• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
Plethora

Understanding Function Pointers and other such things (C++)

5 posts in this topic

I recently started messing around with the SFGUI library, its basically a gui library based in SFML.  On its own, I was able to follow the tutorial here:  http://sfgui.sfml-dev.de/p/docs/guide/hello_world Without a problem.  When I went about adding it to my own program, though, I ran into an issue with this line:

 

button->GetSignal( sfg::Button::OnLeftClick ).Connect( &OnButtonClick );
 

Now, in my program I'm attempting to put all of this within a class called Gui_Manager.  I have a class method called OnButtonClick(), however as I've learned I cannot use a function pointer like the one in the tutorial code with a bound member function.  So I consulted the documentation and found that Connect has two declarations as follows:

 

unsigned int 	Connect (Delegate delegate)
unsigned int 	Connect (void(Class::*function)(), Class *object)

 

The tutorial uses the first constructor with the Delegate being a function pointer (&OnButtonClick).  I'm guessing as I want to connect with a class method, I now want to use the second declaration, however, I'm not even sure how I would call that (I've randomly tried some things with no results).  So I have two questions to anyone who would be so kind...

 

1)  An example of how I would call Connect using the second definition... I feel like just having some code to point me in the right direction would be lovely...

 

2)  I could fairly easily create the required function callbacks outside of my class, but doing so goes against most of the Object Oriented conditioning I've been through in my life.  Would that be an acceptable solution?  Or are there notably drawbacks to doing things that way when every other spec of code in my program is contained in a class?

 

Thanks for any help you can give!  :)

0

Share this post


Link to post
Share on other sites

Did you try

button->GetSignal( sfg::Button::OnLeftClick ).Connect( &OnButtonClick, this );

? Obviously you need to provide a function pointer as first and the actual object as the second paramter, since the function pointer does not store an actual object to call the function on.

Edited by The King2
0

Share this post


Link to post
Share on other sites

Well... I did try your suggestion, and it didn't work, however this:

 

 

button->GetSignal( sfg::Button::OnLeftClick ).Connect( &Gui_Manager::OnButtonClick, this );
 

Did work.  

 

I think I was definitely making this out to be more complicated than it needed to be, thanks for the inspiration!

 

:)

0

Share this post


Link to post
Share on other sites
I know nothing of SFML so all I can offer is some background info for you. The signature looks like the common solution to having class methods as callbacks, i.e. you declare a static method inside said class (which does not take the implicit this pointer as it's first argument) which takes a pointer to an object of said class as an argument. The static method then calls the appropriate method of the object in question.

Your static method would look something like this:

class MyClass
{
public:

static void OnClickCallback(MyClass* obj) {obj->OnClick();}

// and so on

};

You would register the callback like this: Connect(&MyClass::OnClickCallback, this) from some (non-static) method in your class (or elswhere in your code, just replace the this pointer with a pointer to the object you wish to connect).


Edit: whoops, looks like a flurry of posts since I started my reply and you have the problem solved. My bad!
Edit2: and I messed up the code tags, fixed! Edited by GeneralQuery
0

Share this post


Link to post
Share on other sites

Nope, it's a pointer to member function, not static, because of this syntax

 

void(Class::*function)()

 

which needs an object to be called, like so

 

obj->*function();

 

EDIT: Or obj.*function(); if called through a non-pointer

 

That's why the second method takes the this pointer (to know which object to call it with).

 

If it was a normal C compatible function pointer it would be declared like this

 

void (*function)();

 

and then it would require a static member function (but then you'd want to pass it a pointer to the object, so it would have a pointer as first argument most likely).

Edited by Paradigm Shifter
0

Share this post


Link to post
Share on other sites

Well... I did try your suggestion, and it didn't work, however this:

 

Damn, missed the "&" before the function, this happens every now and then :/ You might probably leave out the Gui_Manager:: before the function name, could save you a little typing, as long as you "connect" from inside another function of the same class.

Edited by The King2
0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0