnd, UINT message, WPARAM wParam, 
 LPARAM lParam)
     {
         switch (message)
         {
             ...
         }
     }
     ...
 }


 (Defining wndProc as a global function works, but is not what I 
 want to do...)
 What is the issue here and how do I make it work?


Because wndProc in your case cannot be converted to a delegate. 
You can make it a module-level function (there is no globals in 
D) or try to make it static function - I currently cannot check 
whether it works. In any way, what gives you making wndProc a 
class member function?

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 9/28/12, Maxim Fomin <maxim maxim-fomin.ru> wrote:
 try to make it static function


If only one app is ever supposed to be instantiated you can use a
static function and a static reference to the class instance:
http://dpaste.dzfl.pl/b1497fa1

Otherwise you could use a hashmap to redirect wndProc's to class
instances by using a HWND as the key and App as the value, something
like:

App[HWND] apps;

extern (Windows)
LRESULT winDispatch(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    auto app = hwnd in apps;

    if (app !is null)
    {
        return app.wndProc(hwnd, message, wParam, lParam);
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

apps would be written to any time a new App instance is created.
Anyway there are multiple ways of doing this, it depends on what you need.

"deed" <none none.none> writes:

Thanks to all of you for your informative replies. I was testing 
different code structures and wondered whether this was possible.