• 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
Symphlion

SDL 2.0 handling keyboard input ( onkeydown, onkeypressed, onkeyup, onkeyreleased)

4 posts in this topic

Hello there!

New to the forums, though i`ve been skimming these forums for a while now! FIY I`m new with C++ and totally new with SDL2.

In any case, I`m trying to achieve something which roughly translates to the following use case: Handling keyboard input with SDL2.

So imagine the following cpp:

Player::Update( float dt) {
    if(Input::OnKeyDown("w")){
          /// move player up (or jump w/e)
    }
}


All valid, correct? This is not the hardest part, I can read the current input using SDL_GetKeyboardState(NULL) and my Input class directly reads the returned array to check if the given key was set to 1.

However, I`m also looking for a way to register single key strokes. So, instead of plainly checking if a button is DOWN, I need to differentiate. What I would like to achieve is this; how do I check whether the previous state was UP and the current state is DOWN?

The SDL_GetKeyboardState() returns a pointer to an array which I can use to retrieve information, however I have no clue how to store that array some place else.

Basically, what i`m looking for is something like this ( using SDL_PumpEvents())

// somewhere in the update function of input
SDL_pumpEvents();

oldKeyboardState = currentKeyboardState;
currentKeyboardState = nextKeyboardState;
* nextKeyboardState = < the pointer to the SDL keyboard array>;

I`m not sure, but if I manage to get this working, it should be fairly easy to check whether the previous state was 0 and the current state was 1 correct?

Any tips/pointers(ugh..) to help me out? Any and all help will be much appreciated!

 

0

Share this post


Link to post
Share on other sites

SDL already provides this in the basic SDL_PollEvent loop. Alternatively, you could maintain your own array of the previous keystates (size SDLK_LAST) and copy (using a loop, std::fill, std::memcpy, whatever) the current values once per frame. Where the values of the same index in the arrays differ, you have an event, and by looking at the relative values you can determine whether it was a key press or release.

1

Share this post


Link to post
Share on other sites

I would like to try the alternative, since looping trough all the events seems that you have to individually handle all keystrokes in the code, which would severy limit extensibility or am I wrong in assuming that?

Either way, I would like to learn more about copying the currentstate variable to the oldstate. Thank you for the help, how do I go about using for example the std::memcpy or std::fill? Furthermore, will this help solve the issue at hand? Or am I looking in the wrong direction?

0

Share this post


Link to post
Share on other sites

Solved it! I copied the array, however there was no change, so all I had to do was set the PumpEvents() after the copying.

const Uint8 * currentKeyState;
// shouldn`t be a const
Uint8 * oldKeyState;

//Constructor
currentKeyState = SDL_GetKeyboardState(&this->length);
oldKeyState = new Uint8[this->length];

//Input update
memcpy(oldKeyState, currentKeyState, this->length);
SDL_PumpEvents();
currentKeyState = SDL_GetKeyboardState(NULL);
1

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